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Sample records for light cone qcd

  1. Light-cone quantized QCD in 1 + 1 dimensions

    SciTech Connect

    Hornbostel, K.; Brodsky, S.J.; Pauli, H.C.

    1988-10-01

    The QCD light-cone Hamiltonian is diagonalized in a discrete momentum-space basis. The spectra and wavefunctions for various coupling constants, numbers of color, and baryon number are computed. 20 refs., 8 figs.

  2. Radiative decays of the heavy flavored baryons in light cone QCD sum rules

    SciTech Connect

    Aliev, T. M.; Azizi, K.; Ozpineci, A.

    2009-03-01

    The transition magnetic dipole and electric quadrupole moments of the radiative decays of the sextet heavy flavored spin 3/2 to the heavy spin 1/2 baryons are calculated within the light cone QCD sum rules approach. Using the obtained results, the decay rate for these transitions are also computed and compared with the existing predictions of the other approaches.

  3. Strong decay constants of heavy tensor mesons in light cone QCD sum rules

    NASA Astrophysics Data System (ADS)

    Alhendi, H. A.; Aliev, T. M.; Savcı, M.

    2016-04-01

    Strong decay constants of the heavy tensor to heavy pseudoscalar (vector) and light pseudoscalar mesons are estimated within the light cone QCD sum rules. It is observed that the values of these coupling constants show a significant dependence on the choice of the Lorentz structure. Additionally, the decay widths of these mesons are calculated and discussed within the light of experimental data. A comparison of our results on these coupling constants with the predictions from the 3-point sum rules is performed.

  4. {Sigma}{sub b,c} to Nucleon Transitions in Light Cone QCD Sum Rules

    SciTech Connect

    Bayar, M.; Azizi, K.; Zeyrek, M. T.

    2011-05-23

    The loop level flavor changing neutral current transitions of the {Sigma}{sub b}{yields}nl{sup +}l{sup -} and {Sigma}{sub c}{yields}pl{sup +}l{sup -} are investigated in the light cone QCD sum rules approach. Using the most general form of the interpolating current for {Sigma}{sub Q}, Q = b or c, the transition form factors are calculated using two sets of input parameters entering the nucleon distribution amplitudes, namely, QCD sum rules and lattice QCD inputs. The obtained results are used to estimate the decay rates of the corresponding transitions. Since such type transitions occurred at loop level in the standard model, they can be considered as good candidates to search for the new physics effects beyond the SM.

  5. B ---> pi and B ---> K transitions from QCD sum rules on the light cone

    SciTech Connect

    Ball, P.

    1998-09-01

    I calculate the form factors describing semileptonic and penguin-induced decays of B mesons into light pseudoscalar mesons. The form factors are calculated from QCD sum rules on the light-cone including contributions up to twist 4, radiative corrections to the leading twist contribution and SU(3)-breaking effects. The theoretical uncertainty is estimated to be \\sim 15%. The heavy-quark-limit relations between semileptonic and penguin form factors are found to be valid in the full accessible range of momentum transfer.

  6. QCD corrections to B → π form factors from light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Ming; Shen, Yue-Long

    2015-09-01

    We compute perturbative corrections to B → π form factors from QCD light-cone sum rules with B-meson distribution amplitudes. Applying the method of regions we demonstrate factorization of the vacuum-to-B-meson correlation function defined with an interpolating current for pion, at one-loop level, explicitly in the heavy quark limit. The short-distance functions in the factorization formulae of the correlation function involves both hard and hard-collinear scales; and these functions can be further factorized into hard coefficients by integrating out the hard fluctuations and jet functions encoding the hard-collinear information. Resummation of large logarithms in the short-distance functions is then achieved via the standard renormalization-group approach. We further show that structures of the factorization formulae for fBπ+ (q2) and fBπ0 (q2) at large hadronic recoil from QCD light-cone sum rules match that derived in QCD factorization. In particular, we perform an exploratory phenomenological analysis of B → π form factors, paying attention to various sources of perturbative and systematic uncertainties, and extract |Vub | = (3.05-0.38+0.54|th. ± 0.09|exp.) ×10-3 with the inverse moment of the B-meson distribution amplitude ϕB+ (ω) determined by reproducing fBπ+ (q2 = 0) obtained from the light-cone sum rules with π distribution amplitudes. Furthermore, we present the invariant-mass distributions of the lepton pair for B → πℓνℓ (ℓ = μ, τ) in the whole kinematic region. Finally, we discuss non-valence Fock state contributions to the B → π form factors fBπ+ (q2) and fBπ0 (q2) in brief.

  7. {kappa}K{sup +{pi}-} vertex in light cone QCD sum rules

    SciTech Connect

    Baytemir, G.; Sarac, Y.; Yilmaz, O.

    2010-05-01

    In this work we study the {kappa}K{sup +{pi}-} vertex in the framework of light cone QCD sum rules. We predict the coupling constant g{sub {kappa}K}{sup +}{sub {pi}}{sup -} to be g{sub {kappa}K}{sup +}{sub {pi}}{sup -}=(6.0{+-}1.0) GeV and estimate the scalar f{sub 0}-{sigma} mixing angle from the experimental ratio g{sup 2}({kappa}{yields}K{pi})/g{sup 2}({sigma}{yields}{pi}{pi}).

  8. Perturbative corrections to Λ b → Λ form factors from QCD light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Ming; Shen, Yue-Long

    2016-02-01

    We compute radiative corrections to Λ b → Λ from factors, at next-to-leading logarithmic accuracy, from QCD light-cone sum rules with Λ b -baryon distribution amplitudes. Employing the diagrammatic approach factorization of the vacuum-to-Λ b -baryon correlation function is justified at leading power in Λ /m b , with the aid of the method of regions. Hard functions entering the factorization formulae are identical to the corresponding matching coefficients of heavy-to-light currents from QCD onto soft-collinear effective theory. The universal jet function from integrating out the hard-collinear fluctuations exhibits richer structures compared with the one involved in the factorization expressions of the vacuum-to- B-meson correlation function. Based upon the QCD resummation improved sum rules we observe that the perturbative corrections at {O}({α}_s) shift the Λ b → Λ from factors at large recoil significantly and the dominant contribution originates from the next-to-leading order jet function instead of the hard coefficient functions. Having at hand the sum rule predictions for the Λ b → Λ from factors we further investigate several decay observables in the electro-weak penguin Λ b → Λ ℓ + ℓ - transitions in the factorization limit (i.e., ignoring the "non-factorizable" hadronic effects which cannot be expressed in terms of the Λ b → Λ from factors), including the invariant mass distribution of the lepton pair, the forward-backward asymmetry in the dilepton system and the longitudinal polarization fraction of the leptonic sector.

  9. {sigma}{sub Q}{lambda}{sub Q}{pi} coupling constant in light cone QCD sum rules

    SciTech Connect

    Azizi, K.; Bayar, M.; Ozpineci, A.

    2009-03-01

    The strong coupling constants g{sub {sigma}{sub Q}}Q{sub {lambda}{sub Q}}{sub {pi}} (Q=b and c) are studied in the framework of the light cone QCD sum rules using the most general form of the baryonic currents. The predicted coupling constants are used to estimate the decay widths for the {sigma}{sub Q}{yields}{lambda}{sub Q}{pi} decays which are compared with the predictions of the other approaches and existing experimental data.

  10. {lambda}{sub b}{yields}p, {lambda} transition form factors from QCD light-cone sum rules

    SciTech Connect

    Wang Yuming; Lue Caidian; Shen Yuelong

    2009-10-01

    Light-cone sum rules for the {lambda}{sub b}{yields}p, {lambda} transition form factors are derived from the correlation functions expanded by the twist of the distribution amplitudes of the {lambda}{sub b} baryon. In terms of the {lambda}{sub b} three-quark distribution amplitude models constrained by the QCD theory, we calculate the form factors at small momentum transfers and compare the results with those estimated in the conventional light-cone sum rules (LCSR) and perturbative QCD approaches. Our results indicate that the two different versions of sum rules can lead to the consistent numbers of form factors responsible for {lambda}{sub b}{yields}p transition. The {lambda}{sub b}{yields}{lambda} transition form factors from LCSR with the asymptotic {lambda} baryon distribution amplitudes are found to be almost 1 order larger than those obtained in the {lambda}{sub b}-baryon LCSR, implying that the preasymptotic corrections to the baryonic distribution amplitudes are of great importance. Moreover, the SU(3) symmetry breaking effects between the form factors f{sub 1}{sup {lambda}{sub b}}{sup {yields}}{sup p} and f{sub 1}{sup {lambda}{sub b}}{sup {yields}}{sup {lambda}} are computed as 28{sub -8}{sup +14}% in the framework of {lambda}{sub b}-baryon LCSR.

  11. Light-cone wave function approach to open heavy flavor dynamics in QCD matter

    NASA Astrophysics Data System (ADS)

    Sharma, Rishi; Vitev, Ivan; Zhang, Ben-Wei

    2009-11-01

    We calculate the lowest-order charm and beauty parton distribution functions in and fragmentation functions into D and B mesons using the operator definitions of factorized perturbative quantum chromodynamics (QCD). In the vacuum, we find the leading corrections that arise from the structure of the final-state hadrons. Quark-antiquark potentials extracted from the lattice are employed to demonstrate the existence of open heavy flavor bound-state solutions in the quark-gluon plasma in the vicinity of the critical temperature. We provide first results for the in-medium modification of the heavy-quark distribution and decay probabilities in a comoving plasma. In an improved perturbative QCD description of heavy-flavor dynamics in the thermal medium, we combine D- and B-meson formation and dissociation with parton-level charm and beauty quark quenching to obtain predictions for the heavy-meson and nonphotonic-electron suppression in Cu+Cu and Pb+Pb collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider, respectively.

  12. Reconciling the light-cone and nonrelativistic QCD approaches to calculating e+e-→J/ψ+ηc

    NASA Astrophysics Data System (ADS)

    Bodwin, Geoffrey T.; Kang, Daekyoung; Lee, Jungil

    2006-12-01

    It has been suggested in Ref. [A. E. Bondar and V. L. Chernyak, Phys. Lett. B 612, 215 (2005)PYLBAJ0370-269310.1016/j.physletb.2005.03.021] that the disagreement between theoretical calculations and experimental observations for the rate for the process e+e-→J/ψ+ηc at the B factories might be resolved by using the light-cone method to take into account the relative momentum of the heavy-quark and antiquark in the quarkonia. The light-cone result for the production cross section in Ref. [A. E. Bondar and V. L. Chernyak, Phys. Lett. B 612, 215 (2005)PYLBAJ0370-269310.1016/j.physletb.2005.03.021] is almost an order-of-magnitude larger than existing NRQCD factorization results. We investigate this apparent theoretical discrepancy. We compute light-cone distribution functions by making use of quarkonium wave functions from the Cornell potential model. Our light-cone distribution functions are similar in shape to those of Ref. [A. E. Bondar and V. L. Chernyak, Phys. Lett. B 612, 215 (2005)PYLBAJ0370-269310.1016/j.physletb.2005.03.021] and yield a similar cross section. However, when we subtract parts of the light-cone distribution functions that correspond to corrections of relative-order αs in the NRQCD approach, we find that the cross section decreases by about a factor of three. When we set certain renormalization factors Zi in the light-cone calculation equal to unity, we find a further reduction in the cross section of about a factor of two. The resulting light-cone cross section is similar in magnitude to the NRQCD factorization cross sections and shows only a modest enhancement over the light-cone cross section in which the relative momentum of the heavy-quark and antiquark is neglected.

  13. Light-cone quantization of quantum chromodynamics

    SciTech Connect

    Brodsky, S.J. ); Pauli, H.C. )

    1991-06-01

    We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism.

  14. g{sub {Sigma}{sub Q{Sigma}{sub Q{pi}}}}coupling constant via light cone QCD sum rules

    SciTech Connect

    Azizi, K.; Bayar, M.; Ozpineci, A.; Sarac, Y.

    2010-10-01

    Using the most general form of the interpolating currents, the coupling constants g{sub {Sigma}{sub b{Sigma}{sub b{pi}}}}and g{sub {Sigma}{sub c{Sigma}{sub c{pi}}}}are calculated within the light cone QCD sum rules approach. It is found that g{sub {Sigma}{sub c{Sigma}{sub c{pi}=}}}-8.0{+-}1.7 and g{sub {Sigma}{sub b{Sigma}{sub b{pi}=}}}-11.0{+-}2.1.

  15. Application of the QCD light cone sum rule to tetraquarks: The strong vertices XbXbρ and XcXcρ

    NASA Astrophysics Data System (ADS)

    Agaev, S. S.; Azizi, K.; Sundu, H.

    2016-06-01

    The full version of the QCD light-cone sum rule method is applied to tetraquarks containing a single heavy b or c quark. To this end, investigations of the strong vertices XbXbρ and XcXcρ are performed, where Xb=[s u ][b ¯ d ¯ ] and Xc=[s u ][c ¯d ¯] are the exotic states built of four quarks of different flavors. The strong coupling constants GXbXbρ and GXcXcρ corresponding to these vertices are found using the ρ -meson leading- and higher-twist distribution amplitudes. In the calculations, Xb and Xc are treated as scalar bound states of a diquark and antidiquark.

  16. Form factors in Bbar0 →π+π0 ℓνbarℓ from QCD light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Hambrock, Christian; Khodjamirian, Alexander

    2016-04-01

    The form factors of the semileptonic B → ππℓ ν bar decay are calculated from QCD light-cone sum rules with the distribution amplitudes of dipion states. This method is valid in the kinematical region, where the hadronic dipion state has a small invariant mass and simultaneously a large recoil. The derivation of the sum rules is complicated by the presence of an additional variable related to the angle between the two pions. In particular, we realize that not all invariant amplitudes in the underlying correlation function can be used, some of them generating kinematical singularities in the dispersion relation. The two sum rules that are free from these ambiguities are obtained in the leading twist-2 approximation, predicting the Bbar0 →π+π0 form factors F⊥ and F∥ of the vector and axial b → u current, respectively. We calculate these form factors at the momentum transfers 0

  17. Magnetic moment for the negative parity Λ → Σ0 transition in light cone QCD sum rules

    NASA Astrophysics Data System (ADS)

    Aliev, T. M.; Savcı, M.

    2016-07-01

    The magnetic moment of the Λ →Σ0 transition between negative parity baryons is calculated in framework of the QCD sum rules approach by using the general form of the interpolating currents. The pollution arising from the positive-to-positive, and positive-to-negative parity baryons is eliminated by constructing the sum rules for different Lorentz structures. A comparison of our result with the predictions of the results of other approaches for the positive parity baryons is presented.

  18. Light cone matrix product

    SciTech Connect

    Hastings, Matthew B

    2009-01-01

    We show how to combine the light-cone and matrix product algorithms to simulate quantum systems far from equilibrium for long times. For the case of the XXZ spin chain at {Delta} = 0.5, we simulate to a time of {approx} 22.5. While part of the long simulation time is due to the use of the light-cone method, we also describe a modification of the infinite time-evolving bond decimation algorithm with improved numerical stability, and we describe how to incorporate symmetry into this algorithm. While statistical sampling error means that we are not yet able to make a definite statement, the behavior of the simulation at long times indicates the appearance of either 'revivals' in the order parameter as predicted by Hastings and Levitov (e-print arXiv:0806.4283) or of a distinct shoulder in the decay of the order parameter.

  19. Light-cone quantization and hadron structure

    SciTech Connect

    Brodsky, S.J.

    1996-04-01

    Quantum chromodynamics provides a fundamental description of hadronic and nuclear structure and dynamics in terms of elementary quark and gluon degrees of freedom. In practice, the direct application of QCD to reactions involving the structure of hadrons is extremely complex because of the interplay of nonperturbative effects such as color confinement and multi-quark coherence. In this talk, the author will discuss light-cone quantization and the light-cone Fock expansion as a tractable and consistent representation of relativistic many-body systems and bound states in quantum field theory. The Fock state representation in QCD includes all quantum fluctuations of the hadron wavefunction, including fax off-shell configurations such as intrinsic strangeness and charm and, in the case of nuclei, hidden color. The Fock state components of the hadron with small transverse size, which dominate hard exclusive reactions, have small color dipole moments and thus diminished hadronic interactions. Thus QCD predicts minimal absorptive corrections, i.e., color transparency for quasi-elastic exclusive reactions in nuclear targets at large momentum transfer. In other applications, such as the calculation of the axial, magnetic, and quadrupole moments of light nuclei, the QCD relativistic Fock state description provides new insights which go well beyond the usual assumptions of traditional hadronic and nuclear physics.

  20. Light capture by human cones.

    PubMed Central

    Chen, B; Makous, W

    1989-01-01

    1. The variation in visual efficiency of light with varying pupillary entry (the Stiles-Crawford effect) was measured to determine the proportion of light incident on the cones that escapes them without recovery by other cones. 2. The variation in detectability of interference fringes with varying pupillary entry of the interfering beams was measured to determine the proportion of incident light that was recaptured by cones in the dark stripes after escaping cones in the bright stripes of the fringes. 3. By exclusion, these observations determine the variation, with varying pupillary entry, in the proportion of incident light that was captured and absorbed by the first cones it entered. 4. Some 70-90% of the light absorbed by the cones when it passes through the centre of the pupil, is entirely lost to the visual system if it passes instead through the margin of the (dilated) pupil. 5. Over half the light that cones absorb when the light enters the margin of the pupil is light that has previously passed through other cones. 6. If the spread of recaptured light is assumed to be Gaussian, its standard deviation is at most one minute of visual angle. 7. Such recaptured light makes a previously unknown contribution to the various Stiles-Crawford effects. PMID:2607444

  1. Lattice Formulation of QCD “NEAR the Light CONE”

    NASA Astrophysics Data System (ADS)

    Grünewald, D.

    2007-03-01

    Non-perturbative physics on the light cone is investigated in a Hamiltonian lattice framework. We use near light cone coordinates and perform a limiting procedure onto the light cone. Such a formulation is natural in order to describe high energy scattering. It contains an additional parameter η which represents the distance to the light cone and is varying the energy. The QCD vacuum is planned to be generated by a quantum diffusion Monte Carlo algorithm. In order to minimize the algorithmic variance, a guidance wave functional close to the exact ground state is required. We present a solution for the ground state corresponding to the dominant part of the Hamiltonian in the light cone limit.

  2. The B → K* transition form factors within the QCD light-cone sum rules and their application to the semi-leptonic decay B → K* μ + μ -

    NASA Astrophysics Data System (ADS)

    Fu, Hai-Bing; Wu, Xing-Gang; Ma, Yang; Cheng, Wei; Zhong, Tao

    2016-08-01

    We present a detailed calculation on the B\\to {K}* transition form factors (TFFs), {A}{0,1,2}, V and {T}{1,2,3}, within the QCD light-cone sum rules (LCSRs). To suppress the contributions from high-twist light-cone distribution amplitudes, we adopt a right-handed chiral correlator to do the LCSR calculation. In the resultant LCSRs for the TFFs, the transverse leading-twist distribution amplitude {φ }2;{K*}\\perp provides over 90% contribution, thus those TFFs provide good platforms for testing the property of {φ }2;{K*}\\perp . We suggest a model for {φ }2;{K*}\\perp , in which two parameters {B}2;{K*}\\perp and {C}2;{K*}\\perp dominantly control its longitudinal distribution. With a proper choice of {B}2;{K*}\\perp and {C}2;{K*}\\perp , our predictions on B\\to {K}* TFFs are consistent with those of lattice QCD predictions. As an application, we also calculate the branching fraction of the B-meson rare decay B\\to {K}*{μ }+{μ }-. The predicted differential branching fraction {{d}}{B}/{{d}}{q}2(B\\to {K}*{μ }+{μ }-) is consistent with the LHCb and Belle measurements within errors. After integrating over the allowable q 2-region, we get the branching fraction, {B}(B\\to {K}*{μ }+{μ }-)=≤ft({1.088}-0.205+0.261\\right)× {10}-6, where the errors are squared average of the mentioned error sources. When the precision of experimental measurements or the other source of theoretical uncertainties for this process have been further improved in the future, we may get a definite conclusion on the behavior of {φ }2;{K*}\\perp .

  3. Light-Front Holographic QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    The relation between the hadronic short-distance constituent quark and gluon particle limit and the long-range confining domain is yet one of the most challenging aspects of particle physics due to the strong coupling nature of Quantum Chromodynamics, the fundamental theory of the strong interactions. The central question is how one can compute hadronic properties from first principles; i.e., directly from the QCD Lagrangian. The most successful theoretical approach thus far has been to quantize QCD on discrete lattices in Euclidean space-time. Lattice numerical results follow from computation of frame-dependent moments of distributions in Euclidean space and dynamical observables in Minkowski spacetime, such as the time-like hadronic form factors, are not amenable to Euclidean lattice computations. The Dyson-Schwinger methods have led to many important insights, such as the infrared fixed point behavior of the strong coupling constant, but in practice, the analyses are limited to ladder approximation in Landau gauge. Baryon spectroscopy and the excitation dynamics of nucleon resonances encoded in the nucleon transition form factors can provide fundamental insight into the strong-coupling dynamics of QCD. New theoretical tools are thus of primary interest for the interpretation of the results expected at the new mass scale and kinematic regions accessible to the JLab 12 GeV Upgrade Project. The AdS/CFT correspondence between gravity or string theory on a higher-dimensional anti-de Sitter (AdS) space and conformal field theories in physical space-time has led to a semiclassical approximation for strongly-coupled QCD, which provides physical insights into its nonperturbative dynamics. The correspondence is holographic in the sense that it determines a duality between theories in different number of space-time dimensions. This geometric approach leads in fact to a simple analytical and phenomenologically compelling nonperturbative approximation to the full light

  4. Light-cone matrix product

    SciTech Connect

    Hastings, M. B.

    2009-09-15

    We show how to combine the light-cone and matrix product algorithms to simulate quantum systems far from equilibrium for long times. For the case of the XXZ spin chain at {delta}=0.5, we simulate to a time of {approx_equal}22.5. While part of the long simulation time is due to the use of the light-cone method, we also describe a modification of the infinite time-evolving bond decimation algorithm with improved numerical stability, and we describe how to incorporate symmetry into this algorithm. While statistical sampling error means that we are not yet able to make a definite statement, the behavior of the simulation at long times indicates the appearance of either 'revivals' in the order parameter as predicted by Hastings and Levitov (e-print arXiv:0806.4283) or of a distinct shoulder in the decay of the order parameter.

  5. Prescriptionless light-cone integrals

    NASA Astrophysics Data System (ADS)

    Suzuki, A. T.; Schmidt, A. G. M.

    2000-01-01

    Perturbative quantum gauge field theory as seen within the perspective of physical gauge choices such as the light-cone gauge entails the emergence of troublesome poles of the type (k\\cdot n)^{-α} in the Feynman integrals. These come from the boson field propagator, where α = 1,2,\\cdots and n^{μ} is the external arbitrary four-vector that defines the gauge proper. This becomes an additional hurdle in the computation of Feynman diagrams, since any graph containing internal boson lines will inevitably produce integrands with denominators bearing the characteristic gauge-fixing factor. How one deals with them has been the subject of research over decades, and several prescriptions have been suggested and tried in the course of time, with failures and successes. However, a more recent development at this fronteer which applies the negative dimensional technique to compute light-cone Feynman integrals shows that we can altogether dispense with prescriptions to perform the calculations. An additional bonus comes to us attached to this new technique, in that not only it renders the light-cone prescriptionless but, by the very nature of it, it can also dispense with decomposition formulas or partial fractioning tricks used in the standard approach to separate pole products of the type (k\\cdot n)^{-α}[(k-p)\\cdot n]^{-β} (β = 1,2,\\cdots ). In this work we demonstrate how all this can be done.

  6. Excited light isoscalar mesons from lattice QCD

    SciTech Connect

    Christopher Thomas

    2011-07-01

    I report a recent lattice QCD calculation of an excited spectrum of light isoscalar mesons, something that has up to now proved challenging for lattice QCD. With novel techniques we extract an extensive spectrum with high statistical precision, including spin-four states and, for the first time, light isoscalars with exotic quantum numbers. In addition, the hidden flavour content of these mesons is determined, providing a window on annihilation dynamics in QCD. I comment on future prospects including applications to the study of resonances.

  7. Light-cone distribution amplitudes of the baryon octet

    NASA Astrophysics Data System (ADS)

    Bali, Gunnar S.; Braun, Vladimir M.; Göckeler, Meinulf; Gruber, Michael; Hutzler, Fabian; Schäfer, Andreas; Schiel, Rainer W.; Simeth, Jakob; Söldner, Wolfgang; Sternbeck, Andre; Wein, Philipp

    2016-02-01

    We present results of the first ab initio lattice QCD calculation of the normalization constants and first moments of the leading twist distribution amplitudes of the full baryon octet, corresponding to the small transverse distance limit of the associated S-wave light-cone wave functions. The P-wave (higher twist) normalization constants are evaluated as well. The calculation is done using N f = 2 + 1 flavors of dynamical (clover) fermions on lattices of different volumes and pion masses down to 222 MeV. Significant SU(3) flavor symmetry violation effects in the shape of the distribution amplitudes are observed.

  8. Advances in Light-Front QCD and New Perspectives for QCD from AdS/CFT

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2005-10-26

    The light-front quantization of gauge theories in light-cone gauge provides a frame-independent wavefunction representation of relativistic bound states, simple forms for current matrix elements, explicit unitarity, and a Fock space built on a trivial vacuum. The AdS/CFT correspondence has led to important insights into the properties of quantum chromodynamics even though QCD is a broken conformal theory. We have recently shown how a model based on a truncated AdS space can be used to obtain the hadronic spectrum of q{bar q}, qqq and gg bound states, as well as their respective light-front wavefunctions. Specific hadrons are identified by the correspondence of string modes with the dimension of the interpolating operator of the hadron's valence Fock state, including orbital angular momentum excitations. The predicted mass spectrum is linear M {proportional_to} L at high orbital angular momentum, in contrast to the quadratic dependence M{sup 2}/L found in the description of spinning strings. Since only one parameter, the QCD scale {Lambda}{sub QCD}, is introduced, the agreement with the pattern of physical states is remarkable. In particular, the ratio of {Delta} to nucleon trajectories is determined by the ratio of zeros of Bessel functions. As a specific application of QCD dynamics from AdS/CFT duality, we describe a computation of the proton magnetic form factor in both the space-like and time-like regions. The extended AdS/CFT space-time theory also provides an analytic model for hadronic light-front wavefunctions, thus providing a relativistic description of hadrons in QCD at the amplitude level. The model wavefunctions display confinement at large inter-quark separation and conformal symmetry at short distances. In particular, the scaling and conformal properties of the LFWFs at high relative momenta agree with perturbative QCD. These AdS/CFT model wavefunctions could be used as an initial ansatz for a variational treatment of the light-front QCD Hamiltonian.

  9. QCD and Light-Front Dynamics

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.

    2011-01-10

    AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

  10. Excited light meson spectroscopy from lattice QCD

    SciTech Connect

    Christopher Thomas, Hadron Spectrum Collaboration

    2012-04-01

    I report on recent progress in calculating excited meson spectra using lattice QCD, emphasizing results and phenomenology. With novel techniques we can now extract extensive spectra of excited mesons with high statistical precision, including spin-four states and those with exotic quantum numbers. As well as isovector meson spectra, I will present new calculations of the spectrum of excited light isoscalar mesons, something that has up to now been a challenge for lattice QCD. I show determinations of the flavor content of these mesons, including the eta-eta' mixing angle, providing a window on annihilation dynamics in QCD. I will also discuss recent work on using lattice QCD to map out the energy-dependent phase shift in pi-pi scattering and future applications of the methodology to the study of resonances and decays.

  11. Lightcone: Light-cone generating script

    NASA Astrophysics Data System (ADS)

    Bernyk, Max

    2014-03-01

    Lightcone works with simulated galaxy data stored in a relational database to rearrange the data in a shape of a light-cone; simulated galaxy data is expected to be in a box volume. The light-cone constructing script works with output from the SAGE semi-analytic model, but will work with any other model that has galaxy positions (and other properties) saved per snapshots of the simulation volume distributed in time. The database configuration file is set up for PostgreSQL RDBMS, but can be modified for use with any other SQL database.

  12. Light-Cone Distribution Amplitudes for Non-Relativistic Bound States

    SciTech Connect

    Feldmann, Th.; Bell, G.

    2007-11-19

    We calculate light-cone distribution amplitudes for non-relativistic bound states, including radiative corrections from relativistic gluon exchange to first order in the strong coupling constant. Our results apply to hard exclusive reactions with non-relativistic bound states in the QCD factorization approach like, for instance, B{sub c}{yields}{eta}{sub c}l{nu} or e{sup +}e{sup -}{yields}J/{psi}{eta}{sub c}. They also serve as a toy model for light-cone distribution amplitudes of light mesons or heavy B and D mesons.

  13. Perturbation theory in light-cone quantization

    SciTech Connect

    Langnau, A.

    1992-01-01

    A thorough investigation of light-cone properties which are characteristic for higher dimensions is very important. The easiest way of addressing these issues is by analyzing the perturbative structure of light-cone field theories first. Perturbative studies cannot be substituted for an analysis of problems related to a nonperturbative approach. However, in order to lay down groundwork for upcoming nonperturbative studies, it is indispensable to validate the renormalization methods at the perturbative level, i.e., to gain control over the perturbative treatment first. A clear understanding of divergences in perturbation theory, as well as their numerical treatment, is a necessary first step towards formulating such a program. The first objective of this dissertation is to clarify this issue, at least in second and fourth-order in perturbation theory. The work in this dissertation can provide guidance for the choice of counterterms in Discrete Light-Cone Quantization or the Tamm-Dancoff approach. A second objective of this work is the study of light-cone perturbation theory as a competitive tool for conducting perturbative Feynman diagram calculations. Feynman perturbation theory has become the most practical tool for computing cross sections in high energy physics and other physical properties of field theory. Although this standard covariant method has been applied to a great range of problems, computations beyond one-loop corrections are very difficult. Because of the algebraic complexity of the Feynman calculations in higher-order perturbation theory, it is desirable to automatize Feynman diagram calculations so that algebraic manipulation programs can carry out almost the entire calculation. This thesis presents a step in this direction. The technique we are elaborating on here is known as light-cone perturbation theory.

  14. QCD and Light-Front Holography

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2010-10-27

    The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number N. Light-Front Holography maps the amplitudes which are functions of the fifth dimension variable z of anti-de Sitter space to a corresponding hadron theory quantized on the light front. The resulting Lorentz-invariant relativistic light-front wave equations are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. The result is to a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryon light-quark bound states, which in turn predict the behavior of the pion and nucleon form factors. The theory implements chiral symmetry in a novel way: the effects of chiral symmetry breaking increase as one goes toward large interquark separation, consistent with spectroscopic data, and the the hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. The soft-wall model also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function which agrees with the effective coupling {alpha}{sub g1} extracted from the Bjorken sum rule. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also reviewed.

  15. Strong coupling constants of heavy baryons with light mesons in QCD

    SciTech Connect

    Aliev, T. M.; Azizi, K.; Savci, M.

    2012-10-23

    The strong coupling constants of the heavy spin-1/2 and spin-3/2 baryons with light pseudoscalar and vector mesons are calculated in the framework of the light cone QCD sum rules. Using the symmetry arguments, some structure independent relations among different correlation functions are obtained. It is shown that all possible transitions are described by only one invariant function, whose explicit expression is structure dependent.

  16. Light responses of primate and other mammalian cones

    PubMed Central

    Cao, Li-Hui; Luo, Dong-Gen; Yau, King-Wai

    2014-01-01

    Retinal cones are photoreceptors for daylight vision. For lower vertebrates, cones are known to give monophasic, hyperpolarizing responses to light flashes. For primate cones, however, they have been reported to give strongly biphasic flash responses, with an initial hyperpolarization followed by a depolarization beyond the dark level, now a textbook dogma. We have reexamined this primate-cone observation and, surprisingly, found predominantly monophasic cone responses. Correspondingly, we found that primate cones began to adapt to steady light at much lower intensities than previously reported, explainable by a larger steady response to background light for a monophasic than for a biphasic response. Similarly, we have found a monophasic cone response for several other mammalian species. Thus, a monophasic flash response may in fact be the norm for primate and other mammalian cones as for lower-vertebrate cones. This revised information is important for ultimately understanding human retinal signal processing and correlating with psychophysical data. PMID:24550304

  17. Light-like Wilson line in QCD without path ordering

    NASA Astrophysics Data System (ADS)

    Nayak, Gouranga C.

    2016-07-01

    Unlike the Wilson line in QED the Wilson line in QCD contains path ordering. In this paper we get rid of the path ordering in the light-like Wilson line in QCD by simplifying all the infinite number of noncommuting terms in the SU(3) pure gauge. We prove that the light-like Wilson line in QCD naturally emerges when path integral formulation of QCD is used to prove factorization of soft and collinear divergences at all order in coupling constant in QCD processes at high energy colliders.

  18. Light-front Hamiltonian and path integral formulations of large N scalar QCD2

    NASA Astrophysics Data System (ADS)

    Kulshreshtha, Usha; Kulshreshtha, D. S.; Vary, J. P.

    2012-02-01

    Recently Grinstein, Jora and Polosa (2009) [5] have studied a model of large N scalar quantum chromodynamics (QCD) in one-space one-time dimensions (cf. G. 't Hooft (1974) [6]). This theory admits a Bethe-Salpeter equation describing the discrete spectrum of qqbar bound states. They consider the gauge fields in the adjoint representation of SU (N) and the scalar fields in the fundamental representation. The theory is asymptotically free and linearly confining. In this work, we present the light-front quantization of this theory using the Hamiltonian and path integral formulations under appropriate light-cone gauges.

  19. The application of light-cone quantization to quantum chromodynamics in one-plus-one dimensions

    SciTech Connect

    Hornbostel, K.J.

    1988-12-01

    Formal and computational aspects of light cone quantization are studied by application to quantum chromodynamics (QCD) in one spatial plus one temporal dimension. This quantization scheme, which has been extensively applied to perturbative calculations, is shown to provide an intuitively appealing and numerically tractable approach to non-perturbative computations as well. In the initial section, a light-cone quantization procedure is developed which incorporates fields on the boundaries. This allows for the consistent treatment of massless fermions and the construction of explicitly conserved momentum and charge operators. The next section, which comprises the majority of this work, focuses on the numerical solution of the light-cone Schrodinger equation for bound states. The state space is constructed and the Hamiltonian is evaluated and diagonalized by computer for arbitrary number of colors, baryon number and coupling constant strength. As a result, the full spectrum of mesons and baryons and their associated wavefunctions are determined. These results are compared with those which exist from other approaches to test the reliability of the method. The program also provides a preliminary test for the feasibility of, and an opportunity to develop approximation schemes for, an attack on three-plus-one dimensional QCD. Finally, analytic results are presented which include a discussion of integral equations for wavefunctions and their endpoint behavior. Solutions for hadronic masses and wavefunctions in the limits of both large and small quark mass are discussed. 49 refs., 32 figs., 10 tabs.

  20. Light-Front Holography: A First Approximation to QCD

    SciTech Connect

    Teramond, Guy F. de; Brodsky, Stanley J.

    2009-02-27

    Starting from the Hamiltonian equation of motion in QCD, we identify an invariant light-front coordinate {zeta} which allows the separation of the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schroedinger equation for QCD which determines the eigenspectrum and the light-front wave functions of hadrons for general spin and orbital angular momentum. This light-front wave equation is equivalent to the equations of motion which describe the propagation of spin-J modes on anti-de Sitter (AdS) space.

  1. Enhanced light trapping in periodically truncated cone silicon nanowire structure

    NASA Astrophysics Data System (ADS)

    Kai, Qiu; Yuhua, Zuo; Tianwei, Zhou; Zhi, Liu; Jun, Zheng; Chuanbo, Li; Buwen, Cheng

    2015-10-01

    Light trapping plays an important role in improving the conversion efficiency of thin-film solar cells. The good wideband light trapping is achieved using our periodically truncated cone Si nanowire (NW) structures, and their inherent mechanism is analyzed and simulated by FDTD solution software. Ordered cylinder Si NW structure with initial size of 80 nm and length of 200 nm is grown by pattern transfer and selective epitaxial growth. Truncated cone Si NW array is then obtained by thermal oxidation treatment. Its mean reflection in the range of 300-900 nm is lowered to be 5% using 140 nm long truncated cone Si NW structure, compared with that of 20% using cylinder counterparts. It indicates that periodically truncated Si cone structures trap the light efficiently to enhance the light harvesting in a wide spectral range and have the potential application in highly efficient NW solar cells. Project supported by the National Natural Science Foundation of China (Nos. 51072194, 61021003, 61036001, 61376057).

  2. Dimensional regularization and dimensional reduction in the light cone

    SciTech Connect

    Qiu, J.

    2008-06-15

    We calculate all of the 2 to 2 scattering process in Yang-Mills theory in the light cone gauge, with the dimensional regulator as the UV regulator. The IR is regulated with a cutoff in q{sup +}. It supplements our earlier work, where a Lorentz noncovariant regulator was used, and the final results bear some problems in gauge fixing. Supersymmetry relations among various amplitudes are checked by using the light cone superfields.

  3. Light-Front Holographic QCD and the Confinement Potential

    NASA Astrophysics Data System (ADS)

    Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter

    2014-06-01

    Light-Front Hamiltonian theory, derived from the quantization of the QCD Lagrangian at fixed light-front time τ = t + z / c, provides a rigorous frame-independent framework for solving nonperturbative QCD. The eigenvalues of the light-front QCD Hamiltonian predict the hadronic mass spectrum, and the corresponding eigensolutions provide the light-front wavefunctions which describe hadron structure. The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrödinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. In fact, the potential U has a unique form if one requires that the action for zero quark mass remains conformally invariant. We also show that the holographic mapping of gravity in AdS space to QCD with a specific soft-wall dilaton yields the same light-front Schrödinger equation. Light-front holography also leads to a precise relation between the bound-state amplitudes in the fifth dimension z of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The predictions of the LF equations of motion include a zero-mass pion in the chiral mq → 0 limit, and linear Regge trajectories M2 (n, L) ∝ n + L with the same slope in the radial quantum number n and orbital angular momentum L. The light-front AdS/QCD holographic approach thus gives a frame-independent representation of color-confining dynamics, Regge spectroscopy, and the excitation spectra of relativistic light-quark meson and baryon bound states in QCD in terms of a single mass parameter. We also briefly discuss the implications of the underlying conformal template of QCD for renormalization scale-setting and

  4. Light-Front Holography and Novel Effects in QCD

    SciTech Connect

    Brodsky, Stanley J.; Teramond, Guy F. de

    2009-04-20

    The correspondence between theories in anti-de Sitter space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. We identify the AdS coordinate z with an invariant light-front coordinate {zeta} which separates the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schroedinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The mapping of electromagnetic and gravitational form factors in AdS space to their corresponding expressions in light-front theory confirms this correspondence. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates and the behavior of the QCD coupling in the infrared. The distinction between static structure functions such as the probability distributions computed from the square of the light-front wavefunctions versus dynamical structure functions which include the effects of rescattering is emphasized. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.

  5. Light-Front Holography and Novel Effects in QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.

    2008-12-18

    The correspondence between theories in anti-de Sitter space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. We identify the AdS coordinate z with an invariant light-front coordinate {zeta} which separates the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schroedinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The mapping of electromagnetic and gravitational form factors in AdS space to their corresponding expressions in light-front theory confirms this correspondence. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates and the behavior of the QCD coupling in the infrared. The distinction between static structure functions such as the probability distributions computed from the square of the light-front wavefunctions versus dynamical structure functions which include the effects of rescattering is emphasized. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.

  6. AdS/QCD and Light Front Holography: A New Approximation to QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy

    2010-02-15

    The combination of Anti-de Sitter space (AdS) methods with light-front holography leads to a semi-classical first approximation to the spectrum and wavefunctions of meson and baryon light-quark bound states. Starting from the bound-state Hamiltonian equation of motion in QCD, we derive relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. Its eigenvalues give the hadronic spectrum, and its eigenmodes represent the probability distribution of the hadronic constituents at a given scale. Applications to the light meson and baryon spectra are presented. The predicted meson spectrum has a string-theory Regge form M{sup 2} = 4{kappa}{sup 2}(n+L+S/2); i.e., the square of the eigenmass is linear in both L and n, where n counts the number of nodes of the wavefunction in the radial variable {zeta}. The space-like pion form factor is also well reproduced. One thus obtains a remarkable connection between the description of hadronic modes in AdS space and the Hamiltonian formulation of QCD in physical space-time quantized on the light-front at fixed light-front time {tau}. The model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms.

  7. E7(7) on the light cone

    NASA Astrophysics Data System (ADS)

    Brink, Lars; Kim, Sung-Soo; Ramond, Pierre

    2008-06-01

    We use the Cremmer-Julia E7(7) non-linear symmetry of Script N = 8 Supergravity to derive its order κ2 on-shell Hamiltonian in terms of one chiral light-cone superfield. By requiring that E7(7) commute with the super-Poincaré group, we deduce to lowest non-trivial order in κ, the light cone E7(7) transformations of all fields of the theory, including the graviton. We then derive the dynamical supersymmetry transformation to order κ2, and express the Hamiltonian as a quadratic form in the chiral superfield.

  8. Light-Front Holography and Non-Perturbative QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2009-12-09

    The combination of Anti-de Sitter space (AdS) methods with light-front holography leads to a semi-classical first approximation to the spectrum and wavefunctions of meson and baryon light-quark bound states. Starting from the bound-state Hamiltonian equation of motion in QCD, we derive relativistic light-front wave equations in terms of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti-de Sitter (AdS) space. Its eigenvalues give the hadronic spectrum, and its eigenmodes represent the probability distribution of the hadronic constituents at a given scale. Applications to the light meson and baryon spectra are presented. The predicted meson spectrum has a string-theory Regge form M{sup 2} = 4{kappa}{sup 2}(n + L + S = 2); i.e., the square of the eigenmass is linear in both L and n, where n counts the number of nodes of the wavefunction in the radial variable {zeta}. The space-like pion form factor is also well reproduced. One thus obtains a remarkable connection between the description of hadronic modes in AdS space and the Hamiltonian formulation of QCD in physical space-time quantized on the light-front at fixed light-front time {tau}. The model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms.

  9. Light-cone fluctuations in the cosmic string spacetime

    NASA Astrophysics Data System (ADS)

    Mota, H. F.; Bezerra de Mello, E. R.; Bessa, C. H. G.; Bezerra, V. B.

    2016-07-01

    In this paper we consider light-cone fluctuations arising as a consequence of the nontrivial topology of the locally flat cosmic string spacetime. By setting the light-cone along the z -direction we are able to develop a full analysis to calculate the renormalized graviton two-point function, as well as the mean square fluctuation in the geodesic interval function and the time delay (or advance) in the propagation of a light pulse. We found that all these expressions depend upon the parameter characterizing the conical topology of the cosmic string spacetime and vanish in the absence of it. We also point out that at large distances from the cosmic string the mean square fluctuation in the geodesic interval function is extremely small while in the opposite limit it logarithmically increases.

  10. Structure of the Nucleon Spin on the Light Cone

    SciTech Connect

    Pasquini, B.

    2008-10-13

    The spin structure of the nucleon is studied in a light-cone description of the nucleon where the Fock expansion is truncated to consider only valence quarks. Transverse momentum dependent parton distributions and transverse-spin densities, defined through the generalized parton distributions in the impact parameter space, are investigated as new tools to reveal the spin-spin and spin-orbit correlations for different quark and nucleon polarizations.

  11. The Pion Renormalized Light-Cone Wave Function

    NASA Astrophysics Data System (ADS)

    Trawiński, Arkadiusz P.

    2016-06-01

    An approximate light-cone wave function for the pion effective quark-antiquark Fock sector corresponding to a small value of the renormalization group parameter is presented. The approximate wave function is motivated by the LF-holography and the quadratic confinement potential in the front form of Hamiltonian dynamics, which is in harmony with the linear confining potential in the instant form. The pion radius, decay constant and form-factor are also presented.

  12. Light-front holographic QCD and emerging confinement

    NASA Astrophysics Data System (ADS)

    Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter; Erlich, Joshua

    2015-07-01

    In this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. The light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical space-time. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.

  13. Light-front holographic QCD and emerging confinement

    SciTech Connect

    Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter; Erlich, Joshua

    2015-05-21

    In this study we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. The light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical spacetime. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.

  14. Light-cone averages in a Swiss-cheese universe

    SciTech Connect

    Marra, Valerio; Kolb, Edward W.; Matarrese, Sabino

    2008-01-15

    We analyze a toy Swiss-cheese cosmological model to study the averaging problem. In our Swiss-cheese model, the cheese is a spatially flat, matter only, Friedmann-Robertson-Walker solution (i.e., the Einstein-de Sitter model), and the holes are constructed from a Lemaitre-Tolman-Bondi solution of Einstein's equations. We study the propagation of photons in the Swiss-cheese model, and find a phenomenological homogeneous model to describe observables. Following a fitting procedure based on light-cone averages, we find that the expansion scalar is unaffected by the inhomogeneities (i.e., the phenomenological homogeneous model is the cheese model). This is because of the spherical symmetry of the model; it is unclear whether the expansion scalar will be affected by nonspherical voids. However, the light-cone average of the density as a function of redshift is affected by inhomogeneities. The effect arises because, as the universe evolves, a photon spends more and more time in the (large) voids than in the (thin) high-density structures. The phenomenological homogeneous model describing the light-cone average of the density is similar to the {lambda}CDM concordance model. It is interesting that, although the sole source in the Swiss-cheese model is matter, the phenomenological homogeneous model behaves as if it has a dark-energy component. Finally, we study how the equation of state of the phenomenological homogeneous model depends on the size of the inhomogeneities, and find that the equation-of-state parameters w{sub 0} and w{sub a} follow a power-law dependence with a scaling exponent equal to unity. That is, the equation of state depends linearly on the distance the photon travels through voids. We conclude that, within our toy model, the holes must have a present size of about 250 Mpc to be able to mimic the concordance model.

  15. Azimuthal spin asymmetries in light-cone constituent quark models

    SciTech Connect

    Boffi, S.; Pasquini, B.; Efremov, A. V.; Schweitzer, P.

    2009-05-01

    We present results for all leading-twist azimuthal spin asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to T-even transverse-momentum dependent parton distribution functions on the basis of a light-cone constituent quark model. Attention is paid to discuss the range of applicability of the model, especially with regard to the scale dependence of the observables and the transverse-momentum dependence of the distributions. We find good agreement with available experimental data and present predictions to be further tested by future CLAS, COMPASS, and HERMES data.

  16. Hadronic Spectra and Light-Front Wavefunctions in Holographic QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.

    2006-03-03

    We show how the string amplitude {Phi}(z) defined on the fifth dimension in AdS{sub 5} space can be precisely mapped to the light-front wavefunctions of hadrons in physical spacetime. We find an exact correspondence between the holographic variable z and an impact variable {zeta}, which represents the measure of transverse separation of the constituents within the hadrons. In addition, we derive effective four dimensional Schroedinger equations for the bound states of massless quarks and gluons which exactly reproduce the AdS/CFT results and give a realistic description of the light-quark meson and baryon spectrum as well as the form factors for spacelike Q{sup 2}. Only one parameter which sets the mass scale, {Lambda}{sub QCD}, is introduced.

  17. Light-Front Holography and AdS/QCD Correspondence

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.

    2008-04-23

    Light-Front Holography is a remarkable consequence of the correspondence between string theory in AdS space and conformal field theories in physical-space time. It allows string modes {Phi}(z) in the AdS fifth dimension to be precisely mapped to the light-front wavefunctions of hadrons in terms of a specific light-front impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron. This mapping was originally obtained by matching the exact expression for electromagnetic current matrix elements in AdS space with the corresponding exact expression for the current matrix element using light-front theory in physical space-time. More recently we have shown that one obtains the identical holographic mapping using matrix elements of the energy-momentum tensor, thus providing an important consistency test and verification of holographic mapping from AdS to physical observables defined on the light-front. The resulting light-front Schrodinger equations predicted from AdS/QCD give a good representation of the observed meson and baryon spectra and give excellent phenomenological predictions for amplitudes such as electromagnetic form factors and decay constants.

  18. AdS/CFT and Light-Front QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.

    2008-02-04

    The AdS/CFT correspondence between string theory in AdS space and conformal field theories in physical space-time leads to an analytic, semi-classical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. The AdS/CFT correspondence also provides insights into the inherently nonperturbative aspects of QCD such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of AdS space z and a specific impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection leads to AdS/CFT predictions for the analytic form of the frame-independent light-front wavefunctions (LFWFs) of mesons and baryons, the fundamental entities which encode hadron properties. The LFWFs in turn predict decay constants and spin correlations, as well as dynamical quantities such as form factors, structure functions, generalized parton distributions, and exclusive scattering amplitudes. Relativistic light-front equations in ordinary space-time are found which reproduce the results obtained using the fifth-dimensional theory and have remarkable algebraic structures and integrability properties. As specific examples we describe the behavior of the pion form factor in the space and time-like regions and determine the Dirac nucleon form factors in the space-like region. An extension to nonzero quark mass is used to determine hadronic distribution amplitudes of all mesons, heavy and light. We compare our results with the moments of the distribution amplitudes which have recently been computed from lattice gauge theory.

  19. AdS/CFT and Light-Front QCD

    NASA Astrophysics Data System (ADS)

    Brodsky, Stanley J.; de Téramond, Guy F.

    2010-12-01

    The AdS/CFT correspondence between string theory in AdS space and conformal field theories in physical space-time leads to an analytic, semi-classical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. The AdS/CFT correspondence also provides insights into the inherently nonperturbative aspects of QCD such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of AdS space z and a specific impact variable ζ which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection leads to AdS/CFT predictions for the analytic form of the frame-independent light-front wavefunctions (LFWFs) of mesons and baryons, the fundamental entities which encode hadron properties. The LFWFs in turn predict decay constants and spin correlations, as well as dynamical quantities such as form factors, structure functions, generalized parton distributions, and exclusive scattering amplitudes. Relativistic light-front equations in ordinary space-time are found which reproduce the results obtained using the fifth-dimensional theory and have remarkable algebraic structures and integrability properties. As specific examples we describe the behavior of the pion form factor in the space and time-like regions and determine the Dirac nucleon form factors in the space-like region. An extension to nonzero quark mass is used to determine hadronic distribution amplitudes of all mesons, heavy and light. We compare our results with the moments of the distribution amplitudes which have recently been computed from lattice gauge theory.

  20. Light-front holographic QCD and emerging confinement

    DOE PAGESBeta

    Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter; Erlich, Joshua

    2015-05-21

    In this study we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. Themore » light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical spacetime. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.« less

  1. Geodesic-light-cone coordinates and the Bianchi I spacetime

    NASA Astrophysics Data System (ADS)

    Fleury, Pierre; Nugier, Fabien; Fanizza, Giuseppe

    2016-06-01

    The geodesic-light-cone (GLC) coordinates are a useful tool to analyse light propagation and observations in cosmological models. In this article, we propose a detailed, pedagogical, and rigorous introduction to this coordinate system, explore its gauge degrees of freedom, and emphasize its interest when geometric optics is at stake. We then apply the GLC formalism to the homogeneous and anisotropic Bianchi I cosmology. More than a simple illustration, this application (i) allows us to show that the Weinberg conjecture according to which gravitational lensing does not affect the proper area of constant-redshift surfaces is significantly violated in a globally anisotropic universe; and (ii) offers a glimpse into new ways to constrain cosmic isotropy from the Hubble diagram.

  2. The B3 Subunit of the Cone Cyclic Nucleotide-gated Channel Regulates the Light Responses of Cones and Contributes to the Channel Structural Flexibility.

    PubMed

    Ding, Xi-Qin; Thapa, Arjun; Ma, Hongwei; Xu, Jianhua; Elliott, Michael H; Rodgers, Karla K; Smith, Marci L; Wang, Jin-Shan; Pittler, Steven J; Kefalov, Vladimir J

    2016-04-15

    Cone photoreceptor cyclic nucleotide-gated (CNG) channels play a pivotal role in cone phototransduction, which is a process essential for daylight vision, color vision, and visual acuity. Mutations in the cone channel subunits CNGA3 and CNGB3 are associated with human cone diseases, including achromatopsia, cone dystrophies, and early onset macular degeneration. Mutations in CNGB3 alone account for 50% of reported cases of achromatopsia. This work investigated the role of CNGB3 in cone light response and cone channel structural stability. As cones comprise only 2-3% of the total photoreceptor population in the wild-type mouse retina, we used Cngb3(-/-)/Nrl(-/-) mice with CNGB3 deficiency on a cone-dominant background in our study. We found that, in the absence of CNGB3, CNGA3 was able to travel to the outer segments, co-localize with cone opsin, and form tetrameric complexes. Electroretinogram analyses revealed reduced cone light response amplitude/sensitivity and slower response recovery in Cngb3(-/-)/Nrl(-/-) mice compared with Nrl(-/-) mice. Absence of CNGB3 expression altered the adaptation capacity of cones and severely compromised function in bright light. Biochemical analysis demonstrated that CNGA3 channels lacking CNGB3 were more resilient to proteolysis than CNGA3/CNGB3 channels, suggesting a hindered structural flexibility. Thus, CNGB3 regulates cone light response kinetics and the channel structural flexibility. This work advances our understanding of the biochemical and functional role of CNGB3 in cone photoreceptors. PMID:26893377

  3. Light-front holographic QCD with generic dilaton profile

    NASA Astrophysics Data System (ADS)

    Guo, Zhaoheng; Liu, Tianbo; Ma, Bo-Qiang

    2016-04-01

    We generalize the soft-wall and hard-wall models to a light-front holographic QCD model with a generic dilaton profile. The effective potential induced by a higher power dilaton profile is interpreted as a stronger color confinement at long distance, and it gradually evolves to the hard-wall model when the power increases to infinity. As an application, we investigate the exotic meson states recently discovered in experiments in the generic soft-wall model with a higher power dilaton profile, and the results are in agreement with the spectra of the exotic mesons. Our calculation indicates a weaker interaction at short distance and a stronger interaction at large distance for the components in the exotic mesons. The generic dilaton profile deserves further scrutiny for understanding the strong interaction and for applications.

  4. Discretized Light-Cone Quantization: Application to Quantum Electrodynamics

    NASA Astrophysics Data System (ADS)

    Tang, Andrew Chun-Nien

    In this work, a general method for solving quantum field theories, Discretized Light-Cone Quantization (DLCQ), is presented. The method is very straightforward and essentially consists of diagonalizing the light-cone Hamiltonian matrix for the mass spectrum and wavefunctions. This method has been applied successfully in the past of various one space, one time dimensional theories. In each of these past applications, the mass spectrum and wave functions were successfully obtained, and all results agree with previous analytical and numerical work. The success of DLCQ in 1 + 1 dimensions provides the hope of solving theories in three space and one time dimensions. The application to higher dimensions is much more involved than in 1 + 1 dimensions due to the need to introduce ultraviolet and infrared regulators, and invoke a renormalization scheme consistent with gauge invariance and Lorentz invariance. This is in addition to the extra work involved implementing two extra dimensions with their added degrees of freedom. In this paper, I will present the application of DLCQ to 3 + 1 dimensional Quantum Electrodynamics. The theoretical framework of DLCQ in the context of 3 + 1 QED is shown in the first 8 sections. Issues addressed include the question of self-induced inertias and normal ordering, the agreement of Feynman rule and light-cone answers for one-loop radiative corrections, and ultraviolet and infrared regulation. Many of the results presented here are applicable to quantum field theory in general. Unfortunately, solving 3 + 1 QED in this general framework has so far proven elusive due to a number of difficulties. These problems and a way around them using a truncated Fock space are presented in Section 7, with renormalization in this truncated space presented in Section 8. The next 5 sections show attempts to numerically solve 3 + 1 QED in a truncated Fock space by diagonalization of the Hamiltonian and by a variational calculation for the positronium system

  5. Concentration of light energy within a cone with a metal coating

    SciTech Connect

    Kuznetsova, Tatiana I; Lebedev, Vladimir S

    2003-10-31

    The spatial structure of light waves of the electric type in a cone with perfectly reflecting metal walls is theoretically analysed. The exact formulas and asymptotic expressions are derived which describe the dependences of the energy density of different components of the field inside the cone on the radial coordinate. A special attention is paid to the study of the character of the field decrease near the cone apex depending on the cone angle and the wavelength. The effects of reflection of waves from the truncated cone-free space interface are studied. The obtained results are used for measuring the transmission coefficient of a truncated cone in the optical range for a broad range of parameters, including the diameter of the output aperture of the order of 0.05 - 0.1 of the wavelength. The possibility of obtaining a high transmission coefficient of light in a truncated metallised cone is theoretically substantiated. (laser applications and other topics in quantum electronics)

  6. AdS/QCD and Its Holographic Light-Front Partonic Representation

    SciTech Connect

    de Teramond, Guy F.; Brodsky, Stanley J.; ,

    2008-11-12

    Starting from the Hamiltonian equation of motion in QCD we find a single variable light-front equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. This light-front wave equation is equivalent to the equations of motion which describe the propagation of spin-J modes on anti-de Sitter (AdS) space.

  7. AdS/QCD and its Holographic Light-Front Partonic Representation

    SciTech Connect

    Teramond, Guy F. de; Brodsky, Stanley J.

    2009-03-23

    Starting from the Hamiltonian equation of motion in QCD we find a single variable light-front equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. This light-front wave equation is equivalent to the equations of motion which describe the propagation of spin-J modes on anti-de Sitter (AdS) space.

  8. Chiral symmetry breaking in QCD with two light flavors.

    PubMed

    Engel, Georg P; Giusti, Leonardo; Lottini, Stefano; Sommer, Rainer

    2015-03-20

    A distinctive feature of the presence of spontaneous chiral symmetry breaking in QCD is the condensation of low modes of the Dirac operator near the origin. The rate of condensation must be equal to the slope of M(π)(2)F(π)(2)/2 with respect to the quark mass m in the chiral limit, where M(π) and F(π) are the mass and the decay constant of the Nambu-Goldstone bosons. We compute the spectral density of the (Hermitian) Dirac operator, the quark mass, the pseudoscalar meson mass, and decay constant by numerical simulations of lattice QCD with two light degenerate Wilson quarks. We use lattices generated by the Coordinated Lattice Simulation (CLS) group at three values of the lattice spacing in the range 0.05-0.08 fm, and for several quark masses corresponding to pseudoscalar mesons masses down to 190 MeV. Thanks to this coverage of parameters space, we can extrapolate all quantities to the chiral and continuum limits with confidence. The results show that the low quark modes do condense in the continuum as expected by the Banks-Casher mechanism, and the rate of condensation agrees with the Gell-Mann-Oakes-Renner relation. For the renormalization-group-invariant ratios we obtain [Σ(RGI)](1/3)/F=2.77(2)(4) and Λ(M̅S)/F=3.6(2), which correspond to [Σ(M̅S)(2  GeV)](1/3)=263(3)(4)  MeV and F=85.8(7)(20)  MeV if F(K) is used to set the scale by supplementing the theory with a quenched strange quark. PMID:25839261

  9. Worldsheet theory of light-cone gauge noncritical strings on higher genus Riemann surfaces

    NASA Astrophysics Data System (ADS)

    Ishibashi, Nobuyuki; Murakami, Koichi

    2016-06-01

    It is possible to formulate light-cone gauge string field theory in noncritical dimensions. Such a theory corresponds to conformal gauge worldsheet theory with nonstandard longitudinal part. We study the longitudinal part of the worldsheet theory on higher genus Riemann surfaces. The results in this paper shall be used to study the dimensional regularization of light-cone gauge string field theory.

  10. Analysis of heavy spin-3/2 baryon-heavy spin-1/2 baryon-light vector meson vertices in QCD

    SciTech Connect

    Aliev, T. M.; Savci, M.; Azizi, K; Zamiralov, V. S.

    2011-05-01

    The heavy spin-3/2 baryon-heavy spin-1/2 baryon vertices with light vector mesons are studied within the light cone QCD sum rules method. These vertices are parametrized in terms of three coupling constants. These couplings are calculated for all possible transitions. It is shown that correlation functions for these transitions are described by only one invariant function for every Lorenz structure. The obtained relations between the correlation functions of the different transitions are structure independent while explicit expressions of invariant functions depend on the Lorenz structure.

  11. Meson Transition Form Factors in Light-Front Holographic QCD

    SciTech Connect

    Brodsky, Stanley J.; Cao, Fu-Guang; de Teramond, Guy F.; /Costa Rica U.

    2011-06-22

    We study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The Chern-Simons action, which is a natural form in 5-dimensional anti-de Sitter (AdS) space, leads directly to an expression for the photon-to-pion TFF for a class of confining models. Remarkably, the predicted pion TFF is identical to the leading order QCD result where the distribution amplitude has asymptotic form. The Chern-Simons form is local in AdS space and is thus somewhat limited in its predictability. It only retains the q{bar q} component of the pion wavefunction, and further, it projects out only the asymptotic form of the meson distribution amplitude. It is found that in order to describe simultaneously the decay process {pi}{sup 0} {yields} {gamma}{gamma} and the pion TFF at the asymptotic limit, a probability for the q{bar q} component of the pion wavefunction P{sub q{bar q}} = 0.5 is required; thus giving indication that the contributions from higher Fock states in the pion light-front wavefunction need to be included in the analysis. The probability for the Fock state containing four quarks (anti-quarks) which follows from analyzing the hadron matrix elements, P{sub q{bar q}q{bar q}} {approx} 10%, agrees with the analysis of the pion elastic form factor using light-front holography including higher Fock components in the pion wavefunction. The results for the TFFs for the {eta} and {eta}{prime} mesons are also presented. The rapid growth of the pion TFF exhibited by the BABAR data at high Q{sup 2} is not compatible with the models discussed in this article, whereas the theoretical calculations are in agreement with the experimental data for the {eta} and {eta}{prime} TFFs.

  12. Hadronic light-by-light scattering contribution to the muon anomalous magnetic moment from lattice QCD

    SciTech Connect

    Blum, Thomas; Chowdhury, Saumitra; Hayakawa, Masashi; Izubuchi, Taku

    2015-01-07

    The form factor that yields the light-by-light scattering contribution to the muon anomalous magnetic moment is computed in lattice QCD+QED and QED. A non-perturbative treatment of QED is used and is checked against perturbation theory. The hadronic contribution is calculated for unphysical quark and muon masses, and only the diagram with a single quark loop is computed. Statistically significant signals are obtained. Initial results appear promising, and the prospect for a complete calculation with physical masses and controlled errors is discussed.

  13. B{sub (s)}{yields}S transitions in the light cone sum rules with the chiral current

    SciTech Connect

    Sun Yanjun; Li Zuohong; Huang Tao

    2011-01-15

    We make a QCD light-cone sum rule assessment of B{sub (s)} semileptonic decays to a light scalar meson, B{sub (s)}{yields}Sl{nu}{sub l}, Sll(l=e,{mu},{tau}). Chiral current correlators are used and calculations are performed at leading order in {alpha}{sub s}. Having little knowledge of the ingredients of the scalar mesons, we confine ourself to the two-quark picture for them and work with the two possible scenarios. The resulting sum rules for the form factors receive no contributions from the twist-3 distribution amplitudes, in comparison with the calculation of the conventional light-cone sum rule approach where the twist-3 parts usually play an important role. We specify the range of the squared momentum transfer q{sup 2}, in which the operator product expansion for the correlators remains valid approximately. It is found that the form factors satisfy a relation consistent with the prediction of soft collinear effective theory. In the effective range we investigate behaviors of the form factors and differential decay widths and compare our calculations with the observations from other approaches.

  14. The contribution of single and double cones to spectral sensitivity in budgerigars during changing light conditions.

    PubMed

    Lind, Olle; Chavez, Johanna; Kelber, Almut

    2014-03-01

    Bird colour vision is mediated by single cones, while double cones and rods mediate luminance vision in bright and dim light, respectively. In daylight conditions, birds use colour vision to discriminate large objects such as fruit and plumage patches, and luminance vision to detect fine spatial detail and motion. However, decreasing light intensity favours achromatic mechanisms and eventually, in dim light, luminance vision outperforms colour vision in all visual tasks. We have used behavioural tests in budgerigars (Melopsittacus undulatus) to investigate how single cones, double cones and rods contribute to spectral sensitivity for large (3.4°) static monochromatic stimuli at light intensities ranging from 0.08 to 63.5 cd/m². We found no influences of rods at any intensity level. Single cones dominate the spectral sensitivity function at intensities above 1.1 cd/m², as predicted by a receptor noise-limited colour discrimination model. Below 1.1 cd/m², spectral sensitivity is lower than expected at all wavelengths except 575 nm, which corresponds to double cone function. We suggest that luminance vision mediated by double cones restores visual sensitivity when single cone sensitivity quickly decreases at light intensities close to the absolute threshold of colour vision. PMID:24366429

  15. Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    Light-Front Holography is one of the most remarkable features of the AdS/CFT correspondence. In spite of its present limitations it provides important physical insights into the nonperturbative regime of QCD and its transition to the perturbative domain. This novel framework allows hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The model leads to an effective confining light-front QCD Hamiltonian and a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound-state wavefunctions, and thus the fall-off as a function of the invariant mass of the constituents. The soft-wall holographic model modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics - a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryons. The model predicts a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number n. The hadron eigensolutions projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions {Psi}{sub n/H} (x{sub i}, k{sub {perpendicular}i}, {lambda}{sub i}) which describe the hadron's momentum and spin distributions needed to compute the direct measures of hadron structure at the quark and gluon level, such as elastic and transition form factors, distribution amplitudes, structure functions, generalized parton distributions and transverse

  16. Stray light in cone beam optical computed tomography: II. Reduction using a convergent light source

    NASA Astrophysics Data System (ADS)

    Dekker, Kurtis H.; Battista, Jerry J.; Jordan, Kevin J.

    2016-04-01

    Optical cone beam computed tomography (CBCT) using a broad beam and CCD camera is a fast method for densitometry of 3D optical gel dosimeters. However, diffuse light sources introduce considerable stray light into the imaging system, leading to underestimation of attenuation coefficients and non-uniformities in CT images unless corrections are applied to each projection image. In this study, the light source of a commercial optical CT scanner is replaced with a convergent cone beam source consisting of almost exclusively image forming primary rays. The convergent source is achieved using a small isotropic source and a Fresnel lens. To characterize stray light effects, full-field cone beam CT imaging is compared to fan beam CT (FBCT) using a 1 cm high fan beam aperture centered on the optic axis of the system. Attenuating liquids are scanned within a large 96 mm diameter uniform phantom and in a small 13.5 mm diameter finger phantom. For the uniform phantom, cone and fan beam CT attenuation coefficients agree within a maximum deviation of (1  ±  2)% between mean values over a wide range from 0.036 to 0.43 cm-1. For the finger phantom, agreement is found with a maximum deviation of (4  ±  2)% between mean values over a range of 0.1-0.47 cm-1. With the convergent source, artifacts associated with refractive index mismatch and vessel optical features are more pronounced. Further optimization of the source size to achieve a balance between quantitative accuracy and artifact reduction should enable practical, accurate 3D dosimetry, avoiding time consuming 3D scatter measurements.

  17. Stray light in cone beam optical computed tomography: II. Reduction using a convergent light source.

    PubMed

    Dekker, Kurtis H; Battista, Jerry J; Jordan, Kevin J

    2016-04-01

    Optical cone beam computed tomography (CBCT) using a broad beam and CCD camera is a fast method for densitometry of 3D optical gel dosimeters. However, diffuse light sources introduce considerable stray light into the imaging system, leading to underestimation of attenuation coefficients and non-uniformities in CT images unless corrections are applied to each projection image. In this study, the light source of a commercial optical CT scanner is replaced with a convergent cone beam source consisting of almost exclusively image forming primary rays. The convergent source is achieved using a small isotropic source and a Fresnel lens. To characterize stray light effects, full-field cone beam CT imaging is compared to fan beam CT (FBCT) using a 1 cm high fan beam aperture centered on the optic axis of the system. Attenuating liquids are scanned within a large 96 mm diameter uniform phantom and in a small 13.5 mm diameter finger phantom. For the uniform phantom, cone and fan beam CT attenuation coefficients agree within a maximum deviation of (1  ±  2)% between mean values over a wide range from 0.036 to 0.43 cm(-1). For the finger phantom, agreement is found with a maximum deviation of (4  ±  2)% between mean values over a range of 0.1-0.47 cm(-1). With the convergent source, artifacts associated with refractive index mismatch and vessel optical features are more pronounced. Further optimization of the source size to achieve a balance between quantitative accuracy and artifact reduction should enable practical, accurate 3D dosimetry, avoiding time consuming 3D scatter measurements. PMID:26988107

  18. Modeling the role of mid-wavelength cones in circadian responses to light

    PubMed Central

    Dkhissi-Benyahya, Ouria; Gronfier, Claude; De Vanssay, Wena; Flamant, Frédéric; Cooper, Howard M.

    2007-01-01

    Summary Non-visual responses to light, such as photic entrainment of the circadian clock, involve intrinsically light sensitive melanopsin-expressing ganglion cells as well as rod and cone photoreceptors. However, previous studies have been unable to demonstrate a specific contribution of cones in the photic control of circadian responses to light. Using a mouse model that specifically lacks mid-wavelength (MW) cones we show that these photoreceptors play a significant role in light entrainment and in phase shifting of the circadian oscillator. The contribution of MW cones is mainly observed for light exposures of short duration and towards the longer wavelength region of the spectrum, consistent with the known properties of this opsin. Modelling the contributions of the various photoreceptors stresses the importance of considering the particular spectral, temporal and irradiance response domains of the photopigments when assessing their role and contribution in circadian responses to light. PMID:17329208

  19. Endogenous nitric oxide enhances the light-response of cones during light-adaptation in the rat retina.

    PubMed

    Sato, Masaki; Ohtsuka, Teruya; Stell, William K

    2011-01-01

    The electroretinogram (ERG) is a non-invasive indicator of retinal function. Light flashes evoke a cornea-negative a-wave followed by a cornea-positive b-wave. Light-adaptation is known to increase the amplitude of cone-dependent b-waves. To identify the underlying mechanism, we recorded rat cone photoresponses in situ, using intravitreally-injected glutamate to block synaptic transmission and intense paired-flash stimuli to isolate cone a-waves. Steady adapting illumination caused a progressive increase in cone a-wave amplitude, which was suppressed in a dose-dependent manner by intravitreal CPTIO, a nitric oxide scavenger. We conclude that light-adaptation causes release of nitric oxide, which enhances the cone photoresponse. PMID:20951158

  20. Light-Front Holography and QCD Hadronization at the Amplitude Level

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; ,

    2009-01-09

    Light-front holography allows hadronic amplitudes in the AdS/QCD fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. The AdS coordinate z is identified with an invariant light-front coordinate {zeta} which separates the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schroedinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. A new method for computing the hadronization of quark and gluon jets at the amplitude level using AdS/QCD light-front wavefunctions is outlined.

  1. Transverse momentum dependent parton distributions in a light-cone quark model

    NASA Astrophysics Data System (ADS)

    Pasquini, B.; Cazzaniga, S.; Boffi, S.

    2008-08-01

    The leading twist transverse momentum dependent parton distributions (TMDs) are studied in a light-cone description of the nucleon where the Fock expansion is truncated to consider only valence quarks. General analytic expressions are derived in terms of the six amplitudes needed to describe the three-quark sector of the nucleon light-cone wave function. Numerical calculations for the T-even TMDs are presented in a light-cone constituent quark model, and the role of the so-called pretzelosity is investigated to produce a nonspherical shape of the nucleon.

  2. Exclusive C=+ charmonium production in e{sup +}e{sup -{yields}}H+{gamma} at B factories within the light cone formalism

    SciTech Connect

    Braguta, V. V.

    2010-10-01

    In this paper the cross sections of the processes e{sup +}e{sup -{yields}}H+{gamma}, H={eta}{sub c}, {eta}{sub c}{sup '}, {chi}{sub c0}, {chi}{sub c1}, {chi}{sub c2} are calculated. The calculation is carried out at the leading twist approximation of the light cone formalism. Within this approach the leading logarithmic radiative and relativistic corrections to the amplitudes are resummed. For the processes e{sup +}e{sup -{yields}{eta}}{sub c}, {eta}{sub c}{sup '}+{gamma} one-loop radiative corrections are taken into account. It is also shown that one-loop leading logarithmic radiative corrections calculated within the light cone formalism for the processes under study coincide with that obtained by direct calculations of one-loop diagrams within nonrelativistic QCD.

  3. Meson transition form factors in light-front holographic QCD

    SciTech Connect

    Brodsky, Stanley J.; Cao Fuguang; de Teramond, Guy F.

    2011-10-01

    We study the photon-to-meson transition form factors (TFFs) F{sub M}{gamma}(Q{sup 2}) for {gamma}{gamma}{sup *}{yields}M using light-front holographic methods. The Chern-Simons action, which is a natural form in five-dimensional anti-de Sitter (AdS) space, is required to describe the anomalous coupling of mesons to photons using holographic methods and leads directly to an expression for the photon-to-pion TFF for a class of confining models. Remarkably, the predicted pion TFF is identical to the leading order QCD result where the distribution amplitude has asymptotic form. The Chern-Simons form is local in AdS space and is thus somewhat limited in its predictability. It only retains the qq component of the pion wave function, and further, it projects out only the asymptotic form of the meson distribution amplitude. It is found that in order to describe simultaneously the decay process {pi}{sup 0}{yields}{gamma}{gamma} and the pion TFF at the asymptotic limit, a probability for the qq component of the pion wave function P{sub qq}=0.5 is required, thus giving indication that the contributions from higher Fock states in the pion light-front wave function need to be included in the analysis. The probability for the Fock state containing four quarks P{sub qqqq}{approx}10%, which follows from analyzing the hadron matrix elements for a dressed current model, agrees with the analysis of the pion elastic form factor using light-front holography including higher Fock components in the pion wave function. The results for the TFFs for the {eta} and {eta}{sup '} mesons are also presented. The rapid growth of the pion TFF exhibited by the BABAR data at high Q{sup 2} is not compatible with the models discussed in this article, whereas the theoretical calculations are in agreement with the experimental data for the {eta} and {eta}{sup '} TFFs.

  4. QCD

    NASA Astrophysics Data System (ADS)

    Fleming, Sean

    In this talk I review recent experimental and theoretical results in QCD. Since the topic is too vast to cover within given time constraints I choose to highlight some of the subjects that I find particularly exciting. On the experimental side I focus on measurements made at the Tevatron. Specifically jet production rates, and the cross section for B meson production. In addition I discuss an interesting measurement made by the Belle collaboration of double exclusive charmonium production. On the theory side I quickly review recent advances in computing hadronic cross sections at subleading order in perturbation theory. I then move on to soft-collinear effective theory. After a lightning review of the formalism I discuss recently published results on color-suppressed B → D decays.

  5. E{sub 7(7)} on the Light-Cone

    SciTech Connect

    Kim, Sung-Soo

    2008-11-23

    We study the E{sub 7(7)} on-shell duality symmetry of N = 8 supergravity in four dimensions and show that all physical fields transform under E{sub 7(7)} on the light-cone. We then use this symmetry to construct order {kappa}{sup 2} interactions in light-cone superspace, by requiring this E{sub 7(7)} transformations commutes with the supersymmetry transformations.

  6. QCD on the Light-Front. A Systematic Approach to Hadron Physics

    NASA Astrophysics Data System (ADS)

    Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter

    2014-06-01

    Light-front Hamiltonian theory, derived from the quantization of the QCD Lagrangian at fixed light-front time x + = x 0 + x 3, provides a rigorous frame-independent framework for solving nonperturbative QCD. The eigenvalues of the light-front QCD Hamiltonian H LF predict the hadronic mass spectrum, and the corresponding eigensolutions provide the light-front wavefunctions which describe hadron structure, providing a direct connection to the QCD Lagrangian. In the semiclassical approximation the valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrödinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. Remarkably, the potential U has a unique form of a harmonic oscillator potential if one requires that the chiral QCD action remains conformally invariant. A mass gap and the color confinement scale also arises when one extends the formalism of de Alfaro, Fubini and Furlan to light-front Hamiltonian theory. In the case of mesons, the valence Fock-state wavefunctions of H LF for zero quark mass satisfy a single-variable relativistic equation of motion in the invariant variable , which is conjugate to the invariant mass squared . The result is a nonperturbative relativistic light-front quantum mechanical wave equation which incorporates color confinement and other essential spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the same slope in the radial quantum number n and orbital angular momentum L. Only one mass parameter appears. The corresponding light-front Dirac equation provides a dynamical and spectroscopic model of nucleons. The same light-front equations arise from the holographic mapping of the soft-wall model modification of AdS5 space with a unique dilaton profile to QCD

  7. Light-light and heavy-light mesons in the model of QCD string with quarks at the ends

    NASA Astrophysics Data System (ADS)

    Nefediev, A. V.

    2002-06-01

    The variational einbein field method is applied to the model of the QCD string with quarks at the ends for the case of light-light and heavy-light mesons. Special attention is payed to the proper string dynamics. The correct string slope of the Regge trajectories is reproduced for light-light states which comes out from the picture of rotating string. Masses of several low-lying orbitally and radially excited states in the D, Ds, B, and Bs meson spectra are calculated and a good agreement with the experimental data as well as with recent lattice calculations is found. The role of the string correction to the interquark interaction is discussed at the example of the identification of D*' (2637) state recently claimed by DELPHI Collaboration. For the heavy-light mesons the standard constants used in Heavy Quark Effective Theory are extracted and compared to the results of other approaches.

  8. Applications of AdS/QCD and Light-Front Holography to Baryon Physics

    SciTech Connect

    Brodsky, Stanley J.; Teramond, Guy F. de

    2011-10-21

    The correspondence between theories in anti--de Sitter space and field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance at short distances and color confinement at large distances. These equations, for both mesons and baryons, give a very good representation of the observed hadronic spectrum, including a zero mass pion. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. The meson and baryon wave-functions derived from light-front holography and AdS/QCD also have remarkable phenomenological features, including predictions for the electromagnetic form factors and decay constants. The approach can be systematically improved using light-front Hamiltonian methods. Some novel features of QCD for baryon physics are also discussed.

  9. Applications of AdS/QCD and Light-Front Holography to Baryon Physics

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2011-08-22

    The correspondence between theories in anti-de Sitter space and field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance at short distances and color confinement at large distances. These equations, for both mesons and baryons, give a very good representation of the observed hadronic spectrum, including a zero mass pion. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. The meson and baryon wavefunctions derived from light-front holography and AdS/QCD also have remarkable phenomenological features, including predictions for the electromagnetic form factors and decay constants. The approach can be systematically improved using light-front Hamiltonian methods. Some novel features of QCD for baryon physics are also discussed.

  10. Light composite scalar in twelve-flavor QCD on the lattice.

    PubMed

    Aoki, Yasumichi; Aoyama, Tatsumi; Kurachi, Masafumi; Maskawa, Toshihide; Nagai, Kei-ichi; Ohki, Hiroshi; Rinaldi, Enrico; Shibata, Akihiro; Yamawaki, Koichi; Yamazaki, Takeshi

    2013-10-18

    On the basis of lattice simulations using highly improved staggered quarks for twelve-flavor QCD with several bare fermion masses, we observe a flavor-singlet scalar state lighter than the pion in the correlators of fermionic interpolating operators. The same state is also investigated using correlators of gluonic interpolating operators. Combined with our previous study that showed twelve-flavor QCD to be consistent with being in the conformal window, we infer that the lightness of the scalar state is due to infrared conformality. This result shed some light on the possibility of a light composite Higgs boson ("technidilaton") in walking technicolor theories. PMID:24182255

  11. Magnetic structure of light nuclei from lattice QCD

    DOE PAGESBeta

    Chang, Emmanuel; Detmold, William; Orginos, Kostas; Parreño, Assumpta; Savage, Martin J.; Tiburzi, Brian C.; Beane, Silas R.

    2015-12-09

    Lattice QCD with background magnetic fields is used to calculate the magnetic moments and magnetic polarizabilities of the nucleons and of light nuclei withmore » $$A\\le4$$, along with the cross-section for the $M1$ transition $$np\\rightarrow d\\gamma$$, at the flavor SU(3)-symmetric point where the pion mass is $$m_\\pi\\sim 806$$ MeV. These magnetic properties are extracted from nucleon and nuclear energies in six uniform magnetic fields of varying strengths. The magnetic moments are presented in a recent Letter. For the charged states, the extraction of the polarizability requires careful treatment of Landau levels, which enter non-trivially in the method that is employed. The nucleon polarizabilities are found to be of similar magnitude to their physical values, with $$\\beta_p=5.22(+0.66/-0.45)(0.23) \\times 10^{-4}$$ fm$^3$ and $$\\beta_n=1.253(+0.056/-0.067)(0.055) \\times 10^{-4}$$ fm$^3$, exhibiting a significant isovector component. The dineutron is bound at these heavy quark masses and its magnetic polarizability, $$\\beta_{nn}=1.872(+0.121/-0.113)(0.082) \\times 10^{-4}$$ fm$^3$ differs significantly from twice that of the neutron. A linear combination of deuteron scalar and tensor polarizabilities is determined by the energies of the $$j_z=\\pm 1$$ deuteron states, and is found to be $$\\beta_{d,\\pm 1}=4.4(+1.6/-1.5)(0.2) \\times 10^{-4}$$ fm$^3$. The magnetic polarizabilities of the three-nucleon and four-nucleon systems are found to be positive and similar in size to those of the proton, $$\\beta_{^{3}\\rm He}=5.4(+2.2/-2.1)(0.2) \\times 10^{-4}$$ fm$^3$, $$\\beta_{^{3}\\rm H}=2.6(1.7)(0.1) \\times 10^{-4}$$ fm$^3$, $$\\beta_{^{4}\\rm He}=3.4(+2.0/-1.9)(0.2) \\times 10^{-4}$$ fm$^3$. Mixing between the $j_z=0$ deuteron state and the spin-singlet $np$ state induced by the background magnetic field is used to extract the short-distance two-nucleon counterterm, $${\\bar L}_1$$, of the pionless effective theory for $NN$ systems (equivalent to the

  12. Magnetic structure of light nuclei from lattice QCD

    SciTech Connect

    Chang, Emmanuel; Detmold, William; Orginos, Kostas; Parreño, Assumpta; Savage, Martin J.; Tiburzi, Brian C.; Beane, Silas R.

    2015-12-09

    Lattice QCD with background magnetic fields is used to calculate the magnetic moments and magnetic polarizabilities of the nucleons and of light nuclei with $A\\le4$, along with the cross-section for the $M1$ transition $np\\rightarrow d\\gamma$, at the flavor SU(3)-symmetric point where the pion mass is $m_\\pi\\sim 806$ MeV. These magnetic properties are extracted from nucleon and nuclear energies in six uniform magnetic fields of varying strengths. The magnetic moments are presented in a recent Letter. For the charged states, the extraction of the polarizability requires careful treatment of Landau levels, which enter non-trivially in the method that is employed. The nucleon polarizabilities are found to be of similar magnitude to their physical values, with $\\beta_p=5.22(+0.66/-0.45)(0.23) \\times 10^{-4}$ fm$^3$ and $\\beta_n=1.253(+0.056/-0.067)(0.055) \\times 10^{-4}$ fm$^3$, exhibiting a significant isovector component. The dineutron is bound at these heavy quark masses and its magnetic polarizability, $\\beta_{nn}=1.872(+0.121/-0.113)(0.082) \\times 10^{-4}$ fm$^3$ differs significantly from twice that of the neutron. A linear combination of deuteron scalar and tensor polarizabilities is determined by the energies of the $j_z=\\pm 1$ deuteron states, and is found to be $\\beta_{d,\\pm 1}=4.4(+1.6/-1.5)(0.2) \\times 10^{-4}$ fm$^3$. The magnetic polarizabilities of the three-nucleon and four-nucleon systems are found to be positive and similar in size to those of the proton, $\\beta_{^{3}\\rm He}=5.4(+2.2/-2.1)(0.2) \\times 10^{-4}$ fm$^3$, $\\beta_{^{3}\\rm H}=2.6(1.7)(0.1) \\times 10^{-4}$ fm$^3$, $\\beta_{^{4}\\rm He}=3.4(+2.0/-1.9)(0.2) \\times 10^{-4}$ fm$^3$. Mixing between the $j_z=0$ deuteron state and the spin-singlet $np$ state induced by the background magnetic field is used to extract the short-distance two-nucleon counterterm, ${\\bar L}_1$, of the pionless effective theory for $NN$ systems (equivalent to the meson-exchange current

  13. Novel Perspectives from Light-Front QCD, Super-Conformal Algebra, and Light-Front Holography

    SciTech Connect

    Brodsky, Stanley J.

    2015-12-01

    Light-Front Quantization – Dirac’s “Front Form” – provides a physical, frame-independent formalism for hadron dynamics and structure. Observables such as structure functions, transverse momentum distributions, and distribution amplitudes are defined from the hadronic LFWFs. One obtains new insights into the hadronic mass scale, the hadronic spectrum, and the functional form of the QCD running coupling in the nonperturbative domain using light-front holography. In addition, superconformal algebra leads to remarkable supersymmetric relations between mesons and baryons. I also discuss evidence that the antishadowing of nuclear structure functions is nonuniversal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with the momentum and other sum rules for the nuclear parton distribution functions.

  14. Novel QCD effects in nuclear collisions

    SciTech Connect

    Brodsky, S.J.

    1991-12-01

    Heavy ion collisions can provide a novel environment for testing fundamental dynamical processes in QCD, including minijet formation and interactions, formation zone phenomena, color filtering, coherent co-mover interactions, and new higher twist mechanisms which could account for the observed excess production and anomalous nuclear target dependence of heavy flavor production. The possibility of using light-cone thermodynamics and a corresponding covariant temperature to describe the QCD phases of the nuclear fragmentation region is also briefly discussed.

  15. Magnetic structure of light nuclei from lattice QCD

    NASA Astrophysics Data System (ADS)

    Chang, Emmanuel; Detmold, William; Orginos, Kostas; Parreño, Assumpta; Savage, Martin J.; Tiburzi, Brian C.; Beane, Silas R.; Nplqcd Collaboration

    2015-12-01

    Lattice QCD with background magnetic fields is used to calculate the magnetic moments and magnetic polarizabilities of the nucleons and of light nuclei with A ≤4 , along with the cross section for the M 1 transition n p →d γ , at the flavor SU(3)-symmetric point where the pion mass is mπ˜806 MeV . These magnetic properties are extracted from nucleon and nuclear energies in six uniform magnetic fields of varying strengths. The magnetic moments are presented in a recent article [S. Beane et al., Phys. Rev. Lett. 113, 252001 (2014)]. For the charged states, the extraction of the polarizability requires careful treatment of Landau levels, which enter nontrivially in the method that is employed. The nucleon polarizabilities are found to be of similar magnitude to their physical values, with βp=5.22 (+0.66/-0.45) (0.23 )×10-4 fm3 and βn=1.253 (+0.056/-0.067) (0.055 )×10-4 fm3 , exhibiting a significant isovector component. The dineutron is bound at these heavy quark masses, and its magnetic polarizability, βn n=1.872 (+0.121/-0.113) (0.082 )×10-4 fm3 , differs significantly from twice that of the neutron. A linear combination of deuteron scalar and tensor polarizabilities is determined by the energies of the jz=±1 deuteron states and is found to be βd ,±1=4.4 (+1.6/-1.5) (0.2 )×10-4 fm3 . The magnetic polarizabilities of the three-nucleon and four-nucleon systems are found to be positive and similar in size to those of the proton, β3He =5.4 (+2.2/-2.1) (0.2 )×10-4 fm3 , β​3H=2.6 (1.7 )(0.1 )×10-4 fm3 , and β4He=3.4 (+2.0/-1.9) (0.2 )×10-4 fm3 . Mixing between the jz=0 deuteron state and the spin-singlet n p state induced by the background magnetic field is used to extract the short-distance two-nucleon counterterm, L¯1, of the pionless effective theory for N N systems (equivalent to the meson-exchange current contribution in nuclear potential models) that dictates the cross section for the n p →d γ process near threshold. Combined with

  16. Reionization on Large Scales. IV. Predictions for the 21 cm Signal Incorporating the Light Cone Effect

    NASA Astrophysics Data System (ADS)

    La Plante, P.; Battaglia, N.; Natarajan, A.; Peterson, J. B.; Trac, H.; Cen, R.; Loeb, A.

    2014-07-01

    We present predictions for the 21 cm brightness temperature power spectrum during the Epoch of Reionization (EoR). We discuss the implications of the "light cone" effect, which incorporates evolution of the neutral hydrogen fraction and 21 cm brightness temperature along the line of sight. Using a novel method calibrated against radiation-hydrodynamic simulations, we model the neutral hydrogen density field and 21 cm signal in large volumes (L = 2 Gpc h -1). The inclusion of the light cone effect leads to a relative decrease of about 50% in the 21 cm power spectrum on all scales. We also find that the effect is more prominent at the midpoint of reionization and later. The light cone effect can also introduce an anisotropy along the line of sight. By decomposing the 3D power spectrum into components perpendicular to and along the line of sight, we find that in our fiducial reionization model, there is no significant anisotropy. However, parallel modes can contribute up to 40% more power for shorter reionization scenarios. The scales on which the light cone effect is relevant are comparable to scales where one measures the baryon acoustic oscillation. We argue that due to its large comoving scale and introduction of anisotropy, the light cone effect is important when considering redshift space distortions and future application to the Alcock-Paczyński test for the determination of cosmological parameters.

  17. Reionization on large scales. IV. Predictions for the 21 cm signal incorporating the light cone effect

    SciTech Connect

    La Plante, P.; Battaglia, N.; Natarajan, A.; Peterson, J. B.; Trac, H.; Cen, R.; Loeb, A.

    2014-07-01

    We present predictions for the 21 cm brightness temperature power spectrum during the Epoch of Reionization (EoR). We discuss the implications of the 'light cone' effect, which incorporates evolution of the neutral hydrogen fraction and 21 cm brightness temperature along the line of sight. Using a novel method calibrated against radiation-hydrodynamic simulations, we model the neutral hydrogen density field and 21 cm signal in large volumes (L = 2 Gpc h {sup –1}). The inclusion of the light cone effect leads to a relative decrease of about 50% in the 21 cm power spectrum on all scales. We also find that the effect is more prominent at the midpoint of reionization and later. The light cone effect can also introduce an anisotropy along the line of sight. By decomposing the 3D power spectrum into components perpendicular to and along the line of sight, we find that in our fiducial reionization model, there is no significant anisotropy. However, parallel modes can contribute up to 40% more power for shorter reionization scenarios. The scales on which the light cone effect is relevant are comparable to scales where one measures the baryon acoustic oscillation. We argue that due to its large comoving scale and introduction of anisotropy, the light cone effect is important when considering redshift space distortions and future application to the Alcock-Paczyński test for the determination of cosmological parameters.

  18. Optical Imaging of Human Cone Photoreceptors Directly Following the Capture of Light

    PubMed Central

    Bedggood, Phillip; Metha, Andrew

    2013-01-01

    Capture of light in the photoreceptor outer segment initiates a cascade of chemical events that inhibit neurotransmitter release, ultimately resulting in vision. The massed response of the photoreceptor population can be measured non-invasively by electrical recordings, but responses from individual cells cannot be measured without dissecting the retina. Here we used optical imaging to observe individual human cones in the living eye as they underwent bleaching of photopigment and associated phototransduction. The retina was simultaneously stimulated and observed with high intensity visible light at 1 kHz, using adaptive optics. There was marked variability between individual cones in both photosensitivity and pigment optical density, challenging the conventional assumption that photoreceptors act as identical subunits (coefficient of variation in rate of photoisomerization = 23%). There was also a pronounced inverse correlation between these two parameters (p<10−7); the temporal evolution of image statistics revealed this to be a dynamic relationship, with cone waveguiding efficiency beginning a dramatic increase within 3 ms of light onset. Beginning as early as 2 ms after light onset and including half of cells by ∼7 ms, cone intensity showed reversals characteristic of interference phenomena, with greater delays in reversal corresponding to cones with more photopigment (p<10−3). The timing of these changes is argued to best correspond with either the cessation of dark current, or to related events such as changes in intracellular cGMP. Cone intensity also showed fluctuations of high frequency (332±25 Hz) and low amplitude (3.0±0.85%). Other groups have shown similar fluctuations that were directly evoked by light; if this corresponds to the same phenomenon, we propose that the amplitude of fluctuation may be increased by the use of a bright flash followed by a brief pause, to allow recovery of cone circulating current. PMID:24260177

  19. AdS/QCD, Light-Front Holography, and Sublimated Gluons

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    The gauge/gravity duality leads to a simple analytical and phenomenologically compelling nonperturbative approximation to the full light-front QCD Hamiltonian - 'Light-Front Holography', which provides a Lorentz-invariant first-approximation to QCD, and successfully describes the spectroscopy of light-quark meson and baryons, their elastic and transition form factors, and other hadronic properties. The bound-state Schroedinger and Dirac equations of the soft-wall AdS/QCD model predict linear Regge trajectories which have the same slope in orbital angular momentum L and radial quantum number n for both mesons and baryons. Light-front holography connects the fifth-dimensional coordinate of AdS space z to an invariant impact separation variable {zeta} in 3+1 space at fixed light-front time. A key feature is the determination of the frame-independent light-front wavefunctions of hadrons - the relativistic analogs of the Schroedinger wavefunctions of atomic physics which allow one to compute form factors, transversity distributions, spin properties of the valence quarks, jet hadronization, and other hadronic observables. One thus obtains a one-parameter color-confining model for hadron physics at the amplitude level. AdS/QCD also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function with an infrared fixed point which agrees with the effective coupling a{sub g1} (Q{sup 2}) extracted from measurements of the Bjorken sum rule below Q{sup 2} < 1 GeV{sup 2}. This is consistent with a flux-tube interpretation of QCD where soft gluons with virtualities Q{sup 2} < 1 GeV{sup 2} are sublimated into a color-confining potential for quarks. We discuss a number of phenomenological hadronic properties which support this picture.

  20. Light-cone effect and supersonic correlations in one- and two-dimensional bosonic superfluids

    NASA Astrophysics Data System (ADS)

    Carleo, Giuseppe; Becca, Federico; Sanchez-Palencia, Laurent; Sorella, Sandro; Fabrizio, Michele

    2014-03-01

    We study the spreading of density-density correlations in Bose-Hubbard models after a quench of the interaction strength, using time-dependent variational Monte Carlo simulations. It gives access to unprecedented long propagation times and to dimensions higher than one. In both one and two dimensions, we find ballistic light-cone spreading of correlations and extract accurate values of the light-cone velocity in the superfluid regime. We show that the spreading of correlations is generally supersonic, with a light-cone propagating faster than sound modes but slower than the maximum group velocity of density excitations, except at the Mott transition, where all the characteristic velocities are equal. Further, we show that in two dimensions the correlation spreading is highly anisotropic and presents nontrivial interference effects.

  1. Nucleon tensor form factors induced by isovector and isoscalar currents in QCD

    SciTech Connect

    Aliev, T. M.; Savci, M.; Azizi, K.

    2011-10-01

    Using the most general form of the nucleon interpolating current, we calculate the tensor form factors of the nucleon within light cone QCD sum rules. A comparison of our results on tensor form factors with those of the chiral-soliton model and lattice QCD is given.

  2. Learned arbitrary responses to light in mice without rods or cones

    NASA Astrophysics Data System (ADS)

    Mrosovsky, N.; Salmon, Peggy

    2002-10-01

    The aim of this investigation was to discover whether mice lacking classical photoreceptors (rods and cones) can nevertheless be trained to respond to light. Mice with the coneless (cl) transgene have an attenuated diphtheria toxin fused to a cone opsin promotor. Mutant mice homozygous for the retinal degeneration (rd) gene undergo loss of their rods. By mating these two strains, mice lacking both cones and rods can be generated (Lucas et al. 1999). Such coneless-rodless mice were able to use light as a signal to make a behavioural response to avoid impending shock. Nevertheless, especially initially, they used the light as a cue less often than wildtype controls, indicating that normally the rods and cones are used for such responses. However, other photoreceptors are able to take over this role to some extent. When the lights were covered with opaque material, the performance of rodless-coneless mice dropped to chance level, indicating that they had been using the light as a cue for avoidance.

  3. Hamiltonian Light-front Field Theory Within an AdS/QCD Basis

    SciTech Connect

    Vary, J.P.; Honkanen, H.; Li, Jun; Maris, P.; Brodsky, S.J.; Harindranath, A.; de Teramond, G.F.; Sternberg, P.; Ng, E.G.; Yang, C.; /LBL, Berkeley

    2009-12-16

    Non-perturbative Hamiltonian light-front quantum field theory presents opportunities and challenges that bridge particle physics and nuclear physics. Fundamental theories, such as Quantum Chromodynamics (QCD) and Quantum Electrodynamics (QED) offer the promise of great predictive power spanning phenomena on all scales from the microscopic to cosmic scales, but new tools that do not rely exclusively on perturbation theory are required to make connection from one scale to the next. We outline recent theoretical and computational progress to build these bridges and provide illustrative results for nuclear structure and quantum field theory. As our framework we choose light-front gauge and a basis function representation with two-dimensional harmonic oscillator basis for transverse modes that corresponds with eigensolutions of the soft-wall AdS/QCD model obtained from light-front holography.

  4. Dark Light, Rod Saturation, and the Absolute and Incremental Sensitivity of Mouse Cone Vision

    PubMed Central

    Naarendorp, Frank; Esdaille, Tricia M.; Banden, Serenity M.; Andrews-Labenski, John; Gross, Owen P.; Pugh, Edward N.

    2012-01-01

    Visual thresholds of mice for the detection of small, brief targets were measured with a novel behavioral methodology in the dark and in the presence of adapting lights spanning ∼8 log10 units of intensity. To help dissect the contributions of rod and cone pathways, both wild-type mice and mice lacking rod (Gnat1−/−) or cone (Gnat2cpfl3) function were studied. Overall, the visual sensitivity of mice was found to be remarkably similar to that of the human peripheral retina. Rod absolute threshold corresponded to 12-15 isomerized pigment molecules (R*) in image fields of 800 to 3000 rods. Rod “dark light” (intrinsic retinal noise in darkness) corresponded to that estimated previously from single-cell recordings, 0.012R*s−1rod−1, indicating that spontaneous thermalisomerizations are responsible. Psychophysical rod saturation was measured for the first time in a nonhman species and found to be very similar to that of the human rod monochromat. Cone threshold corresponded to ∼5 R* cone−1 in an image field of 280 cones. Cone dark light was equivalent to ∼5000 R*s−1 cone−1, consistent with primate single-cell data but 100-fold higher than predicted by recent measurements of the rate of thermal isomerization of mouse cone opsins, indicating that nonopsin sources of noise determine cone threshold. The new, fully automated behavioral method is based on the ability of mice to learn to interrupt spontaneous wheel running on the presentation of a visual cue and provides an efficient and highly reliable means of examining visual function in naturally behaving normal and mutant mice. PMID:20844144

  5. Speed, sensitivity, and stability of the light response in rod and cone photoreceptors: Facts and models

    PubMed Central

    Korenbrot, Juan I.

    2012-01-01

    The light responses of rod and cone photoreceptors in the vertebrate retina are quantitatively different, yet extremely stable and reproducible because of the extraordinary regulation of the cascade of enzymatic reactions that link photon absorption and visual pigment excitation to the gating of cGMP-gated ion channels in the outer segment plasma membrane. While the molecular scheme of the phototransduction pathway is essentially the same in rods and cones, the enzymes and protein regulators that constitute the pathway are distinct. These enzymes and regulators can differ in the quantitative features of their functions or in concentration if their functions are similar or both can be true. The molecular identity and distinct function of the molecules of the transduction cascade in rods and cones are summarized. The functional significance of these molecular differences is examined with a mathematical model of the signal-transducing enzymatic cascade. Constrained by available electrophysiological, biochemical and biophysical data, the model simulates photocurrents that match well the electrical photoresponses measured in both rods and cones. Using simulation computed with the mathematical model, the time course of light-dependent changes in enzymatic activities and second messenger concentrations in non-mammalian rods and cones are compared side by side. PMID:22658984

  6. TMDs and Azimuthal Spin Asymmetries in a Light-Cone Quark Model

    SciTech Connect

    Pasquini, B.; Boffi, S.; Efremov, A. V.; Schweitzer, P.

    2009-08-04

    The main properties of the leading-twist transverse momentum dependent parton distributions in a light-cone constituent quark model of the nucleon are reviewed, with focus on the role of the spin-spin and spin-orbit correlations of quarks. Results for azimuthal single spin asymmetries in semi-inclusive deep inelastic scattering are also discussed.

  7. Adding light to the gravitational waves on the null cone

    NASA Astrophysics Data System (ADS)

    Babiuc, Maria

    2014-03-01

    Recent interesting astrophysical observations point towards a multi-messenger, multi-wavelength approach to understanding strong gravitational sources, like compact stars or black hole collisions, supernovae explosions, or even the big bang. Gravitational radiation is properly defined only at future null infinity, but usually is estimated at a finite radius, and then extrapolated. Our group developed a characteristic waveform extraction tool, implemented in an open source code, which computes the gravitational waves infinitely far from their source, in terms of compactified null cones, by numerically solving Einstein equation in Bondi space-time coordinates. The goal is extend the capabilities of the code, by solving Einstein-Maxwell's equations together with the Maxwell's equations, to obtain the energy radiated asymptotically at infinity, both in gravitational and electromagnetic waves. The purpose is to analytically derive and numerically calculate both the gravitational waves and the electromagnetic counterparts at infinity, in this characteristic framework. The method is to treat the source of gravitational and electromagnetic radiation as a black box, and therefore the code will be very flexible, with potentially large applicability.

  8. Light-Front Holography, Color Confinement, and Supersymmetric Features of QCD

    NASA Astrophysics Data System (ADS)

    Brodsky, Stanley J.

    2016-03-01

    Light-Front Quantization—Dirac's "Front Form"—provides a physical, frame-independent formalism for hadron dynamics and structure. Observables such as structure functions, transverse momentum distributions, and distribution amplitudes are defined from the hadronic light-front wavefunctions. One obtains new insights into the hadronic spectrum, light-front wavefunctions, and the functional form of the QCD running coupling in the nonperturbative domain using light-front holography—the duality between the front form and AdS5, the space of isometries of the conformal group. In addition, superconformal algebra leads to remarkable supersymmetric relations between mesons and baryons of the same parity. The mass scale κ underlying confinement and hadron masses can be connected to the parameter {Λ_{overline {MS}}} in the QCD running coupling by matching the nonperturbative dynamics, as described by the effective conformal theory mapped to the light-front and its embedding in AdS space, to the perturbative QCD regime. The result is an effective coupling defined at all momenta. This matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. The use of Q 0 to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with the principle of maximal conformality for setting the renormalization scales, can greatly improve the precision of perturbative QCD predictions for collider phenomenology. The absence of vacuum excitations of the causal, frame-independent front form vacuum has important consequences for the cosmological constant. I also discuss evidence that the antishadowing of nuclear structure functions is non-universal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with the momentum and other sum rules for nuclear parton distribution functions.

  9. Light-Front Holography, Color Confinement, and Supersymmetric Features of QCD

    NASA Astrophysics Data System (ADS)

    Brodsky, Stanley J.

    2016-08-01

    Light-Front Quantization—Dirac's "Front Form"—provides a physical, frame-independent formalism for hadron dynamics and structure. Observables such as structure functions, transverse momentum distributions, and distribution amplitudes are defined from the hadronic light-front wavefunctions. One obtains new insights into the hadronic spectrum, light-front wavefunctions, and the functional form of the QCD running coupling in the nonperturbative domain using light-front holography—the duality between the front form and AdS5, the space of isometries of the conformal group. In addition, superconformal algebra leads to remarkable supersymmetric relations between mesons and baryons of the same parity. The mass scale {κ} underlying confinement and hadron masses can be connected to the parameter {Λ_{overline {MS}}} in the QCD running coupling by matching the nonperturbative dynamics, as described by the effective conformal theory mapped to the light-front and its embedding in AdS space, to the perturbative QCD regime. The result is an effective coupling defined at all momenta. This matching of the high and low momentum transfer regimes determines a scale Q 0 which sets the interface between perturbative and nonperturbative hadron dynamics. The use of Q 0 to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with the principle of maximal conformality for setting the renormalization scales, can greatly improve the precision of perturbative QCD predictions for collider phenomenology. The absence of vacuum excitations of the causal, frame-independent front form vacuum has important consequences for the cosmological constant. I also discuss evidence that the antishadowing of nuclear structure functions is non-universal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with the momentum and other sum rules for nuclear parton distribution functions.

  10. Superconformal Baryon-Meson Symmetry and Light-Front Holographic QCD

    SciTech Connect

    Dosch, Hans Guenter; de Teramond, Guy F.; Brodsky, Stanley J.

    2015-04-10

    We construct an effective QCD light-front Hamiltonian for both mesons and baryons in the chiral limit based on the generalized supercharges of a superconformal graded algebra. The superconformal construction is shown to be equivalent to a semi-classical approximation to light-front QCD and its embedding in AdS space. The specific breaking of conformal invariance inside the graded algebra uniquely determines the effective confinement potential. The generalized supercharges connect the baryon and meson spectra to each other in a remarkable manner. In particular, the π/b1 Regge trajectory is identified as the superpartner of the nucleon trajectory. However, the lowest-lying state on this trajectory, the π-meson is massless in the chiral limit and has no supersymmetric partner.

  11. Superconformal Baryon-Meson Symmetry and Light-Front Holographic QCD

    DOE PAGESBeta

    Dosch, Hans Guenter; de Teramond, Guy F.; Brodsky, Stanley J.

    2015-04-10

    We construct an effective QCD light-front Hamiltonian for both mesons and baryons in the chiral limit based on the generalized supercharges of a superconformal graded algebra. The superconformal construction is shown to be equivalent to a semi-classical approximation to light-front QCD and its embedding in AdS space. The specific breaking of conformal invariance inside the graded algebra uniquely determines the effective confinement potential. The generalized supercharges connect the baryon and meson spectra to each other in a remarkable manner. In particular, the π/b1 Regge trajectory is identified as the superpartner of the nucleon trajectory. However, the lowest-lying state on thismore » trajectory, the π-meson is massless in the chiral limit and has no supersymmetric partner.« less

  12. Light-dependent Changes in Outer Segment Free-Ca2+ Concentration in Salamander Cone Photoreceptors

    PubMed Central

    Sampath, A.P.; Matthews, H.R.; Cornwall, M.C.; Bandarchi, J.; Fain, G.L.

    1999-01-01

    Simultaneous measurements of photocurrent and outer segment Ca2+ were made from isolated salamander cone photoreceptors. While recording the photocurrent from the inner segment, which was drawn into a suction pipette, a laser spot confocal technique was employed to evoke fluorescence from the outer segment of a cone loaded with the Ca2+ indicator fluo-3. When a dark-adapted cone was exposed to the intense illumination of the laser, the circulating current was completely suppressed and fluo-3 fluorescence rapidly declined. In the more numerous red-sensitive cones this light-induced decay in fluo-3 fluorescence was best fitted as the sum of two decaying exponentials with time constants of 43 ± 2.4 and 640 ± 55 ms (mean ± SEM, n = 25) and unequal amplitudes: the faster component was 1.7-fold larger than the slower. In blue-sensitive cones, the decay in fluorescence was slower, with time constants of 140 ± 30 and 1,400 ± 300 ms, and nearly equal amplitudes. Calibration of fluo-3 fluorescence in situ from red-sensitive cones allowed the calculation of the free-Ca2+ concentration, yielding values of 410 ± 37 nM in the dark-adapted outer segment and 5.5 ± 2.4 nM after saturating illumination (mean ± SEM, n = 8). Photopigment bleaching by the laser resulted in a considerable reduction in light sensitivity and a maintained decrease in outer segment Ca2+ concentration. When the photopigment was regenerated by applying exogenous 11-cis-retinal, both the light sensitivity and fluo-3 fluorescence recovered rapidly to near dark-adapted levels. Regeneration of the photopigment allowed repeated measurements of fluo-3 fluorescence to be made from a single red-sensitive cone during adaptation to steady light over a range of intensities. These measurements demonstrated that the outer segment Ca2+ concentration declines in a graded manner during adaptation to background light, varying linearly with the magnitude of the circulating current. PMID:9925824

  13. Light-Front Holography, AdS/QCD, and Hadronic Phenomena

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2009-12-09

    AdS/QCD, the correspondence between theories in a modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. We identify the AdS coordinate z with an invariant light-front coordinate {zeta} which separates the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schroedinger equation with a confining potential which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The mapping of electromagnetic and gravitational form factors in AdS space to their corresponding expressions in light-front theory confirms this correspondence. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. The distinction between static structure functions, such as the probability distributions computed from the square of the light-front wavefunctions, versus dynamical structure functions which include the effects of rescattering, is emphasized. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.

  14. AdS/QCD and Applications of Light-Front Holography

    SciTech Connect

    Brodsky, Stanley J.; Cao, Fu-Guang; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    Light-Front Holography leads to a rigorous connection between hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space and frame-independent light-front wavefunctions of hadrons in 3 + 1 physical space-time, thus providing a compelling physical interpretation of the AdS/CFT correspondence principle and AdS/QCD, a useful framework which describes the correspondence between theories in a modified AdS5 background and confining field theories in physical space-time. To a first semiclassical approximation, where quantum loops and quark masses are not included, this approach leads to a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time. The internal structure of hadrons is explicitly introduced and the angular momentum of the constituents plays a key role. We give an overview of the light-front holographic approach to strongly coupled QCD. In particular, we study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The results for the TFFs for the {eta} and {eta}' mesons are also presented. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

  15. Light-Front Quantization and AdS/QCD: An Overview

    SciTech Connect

    de Teramond, Guy F.; Brodsky, Stanley J.; /SLAC /Stanford U., Phys. Dept.

    2011-08-19

    We give an overview of the light-front holographic approach to strongly coupled QCD, whereby a confining gauge theory, quantized on the light front, is mapped to a higher-dimensional anti de Sitter (AdS) space. The framework is guided by the AdS/CFT correspondence incorporating a gravitational background asymptotic to AdS space which encodes the salient properties of QCD, such as the ultraviolet conformal limit at the AdS boundary at z {yields} 0, as well as modifications of the geometry in the large z infrared region to describe confinement and linear Regge behavior. There are two equivalent procedures for deriving the AdS/QCD equations of motion: one can start from the Hamiltonian equation of motion in physical space time by studying the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. To a first semiclassical approximation, where quantum loops and quark masses are not included, this leads to a light-front Hamiltonian equation which describes the bound state dynamics of light hadrons in terms of an invariant impact variable {zeta} which measures the separation of the partons within the hadron at equal light-front time. Alternatively, one can start from the gravity side by studying the propagation of hadronic modes in a fixed effective gravitational background. Both approaches are equivalent in the semiclassical approximation. This allows us to identify the holographic variable z in AdS space with the impact variable {zeta}. Light-front holography thus allows a precise mapping of transition amplitudes from AdS to physical space-time. The internal structure of hadrons is explicitly introduced and the angular momentum of the constituents plays a key role.

  16. Sivers and Boer-Mulders functions in Light-Cone Quark Models

    SciTech Connect

    Pasquini, Barbara; Yuan, Feng

    2010-01-29

    Results for the naive-time-reversal-odd quark distributions in a light-cone quark model are presented. The final-state interaction effects are generated via single-gluon exchange mechanism. The formalism of light-cone wave functions is used to derive general expressions in terms of overlap of wave-function amplitudes describing the different orbital angular momentum components of the nucleon. In particular, the model predictions show a dominant contribution from S- and P-wave interference in the Sivers function and a significant contribution also from the interference of P and D waves in the Boer-Mulders function. The favourable comparison with existing phenomenological parametrizations motivates further applications to describe azimuthal asymmetries in hadronic reactions.

  17. Nucleon form factors to next-to-leading order with light-cone sum rules

    SciTech Connect

    Passek-Kumericki, K.; Peters, G.

    2008-08-01

    We have calculated the leading-twist next-to-leading order (NLO), i.e., O({alpha}{sub s}), correction to the light-cone sum rules prediction for the electromagnetic form factors of the nucleon. We have used the Ioffe nucleon interpolation current and worked in M{sub N}=0 approximation, with M{sub N} being the mass of the nucleon. In this approximation, only the Pauli form factor F{sub 2} receives a correction and the calculated correction is quite sizable (ca. 60%). The numerical results for the proton form factors show the improved agreement with the experimental data. We also discuss the problems encountered when going away from M{sub N}=0 approximation at NLO, as well as gauge invariance of the perturbative results. This work presents the first step towards the NLO accuracy in the light-cone sum rules for baryon form factors.

  18. Light-Cone Effect of Radiation Fields in Cosmological Radiative Transfer Simulations

    NASA Astrophysics Data System (ADS)

    Ahn, Kyungjin

    2015-02-01

    We present a novel method to implement time-delayed propagation of radiation fields in cosmo-logical radiative transfer simulations. Time-delayed propagation of radiation fields requires construction of retarded-time fields by tracking the location and lifetime of radiation sources along the corresponding light-cones. Cosmological radiative transfer simulations have, until now, ignored this "light-cone effect" or implemented ray-tracing methods that are computationally demanding. We show that radiative trans-fer calculation of the time-delayed fields can be easily achieved in numerical simulations when periodic boundary conditions are used, by calculating the time-discretized retarded-time Green's function using the Fast Fourier Transform (FFT) method and convolving it with the source distribution. We also present a direct application of this method to the long-range radiation field of Lyman-Werner band photons, which is important in the high-redshift astrophysics with first stars.

  19. Free vector propagator in the light-cone gauge and the Mandelstam-Leibbrandt prescription

    SciTech Connect

    Bassetto, A. Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova )

    1992-10-15

    We show that the Mandelstam-Leibbrandt causal prescription in the light-cone gauge leads to a free vector propagator which is a tempered distribution, at variance with the Cauchy principal-value prescription and other ones related to it by residual gauge transformations, which unavoidably entail infrared singularities already at the free level of the theory. In this respect the causal prescription seems to enjoy a privileged status.

  20. Black hole perturbation theory in a light cone gauge

    NASA Astrophysics Data System (ADS)

    Preston, Brent

    The metric of a Schwarzschild black hole immersed in a uniform magnetic field is studied using black hole perturbation theory in a light crone coordinate system that penetrates the event horizon and possesses a clear geometrical meaning. The magnetic field, which is distorted due to the presence of the black hole, has strength B which is assumed to be small compared to the curvature of the spacetime which allows the perturbed metric to be calculated to order B 2 only. The coordinates allow for an easy identification of the event horizon and the properties of the perturbed black hole are studied. To interpret this perturbed metric, the advanced coordinates are decomposed into irreducible parts which yields the metric of a perturbed black hole in the limit r >> 2 M . Finally we compare our perturbed solution to an exact solution. We show that our perturbed solution is able to match the exact solution but has the freedom to describe a larger class of physically relevant solutions.

  1. Light-induced Ca2+ release in the visible cones of the zebrafish.

    PubMed

    Cilluffo, Marianne C; Matthews, Hugh R; Brockerhoff, Susan E; Fain, Gordon L

    2004-01-01

    We used suction-pipette recording and fluo-4 fluorescence to study light-induced Ca2+ release from the visible double cones of zebrafish. In Ringer, light produces a slow decrease in fluorescence which can be fitted by the sum of two decaying exponentials with time constants of 0.5 and 3.8 s. In 0Ca2+-0Na+ solution, for which fluxes of Ca2+ across the outer segment plasma membrane are greatly reduced, light produces a slow increase in fluorescence. Both the decrease and increase are delayed after incorporation of the Ca2+ chelator BAPTA, indicating that both are produced by a change in Ca2+. If the Ca2+ pool is first released by bright light in 0Ca2+-0Na+ solution and the cone returned to Ringer, the time course of Ca2+ decline is much faster than in Ringer without previous light exposure. This indicates that the time constants of 0.5 and 3.8 s actually reflect a sum of Na+/Ca2+-K+ exchange and light-induced release of Ca2+. The Ca2+ released by light appears to come from at least two sites, the first comprising 66% of the total pool and half-released by bleaching 4.8% of the pigment. Release of the remaining Ca2+ from the second site requires the bleaching of nearly all of the pigment. If, after release, the cone is maintained in darkness, a substantial fraction of the Ca2+ returns to the release pool even in the absence of pigment regeneration. The light-induced release of Ca2+ can produce a modulation of the dark current as large as 0.75 pA independently of the normal transduction cascade, though the rise time of the current is considerably slower than the normal light response. These experiments show that Ca2+ can be released within the cone outer segment by light intensities within the physiological range of photopic vision. The role this Ca2+ release plays remains unresolved. PMID:15579223

  2. Melanopsin and rod-cone photoreceptors play different roles in mediating pupillary light responses during exposure to continuous light in humans.

    PubMed

    Gooley, Joshua J; Ho Mien, Ivan; St Hilaire, Melissa A; Yeo, Sing-Chen; Chua, Eric Chern-Pin; van Reen, Eliza; Hanley, Catherine J; Hull, Joseph T; Czeisler, Charles A; Lockley, Steven W

    2012-10-10

    In mammals, the pupillary light reflex is mediated by intrinsically photosensitive melanopsin-containing retinal ganglion cells that also receive input from rod-cone photoreceptors. To assess the relative contribution of melanopsin and rod-cone photoreceptors to the pupillary light reflex in humans, we compared pupillary light responses in normally sighted individuals (n = 24) with a blind individual lacking rod-cone function. Here, we show that visual photoreceptors are required for normal pupillary responses to continuous light exposure at low irradiance levels, and for sustained pupillary constriction during exposure to light in the long-wavelength portion of the visual spectrum. In the absence of rod-cone function, pupillomotor responses are slow and sustained, and cannot track intermittent light stimuli, suggesting that rods/cones are required for encoding fast modulations in light intensity. In sighted individuals, pupillary constriction decreased monotonically for at least 30 min during exposure to continuous low-irradiance light, indicating that steady-state pupillary responses are an order of magnitude slower than previously reported. Exposure to low-irradiance intermittent green light (543 nm; 0.1-4 Hz) for 30 min, which was given to activate cone photoreceptors repeatedly, elicited sustained pupillary constriction responses that were more than twice as great compared with exposure to continuous green light. Our findings demonstrate nonredundant roles for rod-cone photoreceptors and melanopsin in mediating pupillary responses to continuous light. Moreover, our results suggest that it might be possible to enhance nonvisual light responses to low-irradiance exposures by using intermittent light to activate cone photoreceptors repeatedly in humans. PMID:23055493

  3. 21 cm signal from cosmic dawn - II. Imprints of the light-cone effects

    NASA Astrophysics Data System (ADS)

    Ghara, Raghunath; Datta, Kanan K.; Choudhury, T. Roy

    2015-11-01

    Details of various unknown physical processes during the cosmic dawn and the epoch of reionization can be extracted from observations of the redshifted 21 cm signal. These observations, however, will be affected by the evolution of the signal along the line of sight which is known as the `light-cone effect'. We model this effect by post-processing a dark matter N-body simulation with an 1D radiative transfer code. We find that the effect is much stronger and dramatic in presence of inhomogeneous heating and Ly α coupling compared to the case where these processes are not accounted for. One finds increase (decrease) in the spherically averaged power spectrum up to a factor of 3 (0.6) at large scales (k ˜ 0.05 Mpc- 1) when the light-cone effect is included, though these numbers are highly dependent on the source model. The effect is particularly significant near the peak and dip-like features seen in the power spectrum. The peaks and dips are suppressed and thus the power spectrum can be smoothed out to a large extent if the width of the frequency band used in the experiment is large. We argue that it is important to account for the light-cone effect for any 21-cm signal prediction during cosmic dawn.

  4. Automatic detection of cone photoreceptors in split detector adaptive optics scanning light ophthalmoscope images

    PubMed Central

    Cunefare, David; Cooper, Robert F.; Higgins, Brian; Katz, David F.; Dubra, Alfredo; Carroll, Joseph; Farsiu, Sina

    2016-01-01

    Quantitative analysis of the cone photoreceptor mosaic in the living retina is potentially useful for early diagnosis and prognosis of many ocular diseases. Non-confocal split detector based adaptive optics scanning light ophthalmoscope (AOSLO) imaging reveals the cone photoreceptor inner segment mosaics often not visualized on confocal AOSLO imaging. Despite recent advances in automated cone segmentation algorithms for confocal AOSLO imagery, quantitative analysis of split detector AOSLO images is currently a time-consuming manual process. In this paper, we present the fully automatic adaptive filtering and local detection (AFLD) method for detecting cones in split detector AOSLO images. We validated our algorithm on 80 images from 10 subjects, showing an overall mean Dice’s coefficient of 0.95 (standard deviation 0.03), when comparing our AFLD algorithm to an expert grader. This is comparable to the inter-observer Dice’s coefficient of 0.94 (standard deviation 0.04). To the best of our knowledge, this is the first validated, fully-automated segmentation method which has been applied to split detector AOSLO images. PMID:27231641

  5. Automatic detection of cone photoreceptors in split detector adaptive optics scanning light ophthalmoscope images.

    PubMed

    Cunefare, David; Cooper, Robert F; Higgins, Brian; Katz, David F; Dubra, Alfredo; Carroll, Joseph; Farsiu, Sina

    2016-05-01

    Quantitative analysis of the cone photoreceptor mosaic in the living retina is potentially useful for early diagnosis and prognosis of many ocular diseases. Non-confocal split detector based adaptive optics scanning light ophthalmoscope (AOSLO) imaging reveals the cone photoreceptor inner segment mosaics often not visualized on confocal AOSLO imaging. Despite recent advances in automated cone segmentation algorithms for confocal AOSLO imagery, quantitative analysis of split detector AOSLO images is currently a time-consuming manual process. In this paper, we present the fully automatic adaptive filtering and local detection (AFLD) method for detecting cones in split detector AOSLO images. We validated our algorithm on 80 images from 10 subjects, showing an overall mean Dice's coefficient of 0.95 (standard deviation 0.03), when comparing our AFLD algorithm to an expert grader. This is comparable to the inter-observer Dice's coefficient of 0.94 (standard deviation 0.04). To the best of our knowledge, this is the first validated, fully-automated segmentation method which has been applied to split detector AOSLO images. PMID:27231641

  6. Baryon-Baryon-Meson Coupling Constants in QCD

    SciTech Connect

    Aliev, T. M.; Ozpineci, A.; Savci, M.; Azizi, K.; Zamiralov, V.

    2010-12-22

    The strong coupling constant of decuplet and octet baryons to vector and pseudoscalar mesons are calculated in light cone QCD sum rules in general case and when the SU(3){sub f} symmetry is taken into account. A comparison of the obtained results with the existing experimental data and predictions of the other nonperturbative approaches is also made.

  7. Possible Roles of Glutamate Transporter EAAT5 in Mouse Cone Depolarizing Bipolar Cell Light Responses

    PubMed Central

    Tse, Dennis Y.; Chung, Inyoung; Wu, Samuel M.

    2015-01-01

    A remarkable feature of neuronal glutamate transporters (EAATs) is their dual functions of classical carriers and ligand-gated chloride (CI−) channels. CI− conductance is rapidly activated by glutamate in subtype EAAT5, which mediates light responses in depolarizing bipolar cells (DBC) in retinae of lower vertebrates. In this study, we examine whether EAAT5 also mediates the DBC light response in mouse. We took advantage of an infrared illuminated micro-injection system, and studied the effects of the EAAT blocker (TBOA) and a glutamate receptor agonist (LAP4) on the mouse electroretinogram (ERG) b-wave responses. Our results showed that TBOA and LAP4 shared similar temporal patterns of inhibition: both inhibited the ERG b-wave shortly after injection and recovered with similar time courses. TBOA inhibited the b-wave completely at mesopic light intensity with an IC50 value about 1 log unit higher than that of LAP4. The inhibitory effects of TBOA and LAP4 were found to be additive in the photopic range. Furthermore, TBOA alone inhibited the b-wave in the cone operative range in knockout mice lacking DBCRs at a low concentration that did not alter synaptic glutamate clearance activity. It also produced a stronger inhibition than that of LAP4 on the cone-driven b-wave measured with a double flash method in wildtype mice. These electrophysiological data suggest a significant role for EAAT5 in mediating cone-driven DBC light responses. Our immunohistochemistry data indicated the presence of postsynaptic EAAT5 on some DBCCs and some DBCRs, providing an anatomical basis for EAAT5’s role in DBC light responses. PMID:24972005

  8. Quark transversity distribution in perturbative QCD: light-front Hamiltonian approach

    NASA Astrophysics Data System (ADS)

    Mukherjee, A.; Chakrabarti, D.

    2001-05-01

    To resolve the current ambiguity in the splitting function corresponding to the quark transversity distribution h1(x), we calculate h1(x) for a dressed quark in light-front Hamiltonian perturbation theory. Our result agrees with the expected form of the splitting function found in the literature and disagrees with the recent calculation in M. Meyer-Hermann et al., hep-ph/0012226. We emphasize the importance of quark mass in h1(x) in perturbative QCD and show its connection with a part of gT.

  9. EML1 (CNG-Modulin) Controls Light Sensitivity in Darkness and under Continuous Illumination in Zebrafish Retinal Cone Photoreceptors

    PubMed Central

    Mehta, Milap; Tserentsoodol, Nomingerel; Postlethwait, John H.; Rebrik, Tatiana I.

    2013-01-01

    The ligand sensitivity of cGMP-gated (CNG) ion channels in cone photoreceptors is modulated by CNG-modulin, a Ca2+-binding protein. We investigated the functional role of CNG-modulin in phototransduction in vivo in morpholino-mediated gene knockdown zebrafish. Through comparative genomic analysis, we identified the orthologue gene of CNG-modulin in zebrafish, eml1, an ancient gene present in the genome of all vertebrates sequenced to date. We compare the photoresponses of wild-type cones with those of cones that do not express the EML1 protein. In the absence of EML1, dark-adapted cones are ∼5.3-fold more light sensitive than wild-type cones. Previous qualitative studies in several nonmammalian species have shown that immediately after the onset of continuous illumination, cones are less light sensitive than in darkness, but sensitivity then recovers over the following 15–20 s. We characterize light sensitivity recovery in continuously illuminated wild-type zebrafish cones and demonstrate that sensitivity recovery does not occur in the absence of EML1. PMID:24198367

  10. Light-cone-like spreading of correlations in a quantum many-body system.

    PubMed

    Cheneau, Marc; Barmettler, Peter; Poletti, Dario; Endres, Manuel; Schauss, Peter; Fukuhara, Takeshi; Gross, Christian; Bloch, Immanuel; Kollath, Corinna; Kuhr, Stefan

    2012-01-26

    In relativistic quantum field theory, information propagation is bounded by the speed of light. No such limit exists in the non-relativistic case, although in real physical systems, short-range interactions may be expected to restrict the propagation of information to finite velocities. The question of how fast correlations can spread in quantum many-body systems has been long studied. The existence of a maximal velocity, known as the Lieb-Robinson bound, has been shown theoretically to exist in several interacting many-body systems (for example, spins on a lattice)--such systems can be regarded as exhibiting an effective light cone that bounds the propagation speed of correlations. The existence of such a 'speed of light' has profound implications for condensed matter physics and quantum information, but has not been observed experimentally. Here we report the time-resolved detection of propagating correlations in an interacting quantum many-body system. By quenching a one-dimensional quantum gas in an optical lattice, we reveal how quasiparticle pairs transport correlations with a finite velocity across the system, resulting in an effective light cone for the quantum dynamics. Our results open perspectives for understanding the relaxation of closed quantum systems far from equilibrium, and for engineering the efficient quantum channels necessary for fast quantum computations. PMID:22281597

  11. Gluon distributions and color charge correlations in a saturated light-cone wavefunction

    NASA Astrophysics Data System (ADS)

    Mueller, A. H.

    2002-11-01

    We describe the light-cone wavefunction in the saturation regime in terms of the density of gluons per unit of transverse phase space, the occupation number, and in terms of the color charge correlator. The simple McLerran-Venugopalan model gives what are claimed to be general results for the phase space gluon density, but it does not well describe the general case for the charge correlator. We derive the general momentum dependence and rapidity dependence of the color charge correlator which exhibits strong color shielding. A simple physical picture which leads to these general results is described.

  12. The geometry of the light-cone cell decomposition of moduli space

    SciTech Connect

    Garner, David Ramgoolam, Sanjaye

    2015-11-15

    The moduli space of Riemann surfaces with at least two punctures can be decomposed into a cell complex by using a particular family of ribbon graphs called Nakamura graphs. We distinguish the moduli space with all punctures labelled from that with a single labelled puncture. In both cases, we describe a cell decomposition where the cells are parametrised by graphs or equivalence classes of finite sequences (tuples) of permutations. Each cell is a convex polytope defined by a system of linear equations and inequalities relating light-cone string parameters, quotiented by the automorphism group of the graph. We give explicit examples of the cell decomposition at low genus with few punctures.

  13. Mesons in (2+1)-dimensional light front QCD: Investigation of a Bloch effective Hamiltonian

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Dipankar; Harindranath, A.

    2001-11-01

    We study the meson sector of (2+1)-dimensional light front QCD using a Bloch effective Hamiltonian in the first nontrivial order. The resulting two-dimensional integral equation is converted into a matrix equation and solved numerically. We investigate the efficiency of Gaussian quadrature in achieving the cancellation of linear and logarithmic light front infrared divergences. The vanishing energy denominator problem, which leads to severe infrared divergences in 2+1 dimensions, is investigated in detail. Our study indicates that in the context of Fock space based effective Hamiltonian methods to tackle gauge theories in 2+1 dimensions, approaches such as the similarity renormalization method may be mandatory due to uncanceled infrared divergences caused by the vanishing energy denominator problem. We define and numerically study a reduced model which is relativistic, free from infrared divergences, and exhibits logarithmic confinement. The manifestation and violation of rotational symmetry as a function of the coupling are studied quantitatively.

  14. Hadronic Spectra and Light-Front Wave Functions in Holographic QCD

    SciTech Connect

    Brodsky, Stanley J.; Teramond, Guy F. de

    2006-05-26

    We show how the string amplitude {phi}(z) defined on the fifth dimension in AdS{sub 5} space can be precisely mapped to the light-front wave functions of hadrons in physical space-time. We find an exact correspondence between the holographic variable z and an impact variable {zeta}, which represents the measure of transverse separation of the constituents within the hadrons. In addition, we derive effective four dimensional Schroedinger equations for the bound states of massless quarks and gluons which exactly reproduce the anti-de Sitter conformal field theory results and give a realistic description of the light-quark meson and baryon spectrum as well as the form factors for spacelike Q{sup 2}. Only one parameter which sets the mass scale, {lambda}{sub QCD}, is introduced.

  15. The Light-Front Schrödinger Equation and the Determination of the Perturbative QCD Scale from Color Confinement: A First Approximation to QCD

    NASA Astrophysics Data System (ADS)

    Brodsky, Stanley J.; de Téramond, Guy F.; Deur, Alexandre; Dosch, Hans Günter

    2015-09-01

    The valence Fock-state wavefunctions of the light-front (LF) QCD Hamiltonian satisfy a relativistic equation of motion, analogous to the nonrelativistic radial Schrödinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. If one requires that the effective action which underlies the QCD Lagrangian remains conformally invariant and extends the formalism of de Alfaro, Fubini and Furlan to LF Hamiltonian theory, the potential U has a unique form of a harmonic oscillator potential, and a mass gap arises. The result is a nonperturbative relativistic LF quantum mechanical wave equation which incorporates color confinement and other essential spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the same slope in the radial quantum number n and orbital angular momentum L. Only one mass parameter κ appears. The corresponding LF Dirac equation provides a dynamical and spectroscopic model of nucleons. The same LF equations arise from the holographic mapping of the soft-wall model modification of AdS5 space with a unique dilaton profile to QCD (3+1) at fixed LF time. LF holography thus provides a precise relation between the bound-state amplitudes in the fifth dimension of Anti-de Sitter (AdS) space and the boost-invariant LFWFs describing the internal structure of hadrons in physical space-time. We also show how the mass scale underlying confinement and the masses of light-quark hadrons determines the scale controlling the evolution of the perturbative QCD coupling. The relation between scales is obtained by matching the nonperturbative dynamics, as described by an effective conformal theory mapped to the LF and its embedding in AdS space, to the perturbative QCD regime computed to four-loop order. The data for the effective coupling defined from the Bjorken sum rule are remarkably consistent with the

  16. Nonperturbative QCD Coupling and its $$\\beta$$-function from Light-Front Holography

    DOE PAGESBeta

    Brodskey, Stanley J.; de Teramond, Guy; Deur, Alexandre P.

    2010-05-28

    The light-front holographic mapping of classical gravity in AdS space, modified by a positive-sign dilaton background, leads to a non-perturbative effective couplingmore » $$\\alpha_s^{AdS}(Q^2)$$. It agrees with hadron physics data extracted from different observables, such as the effective charge defined by the Bjorken sum rule, as well as with the predictions of models with built-in confinement and lattice simulations. It also displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale $$ \\sim 1$$ GeV. The resulting $$\\beta$$-function appears to capture the essential characteristics of the full $$\\beta$$-function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD. Commensurate scale relations relate observables to each other without scheme or scale ambiguity. In this paper we extrapolate these relations to the nonperturbative domain, thus extending the range of predictions based on $$\\alpha_s^{AdS}(Q^2)$$.« less

  17. Nonperturbative QCD coupling and its {beta} function from light-front holography

    SciTech Connect

    Brodsky, Stanley J.; Teramond, Guy F. de; Deur, Alexandre

    2010-05-01

    The light-front holographic mapping of classical gravity in anti-de Sitter space, modified by a positive-sign dilaton background, leads to a nonperturbative effective coupling {alpha}{sub s}{sup AdS}(Q{sup 2}). It agrees with hadron physics data extracted from different observables, such as the effective charge defined by the Bjorken sum rule, as well as with the predictions of models with built-in confinement and lattice simulations. It also displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale {approx}1 GeV. The resulting {beta} function appears to capture the essential characteristics of the full {beta} function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD. Commensurate scale relations relate observables to each other without scheme or scale ambiguity. In this paper we extrapolate these relations to the nonperturbative domain, thus extending the range of predictions based on {alpha}{sub s}{sup AdS}(Q{sup 2}).

  18. Nonperturbative QCD coupling and its β function from light-front holography

    NASA Astrophysics Data System (ADS)

    Brodsky, Stanley J.; de Téramond, Guy F.; Deur, Alexandre

    2010-05-01

    The light-front holographic mapping of classical gravity in anti-de Sitter space, modified by a positive-sign dilaton background, leads to a nonperturbative effective coupling αsAdS(Q2). It agrees with hadron physics data extracted from different observables, such as the effective charge defined by the Bjorken sum rule, as well as with the predictions of models with built-in confinement and lattice simulations. It also displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale ˜1GeV. The resulting β function appears to capture the essential characteristics of the full β function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD. Commensurate scale relations relate observables to each other without scheme or scale ambiguity. In this paper we extrapolate these relations to the nonperturbative domain, thus extending the range of predictions based on αsAdS(Q2).

  19. Non-Perturbative QCD Coupling and Beta Function from Light Front Holography

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; Deur, Alexandre

    2010-05-26

    The light-front holographic mapping of classical gravity in AdS space, modified by a positive-sign dilaton background, leads to a non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q{sup 2}). It agrees with hadron physics data extracted from different observables, such as the effective charge defined by the Bjorken sum rule, as well as with the predictions of models with built-in confinement and lattice simulations. It also displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale {approx} 1 GeV. The resulting {beta}-function appears to capture the essential characteristics of the full {beta}-function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD. Commensurate scale relations relate observables to each other without scheme or scale ambiguity. In this paper we extrapolate these relations to the nonperturbative domain, thus extending the range of predictions based on {alpha}{sub s}{sup AdS} (Q{sup 2}).

  20. Nonperturbative QCD Coupling and its $\\beta$-function from Light-Front Holography

    SciTech Connect

    Brodskey, Stanley J.; de Teramond, Guy; Deur, Alexandre P.

    2010-05-28

    The light-front holographic mapping of classical gravity in AdS space, modified by a positive-sign dilaton background, leads to a non-perturbative effective coupling $\\alpha_s^{AdS}(Q^2)$. It agrees with hadron physics data extracted from different observables, such as the effective charge defined by the Bjorken sum rule, as well as with the predictions of models with built-in confinement and lattice simulations. It also displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale $ \\sim 1$ GeV. The resulting $\\beta$-function appears to capture the essential characteristics of the full $\\beta$-function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD. Commensurate scale relations relate observables to each other without scheme or scale ambiguity. In this paper we extrapolate these relations to the nonperturbative domain, thus extending the range of predictions based on $\\alpha_s^{AdS}(Q^2)$.

  1. Orbital structure of quarks inside the nucleon in the light-cone diquark model

    SciTech Connect

    Lu Zhun; Schmidt, Ivan

    2010-11-01

    We study the orbital angular momentum structure of the quarks inside the proton. By employing the light-cone diquark model and the overlap representation formalism, we calculate the chiral-even generalized parton distribution functions H{sub q}(x,{xi},{Delta}{sup 2}), H-tilde{sub q}(x,{xi},{Delta}{sup 2}), and E{sub q}(x,{xi},{Delta}{sup 2}) at zero skewedness for q=u and d quarks. In our model, E{sub u} and E{sub d} have opposite sign with similar size. Those generalized parton distribution functions are applied to calculate the orbital angular momentum distributions, showing that L{sub u}(x) is positive, while L{sub d}(x) is consistent with zero compared with L{sub u}(x). We introduce the impact parameter dependence of the quark orbital angular momentum distribution. It describes the position space distribution of the quark orbital angular momentum at given x. We found that the impact parameter dependence of the quark orbital angular momentum distribution is axially symmetric in the light-cone diquark model.

  2. Automated laser guidance of neuronal growth cones using a spatial light modulator.

    PubMed

    Carnegie, David J; Cizmár, Tomás; Baumgartl, Jörg; Gunn-Moore, Frank J; Dholakia, Kishan

    2009-11-01

    The growth cone of a developing neuron can be guided using a focused infra-red (IR) laser beam [1]. In previous setups this process has required a significant amount of user intervention to adjust continuously the laser beam to guide the growing neuron. Previously, a system using an acousto-optical deflector (AOD) has been developed to steer the beam [2]. However, to enhance the controllability of this system, here we demonstrate the use of a computer controlled spatial light modulator (SLM) to steer and manipulate the shape of a laser beam for use in guided neuronal growth. This new experimental setup paves the way to enable a comprehensive investigation into beam shaping effects on neuronal growth and we show neuronal growth initiated by a Bessel light mode. This is a robust platform to explore the biochemistry of this novel phenomenon. PMID:19705368

  3. Effects of Intraframe Distortion on Measures of Cone Mosaic Geometry from Adaptive Optics Scanning Light Ophthalmoscopy

    PubMed Central

    Cooper, Robert F.; Sulai, Yusufu N.; Dubis, Adam M.; Chui, Toco Y.; Rosen, Richard B.; Michaelides, Michel; Dubra, Alfredo; Carroll, Joseph

    2016-01-01

    Purpose To characterize the effects of intraframe distortion due to involuntary eye motion on measures of cone mosaic geometry derived from adaptive optics scanning light ophthalmoscope (AOSLO) images. Methods We acquired AOSLO image sequences from 20 subjects at 1.0, 2.0, and 5.0° temporal from fixation. An expert grader manually selected 10 minimally distorted reference frames from each 150-frame sequence for subsequent registration. Cone mosaic geometry was measured in all registered images (n = 600) using multiple metrics, and the repeatability of these metrics was used to assess the impact of the distortions from each reference frame. In nine additional subjects, we compared AOSLO-derived measurements to those from adaptive optics (AO)-fundus images, which do not contain system-imposed intraframe distortions. Results We observed substantial variation across subjects in the repeatability of density (1.2%–8.7%), inter-cell distance (0.8%–4.6%), percentage of six-sided Voronoi cells (0.8%–10.6%), and Voronoi cell area regularity (VCAR) (1.2%–13.2%). The average of all metrics extracted from AOSLO images (with the exception of VCAR) was not significantly different than those derived from AO-fundus images, though there was variability between individual images. Conclusions Our data demonstrate that the intraframe distortion found in AOSLO images can affect the accuracy and repeatability of cone mosaic metrics. It may be possible to use multiple images from the same retinal area to approximate a “distortionless” image, though more work is needed to evaluate the feasibility of this approach. Translational Relevance Even in subjects with good fixation, images from AOSLOs contain intraframe distortions due to eye motion during scanning. The existence of these artifacts emphasizes the need for caution when interpreting results derived from scanning instruments. PMID:26933523

  4. Direct Measurement of the Pion Valence-Quark Momentum Distribution, the Pion Light-Cone Wave Function Squared

    NASA Astrophysics Data System (ADS)

    Aitala, E. M.; Amato, S.; Anjos, J. C.; Appel, J. A.; Ashery, D.; Banerjee, S.; Bediaga, I.; Blaylock, G.; Bracker, S. B.; Burchat, P. R.; Burnstein, R. A.; Carter, T.; Carvalho, H. S.; Copty, N. K.; Cremaldi, L. M.; Darling, C.; Denisenko, K.; Deval, S.; Fernandez, A.; Fox, G. F.; Gagnon, P.; Gerzon, S.; Gobel, C.; Gounder, K.; Halling, A. M.; Herrera, G.; Hurvits, G.; James, C.; Kasper, P. A.; Kwan, S.; Langs, D. C.; Leslie, J.; Lichtenstadt, J.; Lundberg, B.; Maytal-Beck, S.; Meadows, B.; de Mello Neto, J. R.; Mihalcea, D.; Milburn, R. H.; de Miranda, J. M.; Napier, A.; Nguyen, A.; D'Oliveira, A. B.; O'Shaughnessy, K.; Peng, K. C.; Perera, L. P.; Purohit, M. V.; Quinn, B.; Radeztsky, S.; Rafatian, A.; Reay, N. W.; Reidy, J. J.; Dos Reis, A. C.; Rubin, H. A.; Sanders, D. A.; Santha, A. K.; Santoro, A. F.; Schwartz, A. J.; Sheaff, M.; Sidwell, R. A.; Slaughter, A. J.; Sokoloff, M. D.; Solano, J.; Stanton, N. R.; Stefanski, R. J.; Stenson, K.; Summers, D. J.; Takach, S.; Thorne, K.; Tripathi, A. K.; Watanabe, S.; Weiss-Babai, R.; Wiener, J.; Witchey, N.; Wolin, E.; Yang, S. M.; Yi, D.; Yoshida, S.; Zaliznyak, R.; Zhang, C.

    2001-05-01

    We present the first direct measurements of the pion valence-quark momentum distribution which is related to the square of the pion light-cone wave function. The measurements were carried out using data on diffractive dissociation of 500 GeV/c π- into dijets from a platinum target at Fermilab experiment E791. The results show that the \\|qq¯> light-cone asymptotic wave function describes the data well for Q2~10 \\(GeV/c\\)2 or more. We also measured the transverse momentum distribution of the diffractive dijets.

  5. Light-cone anisotropy in the 21 cm signal from the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Zawada, Karolina; Semelin, Benoît; Vonlanthen, Patrick; Baek, Sunghye; Revaz, Yves

    2014-04-01

    Using a suite of detailed numerical simulations, we estimate the level of anisotropy generated by the time evolution along the light cone of the 21 cm signal from the epoch of reionization. Our simulations include the physics necessary to model the signal during both the late emission regime and the early absorption regime, namely X-ray and Lyman band 3D radiative transfer in addition to the usual dynamics and ionizing UV transfer. The signal is analysed using correlation functions perpendicular and parallel to the line of sight. We reproduce general findings from previous theoretical studies: the overall amplitude of the correlations and the fact that the light-cone anisotropy is visible only on large scales (100 comoving Mpc). However, the detailed behaviour is different. We find that, at three different epochs, the amplitudes of the correlations along and perpendicular to the line of sight differ from each other, indicating anisotropy. We show that these three epochs are associated with three events of the global reionization history: the overlap of ionized bubbles, the onset of mild heating by X-rays in regions around the sources, and the onset of efficient Lyman α coupling in regions around the sources. We find that a 20 × 20 deg2 survey area may be necessary to mitigate sample variance when we use the directional correlation functions. On a 100 Mpc (comoving) scale, we show that the light-cone anisotropy dominates over the anisotropy generated by peculiar velocity gradients computed in the linear regime. By modelling instrumental noise and limited resolution, we find that the anisotropy should be easily detectable by the Square Kilometre Array, assuming perfect foreground removal, the limiting factor being a large enough survey size. In the case of the Low-Frequency Array for radio astronomy, it is likely that only one anisotropy episode (ionized bubble overlap) will fall in the observing frequency range. This episode will be detectable only if sample

  6. Light hadron spectroscopy in two-flavor QCD with small sea quark masses

    SciTech Connect

    Namekawa, Y.; Aoki, S.; Iwasaki, Y.; Kanaya, K.; Fukugita, M.; Ishikawa, K.-I.; Ishizuka, N.; Ukawa, A.; Yoshie, T.; Kaneko, T.; Kuramashi, Y.; Lesk, V. I.; Umeda, T.; Okawa, M.

    2004-10-01

    We extend the study of the light hadron spectrum and the quark mass in two-flavor QCD to smaller sea quark mass, corresponding to m{sub PS}/m{sub V}=0.60-0.35. Numerical simulations are carried out using the RG-improved gauge action and the meanfield-improved clover quark action at {beta}=1.8 (a=0.2 fm from {rho} meson mass). We observe that the light hadron spectrum for small sea quark mass does not follow the expectation from chiral extrapolations with quadratic functions made from the region of m{sub PS}/m{sub V}=0.80-0.55. Whereas fits with either polynomial or continuum chiral perturbation theory (ChPT) fail, the Wilson ChPT (WChPT) that includes a{sup 2} effects associated with explicit chiral symmetry breaking successfully fits the whole data: In particular, WChPT correctly predicts the light quark mass spectrum from simulations for medium heavy quark mass, such as m{sub PS}/m{sub V} > or approx. 0.5. Reanalyzing the previous data with the use of WChPT, we find the mean up and down quark mass being smaller than the previous result from quadratic chiral extrapolation by approximately 10%, m{sub ud}{sup MS-bar}({mu}=2 GeV)=3.11(17) [MeV] in the continuum limit.

  7. Hamiltonian formulation of the D-brane action and the light-cone Hamiltonian

    NASA Astrophysics Data System (ADS)

    Lee, Julian

    1998-04-01

    We present the Hamiltonian formulation of the bosonic Dirichlet p-brane action. We rewrite the recently proposed quadratic D-brane action in terms of generalized shift vector and lapse function. The first class and the second class constraints are explicitly separated for the bosonic case. We then impose the gauge conditions in such a way that only time-independent gauge transformations are left. In this gauge we obtain the light-cone Hamiltonian which is quadratic in the field momenta of scalar and vector fields. The constraints are explicitly solved to eliminate part of the canonical variables. The Dirac brackets between the remaining variables are computed and shown to be equal to simple Poisson brackets.

  8. On Quantization in Light-cone Variables Compatible with Wavelet Transform

    NASA Astrophysics Data System (ADS)

    Altaisky, M. V.; Kaputkina, N. E.

    2016-06-01

    Canonical quantization of quantum field theory models is inherently related to the Lorentz invariant partition of classical fields into the positive and the negative frequency parts u( x) = u +( x) + u -( x), performed with the help of Fourier transform in Minkowski space. That is the commutation relations are being established between nonlocalized solutions of field equations. At the same time the construction of divergence free physical theory requires the separation of the contributions of different space-time scales. In present paper, using the light-cone variables, we propose a quantization procedure which is compatible with separation of scales using continuous wavelet transform, as described in our previous paper (Altaisky, M.V., Kaputkina, N.E.: Phys. Rev. D 88, 025015 2013).

  9. The Light-Front Schrödinger Equation and Determination of the Perturbative QCD Scale from Color Confinement

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; Deur, Alexandre P.; Dosch, Hans G.

    2015-09-01

    The valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a relativistic equation of motion with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. If one requires that the effective action which underlies the QCD Lagrangian remains conformally invariant and extends the formalism of de Alfaro, Fubini and Furlan to light front Hamiltonian theory, the potential U has a unique form of a harmonic oscillator potential, and a mass gap arises. The result is a nonperturbative relativistic light-front quantum mechanical wave equation which incorporates color confinement and other essential spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the same slope in the radial quantum number n and orbital angular momentum L. Only one mass parameter κ appears. Light-front holography thus provides a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. We also show how the mass scale κ underlying confinement and hadron masses determines the scale Λ{ovr MS} controlling the evolution of the perturbative QCD coupling. The relation between scales is obtained by matching the nonperturbative dynamics, as described by an effective conformal theory mapped to the light-front and its embedding in AdS space, to the perturbative QCD regime computed to four-loop order. The result is an effective coupling defined at all momenta. The predicted value Λ{ovr MS}=0.328±0.034 GeV is in agreement with the world average 0.339±0.010 GeV. The analysis applies to any renormalization scheme.

  10. Light-heavy-ion collisions: a window into pre-equilibrium QCD dynamics?

    NASA Astrophysics Data System (ADS)

    Romatschke, P.

    2015-07-01

    Relativistic collisions of light on heavy ions (p + Au at GeV, p + Au , d + Au ,He + Au at GeV and 200 GeV and p + Pb ,He + Pb at TeV) are simulated using "superSONIC", a model that includes pre-equilibrium flow, viscous hydrodynamics and a hadronic cascade afterburner. Even though these systems have strong gradients and only consist of at most a few tens of charged particles per unit rapidity, one finds evidence that a hydrodynamic description applies to these systems. Based on these simulations, the presence of a triangular flow component in d + Au collisions at GeV is predicted to be similar in magnitude to that found in He + Au collisions. Furthermore, the ratio of He + Au to d + Au is found to be sensitive to the presence of pre-equilibrium flow. This would imply an experimentally accessible window into pre-equilibrium QCD dynamics using light-heavy-ion collisions.

  11. Light-output enhancement of GaN-based light-emitting diodes with three-dimensional backside reflectors patterned by microscale cone array.

    PubMed

    Huang, Huamao; Hu, Jinyong; Wang, Hong

    2014-01-01

    Three-dimensional (3D) backside reflector, compared with flat reflectors, can improve the probability of finding the escape cone for reflecting lights and thus enhance the light-extraction efficiency (LEE) for GaN-based light-emitting diode (LED) chips. A triangle-lattice of microscale SiO2 cone array followed by a 16-pair Ti3O5/SiO2 distributed Bragg reflector (16-DBR) was proposed to be attached on the backside of sapphire substrate, and the light-output enhancement was demonstrated by numerical simulation and experiments. The LED chips with flat reflectors or 3D reflectors were simulated using Monte Carlo ray tracing method. It is shown that the LEE increases as the reflectivity of backside reflector increases, and the light-output can be significantly improved by 3D reflectors compared to flat counterparts. It can also be observed that the LEE decreases as the refractive index of the cone material increases. The 3D 16-DBR patterned by microscale SiO2 cone array benefits large enhancement of LEE. This microscale pattern was prepared by standard photolithography and wet-etching technique. Measurement results show that the 3D 16-DBR can provide 12.1% enhancement of wall-plug efficiency, which is consistent with the simulated value of 11.73% for the enhancement of LEE. PMID:25133262

  12. Light-Output Enhancement of GaN-Based Light-Emitting Diodes with Three-Dimensional Backside Reflectors Patterned by Microscale Cone Array

    PubMed Central

    Hu, Jinyong; Wang, Hong

    2014-01-01

    Three-dimensional (3D) backside reflector, compared with flat reflectors, can improve the probability of finding the escape cone for reflecting lights and thus enhance the light-extraction efficiency (LEE) for GaN-based light-emitting diode (LED) chips. A triangle-lattice of microscale SiO2 cone array followed by a 16-pair Ti3O5/SiO2 distributed Bragg reflector (16-DBR) was proposed to be attached on the backside of sapphire substrate, and the light-output enhancement was demonstrated by numerical simulation and experiments. The LED chips with flat reflectors or 3D reflectors were simulated using Monte Carlo ray tracing method. It is shown that the LEE increases as the reflectivity of backside reflector increases, and the light-output can be significantly improved by 3D reflectors compared to flat counterparts. It can also be observed that the LEE decreases as the refractive index of the cone material increases. The 3D 16-DBR patterned by microscale SiO2 cone array benefits large enhancement of LEE. This microscale pattern was prepared by standard photolithography and wet-etching technique. Measurement results show that the 3D 16-DBR can provide 12.1% enhancement of wall-plug efficiency, which is consistent with the simulated value of 11.73% for the enhancement of LEE. PMID:25133262

  13. Pion-photon transition form factor using light-cone sum rules: theoretical results, expectations, and a global-data fit

    NASA Astrophysics Data System (ADS)

    Bakulev, A. P.; Mikhailov, S. V.; Pimikov, A. V.; Stefanis, N. G.

    2011-10-01

    A global fit to the data from different collaborations (CELLO, CLEO, BaBar) on the pion-photon transition form factor is carried out using light-cone sum rules. The analysis includes the next-to-leading QCD radiative corrections and the twist-four contributions, while the main next-to-next-to-leading term and the twist-six contribution are taken into account in the form of theoretical uncertainties. We use the information extracted from the data to investigate the pivotal characteristics of the pion distribution amplitude. This is done by dividing the data into two sets: one containing all data up to 9 GeV 2, whereas the other incorporates also the high- Q tail of the BaBar data. We find that it is not possible to accommodate into the fit these BaBar data points with the same accuracy and conclude that it is difficult to explain these data in the standard scheme of OCD.

  14. What has driven the evolution of multiple cone classes in visual systems: object contrast enhancement or light flicker elimination?

    PubMed Central

    2013-01-01

    Background Two competing theories have been advanced to explain the evolution of multiple cone classes in vertebrate eyes. These two theories have important, but different, implications for our understanding of the design and tuning of vertebrate visual systems. The ‘contrast theory’ proposes that multiple cone classes evolved in shallow-water fish to maximize the visual contrast of objects against diverse backgrounds. The competing ‘flicker theory’ states that multiple cone classes evolved to eliminate the light flicker inherent in shallow-water environments through antagonistic neural interactions, thereby enhancing object detection. However, the selective pressures that have driven the evolution of multiple cone classes remain largely obscure. Results We show that two critical assumptions of the flicker theory are violated. We found that the amplitude and temporal frequency of flicker vary over the visible spectrum, precluding its cancellation by simple antagonistic interactions between the output signals of cones. Moreover, we found that the temporal frequency of flicker matches the frequency where sensitivity is maximal in a wide range of fish taxa, suggesting that the flicker may actually enhance the detection of objects. Finally, using modeling of the chromatic contrast between fish pattern and background under flickering illumination, we found that the spectral sensitivity of cones in a cichlid focal species is optimally tuned to maximize the visual contrast between fish pattern and background, instead of to produce a flicker-free visual signal. Conclusions The violation of its two critical assumptions substantially undermines support for the flicker theory as originally formulated. While this alone does not support the contrast theory, comparison of the contrast and flicker theories revealed that the visual system of our focal species was tuned as predicted by the contrast theory rather than by the flicker theory (or by some combination of the two

  15. An exact Jacobi map in the geodesic light-cone gauge

    NASA Astrophysics Data System (ADS)

    Fanizza, G.; Gasperini, M.; Marozzi, G.; Veneziano, G.

    2013-11-01

    The remarkable properties of the recently proposed geodesic light-cone (GLC) gauge allow to explicitly solve the geodesic-deviation equation, and thus to derive an exact expression for the Jacobi map JAB(s,o) connecting a generic source s to a geodesic observer o in a generic space time. In this gauge JAB factorizes into the product of a local quantity at s times one at o, implying similarly factorized expressions for the area and luminosity distance. In any other coordinate system JAB is simply given by expressing the GLC quantities in terms of the corresponding ones in the new coordinates. This is explicitly done, at first and second order, respectively, for the synchronous and Poisson gauge-fixing of a perturbed, spatially-flat cosmological background, and the consistency of the two outcomes is checked. Our results slightly amend previous calculations of the luminosity-redshift relation and suggest a possible non-perturbative way for computing the effects of inhomogeneities on observations based on light-like signals.

  16. Effect of stimulus size and luminance on the rod-, cone-, and melanopsin-mediated pupillary light reflex.

    PubMed

    Park, Jason C; McAnany, J Jason

    2015-01-01

    This study determined if the pupillary light reflex (PLR) driven by brief stimulus presentations can be accounted for by the product of stimulus luminance and area (i.e., corneal flux density, CFD) under conditions biased toward the rod, cone, and melanopsin pathways. Five visually normal subjects participated in the study. Stimuli consisted of 1-s short- and long-wavelength flashes that spanned a large range of luminance and angular subtense. The stimuli were presented in the central visual field in the dark (rod and melanopsin conditions) and against a rod-suppressing short-wavelength background (cone condition). Rod- and cone-mediated PLRs were measured at the maximum constriction after stimulus onset whereas the melanopsin-mediated PLR was measured 5-7 s after stimulus offset. The rod- and melanopsin-mediated PLRs were well accounted for by CFD, such that doubling the stimulus luminance had the same effect on the PLR as doubling the stimulus area. Melanopsin-mediated PLRs were elicited only by short-wavelength, large (>16°) stimuli with luminance greater than 10 cd/m(2), but when present, the melanopsin-mediated PLR was well accounted for by CFD. In contrast, CFD could not account for the cone-mediated PLR because the PLR was approximately independent of stimulus size but strongly dependent on stimulus luminance. These findings highlight important differences in how stimulus luminance and size combine to govern the PLR elicited by brief flashes under rod-, cone-, and melanopsin-mediated conditions. PMID:25788707

  17. Cosmological implications of light sterile neutrinos produced after the QCD phase transition

    NASA Astrophysics Data System (ADS)

    Lello, Louis; Boyanovsky, Daniel

    2015-03-01

    We study the production of sterile neutrinos in the early Universe from π →l νs shortly after the QCD phase transition in the absence of a lepton asymmetry, while including finite-temperature corrections to the π mass and decay constant fπ. Sterile neutrinos with masses ≲1 MeV produced via this mechanism freeze out at Tf≃10 MeV with a distribution function that is highly nonthermal and that features a sharp enhancement at low momentum, thereby making this species cold even for very light masses. Dark matter abundance constraints from the cosmic microwave background and phase space density constraints from the most dark-matter-dominated dwarf spheroidal galaxies provide upper and lower bounds, respectively, on combinations of mass and mixing angles. For π →μ νs, the bounds lead to a narrow region of compatibility with the latest results from the 3.55-keV line. The nonthermal distribution function leads to free-streaming lengths (today) in the range of a few kpc, consistent with the observation of cores in dwarf galaxies. For sterile neutrinos with mass ≲1 eV that are produced by this reaction, the most recent accelerator and astrophysical bounds on Ul s combined with the nonthermal distribution function suggests a substantial contribution from these sterile neutrinos to Neff .

  18. Multi Dark Lens Simulations: weak lensing light-cones and data base presentation

    NASA Astrophysics Data System (ADS)

    Giocoli, Carlo; Jullo, Eric; Metcalf, R. Benton; de la Torre, Sylvain; Yepes, Gustavo; Prada, Francisco; Comparat, Johan; Göttlober, Stefan; Kyplin, Anatoly; Kneib, Jean-Paul; Petkova, Margarita; Shan, Huan Yuan; Tessore, Nicolas

    2016-09-01

    In this paper we present a large data base of weak lensing light cones constructed using different snapshots from the Big MultiDark simulation (BigMDPL). The ray-tracing through different multiple plane has been performed with the GLAMER code accounting both for single source redshifts and for sources distributed along the cosmic time. This first paper presents weak lensing forecasts and results according to the geometry of the VIPERS-W1 and VIPERS-W4 field of view. Additional fields will be available on our data base and new ones can be run upon request. Our data base also contains some tools for lensing analysis. In this paper we present results for convergence power spectra, one point and high order weak lensing statistics useful for forecasts and for cosmological studies. Covariance matrices have also been computed for the different realizations of the W1 and W4 fields. In addition we compute also galaxy-shear and projected density contrasts for different halo masses at two lens redshift according to the CFHTLS source redshift distribution both using stacking and cross-correlation techniques, finding very good agreement.

  19. MultiDarkLens Simulations: weak lensing light-cones and data base presentation

    NASA Astrophysics Data System (ADS)

    Giocoli, Carlo; Jullo, Eric; Metcalf, R. Benton; de la Torre, Sylvain; Yepes, Gustavo; Prada, Francisco; Comparat, Johan; Göttlober, Stefan; Kyplin, Anatoly; Kneib, Jean-Paul; Petkova, Margarita; Shan, HuanYuan; Tessore, Nicolas

    2016-06-01

    In this paper we present a large database of weak lensing light cones constructed using different snapshots from the Big MultiDark simulation (BigMDPL). The ray-tracing through different multiple plane has been performed with the GLAMER code accounting both for single source redshifts and for sources distributed along the cosmic time. This first paper presents weak lensing forecasts and results according to the geometry of the VIPERS-W1 and VIPERS-W4 field of view. Additional fields will be available on our database and new ones can be run upon request. Our database also contains some tools for lensing analysis. In this paper we present results for convergence power spectra, one point and high order weak lensing statistics useful for forecasts and for cosmological studies. Covariance matrices have also been computed for the different realisations of the W1 and W4 fields. In addition we compute also galaxy-shear and projected density contrasts for different halo masses at two lens redshift according to the CFHTLS source redshift distribution both using stacking and cross-correlation techniques, finding very good agreement.

  20. Factorization theorem for Drell-Yan at low q T and transverse-momentum distributions on-the-light-cone

    NASA Astrophysics Data System (ADS)

    Echevarría, Miguel G.; Idilbi, Ahmad; Scimemi, Ignazio

    2012-07-01

    We derive a factorization theorem for Drell-Yan process at low q T using effective field theory methods. In this theorem all the obtained quantities are gauge invariant and the special role of the soft function — and its subtraction thereof — is emphasized. We define transverse-momentum dependent parton distribution functions (TMDPDFs) which are free from light-cone singularities while all the Wilson lines are defined on-the-light-cone. We show explicitly to first order in α s that the partonic Feynman PDF can be obtained from the newly defined partonic TMDPDF by integrating over the transverse momentum of the parton inside the hadron. We obtain a resummed expression for the TMDPDF, and hence for the cross section, in impact parameter space. The universality of the newly defined matrix elements is established perturbatively to first order in α s . The factorization theorem is validated to first order in α s and also the gauge invariance between Feynman and light-cone gauges.

  1. CALCLENS: Curved-sky grAvitational Lensing for Cosmological Light conE simulatioNS

    NASA Astrophysics Data System (ADS)

    Becker, Matthew R.

    2012-10-01

    CALCLENS, written in C and employing widely available software libraries, efficiently computes weak gravitational lensing shear signals from large N-body light cone simulations over a curved sky. The algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift-dependent shear signals including corrections to the Born approximation by using multiple-plane ray tracing, and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multgrid methods. As a result, large areas of sky (~10,000 square degrees) can be ray traced efficiently at high-resolution using only a few hundred cores on widely available machines. Coupled with realistic galaxy populations placed in large N-body light cone simulations, CALCLENS is ideally suited for the construction of synthetic weak lensing shear catalogs to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys.

  2. Nambu-Goto Like Action for the AdS5 × S5 Superstrings in the Generalized Light-Cone Gauge

    NASA Astrophysics Data System (ADS)

    Itoyama, H.; Oota, T.; Yoshioka, R.

    2008-02-01

    We reinvestigate the κ-symmetry-fixed Green-Schwarz action in the AdS_5 × S^5 background in a version of the light-cone gauge. In the generalized light-cone gauge, the action has been written in the phase space variables. We convert it into the standard action written in terms of the fields and their derivatives. We thereby obtain a Nambu-Goto-type action which has the correct flat-space limit.

  3. Thermodynamics of lattice QCD with 2 light dynamical (staggered) quark flavours on a 16{sup 3} {times} 8 lattice

    SciTech Connect

    Gottlieb, S.; Krasnitz, A.; Heller, U.M.; Kennedy, A.D.; Kogut, J.B.; Liu, W.; Renken, R.L.; Sinclair, D.K.; Sugar, R.L.; Toussaint, D.; Wang, K.C.

    1991-12-31

    Lattice QCD with 2 light staggered quark flavours is being simulated on a 16{sup 3} {times} 8 lattice to study the transition from hadronic matter to a quark gluon plasma. We have completed runs at m{sub q} = 0.0125 and are extending this to m{sub q} = 0.00625. We also examine the addition of a non-dynamical ``strange`` quark. Thermodynamic order parameters are being measured across the transition and further into the plasma phase, as are various screening lengths. No evidence for a first order transition is seen, and we estimate the transition temperature to be {Tc} = 143(7)MeV.

  4. Thermodynamics of lattice QCD with 2 light dynamical (staggered) quark flavours on a 16 sup 3 times 8 lattice

    SciTech Connect

    Gottlieb, S.; Krasnitz, A. . Dept. of Physics); Heller, U.M.; Kennedy, A.D. . Supercomputer Computations Research Inst.); Kogut, J.B. . Dept. of Physics); Liu, W. ); Renken, R.L. (University of Central F

    1991-01-01

    Lattice QCD with 2 light staggered quark flavours is being simulated on a 16{sup 3} {times} 8 lattice to study the transition from hadronic matter to a quark gluon plasma. We have completed runs at m{sub q} = 0.0125 and are extending this to m{sub q} = 0.00625. We also examine the addition of a non-dynamical strange'' quark. Thermodynamic order parameters are being measured across the transition and further into the plasma phase, as are various screening lengths. No evidence for a first order transition is seen, and we estimate the transition temperature to be {Tc} = 143(7)MeV.

  5. Blue light-induced retinal lesions, intraretinal vascular leakage and edema formation in the all-cone mouse retina

    PubMed Central

    Geiger, P; Barben, M; Grimm, C; Samardzija, M

    2015-01-01

    Little is known about the mechanisms underlying macular degenerations, mainly for the scarcity of adequate experimental models to investigate cone cell death. Recently, we generated R91W;Nrl−/− double-mutant mice, which display a well-ordered all-cone retina with normal retinal vasculature and a strong photopic function that generates useful vision. Here we exposed R91W;Nrl−/− and wild-type (wt) mice to toxic levels of blue light and analyzed their retinas at different time points post illumination (up to 10 days). While exposure of wt mice resulted in massive pyknosis in a focal region of the outer nuclear layer (ONL), the exposure of R91W;Nrl−/− mice led to additional cell death detected within the inner nuclear layer. Microglia/macrophage infiltration at the site of injury was more pronounced in the all-cone retina of R91W;Nrl−/− than in wt mice. Similarly, vascular leakage was abundant in the inner and outer retina in R91W;Nrl−/− mice, whereas it was mild and restricted to the subretinal space in wt mice. This was accompanied by retinal swelling and the appearance of cystoid spaces in both inner and ONLs of R91W;Nrl−/− mice indicating edema in affected areas. In addition, basal expression levels of tight junction protein-1 encoding ZO1 were lower in R91W;Nrl−/− than in wt retinas. Collectively, our data suggest that exposure of R91W;Nrl−/− mice to blue light not only induces cone cell death but also disrupts the inner blood–retinal barrier. Macular edema in humans is a result of diffuse capillary leakage and microaneurysms in the macular region. Blue light exposure of the R91W;Nrl−/− mouse could therefore be used to study molecular events preceding edema formation in a cone-rich environment, and thus potentially help to develop treatment strategies for edema-based complications in macular degenerations. PMID:26583326

  6. Characterisation of light responses in the retina of mice lacking principle components of rod, cone and melanopsin phototransduction signalling pathways.

    PubMed

    Hughes, Steven; Rodgers, Jessica; Hickey, Doron; Foster, Russell G; Peirson, Stuart N; Hankins, Mark W

    2016-01-01

    Gnat(-/-), Cnga3(-/-), Opn4(-/-) triple knockout (TKO) mice lack essential components of phototransduction signalling pathways present in rods, cones and photosensitive retinal ganglion cells (pRGCs), and are therefore expected to lack all sensitivity to light. However, a number of studies have shown that light responses persist in these mice. In this study we use multielectrode array (MEA) recordings and light-induced c-fos expression to further characterise the light responses of the TKO retina. Small, but robust electroretinogram type responses are routinely detected during MEA recordings, with properties consistent with rod driven responses. Furthermore, a distinctive pattern of light-induced c-fos expression is evident in the TKO retina, with c-fos expression largely restricted to a small subset of amacrine cells that express disabled-1 (Dab1) but lack expression of glycine transporter-1 (GlyT-1). Collectively these data are consistent with the persistence of a novel light sensing pathway in the TKO retina that originates in rod photoreceptors, potentially a rare subset of rods with distinct functional properties, and which is propagated to an atypical subtype of AII amacrine cells. Furthermore, the minimal responses observed following UV light stimulation suggest only a limited role for the non-visual opsin OPN5 in driving excitatory light responses within the mouse retina. PMID:27301998

  7. Characterisation of light responses in the retina of mice lacking principle components of rod, cone and melanopsin phototransduction signalling pathways

    PubMed Central

    Hughes, Steven; Rodgers, Jessica; Hickey, Doron; Foster, Russell G.; Peirson, Stuart N.; Hankins, Mark W.

    2016-01-01

    Gnat−/−, Cnga3−/−, Opn4−/− triple knockout (TKO) mice lack essential components of phototransduction signalling pathways present in rods, cones and photosensitive retinal ganglion cells (pRGCs), and are therefore expected to lack all sensitivity to light. However, a number of studies have shown that light responses persist in these mice. In this study we use multielectrode array (MEA) recordings and light-induced c-fos expression to further characterise the light responses of the TKO retina. Small, but robust electroretinogram type responses are routinely detected during MEA recordings, with properties consistent with rod driven responses. Furthermore, a distinctive pattern of light-induced c-fos expression is evident in the TKO retina, with c-fos expression largely restricted to a small subset of amacrine cells that express disabled-1 (Dab1) but lack expression of glycine transporter-1 (GlyT-1). Collectively these data are consistent with the persistence of a novel light sensing pathway in the TKO retina that originates in rod photoreceptors, potentially a rare subset of rods with distinct functional properties, and which is propagated to an atypical subtype of AII amacrine cells. Furthermore, the minimal responses observed following UV light stimulation suggest only a limited role for the non-visual opsin OPN5 in driving excitatory light responses within the mouse retina. PMID:27301998

  8. Stray light in cone beam optical computed tomography: I. Measurement and reduction strategies with planar diffuse source.

    PubMed

    Granton, Patrick V; Dekker, Kurtis H; Battista, Jerry J; Jordan, Kevin J

    2016-04-01

    Optical cone-beam computed tomographic (CBCT) scanning of 3D radiochromic dosimeters may provide a practical method for 3D dose verification in radiation therapy. However, in cone-beam geometry stray light contaminates the projection images, degrading the accuracy of reconstructed linear attenuation coefficients. Stray light was measured using a beam pass aperture array (BPA) and structured illumination methods. The stray-to-primary ray ratio (SPR) along the central axis was found to be 0.24 for a 5% gelatin hydrogel, representative of radiochromic hydrogels. The scanner was modified by moving the spectral filter from the detector to the source, changing the light's spatial fluence pattern and lowering the acceptance angle by extending distance between the source and object. These modifications reduced the SPR significantly from 0.24 to 0.06. The accuracy of the reconstructed linear attenuation coefficients for uniform carbon black liquids was compared to independent spectrometer measurements. Reducing the stray light increased the range of accurate transmission readings. In order to evaluate scanner performance for the more challenging application to small field dosimetry, a carbon black finger gel phantom was prepared. Reconstructions of the phantom from CBCT and fan-beam CT scans were compared. The modified source resulted in improved agreement. Subtraction of residual stray light, measured with BPA or structured illumination from each projection further improved agreement. Structured illumination was superior to BPA for measuring stray light for the smaller 1.2 and 0.5 cm diameter phantom fingers. At the costs of doubling the scanner size and tripling the number of scans, CBCT reconstructions of low-scattering hydrogel dosimeters agreed with those of fan-beam CT scans. PMID:26988028

  9. Charmed and light pseudoscalar meson decay constants from four-flavor lattice QCD with physical light quarks

    SciTech Connect

    Bazavov, A.; Bernard, C.; Komijani, J.; Bouchard, C. M.; DeTar, C.; Foley, J.; Levkova, L.; Du, D.; Laiho, J.; El-Khadra, A. X.; Freeland, E. D.; Gámiz, E.; Gottlieb, Steven; Heller, U. M.; Kim, J.; Toussaint, D.; Kronfeld, A. S.; Mackenzie, P. B.; Simone, J. N.; Van de Water, R. S.; Zhou, R.; Neil, E. T.; Sugar, R.

    2014-10-30

    We compute the leptonic decay constants fD+, fDs, and fK+ and the quark-mass ratios mc/ms and ms/ml in unquenched lattice QCD using the experimentally determined value of fπ+ for normalization. We use the MILC highly improved staggered quark ensembles with four dynamical quark flavors—up, down, strange, and charm—and with both physical and unphysical values of the light sea-quark masses. The use of physical pions removes the need for a chiral extrapolation, thereby eliminating a significant source of uncertainty in previous calculations. Four different lattice spacings ranging from a0.06 to 0.15 fm are included in the analysis to control the extrapolation to the

  10. Stray light in cone beam optical computed tomography: I. Measurement and reduction strategies with planar diffuse source

    NASA Astrophysics Data System (ADS)

    Granton, Patrick V.; Dekker, Kurtis H.; Battista, Jerry J.; Jordan, Kevin J.

    2016-04-01

    Optical cone-beam computed tomographic (CBCT) scanning of 3D radiochromic dosimeters may provide a practical method for 3D dose verification in radiation therapy. However, in cone-beam geometry stray light contaminates the projection images, degrading the accuracy of reconstructed linear attenuation coefficients. Stray light was measured using a beam pass aperture array (BPA) and structured illumination methods. The stray-to-primary ray ratio (SPR) along the central axis was found to be 0.24 for a 5% gelatin hydrogel, representative of radiochromic hydrogels. The scanner was modified by moving the spectral filter from the detector to the source, changing the light’s spatial fluence pattern and lowering the acceptance angle by extending distance between the source and object. These modifications reduced the SPR significantly from 0.24 to 0.06. The accuracy of the reconstructed linear attenuation coefficients for uniform carbon black liquids was compared to independent spectrometer measurements. Reducing the stray light increased the range of accurate transmission readings. In order to evaluate scanner performance for the more challenging application to small field dosimetry, a carbon black finger gel phantom was prepared. Reconstructions of the phantom from CBCT and fan-beam CT scans were compared. The modified source resulted in improved agreement. Subtraction of residual stray light, measured with BPA or structured illumination from each projection further improved agreement. Structured illumination was superior to BPA for measuring stray light for the smaller 1.2 and 0.5 cm diameter phantom fingers. At the costs of doubling the scanner size and tripling the number of scans, CBCT reconstructions of low-scattering hydrogel dosimeters agreed with those of fan-beam CT scans.

  11. B -meson decay constants from 2 +1 -flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

    NASA Astrophysics Data System (ADS)

    Christ, N. H.; Flynn, J. M.; Izubuchi, T.; Kawanai, T.; Lehner, C.; Soni, A.; van de Water, R. S.; Witzel, O.; Rbc; Ukqcd Collaborations

    2015-03-01

    We calculate the B -meson decay constants fB , fBs , and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ≈0.11 , 0.086 fm with unitary pion masses as light as Mπ≈290 MeV ; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also improve the lattice heavy-light current through O (αsa ) . We extrapolate our results to the physical light-quark masses and continuum using SU(2) heavy-meson chiral perturbation theory, and provide a complete systematic error budget. We obtain fB0=199.5 (12.6 ) MeV , fB+=195.6 (14.9 ) MeV , fBs=235.4 (12.2 ) MeV , fBs/fB0=1.197 (50 ) , and fBs/fB+=1.223 (71 ) , where the errors are statistical and total systematic added in quadrature. These results are in good agreement with other published results and provide an important independent cross-check of other three-flavor determinations of B -meson decay constants using staggered light quarks.

  12. String theoretic QCD axions in the light of PLANCK and BICEP2

    NASA Astrophysics Data System (ADS)

    Choi, Kiwoon; Jeong, Kwang Sik; Seo, Min-Seok

    2014-07-01

    The QCD axion solving the strong CP problem may originate from antisymmetric tensor gauge fields in compactified string theory, with a decay constant around the GUT scale. Such possibility appears to be ruled out now by the detection of tensor modes by BICEP2 and the PLANCK constraints on isocurvature density perturbations. A more interesting and still viable possibility is that the string theoretic QCD axion is charged under an anomalous U(1) A gauge symmetry. In such case, the axion decay constant can be much lower than the GUT scale if moduli are stabilized near the point of vanishing Fayet-Illiopoulos term, and U(1) A -charged matter fields get a vacuum value v ~ ( m SUSY M {/Pl n })1/( n + 1) ( n ≥ 0) induced by a tachyonic SUSY breaking mass m SUSY. We examine the symmetry breaking pattern of such models during the inflationary epoch with H I ≃ 1014 GeV, and identify the range of the QCD axion decay constant, as well as the corresponding relic axion abundance, consistent with known cosmological constraints. In addition to the case that the PQ symmetry is restored during inflation, i.e. v( t I ) = 0, there are other viable scenarios, including that the PQ symmetry is broken during inflation with v( t I ) ˜ (4 πH I M {/Pl n })1/( n + 1) ~ 1016-1017 GeV due to the Hubble-induced D-term D A ~ 8 π 2 H {/I 2} , while v( t 0) ~ ( m SUSY M {/Pl n })1/( n + 1) ~ 109-5 × 1013 GeV in the present universe, where v( t 0) above 1012 GeV requires a fine-tuning of the axion misalignment angle. We also discuss the implications of our results for the size of SUSY breaking soft masses.

  13. Light-evoked current responses in rod bipolar cells, cone depolarizing bipolar cells and all amacrine cells in dark-adapted mouse retina

    PubMed Central

    Pang, Ji-Jie; Gao, Fan; Wu, Samuel M

    2004-01-01

    Light-evoked excitatory cation current (ΔIC) and inhibitory chloride current (ΔICl) of rod and cone depolarizing bipolar cells (DBCRs and DBCCs) and AII amacrine cells (AIIACs) in dark-adapted mouse retinal slices were studied by whole-cell voltage-clamp recording techniques, and the cell morphology was revealed by Lucifer yellow fluorescence with a confocal microscope. ΔIC of all DBCRs exhibited similar high sensitivity to 500 nm light, but two patterns of ΔICl were observed in DBCRs with slightly different axon morphology. At least two types of DBCCs were identified: one with axon terminals ramified in 70–85% of the depth of the inner plexiform layer (IPL) and DBCR-like ΔIC sensitivity, whereas the other with axon terminals ramified in 55–75% of IPL depth and much lower ΔIC sensitivity. The relative rod/cone inputs to DBCs and AIIACs were analysed by comparing the ΔIC and ΔICl thresholds and dynamic ranges with the corresponding values of rods and cones. On average, the sensitivity of a DBCR to the 500 nm light is about 20 times higher than that of a rod. The sensitivity of an AIIAC is more than 1000 times higher than that of a rod, suggesting that AIIAC responses are pooled through a coupled network of about 40 AIIACs. Interactions of rod and cone signals in dark-adapted mouse retina appear asymmetrical: rod signals spread into the cone system more efficiently than cone signals into the rod system. The mouse synaptic circuitry allows small rod signals to be highly amplified, and effectively transmitted to the cone system via rod–cone and AIIAC–DBCC coupling. PMID:15181169

  14. Nucleon scalar and tensor charges from lattice QCD with light Wilson quarks

    NASA Astrophysics Data System (ADS)

    Green, J. R.; Negele, J. W.; Pochinsky, A. V.; Syritsyn, S. N.; Engelhardt, M.; Krieg, S.

    2012-12-01

    We present 2+1 flavor lattice QCD calculations of the nucleon scalar and tensor charges. Using the BMW clover-improved Wilson action with pion masses between 149 and 356 MeV and three source-sink separations between 0.9 and 1.4 fm, we achieve good control over excited-state contamination and extrapolation to the physical pion mass. As a consistency check, we also present results from calculations using unitary domain wall fermions with pion masses between 297 and 403 MeV, and using domain wall valence quarks and staggered sea quarks with pion masses between 293 and 597 MeV.

  15. Light mesons in QCD and unquenching effects from the 3PI effective action

    NASA Astrophysics Data System (ADS)

    Williams, Richard; Fischer, Christian S.; Heupel, Walter

    2016-02-01

    We investigate the impact of unquenching effects on QCD Green's functions, in the form of quark-loop contributions to both the gluon propagator and three-gluon vertex, in a three-loop inspired truncation of the three-particle irreducible (3PI) effective action. The fully coupled system of Dyson-Schwinger equations for the quark-gluon, ghost-gluon and three-gluon vertices, together with the quark propagator, are solved self-consistently; our only input are the ghost and gluon propagators themselves that are constrained by calculations within lattice QCD. We find that the two different unquenching effects have roughly equal, but opposite, impact on the quark-gluon vertex and quark propagator, with an overall negative impact on the latter. By taking further derivatives of the 3PI effective action, we construct the corresponding quark-antiquark kernel of the Bethe-Salpeter equation for mesons. The leading component is gluon exchange between two fully dressed quark-gluon vertices, thus introducing for the first time an obvious scalar-scalar component to the binding. We gain access to time-like properties of bound states by analytically continuing the coupled system of Dyson-Schwinger equations to the complex plane. We observe that the vector axial-vector splitting is in accord with experiment and that the lightest quark-antiquark scalar meson is above 1 GeV in mass.

  16. Isospin splittings in the light-baryon octet from lattice QCD and QED.

    PubMed

    Borsanyi, Sz; Dürr, S; Fodor, Z; Frison, J; Hoelbling, C; Katz, S D; Krieg, S; Kurth, Th; Lellouch, L; Lippert, Th; Portelli, A; Ramos, A; Sastre, A; Szabo, K

    2013-12-20

    While electromagnetic and up-down quark mass difference effects on octet baryon masses are very small, they have important consequences. The stability of the hydrogen atom against beta decay is a prominent example. Here, we include these effects by adding them to valence quarks in a lattice QCD calculation based on Nf=2+1 simulations with five lattice spacings down to 0.054 fm, lattice sizes up to 6 fm, and average up-down quark masses all the way down to their physical value. This allows us to gain control over all systematic errors, except for the one associated with neglecting electromagnetism in the sea. We compute the octet baryon isomultiplet mass splittings, as well as the individual contributions from electromagnetism and the up-down quark mass difference. Our results for the total splittings are in good agreement with experiment. PMID:24483739

  17. State of the art lattice results of QCD with light flavours

    NASA Astrophysics Data System (ADS)

    Ramos, Alberto; Budapest-Marseille-Wuppertal Collaboration

    2010-10-01

    Thanks to recent developments both in our understanding of lattice simulations and in computer power, lattice gauge theory now allows to perform non perturbative QCD computations with all the sources of error under control. I will review some recent results of the Budapest-Marseille-Wuppertal (BMW) collaboration: first computing the mass of the hadrons, an old desire of every particle physicist. Second π and K decay constants can be used to compute CKM matrix elements and constrain physics beyond the standard model. Finally we will see how the lattice can be used to compute quantities not directly accessible to experiments, but anyhow interesting such as the nucleon sigma terms. I will emphasise how the different sources of error are controlled to make physical predictions.

  18. Lattice QCD

    SciTech Connect

    Bornyakov, V.G.

    2005-06-01

    Possibilities that are provided by a lattice regularization of QCD for studying nonperturbative properties of QCD are discussed. A review of some recent results obtained from computer calculations in lattice QCD is given. In particular, the results for the QCD vacuum structure, the hadron mass spectrum, and the strong coupling constant are considered.

  19. Use of a local cone model to predict essential CSF light adaptation behavior used in the design of luminance quantization nonlinearities

    NASA Astrophysics Data System (ADS)

    Daly, Scott; Golestaneh, S. A.

    2015-03-01

    The human visual system's luminance nonlinearity ranges continuously from square root behavior in the very dark, gamma-like behavior in dim ambient, cube-root in office lighting, and logarithmic for daylight ranges. Early display quantization nonlinearities have been developed based on luminance bipartite JND data. More advanced approaches considered spatial frequency behavior, and used the Barten light-adaptive Contrast Sensitivity Function (CSF) modelled across a range of light adaptation to determine the luminance nonlinearity (e.g., DICOM, referred to as a GSDF {grayscale display function}). A recent approach for a GSDF, also referred to as an electrical-to-optical transfer function (EOTF), using that light-adaptive CSF model improves on this by tracking the CSF for the most sensitive spatial frequency, which changes with adaptation level. We explored the cone photoreceptor's contribution to the behavior of this maximum sensitivity of the CSF as a function of light adaptation, despite the CSF's frequency variations and that the cone's nonlinearity is a point-process. We found that parameters of a local cone model could fit the max sensitivity of the CSF model, across all frequencies, and are within the ranges of parameters commonly accepted for psychophysicallytuned cone models. Thus, a linking of the spatial frequency and luminance dimensions has been made for a key neural component. This provides a better theoretical foundation for the recently designed visual signal format using the aforementioned EOTF.

  20. The leading twist light-cone distribution amplitudes for the S-wave and P-wave Bc mesons

    NASA Astrophysics Data System (ADS)

    Xu, Ji; Yang, Deshan

    2016-07-01

    The light-cone distribution amplitudes (LCDAs) serve as important nonperturbative inputs for the study of hard exclusive processes. In this paper, we calculate ten LCDAs at twist-2 for the S-wave and P-wave B c mesons up to the next-to-leading order (NLO) of the strong coupling α s and leading order of the velocity expansion. Each one of these ten LCDAs is expressed as a product of a perturbatively calculable distribution and a universal NRQCD matrix-element. By use of the spin symmetry, only two NRQCD matrix-elements will be involved. The reduction of the number of non-perturbative inputs will improve the predictive power of collinear factorization.

  1. Spin dynamics of qqq wave function on light front in high momentum limit of QCD: Role of qqq force

    SciTech Connect

    Mitra, A.N.

    2008-04-15

    The contribution of a spin-rich qqq force (in conjunction with pairwise qq forces) to the analytical structure of the qqq wave function is worked out in the high momentum regime of QCD where the confining interaction may be ignored, so that the dominant effect is Coulombic. A distinctive feature of this study is that the spin-rich qqq force is generated by a ggg vertex (a genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on as many quark lines, giving rise to a (Mercedes-Benz type) Y-shaped diagram. The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these ingredients, the differential equation for the 3D wave function {phi} receives well-defined contributions from the qq and qqq forces. In particular a negative eigenvalue of the spin operator i{sigma}{sub 1} . {sigma}{sub 2} x {sigma}{sub 3} which is an integral part of the qqq force, causes a characteristic singularity in the differential equation, signalling the dynamical effect of a spin-rich qqq force not yet considered in the literature. The potentially crucial role of this interesting effect vis-a-vis the so-called 'spin anomaly' of the proton, is a subject of considerable physical interest.

  2. Spin dynamics of qqq wave function on light front in high momentum limit of QCD: Role of qqq force

    NASA Astrophysics Data System (ADS)

    Mitra, A. N.

    2008-04-01

    The contribution of a spin-rich qqq force (in conjunction with pairwise qq forces) to the analytical structure of the qqq wave function is worked out in the high momentum regime of QCD where the confining interaction may be ignored, so that the dominant effect is Coulombic. A distinctive feature of this study is that the spin-rich qqq force is generated by a ggg vertex (a genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on as many quark lines, giving rise to a (Mercedes-Benz type) Y-shaped diagram. The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these ingredients, the differential equation for the 3D wave function ϕ receives well-defined contributions from the qq and qqq forces. In particular a negative eigenvalue of the spin operator iσ1 · σ2 × σ3 which is an integral part of the qqq force, causes a characteristic singularity in the differential equation, signalling the dynamical effect of a spin-rich qqq force not yet considered in the literature. The potentially crucial role of this interesting effect vis-a-vis the so-called 'spin anomaly' of the proton, is a subject of considerable physical interest.

  3. The MICE Grand Challenge light-cone simulation - III. Galaxy lensing mocks from all-sky lensing maps

    NASA Astrophysics Data System (ADS)

    Fosalba, P.; Gaztañaga, E.; Castander, F. J.; Crocce, M.

    2015-02-01

    In Paper I of this series, we presented a new N-body light-cone simulation from the MICE Collaboration, the MICE Grand Challenge (MICE-GC), containing about 70 billion dark-matter particles in a (3 h-1 Gpc)3 comoving volume, from which we built halo and galaxy catalogues using a Halo Occupation Distribution and Halo Abundance Matching technique, as presented in the companion Paper II. Given its large volume and fine mass resolution, the MICE-GC simulation also allows an accurate modelling of the lensing observables from upcoming wide and deep galaxy surveys. In the last paper of this series (Paper III), we describe the construction of all-sky lensing maps, following the `Onion Universe' approach, and discuss their properties in the light-cone up to z = 1.4 with sub-arcminute spatial resolution. By comparing the convergence power spectrum in the MICE-GC to lower mass-resolution (i.e. particle mass ˜1011 h-1 M⊙) simulations, we find that resolution effects are at the 5 per cent level for multipoles ℓ ˜ 103 and 20 per cent for ℓ ˜ 104. Resolution effects have a much lower impact on our simulation, as shown by comparing the MICE-GC to recent numerical fits by Takahashi. We use the all-sky lensing maps to model galaxy lensing properties, such as the convergence, shear, and lensed magnitudes and positions, and validate them thoroughly using galaxy shear auto and cross-correlations in harmonic and configuration space. Our results show that the galaxy lensing mocks here presented can be used to accurately model lensing observables down to arcminute scales. Accompanying this series of papers, we make a first public data release of the MICE-GC galaxy mock, the MICECAT v1.0, through a dedicated web-portal for the MICE simulations, http://cosmohub.pic.es, to help developing and exploiting the new generation of astronomical surveys.

  4. Light meson electromagnetic form factors from three-flavor lattice QCD with exact chiral symmetry

    NASA Astrophysics Data System (ADS)

    Aoki, S.; Cossu, G.; Feng, X.; Hashimoto, S.; Kaneko, T.; Noaki, J.; Onogi, T.

    2016-02-01

    We study the chiral behavior of the electromagnetic (EM) form factors of pions and kaons in three-flavor lattice QCD. In order to make a direct comparison of the lattice data with chiral perturbation theory (ChPT), we employ the overlap quark action that has exact chiral symmetry. Gauge ensembles are generated at a lattice spacing of 0.11 fm with four pion masses ranging between Mπ≃290 MeV and 540 MeV and with a strange quark mass ms close to its physical value. We utilize the all-to-all quark propagator technique to calculate the EM form factors with high precision. Their dependence on ms and on the momentum transfer is studied by using the reweighting technique and the twisted boundary conditions for the quark fields, respectively. A detailed comparison with SU(2) and SU(3) ChPT reveals that the next-to-next-to-leading order terms in the chiral expansion are important to describe the chiral behavior of the form factors in the pion mass range studied in this work. We estimate the relevant low-energy constants and the charge radii, and find reasonable agreement with phenomenological and experimental results.

  5. Neutral B-meson mixing from unquenched lattice QCD with domain-wall light quarks and static b quarks

    SciTech Connect

    Albertus, C.; Flynn, J. M.; Sachrajda, C. T.; Aoki, Y.; Ishikawa, T.; Boyle, P. A.; Wennekers, J.; Christ, N. H.; Dumitrescu, T. T.; Loktik, O.; Izubuchi, T.; Soni, A.; Van de Water, R. S.; Witzel, O.

    2010-07-01

    We demonstrate a method for calculating the neutral B-meson decay constants and mixing matrix elements in unquenched lattice QCD with domain-wall light quarks and static b-quarks. Our computation is performed on the '2+1' flavor gauge configurations generated by the RBC and UKQCD Collaborations with a lattice spacing of a{approx_equal}0.11 fm (a{sup -1}=1.729 GeV) and a lattice spatial volume of approximately (1.8 fm){sup 3}. We simulate at three different light sea quark masses with pion masses down to approximately 430 MeV, and extrapolate to the physical quark masses using a phenomenologically-motivated fit function based on next-to-leading order heavy-light meson SU(2) chiral perturbation theory. For the b-quarks, we use an improved formulation of the Eichten-Hill action with static link-smearing to increase the signal-to-noise ratio. We also improve the heavy-light axial current used to compute the B-meson decay constant to O({alpha}{sub s}pa) using one-loop lattice perturbation theory. We present initial results for the SU(3)-breaking ratios f{sub B{sub s}}/f{sub B{sub d}} and {xi}=f{sub B{sub s{radical}}}(B{sub B{sub s}})/f{sub B{sub d{radical}}}(B{sub B{sub d}}), thereby demonstrating the viability of the method. For the ratio of decay constants, we find f{sub B{sub s}}/f{sub B{sub d}}=1.15(12) and for the ratio of mixing matrix elements, we find {xi}=1.13(12), where in both cases the errors reflect the combined statistical and systematic uncertainties, including an estimate of the size of neglected O(1/m{sub b}) effects.

  6. Relative contributions of rod and cone bipolar cell inputs to AII amacrine cell light responses in the mouse retina

    PubMed Central

    Pang, Ji-Jie; Abd-El-Barr, Muhammad M; Gao, Fan; Bramblett, Debra E; Paul, David L; Wu, Samuel M

    2007-01-01

    AII amacrine cells (AIIACs) are crucial relay stations for rod-mediated signals in the mammalian retina and they receive synaptic inputs from depolarizing and hyperpolarizing bipolar cells (DBCs and HBCs) as well as from other amacrine cells. Using whole-cell voltage-clamp technique in conjunction with pharmacological tools, we found that the light-evoked current response of AIIACs in the mouse retina is almost completely mediated by two DBC synaptic inputs: a 6,7-dinitro-quinoxaline-2,3-dione (DNQX)-resistant component mediated by cone DBCs (DBCCs) through an electrical synapse, and a DNQX-sensitive component mediated by rod DBCs (DBCRs). This scheme is supported by AIIAC current responses recorded from two knockout mice. The dynamic range of the AIIAC light response in the Bhlhb4−/− mouse (which lacks DBCRs) resembles that of the DNQX-resistant component, and that of the connexin36 (Cx36)−/− mouse resembles the DNQX-sensitive component. By comparing the light responses of the DBCCs with the DNQX-resistant AIIAC component, and light responses of the DBCRs with the DNQX-sensitive AIIAC component, we obtained the input–output relations of the DBCC→AIIAC electrical synapse and the DBCR→AIIAC chemical synapse. Similar to other glutamatergic chemical synapses in the retina, the DBCR→AIIAC synapse is non-linear. Its highest voltage gain (approximately 5) is found near the dark membrane potential, and it saturates for presynaptic signals larger than 5.5 mV. The DBCC→AIIAC electrical synapse is approximately linear (voltage gain of 0.92), consistent with the linear junctional conductance found in retinal electrical synapses. Moreover, relative DBCR and DBCC contributions to the AIIAC response at various light intensity levels are determined. PMID:17255172

  7. Exploring the evolution of reionization using a wavelet transform and the light cone effect

    NASA Astrophysics Data System (ADS)

    Trott, Cathryn M.

    2016-09-01

    The Cosmic Dawn and Epoch of Reionization, during which collapsed structures produce the first ionizing photons and proceed to reionize the intergalactic medium, span a large range in redshift (z ˜ 30-6) and time (tage ˜ 0.1-1.0 Gyr). Exploration of these epochs using the redshifted 21 cm emission line from neutral hydrogen is currently limited to statistical detection and estimation metrics (e.g. the power spectrum) due to the weakness of the signal. Brightness temperature fluctuations in the line-of-sight dimension are probed by observing the emission line at different frequencies, and their structure is used as a primary discriminant between the cosmological signal and contaminating foreground extragalactic and Galactic continuum emission. Evolution of the signal over the observing bandwidth leads to the `line cone effect' whereby the H I structures at the start and end of the observing band are not statistically consistent, yielding a biased estimate of the signal power, and potential reduction in signal detectability. We implement a wavelet transform to wide bandwidth radio interferometry experiments to probe the local statistical properties of the signal. We show that use of the wavelet transform yields estimates with improved estimation performance, compared with the standard Fourier Transform over a fixed bandwidth. With the suite of current and future large bandwidth reionization experiments, such as with the 300 MHz instantaneous bandwidth of the Square Kilometre Array, a transform that retains local information will be important.

  8. Exploring the evolution of Reionisation using a wavelet transform and the light cone effect

    NASA Astrophysics Data System (ADS)

    Trott, Cathryn M.

    2016-06-01

    The Cosmic Dawn and Epoch of Reionisation, during which collapsed structures produce the first ionising photons and proceed to reionise the intergalactic medium, span a large range in redshift (z ˜ 30 - 6) and time (tage ˜ 0.1 - 1.0 Gyr). Exploration of these epochs using the redshifted 21 cm emission line from neutral hydrogen is currently limited to statistical detection and estimation metrics (e.g., the power spectrum) due to the weakness of the signal. Brightness temperature fluctuations in the line-of-sight (LOS) dimension are probed by observing the emission line at different frequencies, and their structure is used as a primary discriminant between the cosmological signal and contaminating foreground extragalactic and Galactic continuum emission. Evolution of the signal over the observing bandwidth leads to the `line cone effect' whereby the HI structures at the start and end of the observing band are not statistically consistent, yielding a biased estimate of the signal power, and potential reduction in signal detectability. We implement a wavelet transform to wide bandwidth radio interferometry experiments to probe the local statistical properties of the signal. We show that use of the wavelet transform yields estimates with improved estimation performance, compared with the standard Fourier Transform over a fixed bandwidth. With the suite of current and future large bandwidth reionisation experiments, such as with the 300 MHz instantaneous bandwidth of the Square Kilometre Array, a transform that retains local information will be important.

  9. Resonances in QCD

    NASA Astrophysics Data System (ADS)

    Lutz, Matthias F. M.; Lange, Jens Sören; Pennington, Michael; Bettoni, Diego; Brambilla, Nora; Crede, Volker; Eidelman, Simon; Gillitzer, Albrecht; Gradl, Wolfgang; Lang, Christian B.; Metag, Volker; Nakano, Takashi; Nieves, Juan; Neubert, Sebastian; Oka, Makoto; Olsen, Stephen L.; Pappagallo, Marco; Paul, Stephan; Pelizäus, Marc; Pilloni, Alessandro; Prencipe, Elisabetta; Ritman, Jim; Ryan, Sinead; Thoma, Ulrike; Uwer, Ulrich; Weise, Wolfram

    2016-04-01

    We report on the EMMI Rapid Reaction Task Force meeting 'Resonances in QCD', which took place at GSI October 12-14, 2015. A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions: What is needed to understand the physics of resonances in QCD? Where does QCD lead us to expect resonances with exotic quantum numbers? What experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with up, down and strange quark content were considered. For heavy-light and heavy-heavy meson systems, those with charm quarks were the focus. This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here.

  10. Pikachurin Protein Required for Increase of Cone Electroretinogram B-Wave during Light Adaptation

    PubMed Central

    Nagaya, Masatoshi; Ueno, Shinji; Kominami, Taro; Nakanishi, Ayami; Koyasu, Toshiyuki; Kondo, Mineo; Furukawa, Takahisa; Terasaki, Hiroko

    2015-01-01

    In normal eyes, the amplitude of the b-wave of the photopic ERGs increases during light adaptation, but the mechanism causing this increase has not been fully determined. The purpose of this study was to evaluate the contribution of receptoral and post-receptoral components of the retina to this phenomenon. To accomplish this, we examined the ERGs during light adaptation in Pikachurin null-mutant (Pika -/-) mice, which have a misalignment of the bipolar cell dendritic tips to the photoreceptor ribbon synapses. After dark-adaptation, photopic ERGs were recorded from Pika -/- and wild type (WT) mice during the first 9 minutes of light adaptation. In some of the mice, post-receptoral components were blocked pharmacologically. The photopic b-waves of WT mice increased by 50% during the 9 min of light adaptation as previously reported. On the other hand, the b-waves of the Pika -/- mice decreased by 20% during the same time period. After blocking post-receptoral components, the b-waves were abolished from the WT mice, and the ERGs resembled those of the Pika -/- mice. The extracted post-receptoral component increased during light adaptation in the WT mice, but decreased for the first 3 minutes to a plateau in Pika -/- mice. We conclude that the normal synaptic connection between photoreceptor and retinal ON bipolar cells, which is controlled by pikachurin, is required for the ERGs to increase during light-adaptation. The contributions of post-receptoral components are essential for the photopic b-wave increase during the light adaptation. PMID:26091521

  11. QCD with 2 light quark flavours: Thermodynamics on a 16[sup 3] [times] 8 lattice and glueballs and topological charge on a 16[sup 3] [times] 32 lattice

    SciTech Connect

    Sinclair, D.K.

    1992-11-20

    The HTMCGC collaboration has been simulating lattice QCD with two light staggered quarks with masses m[sub q] = 0.0125 and also m[sub q] = 0.00625 on a 16[sup 3] [times] 8 lattice. We have been studying the behavior of the transition from hadronic matter to a quark-gluon plasma and the properties of that plasma. We have been measuring entropy densities, Debye and hadronic screening lengths, the spacial string tension and topological susceptibility in addition to the standard order parameters. The HEMCGC collaboration has simulated lattice QCD with two light staggered quarks,m[sub q] = 0.025 and m[sub q] = 0.010 on a 16[sup 3] [times] 32 lattice. We have measured the glueball spectrum and topological susceptibilities for these runs.

  12. QCD with 2 light quark flavours: Thermodynamics on a 16{sup 3} {times} 8 lattice and glueballs and topological charge on a 16{sup 3} {times} 32 lattice

    SciTech Connect

    Sinclair, D.K.; HEMCGC collaboration; HTMCGC collaboration

    1992-11-20

    The HTMCGC collaboration has been simulating lattice QCD with two light staggered quarks with masses m{sub q} = 0.0125 and also m{sub q} = 0.00625 on a 16{sup 3} {times} 8 lattice. We have been studying the behavior of the transition from hadronic matter to a quark-gluon plasma and the properties of that plasma. We have been measuring entropy densities, Debye and hadronic screening lengths, the spacial string tension and topological susceptibility in addition to the standard order parameters. The HEMCGC collaboration has simulated lattice QCD with two light staggered quarks,m{sub q} = 0.025 and m{sub q} = 0.010 on a 16{sup 3} {times} 32 lattice. We have measured the glueball spectrum and topological susceptibilities for these runs.

  13. Precise MS light-quark masses from lattice QCD in the regularization invariant symmetric momentum-subtraction scheme

    SciTech Connect

    Gorbahn, Martin; Jaeger, Sebastian

    2010-12-01

    We compute the conversion factors needed to obtain the MS and renormalization-group-invariant (RGI) up, down, and strange quark masses at next-to-next-to-leading order from the corresponding parameters renormalized in the recently proposed RI/SMOM and RI/SMOM{sub {gamma}{sub {mu}} }renormalization schemes. This is important for obtaining the MS masses with the best possible precision from numerical lattice QCD simulations, because the customary RI{sup (')}/MOM scheme is afflicted with large irreducible uncertainties both on the lattice and in perturbation theory. We find that the smallness of the known one-loop matching coefficients is accompanied by even smaller two-loop contributions. From a study of residual scale dependences, we estimate the resulting perturbative uncertainty on the light-quark masses to be about 2% in the RI/SMOM scheme and about 3% in the RI/SMOM{sub {gamma}{sub {mu}} }scheme. Our conversion factors are given in fully analytic form, for general covariant gauge and renormalization point. We provide expressions for the associated anomalous dimensions.

  14. Path integral approach to two-dimensional QCD in the light-front frame

    NASA Astrophysics Data System (ADS)

    Gaete, P.; Gamboa, J.; Schmidt, I.

    1994-05-01

    Two-dimensional quantum chromodynamics in the light-front frame is studied following Hamiltonian methods. The theory is quantized using the path integral formalism and an effective theory similar to the Nambu-Jona-Lasinio model is obtained. Confinement in two dimensions is derived by analyzing directly the constraints in the path integral.

  15. Investigating strangeness in the proton by studying the effects of Light Cone parton distributions in the Meson Cloud Model

    NASA Astrophysics Data System (ADS)

    Tuppan, Sam; Budnik, Garrett; Fox, Jordan

    2014-09-01

    The Meson Cloud Model (MCM) has proven to be a natural explanation for strangeness in the proton because of meson-baryon splitting into kaon-hyperon pairs. Total strangeness is predicted by integrated splitting functions, which represent the probability that the proton will fluctuate into a given meson-baryon pair. However, the momentum distributions s (x) and s (x) in the proton are determined from convolution integrals that depend on the parton distribution functions (PDFs) used for the mesons and baryons in the MCM. Theoretical calculations of these momentum distributions use many different forms for these PDFs. In our investigation, we calculate PDFs for K, K*, Λ, and Σ from two-body wave functions in a Light Cone Model (LCM) of the hadrons. We use these PDFs in conjunction with the MCM to create a hybrid model and compare our results to other theoretical calculations, experimental data from NuTeV, HERMES, ATLAS, and global parton distribution analyses. The Meson Cloud Model (MCM) has proven to be a natural explanation for strangeness in the proton because of meson-baryon splitting into kaon-hyperon pairs. Total strangeness is predicted by integrated splitting functions, which represent the probability that the proton will fluctuate into a given meson-baryon pair. However, the momentum distributions s (x) and s (x) in the proton are determined from convolution integrals that depend on the parton distribution functions (PDFs) used for the mesons and baryons in the MCM. Theoretical calculations of these momentum distributions use many different forms for these PDFs. In our investigation, we calculate PDFs for K, K*, Λ, and Σ from two-body wave functions in a Light Cone Model (LCM) of the hadrons. We use these PDFs in conjunction with the MCM to create a hybrid model and compare our results to other theoretical calculations, experimental data from NuTeV, HERMES, ATLAS, and global parton distribution analyses. This research has been supported in part by the

  16. A Novel In Vivo Model of Focal Light Emitting Diode-Induced Cone-Photoreceptor Phototoxicity: Neuroprotection Afforded by Brimonidine, BDNF, PEDF or bFGF

    PubMed Central

    García-Ayuso, Diego; Alarcón-Martínez, Luis; Jiménez-López, Manuel; Bernal-Garro, José Manuel; Nieto-López, Leticia; Nadal-Nicolás, Francisco Manuel; Villegas-Pérez, María Paz; Wheeler, Larry A.; Vidal-Sanz, Manuel

    2014-01-01

    We have investigated the effects of light-emitting diode (LED)-induced phototoxicity (LIP) on cone-photoreceptors and their protection with brimonidine (BMD), brain-derived neurotrophic factor (BDNF), pigment epithelium-derived factor (PEDF), ciliary neurotrophic factor (CNTF) or basic fibroblast growth factor (bFGF). In anesthetized, dark adapted, adult albino rats a blue (400 nm) LED was placed perpendicular to the cornea (10 sec, 200 lux) and the effects were investigated using Spectral Domain Optical Coherence Tomography (SD-OCT) and/or analysing the retina in oriented cross-sections or wholemounts immune-labelled for L- and S-opsin and counterstained with the nuclear stain DAPI. The effects of topical BMD (1%) or, intravitreally injected BDNF (5 µg), PEDF (2 µg), CNTF (0.4 µg) or bFGF (1 µg) after LIP were examined on wholemounts at 7 days. SD-OCT showed damage in a circular region of the superotemporal retina, whose diameter varied from 1,842.4±84.5 µm (at 24 hours) to 1,407.7±52.8 µm (at 7 days). This region had a progressive thickness diminution from 183.4±5 µm (at 12 h) to 114.6±6 µm (at 7 d). Oriented cross-sections showed within the light-damaged region of the retina massive loss of rods and cone-photoreceptors. Wholemounts documented a circular region containing lower numbers of L- and S-cones. Within a circular area (1 mm or 1.3 mm radius, respectively) in the left and in its corresponding region of the contralateral-fellow-retina, total L- or S-cones were 7,118±842 or 661±125 for the LED exposed retinas (n = 7) and 14,040±1,860 or 2,255±193 for the fellow retinas (n = 7), respectively. BMD, BDNF, PEDF and bFGF but not CNTF showed significant neuroprotective effects on L- or S-cones. We conclude that LIP results in rod and cone-photoreceptor loss, and is a reliable, quantifiable model to study cone-photoreceptor degeneration. Intravitreal BDNF, PEDF or bFGF, or topical BMD afford significant cone neuroprotection in this model

  17. Electroweak properties of octet baryons in a light-cone quark-diquark model

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Ma, Bo-Qiang

    2016-06-01

    We study the electroweak properties of ground state octet baryons in a relativistic quark-spectator-diquark model, with a light-front formalism applied to take relativistic effects into account. Our model provides a consistent picture of the electroweak properties of the ground state octet baryons in the low momentum transfer region. The Melosh-Wigner rotation is applied as the transformation relation between spinors in the instant form and front form. Numerical results are presented for the magnetic moments, weak transition charges, and Sachs form factors. Our results are in good agreement with experimental measurements and other theoretical results.

  18. Lensing in the geodesic light-cone coordinates and its (exact) illustration to an off-center observer in Lemaȋtre-Tolman-Bondi models

    SciTech Connect

    Fanizza, G.; Nugier, F. E-mail: fabienjean.nugier@unibo.it

    2015-02-01

    We present in this paper a new application of the geodesic light-cone (GLC) gauge for weak lensing calculations. Using interesting properties of this gauge, we derive an exact expression of the amplification matrix—involving convergence, magnification and shear—and of the deformation matrix—involving the optical scalars. These expressions are simple and non-perturbative as long as no caustics are created on the past light-cone and are, by construction, free from the thin lens approximation. We apply these general expressions on the example of an Lemaȋtre-Tolman-Bondi (LTB) model with an off-center observer and obtain explicit forms for the lensing quantities as a direct consequence of the non-perturbative transformation between GLC and LTB coordinates. We show their evolution in redshift after a numerical integration, for underdense and overdense LTB models, and interpret their respective variations in the simple non-curvature case.

  19. Electroproduction of tensor mesons in QCD

    NASA Astrophysics Data System (ADS)

    Braun, V. M.; Kivel, N.; Strohmaier, M.; Vladimirov, A. A.

    2016-06-01

    Due to multiple possible polarizations hard exclusive production of tensor mesons by virtual photons or in heavy meson decays offers interesting possibilities to study the helicity structure of the underlying short-distance process. Motivated by the first measurement of the transition form factor γ∗γ → f 2(1270) at large momentum transfers by the BELLE collaboration we present an improved QCD analysis of this reaction in the framework of collinear factorization including contributions of twist-three quark-antiquark-gluon operators and an estimate of soft end-point corrections using light-cone sum rules. The results appear to be in good agreement with the data, in particular the predicted scaling behavior is reproduced in all cases.

  20. CHIRAL LIMIT AND LIGHT QUARK MASSES IN 2+1 FLAVOR DOMAIN WALL QCD.

    SciTech Connect

    SCHOLZ,E.; LIN, M.

    2007-07-30

    We present results for meson masses and decay constants measured on 24{sup 3} x 64 lattices using the domain wall fermion formulation with an extension of the fifth dimension of L{sub s} = 16 for N{sub f} 2 + 1 dynamical quark flavors. The lightest dynamical meson mass in our set-up is around 331MeV. while partially quenched mesons reach masses as low as 250MeV. The applicability of SU(3) x SU(3) and SU(2) x SU(2) (partially quenched) chiral perturbation theory will be compared and we quote values for the low-energy constants from both approaches. We will extract the average light quark and strange quark masses and use a non-perturbative renormalization technique (RI/MOM) to quote their physical values. The pion and kaon decay constants are determined at those values from our chiral fits and their ratio is used to obtain the CKM-matrix element |V{sub us}|. The results presented here include statistical errors only.

  1. Branching ratios and CP violations of B→K0*(1430)K* decays in the perturbative QCD approach

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Xiao, Zhen-Jun; Zou, Zhi-Tian

    2013-11-01

    We investigate B→K0*(1430)K* decays in the perturbative QCD (pQCD) factorization approach, where B denotes Bu, Bd, and Bs mesons, respectively, and the scalar K0*(1430) is considered as a meson based on the model of the conventional two-quark structure. With the light-cone distribution amplitude of K0*(1430) defined in two scenarios, namely Scenario 1 and Scenario 2, we make the first estimation for the branching ratios and CP-violating asymmetries for those concerned decay modes in the pQCD factorization approach. For all considered B→K0*(1430)K* decays in this paper, only one preliminary upper limit on the branching ratio of B0→K0*(1430)0K¯*0 measured at 90% C.L. by the Belle Collaboration is available now. It is therefore of great interest to examine the predicted physical quantities at two B factories, the Large Hadron Collider experiments, and the forthcoming Super-B facility, and then to test the reliability of the pQCD approach employed to study the considered decay modes involving a p-wave scalar meson as one of the final state mesons. Furthermore, these pQCD predictions combined with the future precision measurements are also helpful to explore the complicated QCD dynamics involved in the light scalars.

  2. The QCD running coupling

    NASA Astrophysics Data System (ADS)

    Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

    2016-09-01

    We review the present theoretical and empirical knowledge for αs, the fundamental coupling underlying the interactions of quarks and gluons in Quantum Chromodynamics (QCD). The dependence of αs(Q2) on momentum transfer Q encodes the underlying dynamics of hadron physics-from color confinement in the infrared domain to asymptotic freedom at short distances. We review constraints on αs(Q2) at high Q2, as predicted by perturbative QCD, and its analytic behavior at small Q2, based on models of nonperturbative dynamics. In the introductory part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain. In the second, more technical, part of the review, we discuss the behavior of αs(Q2) in the high momentum transfer domain of QCD. We review how αs is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as "Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization-scale ambiguity. We also report recent significant measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the "Principle of Maximum Conformality", which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of theoretical conventions such as the renormalization scheme. In the last part of the review, we discuss the challenge of understanding the analytic behavior αs(Q2) in the low momentum transfer domain. We survey various theoretical models for the nonperturbative strongly coupled regime, such as the light-front holographic approach to QCD. This new framework predicts the form of the quark-confinement potential underlying hadron spectroscopy and

  3. Isolating prompt photons with narrow cones

    NASA Astrophysics Data System (ADS)

    Catani, S.; Fontannaz, M.; Guillet, J. Ph.; Pilon, E.

    2013-09-01

    We discuss the isolation of prompt photons in hadronic collisions by means of narrow isolation cones and the QCD computation of the corresponding cross sections. We reconsider the occurence of large perturbative terms with logarithmic dependence on the cone size and their impact on the fragmentation scale dependence. We cure the apparent perturbative violation of unitarity for small cone sizes, which had been noticed earlier in next-to-leading-order (NLO) calculations, by resumming the leading logarithmic dependence on the cone size. We discuss possible implications regarding the implementation of some hollow cone variants of the cone criterion, which simulate the experimental difficulty to impose isolation inside the region filled by the electromagnetic shower that develops in the calorimeter.

  4. ρ γ*→π (ρ ) transition form factors in the perturbative QCD factorization approach

    NASA Astrophysics Data System (ADS)

    Zhang, Ya-Lan; Cheng, Shan; Hua, Jun; Xiao, Zhen-Jun

    2015-11-01

    In this paper, we studied the ρ γ*→π and ρ γ*→ρ transition processes and made the calculations for the ρ π transition form factor Q4Fρ π(Q2) and the ρ -meson electromagnetic form factors, FLL ,LT ,TT(Q2) and F1 ,2 ,3(Q2), by employing the perturbative QCD (PQCD) factorization approach. For the ρ γ*→π transition, we found that the contribution to form factor Q4Fρ π(Q2) from the term proportional to the distribution amplitude combination ϕρT(x1)ϕπP(x2) is absolutely dominant, and the PQCD predictions for both the size and the Q2-dependence of this form factor Q4Fρ π(Q2) agree well with those from the extended anti-de Sitter/QCD models or the light-cone QCD sum rule. For the ρ γ*→ρ transition and in the region of Q2≥3 GeV2 , furthermore, we found that the PQCD predictions for the magnitude and their Q2-dependence of the F1(Q2) and F2(Q2) form factors agree well with those from the QCD sum rule, while the PQCD prediction for F3(Q2) is much larger than the one from the QCD sum rule.

  5. Naive time-reversal odd phenomena in semi-inclusive deep-inelastic scattering from light-cone constituent quark models

    SciTech Connect

    Barbara Pasquini, Peter Schweitzer

    2011-06-01

    We present results for leading-twist azimuthal asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to naively time-reversal odd transverse-momentum dependent parton distribution functions from the light-cone constituent quark model. We carefully discuss the range of applicability of the model, especially with regard to positivity constraints and evolution effects. We find good agreement with available experimental data from COMPASS and HERMES, and present predictions to be tested in forthcoming experiments at Jefferson Lab.

  6. Novel QCD Phenomena

    SciTech Connect

    Brodsky, Stanley J.; /SLAC

    2007-07-06

    I discuss a number of novel topics in QCD, including the use of the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. In particular, there is an exact correspondence between the fifth-dimension coordinate z of AdS space and a specific impact variable {zeta} which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. I also discuss a number of novel phenomenological features of QCD. Initial- and final-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and anomalous heavy quark effects. The presence of direct higher-twist processes where a proton is produced in the hard subprocess can explain the large proton-to-pion ratio seen in high centrality heavy ion collisions.

  7. Cone Heads

    ERIC Educational Resources Information Center

    Coy, Mary

    2005-01-01

    The author, a middle school art teacher, describes a sculpture project lesson involving Cone Heads (sculptures made from cardboard cones). Discussion of caricatures with exaggerated facial features and interesting profiles helped students understand that the more expressive the face, the better. This project took approximately four to five…

  8. Light-front dynamics and AdS/QCD correspondence: The pion form factor in the space- and time-like regions

    SciTech Connect

    Brodsky, Stanley J.; Teramond, Guy F. de

    2008-03-01

    The AdS/CFT correspondence between string theory in AdS space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. The AdS/CFT correspondence also provides insights into the inherently nonperturbative aspects of QCD such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of anti-de Sitter (AdS) space z and a specific light-front impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and which allow the computation of decay constants, form factors and other exclusive scattering amplitudes. Relativistic light-front equations in ordinary space-time are found which reproduce the results obtained using the fifth-dimensional theory. As specific examples we compute the pion coupling constant f{sub {pi}}, the pion charge radius and examine the propagation of the electromagnetic current in AdS space, which determines the space and timelike behavior of the pion form factor and the pole of the {rho} meson.

  9. The QCD running coupling

    DOE PAGESBeta

    Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

    2016-05-09

    Here, we review present knowledge onmore » $$\\alpha_{s}$$, the Quantum Chromodynamics (QCD) running coupling. The dependence of $$\\alpha_s(Q^2)$$ on momentum transfer $Q$ encodes the underlying dynamics of hadron physics --from color confinement in the infrared domain to asymptotic freedom at short distances. We will survey our present theoretical and empirical knowledge of $$\\alpha_s(Q^2)$$, including constraints at high $Q^2$ predicted by perturbative QCD, and constraints at small $Q^2$ based on models of nonperturbative dynamics. In the first, introductory, part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain. In the second, more technical, part of the review, we discuss $$\\alpha_s(Q^2)$$ in the high momentum transfer domain of QCD. We review how $$\\alpha_s$$ is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as `` Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization scale ambiguity. We also report recent important experimental measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the ``Principle of Maximum Conformality" which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of the gauge and renormalization scheme. In last part of the review, we discuss $$\\alpha_s(Q^2)$$ in the low momentum transfer domain, where there has been no consensus on how to define $$\\alpha_s(Q^2)$$ or its analytic behavior. We will discuss the various approaches used for low energy calculations. Among them, we will discuss the light-front holographic approach to QCD in the strongly coupled

  10. Speed, adaptation, and stability of the response to light in cone photoreceptors: The functional role of Ca-dependent modulation of ligand sensitivity in cGMP-gated ion channels

    PubMed Central

    2012-01-01

    The response of cone photoreceptors to light is stable and reproducible because of the exceptional regulation of the cascade of enzymatic reactions that link visual pigment (VP) excitation to the gating of cyclic GMP (cGMP)-gated ion channels (cyclic nucleotide–gated [CNG]) in the outer segment plasma membrane. Regulation is achieved in part through negative feedback control of some of these reactions by cytoplasmic free Ca2+. As part of the control process, Ca2+ regulates the phosphorylation of excited VP, the activity of guanylate cyclase, and the ligand sensitivity of the CNG ion channels. We measured photocurrents elicited by stimuli in the form of flashes, steps, and flashes superimposed on steps in voltage-clamped single bass cones isolated from striped bass retina. We also developed a computational model that comprises all the known molecular events of cone phototransduction, including all Ca-dependent controls. Constrained by available experimental data in bass cones and cone transduction biochemistry, we achieved an excellent match between experimental photocurrents and those simulated by the model. We used the model to explore the physiological role of CNG ion channel modulation. Control of CNG channel activity by both cGMP and Ca2+ causes the time course of the light-dependent currents to be faster than if only cGMP controlled their activity. Channel modulation also plays a critical role in the regulation of the light sensitivity and light adaptation of the cone photoresponse. In the absence of ion channel modulation, cone photocurrents would be unstable, oscillating during and at the offset of light stimuli. PMID:22200947

  11. Nonleptonic two-body decays of the B{sub c} meson in the light-front quark model and the QCD factorization approach

    SciTech Connect

    Choi, Ho-Meoyng; Ji, Chueng-Ryong

    2009-12-01

    We study exclusive nonleptonic two-body B{sub c}{yields}(D{sub (s)},{eta}{sub c},B{sub (s)})+F decays with F (pseudoscalar or vector mesons) factored out in the QCD factorization approach. The nonleptonic decay amplitudes are related to the product of meson decay constants and the form factors for semileptonic B{sub c} decays. As inputs in obtaining the branching ratios for a large set of nonleptonic B{sub c} decays, we use the weak form factors for the semileptonic B{sub c}{yields}(D{sub (s)},{eta}{sub c},B{sub (s)}) decays in the whole kinematical region and the unmeasured meson decay constants obtained from our previous light-front quark model. We compare our results for the branching ratios with those of other theoretical studies.

  12. QCD phenomenology

    SciTech Connect

    Hess, Peter O.

    2006-09-25

    A review is presented on the contributions of Mexican Scientists to QCD phenomenology. These contributions range from Constituent Quark model's (CQM) with a fixed number of quarks (antiquarks) to those where the number of quarks is not conserved. Also glueball spectra were treated with phenomenological models. Several other approaches are mentioned.

  13. Excited Baryons in Holographic QCD

    SciTech Connect

    de Teramond, Guy F.; Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins

    2011-11-08

    The light-front holographic QCD approach is used to describe baryon spectroscopy and the systematics of nucleon transition form factors. Baryon spectroscopy and the excitation dynamics of nucleon resonances encoded in the nucleon transition form factors can provide fundamental insight into the strong-coupling dynamics of QCD. The transition from the hard-scattering perturbative domain to the non-perturbative region is sensitive to the detailed dynamics of confined quarks and gluons. Computations of such phenomena from first principles in QCD are clearly very challenging. The most successful theoretical approach thus far has been to quantize QCD on discrete lattices in Euclidean space-time; however, dynamical observables in Minkowski space-time, such as the time-like hadronic form factors are not amenable to Euclidean numerical lattice computations.

  14. Novel QCD Phenomenology

    SciTech Connect

    Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins

    2011-08-12

    I review a number of topics where conventional wisdom in hadron physics has been challenged. For example, hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation. Such 'direct' processes can explain the deviations from perturbative QCD predictions in measurements of inclusive hadron cross sections at fixed x{sub T} = 2p{sub T}/{radical}s, as well as the 'baryon anomaly', the anomalously large proton-to-pion ratio seen in high centrality heavy ion collisions. Initial-state and final-state interactions of the struck quark, the soft-gluon rescattering associated with its Wilson line, lead to Bjorken-scaling single-spin asymmetries, diffractive deep inelastic scattering, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as nuclear shadowing and antishadowing. The Gribov-Glauber theory predicts that antishadowing of nuclear structure functions is not universal, but instead depends on the flavor quantum numbers of each quark and antiquark, thus explaining the anomalous nuclear dependence measured in deep-inelastic neutrino scattering. Since shadowing and antishadowing arise from the physics of leading-twist diffractive deep inelastic scattering, one cannot attribute such phenomena to the structure of the nucleus itself. It is thus important to distinguish 'static' structure functions, the probability distributions computed from the square of the target light-front wavefunctions, versus 'dynamical' structure functions which include the effects of the final-state rescattering of the struck quark. The importance of the J = 0 photon-quark QCD contact interaction in deeply virtual Compton scattering is also emphasized. The scheme-independent BLM method for setting the renormalization scale is discussed. Eliminating the renormalization scale ambiguity greatly improves the precision of QCD predictions and increases the sensitivity of searches for new physics at the LHC

  15. Two-loop conformal generators for leading-twist operators in QCD

    NASA Astrophysics Data System (ADS)

    Braun, V. M.; Manashov, A. N.; Moch, S.; Strohmaier, M.

    2016-03-01

    QCD evolution equations in minimal subtraction schemes have a hidden symmetry: one can construct three operators that commute with the evolution kernel and form an SL(2) algebra, i.e. they satisfy (exactly) the SL(2) commutation relations. In this paper we find explicit expressions for these operators to two-loop accuracy going over to QCD in non-integer d = 4 - 2ɛ space-time dimensions at the intermediate stage. In this way conformal symmetry of QCD is restored on quantum level at the specially chosen (critical) value of the coupling, and at the same time the theory is regularized allowing one to use the standard renormalization procedure for the relevant Feynman diagrams. Quantum corrections to conformal generators in d = 4 - 2ɛ effectively correspond to the conformal symmetry breaking in the physical theory in four dimensions and the SL(2) commutation relations lead to nontrivial constraints on the renormalization group equations for composite operators. This approach is valid to all orders in perturbation theory and the result includes automatically all terms that can be identified as due to a nonvanishing QCD β-function (in the physical theory in four dimensions). Our result can be used to derive three-loop evolution equations for flavor-nonsinglet quark-antiquark operators including mixing with the operators containing total derivatives. These equations govern, e.g., the scale dependence of generalized hadron parton distributions and light-cone meson distribution amplitudes.

  16. Transverse momentum-dependent parton distribution functions from lattice QCD

    SciTech Connect

    Michael Engelhardt, Philipp Haegler, Bernhard Musch, John Negele, Andreas Schaefer

    2012-12-01

    Transverse momentum-dependent parton distributions (TMDs) relevant for semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process can be defined in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection. Starting from such a definition, a scheme to determine TMDs in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are obtained using ensembles at the pion masses 369MeV and 518MeV, focusing in particular on the dependence of these shifts on the staple extent and a Collins-Soper-type evolution parameter quantifying proximity of the staples to the light cone.

  17. B-meson decay constants from 2+1-flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

    SciTech Connect

    Christ, Norman H.; Flynn, Jonathan M.; Izubuchi, Taku; Kawanai, Taichi; Lehner, Christoph; Soni, Amarjit; Van de Water, Ruth S.; Witzel, Oliver

    2015-03-10

    We calculate the B-meson decay constants fB, fBs, and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b-quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ≈ 0.11, 0.086 fm with unitary pion masses as light as Mπ ≈ 290 MeV; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b-quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also improve the lattice heavy-light current through O(αsa). We extrapolate our results to the physical light-quark masses and continuum using SU(2) heavy-meson chiral perturbation theory, and provide a complete systematic error budget. We obtain fB0 = 196.2(15.7) MeV, fB+ = 195.4(15.8) MeV, fBs = 235.4(12.2) MeV, fBs/fB0 = 1.193(59), and fBs/fB+ = 1.220(82), where the errors are statistical and total systematic added in quadrature. In addition, these results are in good agreement with other published results and provide an important independent cross check of other three-flavor determinations of B-meson decay constants using staggered light quarks.

  18. Quantum properties of QCD string fragmentation

    NASA Astrophysics Data System (ADS)

    Todorova-Nová, Šárka

    2016-07-01

    A simple quantization concept for a 3-dim QCD string is used to derive properties of QCD flux tube from the mass spectrum of light mesons and to predict observable quantum effects in correlations between adjacent hadrons. The quantized fragmentation model is presented and compared with experimental observations.

  19. Charge transport and vector meson dissociation across the thermal phase transition in lattice QCD with two light quark flavors

    NASA Astrophysics Data System (ADS)

    Brandt, Bastian B.; Francis, Anthony; Jäger, Benjamin; Meyer, Harvey B.

    2016-03-01

    We compute and analyze correlation functions in the isovector vector channel at vanishing spatial momentum across the deconfinement phase transition in lattice QCD. The simulations are carried out at temperatures T /Tc=0.156 , 0.8, 1.0, 1.25 and 1.67 with Tc≃203 MeV for two flavors of Wilson-Clover fermions with a zero-temperature pion mass of ≃270 MeV . Exploiting exact sum rules and applying a phenomenologically motivated Ansatz allows us to determine the spectral function ρ (ω ,T ) via a fit to the lattice correlation function data. From these results we estimate the electrical conductivity across the deconfinement phase transition via a Kubo formula and find evidence for the dissociation of the ρ meson by resolving its spectral weight at the available temperatures. We also apply the Backus-Gilbert method as a model-independent approach to this problem. At any given frequency, it yields a local weighted average of the true spectral function. We use this method to compare kinetic theory predictions and previously published phenomenological spectral functions to our lattice study.

  20. Interactions of Charmed Mesons with Light Pseudoscalar Mesons from Lattice QCD and Implications on the Nature of the D*s0(2317)

    SciTech Connect

    Liuming, Liu; Orginos, Kostas; Guo, Feng-Kun; Hanhart, Christoph; Meissner, Ulf-G

    2014-11-01

    We study the scattering of light pseudoscalar mesons ( p , K ) off charmed mesons ( D , D s ) in full lattice QCD. The S -wave scattering lengths are calculated using Luscher’s finite volume technique. We use a relativistic formulation for the charm quark. For the light quark, we use domain- wall fermions in the valence sector and improved Kogut-Susskind sea quarks. We calculate the scattering lengths of isospin-3/2 Dπ , D sπ , D s K , isospin-0 DK and isospin-1 DK channels on the lattice. For the chiral extrapolation, we use a chiral unitary approach to next-to-leading order, which at the same time allows us to give predictions for other channels. It turns out that our results support the interpretation of the D*s0( 2317 ) as a DK molecule. At the same time, we also update a prediction for the isospin breaking hadronic decay width G ( D*s0( 2317 )→ D sπ ) to ( 133± 22 ) keV.

  1. Hadron Spectroscopy and Wavefunctions in QCD and the AdS/CFT Correspondence

    SciTech Connect

    Brodsky, Stanley J.; Teramond, Guy F. de

    2006-02-11

    The AdS/CFT correspondence has led to important insights into the properties of quantum chromodynamics even though QCD is a broken conformal theory. We have recently shown how a holographic model based on a truncated AdS space can be used to obtain the hadronic spectrum of light qq-bar, qqq and gg bound states. Specific hadrons are identified by the correspondence of string modes with the dimension of the interpolating operator of the hadron's valence Fock state, including orbital angular momentum excitations. The predicted mass spectrum is linear M {proportional_to} L at high orbital angular momentum, in contrast to the quadratic dependence M2 {proportional_to} L found in the description of spinning strings. Since only one parameter, the QCD scale {lambda}QCD, is introduced, the agreement with the pattern of physical states is remarkable. In particular, the ratio of {delta} to nucleon trajectories is determined by the ratio of zeros of Bessel functions. The light-front quantization of gauge theories in light-cone gauge provides a frame-independent wavefunction representation of relativistic bound states, simple forms for current matrix elements, explicit unitarity, and a trivial vacuum. The light-front Fock-state wavefunctions encode the bound state properties of hadrons in terms of their quark and gluon degrees of freedom at the amplitude level. One can also use the extended AdS/CFT space-time theory to obtain a model for hadronic light-front wavefunctions, thus providing a relativistic description of hadrons in QCD at the amplitude level. The model wavefunctions display confinement at large inter-quark separation and conformal symmetry at short distances. In particular, the scaling and conformal properties of the LFWFs at high relative momenta agree with perturbative QCD. These AdS/CFT model wavefunctions could be used as an initial ansatz for a variational treatment of the light-front QCD Hamiltonian. We also show how hadron form factors in both the space

  2. Hamiltonian, path integral and BRST formulations of large scalar QCD on the light-front and spontaneous symmetry breaking

    NASA Astrophysics Data System (ADS)

    Kulshreshtha, Usha; Kulshreshtha, Daya Shankar; Vary, James P.

    2015-04-01

    Recently Grinstein, Jora, and Polosa have studied a theory of large- scalar quantum chromodynamics in one space and one time dimension. This theory admits a Bethe-Salpeter equation describing the discrete spectrum of quark-antiquark bound states. They consider gauge fields in the adjoint representation of and scalar fields in the fundamental representation. The theory is asymptotically free and linearly confining. The theory could possibly provide a good field theoretic framework for the description of a large class of diquark-antidiquark (tetra-quark) states. Recently we have studied the light-front quantization of this theory without a Higgs potential. In the present work, we study the light-front Hamiltonian, path integral, and BRST formulations of the theory in the presence of a Higgs potential. The light-front theory is seen to be gauge invariant, possessing a set of first-class constraints. The explicit occurrence of spontaneous symmetry breaking in the theory is shown in unitary gauge as well as in the light-front 't Hooft gauge.

  3. Glueball decay in holographic QCD

    SciTech Connect

    Hashimoto, Koji; Tan, C.-I; Terashima, Seiji

    2008-04-15

    Using holographic QCD based on D4-branes and D8-anti-D8-branes, we have computed couplings of glueballs to light mesons. We describe glueball decay by explicitly calculating its decay widths and branching ratios. Interestingly, while glueballs remain less well understood both theoretically and experimentally, our results are found to be consistent with the experimental data for the scalar glueball candidate f{sub 0}(1500). More generally, holographic QCD predicts that decay of any glueball to 4{pi}{sup 0} is suppressed, and that mixing of the lightest glueball with qq mesons is small.

  4. Systematic estimation of theoretical uncertainties in the calculation of the pion-photon transition form factor using light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Mikhailov, S. V.; Pimikov, A. V.; Stefanis, N. G.

    2016-06-01

    We consider the calculation of the pion-photon transition form factor Fγ*γπ0(Q2) within light-cone sum rules focusing attention to the low-mid region of momenta. The central aim is to estimate the theoretical uncertainties which originate from a wide variety of sources related to (i) the relevance of next-to-next-to-leading order radiative corrections (ii) the influence of the twist-four and the twist-six term (iii) the sensitivity of the results on auxiliary parameters, like the Borel scale M2, (iv) the role of the phenomenological description of resonances, and (v) the significance of a small but finite virtuality of the quasireal photon. Predictions for Fγ*γπ0(Q2) are presented which include all these uncertainties and found to comply within the margin of experimental error with the existing data in the Q2 range between 1 and 5 GeV2 , thus justifying the reliability of the applied calculational scheme. This provides a solid basis for confronting theoretical predictions with forthcoming data bearing small statistical errors.

  5. Hadron Spectroscopy and Wavefunctions in QCD and the AdS/CFT Correspondence

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Costa Rica U.

    2005-10-13

    The AdS/CFT correspondence has led to important insights into the properties of quantum chromodynamics even though QCD is a broken conformal theory. We have recently shown how a holographic model based on a truncated AdS space can be used to obtain the hadronic spectrum of light q{bar q}, qqq and gg bound states. Specific hadrons are identified by the correspondence of string modes with the dimension of the interpolating operator of the hadron's valence Fock state, including orbital angular momentum excitations. The predicted mass spectrum is linear M {proportional_to} L at high orbital angular momentum, in contrast to the quadratic dependence M{sup 2} {proportional_to} L found in the description of spinning strings. Since only one parameter, the QCD scale LQCD, is introduced, the agreement with the pattern of physical states is remarkable. In particular, the ratio of D to nucleon trajectories is determined by the ratio of zeros of Bessel functions. The light-front quantization of gauge theories in light-cone gauge provides a frame-independent wavefunction representation of relativistic bound states, simple forms for current matrix elements, explicit unitarity, and a trivial vacuum. The light-front Fock-state wavefunctions encode the bound state properties of hadrons in terms of their quark and gluon degrees of freedom at the amplitude level. One can also use the extended AdS/CFT space-time theory to obtain a model for hadronic light-front wavefunctions, thus providing a relativistic description of hadrons in QCD at the amplitude level. The model wavefunctions display confinement at large inter-quark separation and conformal symmetry at short distances. In particular, the scaling and conformal properties of the LFWFs at high relative momenta agree with perturbative QCD. These AdS/CFT model wavefunctions could be used as an initial ansatz for a variational treatment of the light-front QCD Hamiltonian. We also show how hadron form factors in both the space-like and

  6. Inferred L/M cone opsin polymorphism of ancestral tarsiers sheds dim light on the origin of anthropoid primates

    PubMed Central

    Melin, Amanda D.; Matsushita, Yuka; Moritz, Gillian L.; Dominy, Nathaniel J.; Kawamura, Shoji

    2013-01-01

    Tarsiers are small nocturnal primates with a long history of fuelling debate on the origin and evolution of anthropoid primates. Recently, the discovery of M and L opsin genes in two sister species, Tarsius bancanus (Bornean tarsier) and Tarsius syrichta (Philippine tarsier), respectively, was interpreted as evidence of an ancestral long-to-middle (L/M) opsin polymorphism, which, in turn, suggested a diurnal or cathemeral (arrhythmic) activity pattern. This view is compatible with the hypothesis that stem tarsiers were diurnal; however, a reversion to nocturnality during the Middle Eocene, as evidenced by hyper-enlarged orbits, predates the divergence of T. bancanus and T. syrichta in the Late Miocene. Taken together, these findings suggest that some nocturnal tarsiers possessed high-acuity trichromatic vision, a concept that challenges prevailing views on the adaptive origins of the anthropoid visual system. It is, therefore, important to explore the plausibility and antiquity of trichromatic vision in the genus Tarsius. Here, we show that Sulawesi tarsiers (Tarsius tarsier), a phylogenetic out-group of Philippine and Bornean tarsiers, have an L opsin gene that is more similar to the L opsin gene of T. syrichta than to the M opsin gene of T. bancanus in non-synonymous nucleotide sequence. This result suggests that an L/M opsin polymorphism is the ancestral character state of crown tarsiers and raises the possibility that many hallmarks of the anthropoid visual system evolved under dim (mesopic) light conditions. This interpretation challenges the persistent nocturnal–diurnal dichotomy that has long informed debate on the origin of anthropoid primates. PMID:23536597

  7. Fast electron generation in cones with ultraintense laser pulses

    SciTech Connect

    Van Woerkom, L.; Chowdhury, E.; Link, A.; Offermann, D.; Ovchinnikov, V.; Schumacher, D. W.; Akli, K. U.; Stephens, R. B.; Bartal, T.; Beg, F. N.; Chawla, S.; King, J. A.; Ma, T.; Chen, C. D.; Freeman, R. R.; Hey, D.; Key, M. H.; MacKinnon, A. J.; MacPhee, A. G.; Patel, P. K.

    2008-05-15

    Experimental results from copper cones irradiated with ultraintense laser light are presented. Spatial images and total yields of Cu K{sub {alpha}} fluorescence were measured as a function of the laser focusing properties. The fluorescence emission extends into the cone approximately 300 {mu}m from the cone tip and cannot be explained by ray tracing including cone wall absorption. In addition, the total fluorescence yield from cones is an order of magnitude higher than for equivalent mass foil targets. Indications are that the physics of the laser-cone interaction is dominated by preplasma created from the long duration, low-energy prepulse from the laser.

  8. Origin and Impact of Phototransduction Noise in Primate Cone Photoreceptors

    PubMed Central

    Angueyra, Juan Manuel; Rieke, Fred

    2013-01-01

    Noise in the responses of cone photoreceptors sets a fundamental limit to visual sensitivity, yet the origin of noise in mammalian cones and its relation to behavioral sensitivity are poorly understood. Our work here on primate cones improves understanding of these issues in three ways. First, we find that cone noise is not dominated by spontaneous photopigment activation or by quantal fluctuations in photon absorption but instead by other sources, namely channel noise and fluctuations in cGMP. Second, we find that adaptation in cones, unlike that in rods, affects signals and noise differently. This difference helps explain why thresholds for rod- and cone-mediated signals have different dependencies on background light level. Third, past estimates of noise in mammalian cones are too high to explain behavioral sensitivity. Our measurements indicate a lower level of cone noise, and thus help reconcile physiological and behavioral estimates of cone noise and sensitivity. PMID:24097042

  9. Shape of mesons in holographic QCD

    SciTech Connect

    Torabian, Mahdi; Yee, Ho-Ung

    2009-10-15

    Based on the expectation that the constituent quark model may capture the right physics in the large N limit, we point out that the orbital angular momentum of the quark-antiquark pair inside light mesons of low spins in the constituent quark model may provide a clue for the holographic dual string model of large N QCD. Our discussion, relying on a few suggestive assumptions, leads to a necessity of world-sheet fermions in the bulk of dual strings that can incorporate intrinsic spins of fundamental QCD degrees of freedom. We also comment on the interesting issue of the size of mesons in holographic QCD.

  10. Towards the chiral limit in QCD

    SciTech Connect

    Shailesh Chandrasekharan

    2006-02-28

    Computing hadronic observables by solving QCD from first principles with realistic quark masses is an important challenge in fundamental nuclear and particle physics research. Although lattice QCD provides a rigorous framework for such calculations many difficulties arise. Firstly, there are no good algorithms to solve lattice QCD with realistically light quark masses. Secondly, due to critical slowing down, Monte Carlo algorithms are able to access only small lattice sizes on coarse lattices. Finally, due to sign problems it is almost impossible to study the physics of finite baryon density. Lattice QCD contains roughly three mass scales: the cutoff (or inverse lattice spacing) a{sup -1}, the confinement scale {Lambda}{sub QCD}, and the pion mass m{sub {pi}}. Most conventional Monte Carlo algorithms for QCD become inefficient in two regimes: when {Lambda}{sub QCD} becomes small compared to a{sup -1} and when m{sub {pi}} becomes small compared to {Lambda}{sub QCD}. The former can be largely controlled by perturbation theory thanks to asymptotic freedom. The latter is more difficult since chiral extrapolations are typically non-analytic and can be unreliable if the calculations are not done at sufficiently small quark masses. For this reason it has been difficult to compute quantities close to the chiral limit. The essential goal behind this proposal was to develop a new approach towards understanding QCD and QCD-like theories with sufficiently light quarks. The proposal was based on a novel cluster algorithm discovered in the strong coupling limit with staggered fermions [1]. This algorithm allowed us to explore the physics of exactly massless quarks and as well as light quarks. Thus, the hope was that this discovery would lead to the complete solution of at least a few strongly coupled QCD-like theories. The solution would be far better than those achievable through conventional methods and thus would be able to shed light on the chiral physics from a new

  11. Regulation of Mammalian Cone Phototransduction by Recoverin and Rhodopsin Kinase*

    PubMed Central

    Sakurai, Keisuke; Chen, Jeannie; Khani, Shahrokh C.; Kefalov, Vladimir J.

    2015-01-01

    Cone photoreceptors function under daylight conditions and are essential for color perception and vision with high temporal and spatial resolution. A remarkable feature of cones is that, unlike rods, they remain responsive in bright light. In rods, light triggers a decline in intracellular calcium, which exerts a well studied negative feedback on phototransduction that includes calcium-dependent inhibition of rhodopsin kinase (GRK1) by recoverin. Rods and cones share the same isoforms of recoverin and GRK1, and photoactivation also triggers a calcium decline in cones. However, the molecular mechanisms by which calcium exerts negative feedback on cone phototransduction through recoverin and GRK1 are not well understood. Here, we examined this question using mice expressing various levels of GRK1 or lacking recoverin. We show that although GRK1 is required for the timely inactivation of mouse cone photoresponse, gradually increasing its expression progressively delays the cone response recovery. This surprising result is in contrast with the known effect of increasing GRK1 expression in rods. Notably, the kinetics of cone responses converge and become independent of GRK1 levels for flashes activating more than ∼1% of cone pigment. Thus, mouse cone response recovery in bright light is independent of pigment phosphorylation and likely reflects the spontaneous decay of photoactivated visual pigment. We also find that recoverin potentiates the sensitivity of cones in dim light conditions but does not contribute to their capacity to function in bright light. PMID:25673692

  12. Foundations of Perturbative QCD

    NASA Astrophysics Data System (ADS)

    Collins, John

    2011-04-01

    1. Introduction; 2. Why QCD?; 3. Basics of QCD; 4. Infra-red safety and non-safety; 5. Libby-Sterman analysis and power counting; 6. Parton model to parton theory I; 7. Parton model to parton theory II; 8. Factorization; 9. Corrections to the parton model in QCD; 10. Factorization and subtractions; 11. DIS in QCD; 12. Fragmentation; 13. TMD factorization; 14. Hadron-hadron collisions; 15. More advanced topics; Appendices; References; Index.

  13. Foundations of Perturbative QCD

    NASA Astrophysics Data System (ADS)

    Collins, John

    2013-11-01

    1. Introduction; 2. Why QCD?; 3. Basics of QCD; 4. Infra-red safety and non-safety; 5. Libby-Sterman analysis and power counting; 6. Parton model to parton theory I; 7. Parton model to parton theory II; 8. Factorization; 9. Corrections to the parton model in QCD; 10. Factorization and subtractions; 11. DIS in QCD; 12. Fragmentation; 13. TMD factorization; 14. Hadron-hadron collisions; 15. More advanced topics; Appendices; References; Index.

  14. Loss of cone cyclic nucleotide-gated channel leads to alterations in light response modulating system and cellular stress response pathways: a gene expression profiling study.

    PubMed

    Ma, Hongwei; Thapa, Arjun; Morris, Lynsie M; Michalakis, Stylianos; Biel, Martin; Frank, Mark Barton; Bebak, Melissa; Ding, Xi-Qin

    2013-10-01

    The cone photoreceptor cyclic nucleotide-gated (CNG) channel is essential for central and color vision and visual acuity. Mutations in the channel subunits CNGA3 and CNGB3 are associated with achromatopsia and cone dystrophy. We investigated the gene expression profiles in mouse retina with CNG channel deficiency using whole genome expression microarrays. As cones comprise only 2 to 3% of the total photoreceptor population in the wild-type mouse retina, the mouse lines with CNG channel deficiency on a cone-dominant background, i.e. Cnga3-/-/Nrl-/- and Cngb3-/-/Nrl-/- mice, were used in our study. Comparative data analysis revealed a total of 105 genes altered in Cnga3-/-/Nrl-/- and 92 in Cngb3-/-/Nrl-/- retinas, relative to Nrl-/- retinas, with 27 genes changed in both genotypes. The differentially expressed genes primarily encode proteins associated with cell signaling, cellular function maintenance and gene expression. Ingenuity pathway analysis (IPA) identified 26 and 9 canonical pathways in Cnga3-/-/Nrl-/- and Cngb3-/-/Nrl-/- retinas, respectively, with 6 pathways being shared. The shared pathways include phototransduction, cAMP/PKA-mediated signaling, endothelin signaling, and EIF2/endoplasmic reticulum (ER) stress, whereas the IL-1, CREB, and purine metabolism signaling were found to specifically associate with Cnga3 deficiency. Thus, CNG channel deficiency differentially regulates genes that affect cell processes such as phototransduction, cellular survival and gene expression, and such regulations play a crucial role(s) in the retinal adaptation to impaired cone phototransduction. Though lack of Cnga3 and Cngb3 shares many common pathways, deficiency of Cnga3 causes more significant alterations in gene expression. This work provides insights into how cones respond to impaired phototransduction at the gene expression levels. PMID:23740940

  15. Loss of cone cyclic nucleotide-gated channel leads to alterations in light response modulating system and cellular stress response pathways: a gene expression profiling study

    PubMed Central

    Ma, Hongwei; Thapa, Arjun; Morris, Lynsie M.; Michalakis, Stylianos; Biel, Martin; Frank, Mark Barton; Bebak, Melissa; Ding, Xi-Qin

    2013-01-01

    The cone photoreceptor cyclic nucleotide-gated (CNG) channel is essential for central and color vision and visual acuity. Mutations in the channel subunits CNGA3 and CNGB3 are associated with achromatopsia and cone dystrophy. We investigated the gene expression profiles in mouse retina with CNG channel deficiency using whole genome expression microarrays. As cones comprise only 2 to 3% of the total photoreceptor population in the wild-type mouse retina, the mouse lines with CNG channel deficiency on a cone-dominant background, i.e. Cnga3−/−/Nrl−/− and Cngb3−/−/Nrl−/− mice, were used in our study. Comparative data analysis revealed a total of 105 genes altered in Cnga3−/−/Nrl−/− and 92 in Cngb3−/−/Nrl−/− retinas, relative to Nrl−/− retinas, with 27 genes changed in both genotypes. The differentially expressed genes primarily encode proteins associated with cell signaling, cellular function maintenance and gene expression. Ingenuity pathway analysis (IPA) identified 26 and 9 canonical pathways in Cnga3−/−/Nrl−/− and Cngb3−/−/Nrl−/− retinas, respectively, with 6 pathways being shared. The shared pathways include phototransduction, cAMP/PKA-mediated signaling, endothelin signaling, and EIF2/endoplasmic reticulum (ER) stress, whereas the IL-1, CREB, and purine metabolism signaling were found to specifically associate with Cnga3 deficiency. Thus, CNG channel deficiency differentially regulates genes that affect cell processes such as phototransduction, cellular survival and gene expression, and such regulations play a crucial role(s) in the retinal adaptation to impaired cone phototransduction. Though lack of Cnga3 and Cngb3 shares many common pathways, deficiency of Cnga3 causes more significant alterations in gene expression. This work provides insights into how cones respond to impaired phototransduction at the gene expression levels. PMID:23740940

  16. ADS/CFT and QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U. /SLAC

    2007-02-21

    The AdS/CFT correspondence between string theory in AdS space and conformal .eld theories in physical spacetime leads to an analytic, semi-classical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. Although QCD is not conformally invariant, one can nevertheless use the mathematical representation of the conformal group in five-dimensional anti-de Sitter space to construct a first approximation to the theory. The AdS/CFT correspondence also provides insights into the inherently non-perturbative aspects of QCD, such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of AdS space z and a specific impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions, the fundamental entities which encode hadron properties and allow the computation of decay constants, form factors, and other exclusive scattering amplitudes. New relativistic lightfront equations in ordinary space-time are found which reproduce the results obtained using the 5-dimensional theory. The effective light-front equations possess remarkable algebraic structures and integrability properties. Since they are complete and orthonormal, the AdS/CFT model wavefunctions can also be used as a basis for the diagonalization of the full light-front QCD Hamiltonian, thus systematically improving the AdS/CFT approximation.

  17. QCD with chiral 4-fermion interactions ({chi}QCD)

    SciTech Connect

    Kogut, J.B.; Sinclair, D.K.

    1996-10-01

    Lattice QCD with staggered quarks is augmented by the addition of a chiral 4-fermion interaction. The Dirac operator is now non-singular at m{sub q}=0, decreasing the computing requirements for light quark simulations by at least an order of magnitude. We present preliminary results from simulations at finite and zero temperatures for m{sub q}=0, with and without gauge fields. Chiral QCD enables simulations at physical u and d quark masses with at least an order of magnitude saving in CPU time. It also enables simulations with zero quark masses which is important for determining the equation of state. A renormalization group analysis will be needed to continue to the continuum limit. 7 refs., 2 figs.

  18. Cold knife cone biopsy

    MedlinePlus

    A cold knife cone biopsy (conization) is surgery to remove a sample of abnormal tissue from the cervix. The ... Cold knife cone biopsy is done to detect cervical cancer or early changes that lead to cancer. ...

  19. Cold knife cone biopsy

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003910.htm Cold knife cone biopsy To use the sharing features on this page, please enable JavaScript. A cold knife cone biopsy (conization) is surgery to remove ...

  20. Spectral continuity in dense QCD

    SciTech Connect

    Hatsuda, Tetsuo; Yamamoto, Naoki; Tachibana, Motoi

    2008-07-01

    The vector mesons in three-flavor quark matter with chiral and diquark condensates are studied using the in-medium QCD sum rules. The diquark condensate leads to a mass splitting between the flavor-octet and flavor-singlet channels. At high density, the singlet vector meson disappears from the low-energy spectrum, while the octet vector mesons survive as light excitations with a mass comparable to the fermion gap. A possible connection between the light gluonic modes and the flavor-octet vector mesons at high density is also discussed.

  1. Recoverin depletion accelerates cone photoresponse recovery

    PubMed Central

    Zang, Jingjing; Keim, Jennifer; Kastenhuber, Edda; Gesemann, Matthias; Neuhauss, Stephan C. F.

    2015-01-01

    The neuronal Ca2+-binding protein Recoverin has been shown to regulate phototransduction termination in mammalian rods. Here we identify four recoverin genes in the zebrafish genome, rcv1a, rcv1b, rcv2a and rcv2b, and investigate their role in modulating the cone phototransduction cascade. While Recoverin-1b is only found in the adult retina, the other Recoverins are expressed throughout development in all four cone types, except Recoverin-1a, which is expressed only in rods and UV cones. Applying a double flash electroretinogram (ERG) paradigm, downregulation of Recoverin-2a or 2b accelerates cone photoresponse recovery, albeit at different light intensities. Exclusive recording from UV cones via spectral ERG reveals that knockdown of Recoverin-1a alone has no effect, but Recoverin-1a/2a double-knockdowns showed an even shorter recovery time than Recoverin-2a-deficient larvae. We also showed that UV cone photoresponse kinetics depend on Recoverin-2a function via cone-specific kinase Grk7a. This is the first in vivo study demonstrating that cone opsin deactivation kinetics determine overall photoresponse shut off kinetics. PMID:26246494

  2. Cone Early Maturity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hop cone early maturity is thought to be caused by diffuse infections of cone, just prior to harvest, by Podosphaera macularis. The disease is best managed by limiting the amount of leaf infection by P. macularis prior to bloom. The yield and quality reductions associated with Hop cone early matur...

  3. QCD for Postgraduates (5/5)

    ScienceCinema

    None

    2011-10-06

    Modern QCD - Lecture 5 We will introduce and discuss in some detail the two main classes of jets: cone type and sequential-recombination type. We will discuss their basic properties, as well as more advanced concepts such as jet substructure, jet filtering, ways of optimizing the jet radius, ways of defining the areas of jets, and of establishing the quality measure of the jet-algorithm in terms of discriminating power in specific searches. Finally we will discuss applications for Higgs searches involving boosted particles.

  4. QCD In Extreme Conditions

    NASA Astrophysics Data System (ADS)

    Wilczek, Frank

    Introduction Symmetry and the Phenomena of QCD Apparent and Actual Symmetries Asymptotic Freedom Confinement Chiral Symmetry Breaking Chiral Anomalies and Instantons High Temperature QCD: Asymptotic Properties Significance of High Temperature QCD Numerical Indications for Quasi-Free Behavior Ideas About Quark-Gluon Plasma Screening Versus Confinement Models of Chiral Symmetry Breaking More Refined Numerical Experiments High-Temperature QCD: Phase Transitions Yoga of Phase Transitions and Order Parameters Application to Glue Theories Application to Chiral Transitions Close Up on Two Flavors A Genuine Critical Point! (?) High-Density QCD: Methods Hopes, Doubts, and Fruition Another Renormalization Group Pairing Theory Taming the Magnetic Singularity High-Density QCD: Color-Flavor Locking and Quark-Hadron Continuity Gauge Symmetry (Non)Breaking Symmetry Accounting Elementary Excitations A Modified Photon Quark-Hadron Continuity Remembrance of Things Past More Quarks Fewer Quarks and Reality

  5. Phototransduction in mouse rods and cones

    PubMed Central

    Fu, Yingbin; Yau, King-Wai

    2010-01-01

    Phototransduction is the process by which light triggers an electrical signal in a photoreceptor cell. Image-forming vision in vertebrates is mediated by two types of photoreceptors: the rods and the cones. In this review, we provide a summary of the success in which the mouse has served as a vertebrate model for studying rod phototransduction, with respect to both the activation and termination steps. Cones are still not as well-understood as rods partly because it is difficult to work with mouse cones due to their scarcity and fragility. The situation may change, however. PMID:17226052

  6. Dark energy from QCD

    SciTech Connect

    Urban, Federico R.; Zhitnitsky, Ariel R.

    2010-08-30

    We review two mechanisms rooted in the infrared sector of QCD which, by exploiting the properties of the QCD ghost, as introduced by Veneziano, provide new insight on the cosmological dark energy problem, first, in the form of a Casimir-like energy from quantising QCD in a box, and second, in the form of additional, time-dependent, vacuum energy density in an expanding universe. Based on [1, 2].

  7. Non-image Forming Light Detection by Melanopsin, Rhodopsin, and Long-Middlewave (L/W) Cone Opsin in the Subterranean Blind Mole Rat, Spalax Ehrenbergi: Immunohistochemical Characterization, Distribution, and Connectivity.

    PubMed

    Esquiva, Gema; Avivi, Aaron; Hannibal, Jens

    2016-01-01

    The blind mole rat, Spalax ehrenbergi, can, despite severely degenerated eyes covered by fur, entrain to the daily light/dark cycle and adapt to seasonal changes due to an intact circadian timing system. The present study demonstrates that the Spalax retina contains a photoreceptor layer, an outer nuclear layer (ONL), an outer plexiform layer (OPL), an inner nuclear layer (INL), an inner plexiform layer (IPL), and a ganglion cell layer (GCL). By immunohistochemistry, the number of melanopsin (mRGCs) and non-melanopsin bearing retinal ganglion cells was analyzed in detail. Using the ganglion cell marker RNA-binding protein with multiple splicing (RBPMS) it was shown that the Spalax eye contains 890 ± 62 RGCs. Of these, 87% (752 ± 40) contain melanopsin (cell density 788 melanopsin RGCs/mm(2)). The remaining RGCs were shown to co-store Brn3a and calretinin. The melanopsin cells were located mainly in the GCL with projections forming two dendritic plexuses located in the inner part of the IPL and in the OPL. Few melanopsin dendrites were also found in the ONL. The Spalax retina is rich in rhodopsin and long/middle wave (L/M) cone opsin bearing photoreceptor cells. By using Ctbp2 as a marker for ribbon synapses, both rods and L/M cone ribbons containing pedicles in the OPL were found in close apposition with melanopsin dendrites in the outer plexus suggesting direct synaptic contact. A subset of cone bipolar cells and all photoreceptor cells contain recoverin while a subset of bipolar and amacrine cells contain calretinin. The calretinin expressing amacrine cells seemed to form synaptic contacts with rhodopsin containing photoreceptor cells in the OPL and contacts with melanopsin cell bodies and dendrites in the IPL. The study demonstrates the complex retinal circuitry used by the Spalax to detect light, and provides evidence for both melanopsin and non-melanopsin projecting pathways to the brain. PMID:27375437

  8. Non-image Forming Light Detection by Melanopsin, Rhodopsin, and Long-Middlewave (L/W) Cone Opsin in the Subterranean Blind Mole Rat, Spalax Ehrenbergi: Immunohistochemical Characterization, Distribution, and Connectivity

    PubMed Central

    Esquiva, Gema; Avivi, Aaron; Hannibal, Jens

    2016-01-01

    The blind mole rat, Spalax ehrenbergi, can, despite severely degenerated eyes covered by fur, entrain to the daily light/dark cycle and adapt to seasonal changes due to an intact circadian timing system. The present study demonstrates that the Spalax retina contains a photoreceptor layer, an outer nuclear layer (ONL), an outer plexiform layer (OPL), an inner nuclear layer (INL), an inner plexiform layer (IPL), and a ganglion cell layer (GCL). By immunohistochemistry, the number of melanopsin (mRGCs) and non-melanopsin bearing retinal ganglion cells was analyzed in detail. Using the ganglion cell marker RNA-binding protein with multiple splicing (RBPMS) it was shown that the Spalax eye contains 890 ± 62 RGCs. Of these, 87% (752 ± 40) contain melanopsin (cell density 788 melanopsin RGCs/mm2). The remaining RGCs were shown to co-store Brn3a and calretinin. The melanopsin cells were located mainly in the GCL with projections forming two dendritic plexuses located in the inner part of the IPL and in the OPL. Few melanopsin dendrites were also found in the ONL. The Spalax retina is rich in rhodopsin and long/middle wave (L/M) cone opsin bearing photoreceptor cells. By using Ctbp2 as a marker for ribbon synapses, both rods and L/M cone ribbons containing pedicles in the OPL were found in close apposition with melanopsin dendrites in the outer plexus suggesting direct synaptic contact. A subset of cone bipolar cells and all photoreceptor cells contain recoverin while a subset of bipolar and amacrine cells contain calretinin. The calretinin expressing amacrine cells seemed to form synaptic contacts with rhodopsin containing photoreceptor cells in the OPL and contacts with melanopsin cell bodies and dendrites in the IPL. The study demonstrates the complex retinal circuitry used by the Spalax to detect light, and provides evidence for both melanopsin and non-melanopsin projecting pathways to the brain. PMID:27375437

  9. Distribution of cone photoreceptors in the mammalian retina.

    PubMed

    Szél, A; Röhlich, P; Caffé, A R; van Veen, T

    1996-12-15

    The retina of mammals contains various amounts of cone photoreceptors that are relatively evenly distributed and display a radially or horizontally oriented area of peak density. In most mammalian species two spectrally different classes of cone can be distinguished with various histochemical and physiological methods. These cone classes occur in a relatively constant ratio, middle-to-longwave sensitive cones being predominant over short-wave cones. Recent observations do not support the idea that each cone subpopulation is uniformly distributed across the retina. With appropriate type-specific markers, unexpected patterns of colour cone topography have been revealed in certain species. In the mouse and the rabbit, the "standard" uniform pattern was found to be confined exclusively to the dorsal retina. In a ventral zone of variable width all cones express short-wave pigment, a phenomenon whose biological significance is not known yet. Dorso-ventral asymmetries have been described in lower vertebrates, matching the spectral distribution of light reaching the retina from various sectors of the visual field. It is not clear, however, whether the retinal cone fields in mammals carry out a function similar to that of their counterparts in fish and amphibians. Since in a number of mammalian species short-wave cones are the first to differentiate, and the expression of the short-wave pigment seems to be the default pathway of cone differentiation, we suggest that the short-wave sensitive cone fields are rudimentary areas conserving an ancestral stage of the photopigment evolution. PMID:9016448

  10. Transformation of light double cones in the human retina: the origin of trichromatism, of 4D-spatiotemporal vision, and of patchwise 4D Fourier transformation in Talbot imaging

    NASA Astrophysics Data System (ADS)

    Lauinger, Norbert

    1997-09-01

    The interpretation of the 'inverted' retina of primates as an 'optoretina' (a light cones transforming diffractive cellular 3D-phase grating) integrates the functional, structural, and oscillatory aspects of a cortical layer. It is therefore relevant to consider prenatal developments as a basis of the macro- and micro-geometry of the inner eye. This geometry becomes relevant for the postnatal trichromatic synchrony organization (TSO) as well as the adaptive levels of human vision. It is shown that the functional performances, the trichromatism in photopic vision, the monocular spatiotemporal 3D- and 4D-motion detection, as well as the Fourier optical image transformation with extraction of invariances all become possible. To transform light cones into reciprocal gratings especially the spectral phase conditions in the eikonal of the geometrical optical imaging before the retinal 3D-grating become relevant first, then in the von Laue resp. reciprocal von Laue equation for 3D-grating optics inside the grating and finally in the periodicity of Talbot-2/Fresnel-planes in the near-field behind the grating. It is becoming possible to technically realize -- at least in some specific aspects -- such a cortical optoretina sensor element with its typical hexagonal-concentric structure which leads to these visual functions.

  11. Cone inputs to murine striate cortex

    PubMed Central

    Ekesten, Björn; Gouras, Peter

    2008-01-01

    Background We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods. Results Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner. Conclusion Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex. PMID:19014590

  12. QCD results at CDF

    SciTech Connect

    Norniella, Olga; /Barcelona, IFAE

    2005-01-01

    Recent QCD measurements from the CDF collaboration at the Tevatron are presented, together with future prospects as the luminosity increases. The measured inclusive jet cross section is compared to pQCD NLO predictions. Precise measurements on jet shapes and hadronic energy flows are compared to different phenomenological models that describe gluon emissions and the underlying event in hadron-hadron interactions.

  13. Resumming double logarithms in the QCD evolution of color dipoles

    NASA Astrophysics Data System (ADS)

    Iancu, E.; Madrigal, J. D.; Mueller, A. H.; Soyez, G.; Triantafyllopoulos, D. N.

    2015-05-01

    The higher-order perturbative corrections, beyond leading logarithmic accuracy, to the BFKL evolution in QCD at high energy are well known to suffer from a severe lack-of-convergence problem, due to radiative corrections enhanced by double collinear logarithms. Via an explicit calculation of Feynman graphs in light cone (time-ordered) perturbation theory, we show that the corrections enhanced by double logarithms (either energy-collinear, or double collinear) are associated with soft gluon emissions which are strictly ordered in lifetime. These corrections can be resummed to all orders by solving an evolution equation which is non-local in rapidity. This equation can be equivalently rewritten in local form, but with modified kernel and initial conditions, which resum double collinear logs to all orders. We extend this resummation to the next-to-leading order BFKL and BK equations. The first numerical studies of the collinearly-improved BK equation demonstrate the essential role of the resummation in both stabilizing and slowing down the evolution.

  14. QCD Physics at the Tevatron Collider

    SciTech Connect

    Messina, Andrea

    2005-10-12

    In this contribution some of the prominent QCD physics results from CDF and D0 experiments in Run II are presented. The cross sections and the properties of jets are discussed for both the inclusive and the b-jet production. Results on the associate production of light and heavy flavour jets together with vector bosons are also reported.

  15. Photovoltage of Rods and Cones in the Macaque Retina

    NASA Astrophysics Data System (ADS)

    Schneeweis, David M.; Schnapf, Julie L.

    1995-05-01

    The kinetics, gain, and reliability of light responses of rod and cone photoreceptors are important determinants of overall visual sensitivity. In voltage recordings from photoreceptors in an intact primate retina, rods were found to be functionally isolated from each other, unlike the tightly coupled rods of cold-blooded vertebrates. Cones were observed to receive excitatory input from rods, which indicates that the cone pathway also processes rod signals. This input might be expected to degrade the spatial resolution of mesopic vision.

  16. Modal content of living human cone photoreceptors

    PubMed Central

    Liu, Zhuolin; Kocaoglu, Omer P.; Turner, Timothy L.; Miller, Donald T.

    2015-01-01

    Decades of experimental and theoretical investigations have established that photoreceptors capture light based on the principles of optical waveguiding. Yet considerable uncertainty remains, even for the most basic prediction as to whether photoreceptors support more than a single waveguide mode. To test for modal behavior in human cone photoreceptors in the near infrared, we took advantage of adaptive-optics optical coherence tomography (AO-OCT, λc = 785 nm) to noninvasively image in three dimensions the reflectance profile of cones. Modal content of reflections generated at the cone inner segment and outer segment junction (IS/OS) and cone outer segment tip (COST) was examined over a range of cone diameters in 1,802 cones from 0.6° to 10° retinal eccentricity. Second moment analysis in conjunction with theoretical predictions indicate cone IS and OS have optical properties consistent of waveguides, which depend on segment diameter and refractive index. Cone IS was found to support a single mode near the fovea (≤3°) and multiple modes further away (>4°). In contrast, no evidence of multiple modes was found in the cone OSs. The IS/OS and COST reflections share a common optical aperture, are most circular near the fovea, show no orientation preference, and are temporally stable. We tested mode predictions of a conventional step-index fiber model and found that in order to fit our AO-OCT results required a lower estimate of the IS refractive index and introduction of an IS focusing/tapering effect. PMID:26417509

  17. Bat Eyes Have Ultraviolet-Sensitive Cone Photoreceptors

    PubMed Central

    Müller, Brigitte; Glösmann, Martin; Peichl, Leo; Knop, Gabriel C.; Hagemann, Cornelia; Ammermüller, Josef

    2009-01-01

    Mammalian retinae have rod photoreceptors for night vision and cone photoreceptors for daylight and colour vision. For colour discrimination, most mammals possess two cone populations with two visual pigments (opsins) that have absorption maxima at short wavelengths (blue or ultraviolet light) and long wavelengths (green or red light). Microchiropteran bats, which use echolocation to navigate and forage in complete darkness, have long been considered to have pure rod retinae. Here we use opsin immunohistochemistry to show that two phyllostomid microbats, Glossophaga soricina and Carollia perspicillata, possess a significant population of cones and express two cone opsins, a shortwave-sensitive (S) opsin and a longwave-sensitive (L) opsin. A substantial population of cones expresses S opsin exclusively, whereas the other cones mostly coexpress L and S opsin. S opsin gene analysis suggests ultraviolet (UV, wavelengths <400 nm) sensitivity, and corneal electroretinogram recordings reveal an elevated sensitivity to UV light which is mediated by an S cone visual pigment. Therefore bats have retained the ancestral UV tuning of the S cone pigment. We conclude that bats have the prerequisite for daylight vision, dichromatic colour vision, and UV vision. For bats, the UV-sensitive cones may be advantageous for visual orientation at twilight, predator avoidance, and detection of UV-reflecting flowers for those that feed on nectar. PMID:19636375

  18. Lattice QCD in rotating frames.

    PubMed

    Yamamoto, Arata; Hirono, Yuji

    2013-08-23

    We formulate lattice QCD in rotating frames to study the physics of QCD matter under rotation. We construct the lattice QCD action with the rotational metric and apply it to the Monte Carlo simulation. As the first application, we calculate the angular momenta of gluons and quarks in the rotating QCD vacuum. This new framework is useful to analyze various rotation-related phenomena in QCD. PMID:24010426

  19. Electrical coupling between cones in turtle retina.

    PubMed Central

    Detwiler, P B; Hodgkin, A L

    1979-01-01

    1. The electrical coupling between cones of known spectral sensitivity in the peripheral part of the turtle's retina was studied by passing current through a micro-electrode inserted into one cone and recording with a second micro-electrode inserted into a neighbouring cone. 2. Spatial sensitivity profiles were determined by recording flash responses to a long narrow strip of light which was moved across the impaled cones in orthogonal directions. These measurements gave both the length constant lambda of electrical spread in the cone network and the separation of the two cones. 3. The cone separation determined from the spatial profiles agreed closely with that measured directly by injecting a fluorescent dye into two cones. 4. The length constant lambda varied from 18 to 39 micron with a mean of 25 micron for red-sensitive cones and 26 micron for green-sensitive cones. 5. The majority of cone pairs studied were electrically coupled provided they had the same spectral sensitivity and were separated by less than 60 micron: thirty-two out of thirty-six red-red pairs, two out of two green-green pairs, none out of eight red-green pairs: no blue cones were observed. 6. The strength of electrical coupling was expressed as a mutual resistance defined as the voltage in one cell divided by the current flowing into the other. Mutual resistances decreased from a maximum value of about 30 M omega at separations close to zero to 0.2 M omega, the lower limit of detectable coupling at separations of about 60 micron. Mutual resistances were always positive and were independent of which cell was directly polarized. The coupling seemed to be ohmic and any rectification or non-linearity probably arose in the cone membranes rather than in the coupling resistances. 7. The results were analysed in terms of the Lamb & Simon (1977) theories of square and hexagonal lattices, which approximate to the continuous sheet model except in the case of the cone to which current is applied. 8. The

  20. Observation of string breaking in QCD

    SciTech Connect

    Bali, Gunnar S.; Neff, Hartmut; Duessel, Thomas; Lippert, Thomas; Schilling, Klaus

    2005-06-01

    We numerically investigate the transition of the static quark-antiquark string into a static-light meson-antimeson system. Improving noise reduction techniques, we are able to resolve the signature of string breaking dynamics for n{sub f}=2 lattice QCD at zero temperature. This result can be related to properties of quarkonium systems. We also study short-distance interactions between two static-light mesons.

  1. Functional renormalization group analysis of the soft mode at the QCD critical point

    NASA Astrophysics Data System (ADS)

    Yokota, Takeru; Kunihiro, Teiji; Morita, Kenji

    2016-07-01

    We make an intensive investigation of the soft mode at the quantum chromodynamics (QCD) critical point on the basis of the functional renormalization group (FRG) method in the local potential approximation. We calculate the spectral functions ρ_{σ, π}(ω, p) in the scalar (σ) and pseudoscalar (π) channels beyond the random phase approximation in the quark-meson model. At finite baryon chemical potential μ with a finite quark mass, the baryon-number fluctuation is coupled to the scalar channel and the spectral function in the σ channel has a support not only in the time-like (ω > p) but also in the space-like (ω < p) regions, which correspond to the mesonic and the particle-hole phonon excitations, respectively. We find that the energy of the peak position of the latter becomes vanishingly small with the height being enhanced as the system approaches the QCD critical point, which is a manifestation of the fact that the phonon mode is the soft mode associated with the second-order transition at the QCD critical point, as has been suggested by some authors. Moreover, our extensive calculation of the spectral function in the (ω, p) plane enables us to see that the mesonic and phonon modes have the respective definite dispersion relations ω_{σ.ph}(p), and it turns out that ω_{σ}(p) crosses the light-cone line into the space-like region, and then eventually merges into the phonon mode as the system approaches the critical point more closely. This implies that the sigma-mesonic mode also becomes soft at the critical point. We also provide numerical stability conditions that are necessary for obtaining the accurate effective potential from the flow equation.

  2. Exploring hyperons and hypernuclei with lattice QCD

    SciTech Connect

    Beane, S.R.; Bedaque, P.F.; Parreno, A.; Savage, M.J.

    2003-01-01

    In this work we outline a program for lattice QCD that wouldprovide a first step toward understanding the strong and weakinteractions of strange baryons. The study of hypernuclear physics hasprovided a significant amount of information regarding the structure andweak decays of light nuclei containing one or two Lambda's, and Sigma's.From a theoretical standpoint, little is known about the hyperon-nucleoninteraction, which is required input for systematic calculations ofhypernuclear structure. Furthermore, the long-standing discrepancies inthe P-wave amplitudes for nonleptonic hyperon decays remain to beunderstood, and their resolution is central to a better understanding ofthe weak decays of hypernuclei. We present a framework that utilizesLuscher's finite-volume techniques in lattice QCD to extract thescattering length and effective range for Lambda-N scattering in both QCDand partially-quenched QCD. The effective theory describing thenonleptonic decays of hyperons using isospin symmetry alone, appropriatefor lattice calculations, is constructed.

  3. Analysis of the {Lambda}{sub b{yields}{Lambda}}l{sup +}l{sup -} decay in QCD

    SciTech Connect

    Aliev, T. M.; Savci, M.; Azizi, K.

    2010-03-01

    Taking into account the {Lambda} baryon distribution amplitudes and the most general form of the interpolating current of the {Lambda}{sub b}, the semileptonic {Lambda}{sub b{yields}{Lambda}}l{sup +}l{sup -} transition is investigated in the framework of the light cone QCD sum rules. Sum rules for all 12 form factors responsible for the {Lambda}{sub b{yields}{Lambda}}l{sup +}l{sup -} decay are constructed. The obtained results for the form factors are used to compute the branching fraction. A comparison of the obtained results with the existing predictions of the heavy quark effective theory is presented. The results of the branching ratio shows the detectability of this channel at the Large Hadron Collider beauty in the near future is quite high.

  4. QCD (&) event generators

    SciTech Connect

    Skands, Peter Z.; /Fermilab

    2005-07-01

    Recent developments in QCD phenomenology have spurred on several improved approaches to Monte Carlo event generation, relative to the post-LEP state of the art. In this brief review, the emphasis is placed on approaches for (1) consistently merging fixed-order matrix element calculations with parton shower descriptions of QCD radiation, (2) improving the parton shower algorithms themselves, and (3) improving the description of the underlying event in hadron collisions.

  5. Cone photopigment bleaching abnormalities in diabetes.

    PubMed

    Elsner, A E; Burns, S A; Lobes, L A; Doft, B H

    1987-04-01

    We have used a color-matching technique to obtain estimates of the optical density of cone photopigments as a function of retinal illuminance in patients with insulin-dependent diabetes mellitus (IDDM). We found that the half-bleach illuminance of some patients is abnormally high. That is, it takes more light to bleach an equivalent amount of photopigment in these patients. Since low illuminance color matches for these patients are normal, this implies that these patients have normal amounts of photopigment, but the photopigment is not bleaching normally. This result clearly points to abnormalities in the outer retina of these diabetic patients. The most likely causes of this abnormality are either decreases in the ability of the cones to absorb light, or an increased rate of regeneration of the cone photopigments. PMID:3557875

  6. Microspectrophotometric evidence for cone monochromacy in sharks.

    PubMed

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks-the rays and chimaeras-are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ(max) 484-518 nm) and cone (λ(max) 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology. PMID:21212930

  7. Microspectrophotometric evidence for cone monochromacy in sharks

    NASA Astrophysics Data System (ADS)

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks—the rays and chimaeras—are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λmax 484-518 nm) and cone (λmax 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  8. CRALBP supports the mammalian retinal visual cycle and cone vision

    PubMed Central

    Xue, Yunlu; Shen, Susan Q.; Jui, Jonathan; Rupp, Alan C.; Byrne, Leah C.; Hattar, Samer; Flannery, John G.; Corbo, Joseph C.; Kefalov, Vladimir J.

    2015-01-01

    Mutations in the cellular retinaldehyde–binding protein (CRALBP, encoded by RLBP1) can lead to severe cone photoreceptor–mediated vision loss in patients. It is not known how CRALBP supports cone function or how altered CRALBP leads to cone dysfunction. Here, we determined that deletion of Rlbp1 in mice impairs the retinal visual cycle. Mice lacking CRALBP exhibited M-opsin mislocalization, M-cone loss, and impaired cone-driven visual behavior and light responses. Additionally, M-cone dark adaptation was largely suppressed in CRALBP-deficient animals. While rearing CRALBP-deficient mice in the dark prevented the deterioration of cone function, it did not rescue cone dark adaptation. Adeno-associated virus–mediated restoration of CRALBP expression specifically in Müller cells, but not retinal pigment epithelial (RPE) cells, rescued the retinal visual cycle and M-cone sensitivity in knockout mice. Our results identify Müller cell CRALBP as a key component of the retinal visual cycle and demonstrate that this pathway is important for maintaining normal cone–driven vision and accelerating cone dark adaptation. PMID:25607845

  9. QCD tests with polarized beams

    SciTech Connect

    Maruyama, Takashi; SLD Collaboration

    1996-09-01

    The authors present three QCD studies performed by the SLD experiment at SLAC, utilizing the highly polarized SLC electron beam. They examined particle production differences in light quark and antiquark hemispheres, and observed more high momentum baryons and K{sup {minus}}`s than antibaryons and K{sup +}`s in quark hemispheres, consistent with the leading particle hypothesis. They performed a search for jet handedness in light q- and {anti q}-jets. Assuming Standard Model values of quark polarization in Z{sup 0} decays, they have set an improved upper limit on the analyzing power of the handedness method. They studied the correlation between the Z{sup 0} spin and the event-plane orientation in polarized Z{sup 0} decays into three jets.

  10. Fast Electron Generation in Cones with Ultra-Intense Laser Pulses

    SciTech Connect

    Mackinnon, A; VanWoerkom, L; Akli, K; Bartal, T; Beg, F; Chawla, S; Chen, C; Chowdhury, E; Freeman, R; Hey, D; Key, M; King, J; Link, A; MacPhee, A; Offermann, D; Ovchinnikov, V; Patel, P; Schumacher, D; Stephens, R; Tsui, Y; Ma, T

    2007-12-07

    Experimental results from copper cones irradiated with ultra-intense laser light are presented. Spatial images and total yields of Cu K{sub {alpha}} fluorescence were measured as a function of the laser focusing properties. The fluorescence emission extends into the cone approximately 300 {micro}m from the cone tip and cannot be explained by ray tracing including cone wall absorption. In addition the total fluorescence yield from cones is an order of magnitude higher than for equivalent mass foil targets. Indications are that the physics of the laser cone interaction is dominated by preplasma created from the long duration, low energy pre-pulse from the laser.

  11. Breaking the Covalent Bond—A Pigment Property that Contributes to Desensitization in Cones

    PubMed Central

    Kefalov, Vladimir J.; Estevez, Maureen E.; Kono, Massahiro; Goletz, Patrice W.; Crouch, Rosalie K.; Cornwall, M. Carter; Yau, King-Wai

    2010-01-01

    Summary Retinal rod and cone pigments consist of an apoprotein, opsin, covalently linked to a chromophore, 11-cis retinal. Here we demonstrate that the formation of the covalent bond between opsin and 11-cis retinal is reversible in darkness in amphibian red cones, but essentially irreversible in red rods. This dissociation, apparently a general property of cone pigments, results in a surprisingly large amount of free opsin—about 10% of total opsin—in dark-adapted red cones. We attribute this significant level of free opsin to the low concentration of intracellular free 11-cis retinal, estimated to be only a tiny fraction (~0.1 %) of the pigment content in red cones. With its constitutive transducin-stimulating activity, the free cone opsin produces an ~2-fold desensitization in red cones, equivalent to that produced by a steady light causing 500 photoisomerizations s−1. Cone pigment dissociation therefore contributes to the sensitivity difference between rods and cones. PMID:15953417

  12. FOREWORD: Extreme QCD 2012 (xQCD)

    NASA Astrophysics Data System (ADS)

    Alexandru, Andrei; Bazavov, Alexei; Liu, Keh-Fei

    2013-04-01

    The Extreme QCD 2012 conference, held at the George Washington University in August 2012, celebrated the 10th event in the series. It has been held annually since 2003 at different locations: San Carlos (2011), Bad Honnef (2010), Seoul (2009), Raleigh (2008), Rome (2007), Brookhaven (2006), Swansea (2005), Argonne (2004), and Nara (2003). As usual, it was a very productive and inspiring meeting that brought together experts in the field of finite-temperature QCD, both theoretical and experimental. On the experimental side, we heard about recent results from major experiments, such as PHENIX and STAR at Brookhaven National Laboratory, ALICE and CMS at CERN, and also about the constraints on the QCD phase diagram coming from astronomical observations of one of the largest laboratories one can imagine, neutron stars. The theoretical contributions covered a wide range of topics, including QCD thermodynamics at zero and finite chemical potential, new ideas to overcome the sign problem in the latter case, fluctuations of conserved charges and how they allow one to connect calculations in lattice QCD with experimentally measured quantities, finite-temperature behavior of theories with many flavors of fermions, properties and the fate of heavy quarkonium states in the quark-gluon plasma, and many others. The participants took the time to write up and revise their contributions and submit them for publication in these proceedings. Thanks to their efforts, we have now a good record of the ideas presented and discussed during the workshop. We hope that this will serve both as a reminder and as a reference for the participants and for other researchers interested in the physics of nuclear matter at high temperatures and density. To preserve the atmosphere of the event the contributions are ordered in the same way as the talks at the conference. We are honored to have helped organize the 10th meeting in this series, a milestone that reflects the lasting interest in this

  13. Highly excited and exotic meson spectroscopy from lattice QCD

    SciTech Connect

    Christopher Thomas

    2011-05-01

    I will discuss recent progress in extracting highly excited and exotic meson spectra using lattice QCD. New results in the light meson sector will be presented, where a combination of techniques have enabled us to confidently identify the spin of extracted states. Highlights include many states with exotic quantum numbers and, for the first time in a lattice QCD calculation, spin-four states. I will conclude with comments on future prospects.

  14. 2017 Eclipse Shadow Cones

    NASA Video Gallery

    A solar eclipse occurs when the Moon's shadow falls on the Earth. The shadow comprises two concentric cones called the umbra and the penumbra. Within the smaller, central umbra, the Sun is complete...

  15. QCD physics at CDF

    SciTech Connect

    Harris, R.

    1992-05-01

    We present measurements of jet production and isolated prompt photon production in p{bar p} collisions at {radical}s = 1.8 TeV from the 1988--89 run of the Collider Detector at Fermilab (CDF). To test QCD with jets, the inclusive jet cross section (p{bar p} {yields} J + X) and two jet angular distributions (p{bar P} {yields} JJ + X) are compared to QCD predictions and are used to search for composite quarks. The ratio of the scaled jet cross sections at two Tevatron collision energies ({radical}s= 546 and 1800 GeV) is compared to QCD predictions for X{sub T} scaling violations. Also, we present the first evidence for QCD interference effects (color coherence) in third jet production (p{bar p} {yields} JJJ + X). To test QCD with photons, we present measurements of the transverse momentum spectrum of single isolated prompt photon production (p{bar p} {yields} {gamma} + X), double isolated prompt photon production (p{bar p} {yields} {gamma}{gamma} + X), and the angular distribution of photon-jet events (p{bar p} {yields} {gamma} J + X). We have also measured the isolated production ratio of {eta} and {pi}{sup 0} mesons (p{bar p} {yields} {eta} + X)/(p{bar p} {yields} {pi}{sup 0} + X) = 1.02 {plus minus} .15(stat) {plus minus} .23(sys).

  16. QCD physics at CDF

    SciTech Connect

    Harris, R.; The CDF Collaboration

    1992-05-01

    We present measurements of jet production and isolated prompt photon production in p{bar p} collisions at {radical}s = 1.8 TeV from the 1988--89 run of the Collider Detector at Fermilab (CDF). To test QCD with jets, the inclusive jet cross section (p{bar p} {yields} J + X) and two jet angular distributions (p{bar P} {yields} JJ + X) are compared to QCD predictions and are used to search for composite quarks. The ratio of the scaled jet cross sections at two Tevatron collision energies ({radical}s= 546 and 1800 GeV) is compared to QCD predictions for X{sub T} scaling violations. Also, we present the first evidence for QCD interference effects (color coherence) in third jet production (p{bar p} {yields} JJJ + X). To test QCD with photons, we present measurements of the transverse momentum spectrum of single isolated prompt photon production (p{bar p} {yields} {gamma} + X), double isolated prompt photon production (p{bar p} {yields} {gamma}{gamma} + X), and the angular distribution of photon-jet events (p{bar p} {yields} {gamma} J + X). We have also measured the isolated production ratio of {eta} and {pi}{sup 0} mesons (p{bar p} {yields} {eta} + X)/(p{bar p} {yields} {pi}{sup 0} + X) = 1.02 {plus_minus} .15(stat) {plus_minus} .23(sys).

  17. Lunar cinder cones.

    PubMed

    McGetchin, T R; Head, J W

    1973-04-01

    Data on terrestrial eruptions of pyroclastic material and ballistic considerations suggest that in the lunar environment (vacuum and reduced gravity) low-rimmed pyroclastic rings are formed rather than the high-rimmed cinder cones so abundant on the earth. Dark blanketing deposits in the Taurus-Littrow region (Apollo 17 landing area) are interpreted as being at least partly composed of lunar counterparts of terrestrial cinder cones. PMID:17757977

  18. Vredefort shatter cones revisited

    NASA Astrophysics Data System (ADS)

    Nicolaysen, L. O.; Reimold, W. U.

    1999-03-01

    Shatter cones have been described from a number of circular and polygonal structures worldwide, the origin of which has been alternatively ascribed to the impacts of large extraterrestrial projectiles or to catastrophic endogenic processes. Despite their association with enigmatic, catastrophic processes, the nature of shatter cones and the physics involved in their formation have not been comprehensively researched. Results of detailed field and laboratory studies of shatter cones from three areas in the collar of the Vredefort Dome in South Africa are presented. Vredefort shatter cones are directly related to a widely displayed fracture phenomenon, termed ``multiply striated joint sets (MSJS)''. MSJs are planar to curviplanar fractures occuring at spacings of <1 to several millimeters. The joint sets have a fractal character. When a new measurement protocol is used in the field, involving study of all joint surfaces and all steps and striae exposed on these surfaces, new information is gained on the genesis and significance of the MSJS and on their relationship to striated conical fractures. The internal constitution of a rock specimen with MSJS was examined in detail, by documenting the precise geometry of many fractures in a suite of parallel thin sections transecting the specimen. The steps and striae on shatter cone surfaces have the characteristics of displacement fractures (microfaults), along which evidence of melting is observed. Shatter cone and MSJS surfaces are often covered with glassy films; we evaluate whether these fracture phenomena are linked to the formation of pseudotachylitic (friction) melt. Our field and petrographic observations can be interpreted as consistent with the generation of shatter cones/MSJS relatively late in the formation of the Vredefort structure. This scenario contrasts sharply with the widely held view that shatter cones are formed during the early ``compression'' phase of a shock event that affected horizontal strata.

  19. Nuclear Physics and Lattice QCD

    SciTech Connect

    Beane, Silas

    2003-11-01

    Impressive progress is currently being made in computing properties and interac- tions of the low-lying hadrons using lattice QCD. However, cost limitations will, for the foreseeable future, necessitate the use of quark masses, Mq, that are signif- icantly larger than those of nature, lattice spacings, a, that are not significantly smaller than the physical scale of interest, and lattice sizes, L, that are not sig- nificantly larger than the physical scale of interest. Extrapolations in the quark masses, lattice spacing and lattice volume are therefore required. The hierarchy of mass scales is: L 1 j Mq j â ºC j a 1 . The appropriate EFT for incorporating the light quark masses, the finite lattice spacing and the lattice size into hadronic observables is C-PT, which provides systematic expansions in the small parame- ters e m L, 1/ Lâ ºC, p/â ºC, Mq/â ºC and aâ ºC . The lattice introduces other unphysical scales as well. Lattice QCD quarks will increasingly be artificially separated

  20. B →π ℓν and Bs→K ℓν form factors and |Vu b| from 2 +1 -flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

    NASA Astrophysics Data System (ADS)

    Flynn, J. M.; Izubuchi, T.; Kawanai, T.; Lehner, C.; Soni, A.; van de Water, R. S.; Witzel, O.; Rbc; Ukqcd Collaborations

    2015-04-01

    We calculate the form factors for B →π ℓν and Bs→K ℓν decay in dynamical lattice quantum chromodynamics (QCD) using domain-wall light quarks and relativistic b -quarks. We use the (2 +1 )-flavor gauge-field ensembles generated by the RBC and UKQCD collaborations with the domain-wall fermion action and Iwasaki gauge action. For the b -quarks we use the anisotropic clover action with a relativistic heavy-quark interpretation. We analyze data at two lattice spacings of a ≈0.11 , 0.086 fm with unitary pion masses as light as Mπ≈290 MeV . We simultaneously extrapolate our numerical results to the physical light-quark masses and to the continuum and interpolate in the pion/kaon energy using SU(2) "hard-pion" chiral perturbation theory for heavy-light meson form factors. We provide complete systematic error budgets for the vector and scalar form factors f+(q2) and f0(q2) for both B →π ℓν and Bs→K ℓν at three momenta that span the q2 range accessible in our numerical simulations. Next we extrapolate these results to q2=0 using a model-independent z -parametrization based on analyticity and unitarity. We present our final results for f+(q2) and f0(q2) as the coefficients of the series in z and the matrix of correlations between them; this provides a parametrization of the form factors valid over the entire allowed kinematic range. Our results agree with other three-flavor lattice-QCD determinations using staggered light quarks, and have comparable precision, thereby providing important independent cross-checks. Both B →π ℓν and Bs→K ℓν decays enable determinations of the Cabibbo-Kobayashi-Maskawa matrix element |Vu b|. To illustrate this, we perform a combined z -fit of our numerical B →π ℓν form-factor data with the experimental measurements of the branching fraction from BABAR and Belle leaving the relative normalization as a free parameter; we obtain |Vu b|=3.61 (32 )×1 0-3, where the error includes statistical and all

  1. QCD Evolution 2015

    NASA Astrophysics Data System (ADS)

    These are the proceedings of the QCD Evolution 2015 Workshop which was held 26-30 May, 2015 at Jefferson Lab, Newport News, Virginia, USA. The workshop is a continuation of a series of workshops held during four consecutive years 2011, 2012, 2013 at Jefferson Lab, and in 2014 in Santa Fe, NM. With the rapid developments in our understanding of the evolution of parton distributions including low-x, TMDs, GPDs, higher-twist correlation functions, and the associated progress in perturbative QCD, lattice QCD and effective field theory techniques we look forward with great enthusiasm to the 2015 meeting. A special attention was also paid to participation of experimentalists as the topics discussed are of immediate importance for the JLab 12 experimental program and a future Electron Ion Collider.

  2. Rod and cone photoreceptors: molecular basis of the difference in their physiology.

    PubMed

    Kawamura, Satoru; Tachibanaki, Shuji

    2008-08-01

    Vertebrate retinal photoreceptors consist of two types of cells, the rods and cones. Rods are highly light-sensitive but their flash response time course is slow, so that they can detect a single photon in the dark but are not good at detecting an object moving quickly. Cones are less light-sensitive and their flash response time course is fast, so that cones mediate daylight vision and are more suitable to detect a moving object than rods. The phototransduction mechanism was virtually known by the mid 80s, and detailed mechanisms of the generation of a light response are now understood in a highly quantitative manner at the molecular level. However, most of these studies were performed in rods, but not in cones. Therefore, the mechanisms of low light-sensitivity or fast flash response time course in cones have not been known. The major reason for this slow progress in the study of cone phototransduction was due to the inability of getting a large quantity of purified cones to study them biochemically. We succeeded in its purification using carp retina, and have shown that each step responsible for generation of a light response is less effective in cones and that the reactions responsible for termination of a light response are faster in cones. Based on these findings, we speculated a possible mechanism of evolution of rods that diverged from cones. PMID:18514002

  3. BB Potentials in Quenched Lattice QCD

    SciTech Connect

    William Detmold; Kostas Orginos; Martin J. Savage

    2007-12-01

    The potentials between two B-mesons are computed in the heavy-quark limit using quenched lattice QCD at $m_\\pi\\sim 400~{\\rm MeV}$. Non-zero central potentials are clearly evident in all four spin-isospin channels, (I,s_l) = (0,0) , (0,1) , (1,0) , (1,1), where s_l is the total spin of the light degrees of freedom. At short distance, we find repulsion in the $I\

  4. Nucleon Axial Charge in Full Lattice QCD

    SciTech Connect

    Edwards, R.G.; Richards, D.G.; Fleming, G.T.; Haegler, Ph.; Negele, J.W.; Pochinsky, A.V.; Orginos, K.; Renner, D.B.; Schroers, W.

    2006-02-10

    The nucleon axial charge is calculated as a function of the pion mass in full QCD. Using domain wall valence quarks and improved staggered sea quarks, we present the first calculation with pion masses as light as 354 MeV and volumes as large as (3.5 fm){sup 3}. We show that finite volume effects are small for our volumes and that a constrained fit based on finite volume chiral perturbation theory agrees with experiment within 7% statistical errors.

  5. Forward dijets in high-energy collisions: Evolution of QCD n-point functions beyond the dipole approximation

    SciTech Connect

    Dumitru, Adrian; Jalilian-Marian, Jamal

    2010-10-01

    Present knowledge of QCD n-point functions of Wilson lines at high energies is rather limited. In practical applications, it is therefore customary to factorize higher n-point functions into products of two-point functions (dipoles) which satisfy the Balitsky-Kovchegov-evolution equation. We employ the Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner formalism to derive explicit evolution equations for the 4- and 6-point functions of fundamental Wilson lines and show that if the Gaussian approximation is carried out before the rapidity evolution step is taken, then many leading order N{sub c} contributions are missed. Our evolution equations could specifically be used to improve calculations of forward dijet angular correlations, recently measured by the STAR Collaboration in deuteron-gold collisions at the RHIC collider. Forward dijets in proton-proton collisions at the LHC probe QCD evolution at even smaller light-cone momentum fractions. Such correlations may provide insight into genuine differences between the Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner and Balitsky-Kovchegov approaches.

  6. Analysis of B→a1(1260)(b1(1235))K* decays in the perturbative QCD approach

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Qing; Fu, Jian-Hua

    2015-03-01

    Within the framework of the perturbative quantum chromodynamics (PQCD) approach, we study the charmless two-body decays B→a1(1260)K*, b1(1235)K*. Using the decay constants and the light-cone distribution amplitudes for these mesons derived from the QCD sum rule method, we find the following results. (a) Our predictions for the branching ratios are consistent with the QCD factorization (QCDF) results within errors, but much larger than the naive factorization approach calculation values. (b) We predict that the anomalous polarizations occurring in the decays B→φK*, rHK* also happen in B→a1K* decays, while they do not happen in B→b1K* decays. Here the contributions from the annihilation diagrams play an important role in explaining the larger transverse polarizations in the B→a1K* decays, while they are not sensitive to the polarizations for the B→b1K* decays. (c) Our predictions for the direct CP-asymmetries agree well with the QCDF results within errors. The decays B¯0 → b+1K*-, B- → b01K*- have larger direct CP-asymmetries, which could be measured by the present LHCb experiment and the forthcoming Super-B experiment. Supported by National Natural Science Foundation of China (11147004, 11347030), Program of Youthful Key Teachers in University of Henan Province (001166), and by Foundation of Henan Educational Committee (14HASTIT037)

  7. Exploring Hyperons and Hypernuclei with Lattice QCD

    SciTech Connect

    S.R. Beane; P.F. Bedaque; A. Parreno; M.J. Savage

    2005-01-01

    In this work we outline a program for lattice QCD that would provide a first step toward understanding the strong and weak interactions of strange baryons. The study of hypernuclear physics has provided a significant amount of information regarding the structure and weak decays of light nuclei containing one or two Lambda's, and Sigma's. From a theoretical standpoint, little is known about the hyperon-nucleon interaction, which is required input for systematic calculations of hypernuclear structure. Furthermore, the long-standing discrepancies in the P-wave amplitudes for nonleptonic hyperon decays remain to be understood, and their resolution is central to a better understanding of the weak decays of hypernuclei. We present a framework that utilizes Luscher's finite-volume techniques in lattice QCD to extract the scattering length and effective range for Lambda-N scattering in both QCD and partially-quenched QCD. The effective theory describing the nonleptonic decays of hyperons using isospin symmetry alone, appropriate for lattice calculations, is constructed.

  8. Visualization Tools for Lattice QCD - Final Report

    SciTech Connect

    Massimo Di Pierro

    2012-03-15

    Our research project is about the development of visualization tools for Lattice QCD. We developed various tools by extending existing libraries, adding new algorithms, exposing new APIs, and creating web interfaces (including the new NERSC gauge connection web site). Our tools cover the full stack of operations from automating download of data, to generating VTK files (topological charge, plaquette, Polyakov lines, quark and meson propagators, currents), to turning the VTK files into images, movies, and web pages. Some of the tools have their own web interfaces. Some Lattice QCD visualization have been created in the past but, to our knowledge, our tools are the only ones of their kind since they are general purpose, customizable, and relatively easy to use. We believe they will be valuable to physicists working in the field. They can be used to better teach Lattice QCD concepts to new graduate students; they can be used to observe the changes in topological charge density and detect possible sources of bias in computations; they can be used to observe the convergence of the algorithms at a local level and determine possible problems; they can be used to probe heavy-light mesons with currents and determine their spatial distribution; they can be used to detect corrupted gauge configurations. There are some indirect results of this grant that will benefit a broader audience than Lattice QCD physicists.

  9. QCD and Multiparticle Production - Proceedings of the XXIX International Symposium on Multiparticle Dynamics

    NASA Astrophysics Data System (ADS)

    Sarcevic, Ina; Tan, Chung-I.

    2000-07-01

    The Table of Contents for the full book PDF is as follows: * Preface * Monday morning session: Hadronic Final States - Conveners: E. de Wolf and J. W. Gary * Session Chairman: J. W. Gary * Inclusive Jets at the Tevatron * Forward Jets, Dijets, and Subjets at the Tevatron * Inclusive Hadron Production and Dijets at HERA * Recent Opal Results on Photon Structure and Interactions * Review of Two-Photon Physics at LEP * Session Chairman: E. de Wolf * An Intriguing Area-Law-Based Hadron Production Scheme in e+e- Annihilation and Its Possible Extensions * Hyperfine Splitting in Hadron Production at High Energies * Event Selection Effects on Multiplicities in Quark and Gluon Jets * Quark and Gluon Jet Properties at LEP * Rapidity Gaps in Quark and Gluon Jets -- A Perturbative Approach * Monday afternoon session: Diffractive and Small-x - Conveners: M. Derrick and A. White * Session Chairman: A. White * Structure Functions: Low x, High y, Low Q2 * The Next-to-Leading Dynamics of the BFKL Pomeron * Renormalization Group Improved BFKL Equation * Session Chairman: G. Briskin * New Experimental Results on Diffraction at HERA * Diffractive Parton Distributions in Light-Cone QCD * The Logarithmic Derivative of the F2 Structure Function and Saturation * Spin Dependence of Diffractive DIS * Monday evening session * Session Chairman: M. Braun * Tests of QCD with Particle Production at HERA: Review and Outlook * Double Parton Scattering and Hadron Structure in Transverse Space * The High Density Parton Dynamics from Eikonal and Dipole Pictures * Hints of Higher Twist Effects in the Slope of the Proton Structure Function * Tuesday morning session: Correlations and Fluctuations - Conveners: R. Hwa and M. Tannenbaum * Session Chairman: A. Giovannini -- Fluctuations and Correlations * Bose-Einstein Results from L3 * Short-Range and Long-Range Correlations in DIS at HERA * Coior Mutation Model, Intermittency, and Erraticity * QCD Queuing and Hadron Multiplicity * Soft and Semi

  10. From QCD to physical resonances

    NASA Astrophysics Data System (ADS)

    Bolton, Daniel R.; Briceño, Raúl A.; Wilson, David J.

    2016-05-01

    In this talk, we present the first chiral extrapolation of a resonant scattering amplitude obtained from lattice QCD. Finite-volume spectra, determined by the Hadron Spectrum Collaboration at mπ = 236 MeV [1], for the isotriplet ππ channel are analyzed using the Lüscher method to determine the infinite-volume scattering amplitude. Unitarized Chiral Perturbation Theory is then used to extrapolate the scattering amplitude to the physical light quark masses. The viability of this procedure is demonstrated by its agreement with the experimentally determined scattering phase shift up to center-of-mass energies of 1.2 GeV. Finally, we analytically continue the amplitude to the complex plane to obtain the ρ-pole at [ 755 (2 )(1 )(02 20 ) -i/2 129 (3 )(1 )(1 7 ) ] MeV.

  11. Gluonic transversity from lattice QCD

    NASA Astrophysics Data System (ADS)

    Detmold, W.; Shanahan, P. E.

    2016-07-01

    We present an exploratory study of the gluonic structure of the ϕ meson using lattice QCD (LQCD). This includes the first investigation of gluonic transversity via the leading moment of the twist-2 double-helicity-flip gluonic structure function Δ (x ,Q2). This structure function only exists for targets of spin J ≥1 and does not mix with quark distributions at leading twist, thereby providing a particularly clean probe of gluonic degrees of freedom. We also explore the gluonic analogue of the Soffer bound which relates the helicity flip and nonflip gluonic distributions, finding it to be saturated at the level of 80%. This work sets the stage for more complex LQCD studies of gluonic structure in the nucleon and in light nuclei where Δ (x ,Q2) is an "exotic glue" observable probing gluons in a nucleus not associated with individual nucleons.

  12. Modeling QCD for Hadron Physics

    NASA Astrophysics Data System (ADS)

    Tandy, P. C.

    2011-10-01

    We review the approach to modeling soft hadron physics observables based on the Dyson-Schwinger equations of QCD. The focus is on light quark mesons and in particular the pseudoscalar and vector ground states, their decays and electromagnetic couplings. We detail the wide variety of observables that can be correlated by a ladder-rainbow kernel with one infrared parameter fixed to the chiral quark condensate. A recently proposed novel perspective in which the quark condensate is contained within hadrons and not the vacuum is mentioned. The valence quark parton distributions, in the pion and kaon, as measured in the Drell Yan process, are investigated with the same ladder-rainbow truncation of the Dyson-Schwinger and Bethe-Salpeter equations.

  13. Modeling QCD for Hadron Physics

    SciTech Connect

    Tandy, P. C.

    2011-10-24

    We review the approach to modeling soft hadron physics observables based on the Dyson-Schwinger equations of QCD. The focus is on light quark mesons and in particular the pseudoscalar and vector ground states, their decays and electromagnetic couplings. We detail the wide variety of observables that can be correlated by a ladder-rainbow kernel with one infrared parameter fixed to the chiral quark condensate. A recently proposed novel perspective in which the quark condensate is contained within hadrons and not the vacuum is mentioned. The valence quark parton distributions, in the pion and kaon, as measured in the Drell Yan process, are investigated with the same ladder-rainbow truncation of the Dyson-Schwinger and Bethe-Salpeter equations.

  14. Ideal illuminants for rod/L-cone color

    NASA Astrophysics Data System (ADS)

    McCann, John J.

    2006-01-01

    Humans see multicolor complex images with illuminants that have very low amounts of 400 to 580nm light when there is enough long-wave light greater than 590nm. Interactions between rods and long-wave (L) cones generate these colors. They are observed when there is insufficient light for a threshold response from M- and S-cones. This paper measures the spectral emission of a wood fire and a wax candle and it compares these low-color temperature spectral radiant exitances with the sensitivities of rods and long-wave cones. The paper reviews some of the literature on the evolution of human cone pigments and the early use of fire by hominids.

  15. Lattice QCD for parallel computers

    NASA Astrophysics Data System (ADS)

    Quadling, Henley Sean

    Lattice QCD is an important tool in the investigation of Quantum Chromodynamics (QCD). This is particularly true at lower energies where traditional perturbative techniques fail, and where other non-perturbative theoretical efforts are not entirely satisfactory. Important features of QCD such as confinement and the masses of the low lying hadronic states have been demonstrated and calculated in lattice QCD simulations. In calculations such as these, non-lattice techniques in QCD have failed. However, despite the incredible advances in computer technology, a full solution of lattice QCD may still be in the too-distant future. Much effort is being expended in the search for ways to reduce the computational burden so that an adequate solution of lattice QCD is possible in the near future. There has been considerable progress in recent years, especially in the research of improved lattice actions. In this thesis, a new approach to lattice QCD algorithms is introduced, which results in very significant efficiency improvements. The new approach is explained in detail, evaluated and verified by comparing physics results with current lattice QCD simulations. The new sub-lattice layout methodology has been specifically designed for current and future hardware. Together with concurrent research into improved lattice actions and more efficient numerical algorithms, the very significant efficiency improvements demonstrated in this thesis can play an important role in allowing lattice QCD researchers access to much more realistic simulations. The techniques presented in this thesis also allow ambitious QCD simulations to be performed on cheap clusters of commodity computers.

  16. REGGE TRAJECTORIES IN QCD

    SciTech Connect

    Radyushkin, Anatoly V.; Efremov, Anatoly Vasilievich; Ginzburg, Ilya F.

    2013-04-01

    We discuss some problems concerning the application of perturbative QCD to high energy soft processes. We show that summing the contributions of the lowest twist operators for non-singlet $t$-channel leads to a Regge-like amplitude. Singlet case is also discussed.

  17. QCD and Hadron Physics

    SciTech Connect

    Brodsky, Stanley J.; Deshpande, Abhay L.; Gao, Haiyan; McKeown, Robert D.; Meyer, Curtis A.; Meziani, Zein-Eddine; Milner, Richard G.; Qiu, Jianwei; Richards, David G.; Roberts, Craig D.

    2015-02-26

    This White Paper presents the recommendations and scientific conclusions from the Town Meeting on QCD and Hadronic Physics that took place in the period 13-15 September 2014 at Temple University as part of the NSAC 2014 Long Range Planning process. The meeting was held in coordination with the Town Meeting on Phases of QCD and included a full day of joint plenary sessions of the two meetings. The goals of the meeting were to report and highlight progress in hadron physics in the seven years since the 2007 Long Range Plan (LRP07), and present a vision for the future by identifying the key questions and plausible paths to solutions which should define the next decade. The introductory summary details the recommendations and their supporting rationales, as determined at the Town Meeting on QCD and Hadron Physics, and the endorsements that were voted upon. The larger document is organized as follows. Section 2 highlights major progress since the 2007 LRP. It is followed, in Section 3, by a brief overview of the physics program planned for the immediate future. Finally, Section 4 provides an overview of the physics motivations and goals associated with the next QCD frontier: the Electron-Ion-Collider.

  18. Progress in lattice QCD

    SciTech Connect

    Andreas S. Kronfeld

    2002-09-30

    After reviewing some of the mathematical foundations and numerical difficulties facing lattice QCD, I review the status of several calculations relevant to experimental high-energy physics. The topics considered are moments of structure functions, which may prove relevant to search for new phenomena at the LHC, and several aspects of flavor physics, which are relevant to understanding CP and flavor violation.

  19. QCD: Quantum Chromodynamics

    ScienceCinema

    Lincoln, Don

    2016-06-28

    The strongest force in the universe is the strong nuclear force and it governs the behavior of quarks and gluons inside protons and neutrons. The name of the theory that governs this force is quantum chromodynamics, or QCD. In this video, Fermilab?s Dr. Don Lincoln explains the intricacies of this dominant component of the Standard Model.

  20. QCD physics at CDF

    SciTech Connect

    Devlin, T.; CDF Collaboration

    1996-10-01

    The CDF collaboration is engaged in a broad program of QCD measurements at the Fermilab Tevatron Collider. I will discuss inclusive jet production at center-of-mass energies of 1800 GeV and 630 GeV, properties of events with very high total transverse energy and dijet angular distributions.

  1. QCD results from CDF

    SciTech Connect

    Plunkett, R.; The CDF Collaboration

    1991-10-01

    Results are presented for hadronic jet and direct photon production at {radical}{bar s} = 1800 GeV. The data are compared with next-to-leading QCD calculations. A new limit on the scale of possible composite structure of the quarks is also reported. 12 refs., 4 figs.

  2. Baryons and QCD

    SciTech Connect

    Nathan Isgur

    1997-03-01

    The author presents an idiosyncratic view of baryons which calls for a marriage between quark-based and hadronic models of QCD. He advocates a treatment based on valence quark plus glue dominance of hadron structure, with the sea of q pairs (in the form of virtual hadron pairs) as important corrections.

  3. Lighting.

    SciTech Connect

    United States. Bonneville Power Administration.

    1992-09-01

    Since lighting accounts for about one-third of the energy used in commercial buildings, there is opportunity to conserve. There are two ways to reduce lighting energy use: modify lighting systems so that they used less electricity and/or reduce the number of hours the lights are used. This booklet presents a number of ways to do both. Topics covered include: reassessing lighting levels, reducing lighting levels, increasing bulb & fixture efficiency, using controls to regulate lighting, and taking advantage of daylight.

  4. Baryons in holographic QCD

    SciTech Connect

    Nawa, Kanabu; Suganuma, Hideo; Kojo, Toru

    2007-04-15

    We study baryons in holographic QCD with D4/D8/D8 multi-D-brane system. In holographic QCD, the baryon appears as a topologically nontrivial chiral soliton in a four-dimensional effective theory of mesons. We call this topological soliton brane-induced Skyrmion. Some review of D4/D8/D8 holographic QCD is presented from the viewpoints of recent hadron physics and QCD phenomenologies. A four-dimensional effective theory with pions and {rho} mesons is uniquely derived from the non-Abelian Dirac-Born-Infeld (DBI) action of D8 brane with D4 supergravity background at the leading order of large N{sub c}, without small amplitude expansion of meson fields to discuss chiral solitons. For the hedgehog configuration of pion and {rho}-meson fields, we derive the energy functional and the Euler-Lagrange equation of brane-induced Skyrmion from the meson effective action induced by holographic QCD. Performing the numerical calculation, we obtain the soliton solution and figure out the pion profile F(r) and the {rho}-meson profile G-tilde(r) of the brane-induced Skyrmion with its total energy, energy density distribution, and root-mean-square radius. These results are compared with the experimental quantities of baryons and also with the profiles of standard Skyrmion without {rho} mesons. We analyze interaction terms of pions and {rho} mesons in brane-induced Skyrmion, and find a significant {rho}-meson component appearing in the core region of a baryon.

  5. The Na(+)/Ca(2+), K(+) exchanger 2 modulates mammalian cone phototransduction.

    PubMed

    Sakurai, Keisuke; Vinberg, Frans; Wang, Tian; Chen, Jeannie; Kefalov, Vladimir J

    2016-01-01

    Calcium ions (Ca(2+)) modulate the phototransduction cascade of vertebrate cone photoreceptors to tune gain, inactivation, and light adaptation. In darkness, the continuous current entering the cone outer segment through cGMP-gated (CNG) channels is carried in part by Ca(2+), which is then extruded back to the extracellular space. The mechanism of Ca(2+) extrusion from mammalian cones is not understood. The dominant view has been that the cone-specific isoform of the Na(+)/Ca(2+), K(+) exchanger, NCKX2, is responsible for removing Ca(2+) from their outer segments. However, indirect evaluation of cone function in NCKX2-deficient (Nckx2(-/-)) mice by electroretinogram recordings revealed normal photopic b-wave responses. This unexpected result suggested that NCKX2 may not be involved in the Ca(2+) homeostasis of mammalian cones. To address this controversy, we examined the expression of NCKX2 in mouse cones and performed transretinal recordings from Nckx2(-/-) mice to determine the effect of NCKX2 deletion on cone function directly. We found that Nckx2(-/-) cones exhibit compromised phototransduction inactivation, slower response recovery and delayed background adaptation. We conclude that NCKX2 is required for the maintenance of efficient Ca(2+) extrusion from mouse cones. However, surprisingly, Nckx2(-/-) cones adapted normally in steady background light, indicating the existence of additional Ca(2+)-extruding mechanisms in mammalian cones. PMID:27580676

  6. The Na+/Ca2+, K+ exchanger 2 modulates mammalian cone phototransduction

    PubMed Central

    Sakurai, Keisuke; Vinberg, Frans; Wang, Tian; Chen, Jeannie; Kefalov, Vladimir J.

    2016-01-01

    Calcium ions (Ca2+) modulate the phototransduction cascade of vertebrate cone photoreceptors to tune gain, inactivation, and light adaptation. In darkness, the continuous current entering the cone outer segment through cGMP-gated (CNG) channels is carried in part by Ca2+, which is then extruded back to the extracellular space. The mechanism of Ca2+ extrusion from mammalian cones is not understood. The dominant view has been that the cone-specific isoform of the Na+/Ca2+, K+ exchanger, NCKX2, is responsible for removing Ca2+ from their outer segments. However, indirect evaluation of cone function in NCKX2-deficient (Nckx2−/−) mice by electroretinogram recordings revealed normal photopic b-wave responses. This unexpected result suggested that NCKX2 may not be involved in the Ca2+ homeostasis of mammalian cones. To address this controversy, we examined the expression of NCKX2 in mouse cones and performed transretinal recordings from Nckx2−/− mice to determine the effect of NCKX2 deletion on cone function directly. We found that Nckx2−/− cones exhibit compromised phototransduction inactivation, slower response recovery and delayed background adaptation. We conclude that NCKX2 is required for the maintenance of efficient Ca2+ extrusion from mouse cones. However, surprisingly, Nckx2−/− cones adapted normally in steady background light, indicating the existence of additional Ca2+-extruding mechanisms in mammalian cones. PMID:27580676

  7. Bleached pigment activates transduction in salamander cones

    PubMed Central

    1995-01-01

    We have used suction electrode recording together with rapid steps into 0.5 mM IBMX solution to investigate changes in guanylyl cyclase velocity produced by pigment bleaching in isolated cones of the salamander Ambystoma tigrinum. Both backgrounds and bleaches accelerate the time course of current increase during steps into IBMX. We interpret this as evidence that the velocity of the guanylyl cyclase is increased in background light or after bleaching. Our results indicate that cyclase velocity increases nearly linearly with increasing percent pigment bleached but nonlinearly (and may saturate) with increasing back-ground intensity. In cones (as previously demonstrated for rods), light-activated pigment and bleached pigment appear to have somewhat different effects on the transduction cascade. The effect of bleaching on cyclase rate is maintained for at least 15-20 min after the light is removed, much longer than is required after a bleach for circulating current and sensitivity to stabilize in an isolated cone. The effect on the cyclase rate can be completely reversed by treatment with liposomes containing 11-cis retinal. The effects of bleaching can also be partially reversed by beta-ionone, an analogue of the chromophore 11- cis-retinal which does not form a covalent attachment to opsin. Perfusion of a bleached cone with beta-ionone produces a rapid increase in circulating current and sensitivity, which rapidly reverses when the beta-ionone is removed. Perfusion with beta-ionone also causes a partial reversal of the bleach-induced acceleration of cyclase velocity. We conclude that bleaching produces an "equivalent background" excitation of the transduction cascade in cones, perhaps by a mechanism similar to that in rods. PMID:8786347

  8. Intraretinal variability and specialization of cones in Japanese anchovy (Engraulis japonicus, Engraulidae).

    PubMed

    Kondrashev, S L; Kornienko, M S; Gnyubkina, V P; Frolova, L T

    2016-04-01

    The retina of anchovies is characterized by an unusual arrangement and ultrastructure of cones. In the retina of Japanese anchovies, Engraulis japonicus, three types of cones are distributed into rows. The nasal, central, temporal, and ventro-temporal regions of the retina were occupied exclusively by the long and short cones. Triple cones, made up of two lateral components and one smaller central component, were found only in the dorsal and ventro-nasal retinal regions. In the outer segments of all short and long cones from the ventro-temporal region, the lamellae were oriented along the cell axis and were perpendicular to the lamellae in the long cones, providing a morphological basis for the detection of polarization. This lamellar orientation is unique to all vertebrates. The cones were examined with respect to regional differentiation in their size and spectral properties via light microscopy, transmission electron microscopy, and microspectrophotometry. Various dimensions of cones were measured in preparations of isolated cells. The cones from the ventro-temporal region had different dimensions than cones of the same type located in other retinal regions. Triple cones from the dorsal region were significantly larger than triple cones from the ventro-nasal region. The spectral absorbance of the lateral components of triple cones in the ventro-nasal retina was identical to the absorbance of all long and short cones from the ventro-temporal region. These are shifted to shorter wavelengths relative to the absorbance of the lateral components of the triple cones located in the dorsal retina. Thus, the retina of the Japanese anchovy shows some features of regional specialization common in other fishes that improves spatial resolution for the upwards and forwards visual axis and provides spectral tuning in downwelling light environment. That results from the differentiation of cone types by size and by different spectral sensitivity of various retinal areas. J

  9. Formation of shatter cones in MEMIN impact experiments

    NASA Astrophysics Data System (ADS)

    Wilk, J.; Kenkmann, T.

    2016-08-01

    Shatter cones are the only macroscopic feature considered as evidence for shock metamorphism. Their presence is diagnostic for the discovery and verification of impact structures. The occurrence of shatter cones is heterogeneous throughout the crater record and their geometry can diverge from the typical cone shape. The precise formation mechanism of shatter cones is still not resolved. In this study, we aim at better constraining the boundary conditions of shatter cone formation in impact experiments and test a novel approach to qualitatively and quantitatively describe shatter cone geometries by white light interferometry. We recovered several ejected fragments from MEMIN cratering experiments that show slightly curved, striated surfaces and conical geometries with apices of 36°-52°. These fragments fulfilling the morphological criteria of shatter cones were found in experiments with 20-80 cm sized target cubes of sandstone, quartzite and limestone, but not in highly porous tuff. Targets were impacted by aluminum, steel, and iron meteorite projectiles at velocities of 4.6-7.8 km s-1. The projectile sizes ranged from 2.5-12 mm in diameter and produced experimental peak pressures of up to 86 GPa. In experiments with lower impact velocities shatter cones could not be found. A thorough morphometric analysis of the experimentally generated shatter cones was made with 3D white light interferometry scans at micrometer accuracy. SEM analysis of the surfaces of recovered fragments showed vesicular melt films alternating with smoothly polished surfaces. We hypothesize that the vesicular melt films predominantly form at strain releasing steps and suggest that shatter cones are probably mixed mode fractures.

  10. Formation of shatter cones in MEMIN impact experiments

    NASA Astrophysics Data System (ADS)

    Wilk, J.; Kenkmann, T.

    2016-07-01

    Shatter cones are the only macroscopic feature considered as evidence for shock metamorphism. Their presence is diagnostic for the discovery and verification of impact structures. The occurrence of shatter cones is heterogeneous throughout the crater record and their geometry can diverge from the typical cone shape. The precise formation mechanism of shatter cones is still not resolved. In this study, we aim at better constraining the boundary conditions of shatter cone formation in impact experiments and test a novel approach to qualitatively and quantitatively describe shatter cone geometries by white light interferometry. We recovered several ejected fragments from MEMIN cratering experiments that show slightly curved, striated surfaces and conical geometries with apices of 36°-52°. These fragments fulfilling the morphological criteria of shatter cones were found in experiments with 20-80 cm sized target cubes of sandstone, quartzite and limestone, but not in highly porous tuff. Targets were impacted by aluminum, steel, and iron meteorite projectiles at velocities of 4.6-7.8 km s-1. The projectile sizes ranged from 2.5-12 mm in diameter and produced experimental peak pressures of up to 86 GPa. In experiments with lower impact velocities shatter cones could not be found. A thorough morphometric analysis of the experimentally generated shatter cones was made with 3D white light interferometry scans at micrometer accuracy. SEM analysis of the surfaces of recovered fragments showed vesicular melt films alternating with smoothly polished surfaces. We hypothesize that the vesicular melt films predominantly form at strain releasing steps and suggest that shatter cones are probably mixed mode fractures.

  11. QCD with many fermions and QCD topology

    NASA Astrophysics Data System (ADS)

    Shuryak, Edward

    2013-04-01

    Major nonperturbative phenomena in QCD - confinement and chiral symmetry breaking - are known to be related with certain topological objects. Recent lattice advances into the domain of many Nf = O(10) fermion flavors have shown that both phase transitions had shifted in this case to much stronger coupling. We discuss confinement in terms of monopole Bose condensation, and discuss how it is affected by fermions "riding" on the monopoles, ending with the Nf dependence of the critical line. Chiral symmetry breaking is discussed in terms of the (anti)selfdual dyons, the instanton constituents. The fermionic zero modes of those have a different meaning and lead to strong interaction between dyons and antidyons. We report some qualitative consequences of this theory and also some information about our first direct numerical study of the dyonic ensemble, in respect to both chiral symmetry breaking and confinement (via back reaction to the holonomy potential).

  12. Ultra-short pulses to signal neuronal growth cone machinery

    NASA Astrophysics Data System (ADS)

    Mathew, Manoj; Amat-Roldan, Ivan; Andres, Rosa; Cormack, Iain G.; Artigas, David; Soriano, Eduardo; Loza-Alvarez, Pablo

    2007-02-01

    Measurable change in the sensory motor machinery of growth cones are induced by non contact femtosecond laser. The focused laser beam with an average power of 3 mW was positioned at some distance away from the closest fillopodia of cortical neurons from primary cell cultures (mice E15). By identifying a set of preliminary parameters we were able to statistically analyze the phenomenological behavior of the fillopodia and classify the effects different conditions of laser light has on the growth cone. Results show that fillopodia become significantly biased towards the focused femtosecond laser light. The same experiment performed with continuous wave (CW) produced results which were indistinguishable from the case where there is no laser light present (placebo condition) indicating no clear effects of the CW laser light on the fillopodia at a distance. These findings show the potential for ultrashort pulsed light to become a new type of pathfinding cue for neuronal growth cones.

  13. QCD quark condensate in external magnetic fields

    NASA Astrophysics Data System (ADS)

    Bali, G. S.; Bruckmann, F.; Endrődi, G.; Fodor, Z.; Katz, S. D.; Schäfer, A.

    2012-10-01

    We present a comprehensive analysis of the light condensates in QCD with 1+1+1 sea quark flavors (with mass-degenerate light quarks of different electric charges) at zero and nonzero temperatures of up to 190 MeV and external magnetic fields B<1GeV2/e. We employ stout smeared staggered fermions with physical quark masses and extrapolate the results to the continuum limit. At low temperatures we confirm the magnetic catalysis scenario predicted by many model calculations while around the crossover the condensate develops a complex dependence on the external magnetic field, resulting in a decrease of the transition temperature.

  14. RECENT LATTICE RESULTS ON FINITE TEMPERATURE AND DENSITY QCD, PART II.

    SciTech Connect

    KARSCH,F.

    2007-07-09

    We discuss recent progress in studies of QCD thermodynamics with almost physical light quark masses and a physical value of the strange quark mass. We summarize results on the transition temperature in QCD and analyze the relation between deconfinement and chiral symmetry restoration.

  15. Light-Front Quantization of Gauge Theories

    SciTech Connect

    Brodskey, Stanley

    2002-12-01

    Light-front wavefunctions provide a frame-independent representation of hadrons in terms of their physical quark and gluon degrees of freedom. The light-front Hamiltonian formalism provides new nonperturbative methods for obtaining the QCD spectrum and eigensolutions, including resolvant methods, variational techniques, and discretized light-front quantization. A new method for quantizing gauge theories in light-cone gauge using Dirac brackets to implement constraints is presented. In the case of the electroweak theory, this method of light-front quantization leads to a unitary and renormalizable theory of massive gauge particles, automatically incorporating the Lorentz and 't Hooft conditions as well as the Goldstone boson equivalence theorem. Spontaneous symmetry breaking is represented by the appearance of zero modes of the Higgs field leaving the light-front vacuum equal to the perturbative vacuum. I also discuss an ''event amplitude generator'' for automatically computing renormalized amplitudes in perturbation theory. The importance of final-state interactions for the interpretation of diffraction, shadowing, and single-spin asymmetries in inclusive reactions such as deep inelastic lepton-hadron scattering is emphasized.

  16. Cone photopigment in older subjects: decreased optical density in early age-related macular degeneration

    NASA Astrophysics Data System (ADS)

    Elsner, Ann E.; Burns, Stephen A.; Weiter, John J.

    2002-01-01

    We measured changes to cone photoreceptors in patients with early age-related macular degeneration. The data of 53 patients were compared with normative data for color matching measurements of long- and middle-wavelength-sensitive cones in the central macula. A four-parameter model quantified cone photopigment optical density and kinetics. Cone photopigment optical density was on average less for the patients than for normal subjects and was uncorrelated with visual acuity. More light was needed to reduce the photopigment density by 50% in the steady state for patients. These results imply that cone photopigment optical density is reduced by factors other than slowed kinetics.

  17. Classification of QCD defects via holography

    SciTech Connect

    Gorsky, Alexander S.; Zakharov, Valentin I.; Zhitnitsky, Ariel R.

    2009-05-15

    We discuss classification of defects of various codimensions within a holographic model of pure Yang-Mills theories or gauge theories with fundamental matter. We focus on their role below and above the phase transition point as well as their weights in the partition function. The general result is that objects which are stable and heavy in one phase are becoming very light (tensionless) in the other phase. We argue that the {theta} dependence of the partition function drastically changes at the phase transition point, and therefore it correlates with stability properties of configurations. We also explore the possibility that novel stable glueballlike particles, with mass which scales like N{sub c} and which are analogous to carbon Fullerenes, may exist in nature on the QCD scale. Some possible applications for studying the QCD vacuum properties above and below the phase transition are also discussed.

  18. Optics of cone photoreceptors in the chicken (Gallus gallus domesticus).

    PubMed

    Wilby, David; Toomey, Matthew B; Olsson, Peter; Frederiksen, Rikard; Cornwall, M Carter; Oulton, Ruth; Kelber, Almut; Corbo, Joseph C; Roberts, Nicholas W

    2015-10-01

    Vision is the primary sensory modality of birds, and its importance is evident in the sophistication of their visual systems. Coloured oil droplets in the cone photoreceptors represent an adaptation in the avian retina, acting as long-pass colour filters. However, we currently lack understanding of how the optical properties and morphology of component structures (e.g. oil droplet, mitochondrial ellipsoid and outer segment) of the cone photoreceptor influence the transmission of light into the outer segment and the ultimate effect they have on receptor sensitivity. In this study, we use data from microspectrophotometry, digital holographic microscopy and electron microscopy to inform electromagnetic models of avian cone photoreceptors to quantitatively investigate the integrated optical function of the cell. We find that pigmented oil droplets primarily function as spectral filters, not light collection devices, although the mitochondrial ellipsoid improves optical coupling between the inner segment and oil droplet. In contrast, unpigmented droplets found in violet-sensitive cones double sensitivity at its peak relative to other cone types. Oil droplets and ellipsoids both narrow the angular sensitivity of single cone photoreceptors, but not as strongly as those in human cones. PMID:26423439

  19. Optics of cone photoreceptors in the chicken (Gallus gallus domesticus)

    PubMed Central

    Wilby, David; Toomey, Matthew B.; Olsson, Peter; Frederiksen, Rikard; Cornwall, M. Carter; Oulton, Ruth; Kelber, Almut; Corbo, Joseph C.; Roberts, Nicholas W.

    2015-01-01

    Vision is the primary sensory modality of birds, and its importance is evident in the sophistication of their visual systems. Coloured oil droplets in the cone photoreceptors represent an adaptation in the avian retina, acting as long-pass colour filters. However, we currently lack understanding of how the optical properties and morphology of component structures (e.g. oil droplet, mitochondrial ellipsoid and outer segment) of the cone photoreceptor influence the transmission of light into the outer segment and the ultimate effect they have on receptor sensitivity. In this study, we use data from microspectrophotometry, digital holographic microscopy and electron microscopy to inform electromagnetic models of avian cone photoreceptors to quantitatively investigate the integrated optical function of the cell. We find that pigmented oil droplets primarily function as spectral filters, not light collection devices, although the mitochondrial ellipsoid improves optical coupling between the inner segment and oil droplet. In contrast, unpigmented droplets found in violet-sensitive cones double sensitivity at its peak relative to other cone types. Oil droplets and ellipsoids both narrow the angular sensitivity of single cone photoreceptors, but not as strongly as those in human cones. PMID:26423439

  20. Hadron Resonances from QCD

    NASA Astrophysics Data System (ADS)

    Dudek, Jozef J.

    2016-03-01

    I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study ππ elastic scattering, including the ρ resonance, as well as coupled-channel πK, ηK scattering. The very recent extension to the case where an external current acts is also presented, considering the reaction πγ* → ππ, from which the unstable ρ → πγ transition form factor is extracted. Ongoing calculations are advertised and the outlook for finite volume approaches is presented.

  1. Exponentially modified QCD coupling

    SciTech Connect

    Cvetic, Gorazd; Valenzuela, Cristian

    2008-04-01

    We present a specific class of models for an infrared-finite analytic QCD coupling, such that at large spacelike energy scales the coupling differs from the perturbative one by less than any inverse power of the energy scale. This condition is motivated by the Institute for Theoretical and Experimental Physics operator product expansion philosophy. Allowed by the ambiguity in the analytization of the perturbative coupling, the proposed class of couplings has three parameters. In the intermediate energy region, the proposed coupling has low loop-level and renormalization scheme dependence. The present modification of perturbative QCD must be considered as a phenomenological attempt, with the aim of enlarging the applicability range of the theory of the strong interactions at low energies.

  2. Hybrid baryons in QCD

    SciTech Connect

    Dudek, Jozef J.; Edwards, Robert G.

    2012-03-21

    In this study, we present the first comprehensive study of hybrid baryons using lattice QCD methods. Using a large basis of composite QCD interpolating fields we extract an extensive spectrum of baryon states and isolate those of hybrid character using their relatively large overlap onto operators which sample gluonic excitations. We consider the spectrum of Nucleon and Delta states at several quark masses finding a set of positive parity hybrid baryons with quantum numbers $N_{1/2^+},\\,N_{1/2^+},\\,N_{3/2^+},\\, N_{3/2^+},\\,N_{5/2^+},\\,$ and $\\Delta_{1/2^+},\\, \\Delta_{3/2^+}$ at an energy scale above the first band of `conventional' excited positive parity baryons. This pattern of states is compatible with a color octet gluonic excitation having $J^{P}=1^{+}$ as previously reported in the hybrid meson sector and with a comparable energy scale for the excitation, suggesting a common bound-state construction for hybrid mesons and baryons.

  3. Introduction to lattice QCD

    SciTech Connect

    Gupta, R.

    1998-12-31

    The goal of the lectures on lattice QCD (LQCD) is to provide an overview of both the technical issues and the progress made so far in obtaining phenomenologically useful numbers. The lectures consist of three parts. The author`s charter is to provide an introduction to LQCD and outline the scope of LQCD calculations. In the second set of lectures, Guido Martinelli will discuss the progress they have made so far in obtaining results, and their impact on Standard Model phenomenology. Finally, Martin Luescher will discuss the topical subjects of chiral symmetry, improved formulation of lattice QCD, and the impact these improvements will have on the quality of results expected from the next generation of simulations.

  4. QCD tests at CDF

    SciTech Connect

    Kovacs, E.; CDF Collaboration

    1996-02-01

    We present results for the inclusive jet cross section and the dijet mass distribution. The inclusive cross section and dijet mass both exhibit significant deviations from the predictions of NLO QCD for jets with E{sub T}>200 GeV, or dijet masses > 400 GeV/c{sup 2}. We show that it is possible, within a global QCD analysis that includes the CDF inclusive jet data, to modify the gluon distribution at high x. The resulting increase in the jet cross-section predictions is 25-35%. Owing to the presence of k{sub T} smearing effects, the direct photon data does not provide as strong a constraint on the gluon distribution as previously thought. A comparison of the CDF and UA2 jet data, which have a common range in x, is plagued by theoretical and experimental uncertainties, and cannot at present confirm the CDF excess or the modified gluon distribution.

  5. Future directions for QCD

    SciTech Connect

    Bjorken, J.D.

    1996-10-01

    New directions for exploring QCD at future high-energy colliders are sketched. These include jets within jets. BFKL dynamics, soft and hard diffraction, searches for disoriented chiral condensate, and doing a better job on minimum bias physics. The new experimental opportunities include electron-ion collisions at HERA, a new collider detector at the C0 region of the TeVatron, and the FELIX initiative at the LHC.

  6. Predictions from lattice QCD

    SciTech Connect

    Kronfeld, A.S.; Allison, I.F.; Aubin, C.; Bernard, C.; Davies, C.T.H.; DeTar, C.; Di Pierro, M.; Freeland, E.D.; Gottlieb, Steven; Gray, A.; Gregor, E.; Heller, U.M.; Hetrick, J.E.; El-Khadra, Aida X.; Levkova, L.; Mackenzie, P.B.; Maresca, F.; Menscher, D.; Nobes, M.; Okamoto, M.; Oktay, M.B.; /Fermilab /Glasgow U. /Columbia U. /Washington U., St. Louis /Utah U. /DePaul U. /Art Inst. of Chicago /Indiana U. /Ohio State U. /Arizona U. /APS, New York /U. Pacific, Stockton /Illinois U., Urbana /Cornell U., LEPP /Simon Fraser U. /UC, Santa Barbara

    2005-09-01

    In the past year, we calculated with lattice QCD three quantities that were unknown or poorly known. They are the q{sup 2} dependence of the form factor in semileptonic D {yields} K/{nu} decay, the decay constant of the D meson, and the mass of the B{sub c} meson. In this talk, we summarize these calculations, with emphasis on their (subsequent) confirmation by experiments.

  7. QCD tests at CDF

    SciTech Connect

    Giannetti, P. )

    1991-05-01

    Recent analysis of jet data taken at the Fermilab Tevatron Collider at {radical}S = 1.8 Tev are presented. Inclusive jet, dijet, trijet and direct photon measurements are compared to QCD parton level calculations, at orders {alpha}{sub s}{sup 3} or {alpha}{sub s}{sup 2}. The large total transverse energy events are well described by the Herwig shower Montecarlo. 19 refs., 20 figs., 1 tab.

  8. Pion observables and QCD

    SciTech Connect

    Roberts, C.D.

    1994-09-01

    The Dyson-Schwinger equations (DSEs) are a tower of coupled integral equations that relate the Green functions of QCD to one another. Solving these equations provides the solution of QCD. This tower of equations includes the equation for the quark self-energy, which is the analogue of the gap equation in superconductivity, and the Bethe-Salpeter equation, the solution of which is the quark-antiquark bound state amplitude in QCD. The application of this approach to solving Abelian and non-Abelian gauge theories is reviewed. The nonperturbative DSE approach is being developed as both: (1) a computationally less intensive alternative and; (2) a complement to numerical simulations of the lattice action of QCD. In recent years, significant progress has been made with the DSE approach so that it is now possible to make sensible and direct comparisons between quantities calculated using this approach and the results of numerical simulations of Abelian gauge theories. Herein the application of the DSE approach to the calculation of pion observables is described: the {pi}-{pi} scattering lengths (a{sub 0}{sup 0}, a{sub 0}{sup 2}, A{sub 1}{sup 1}, a{sub 2}{sup 2}) and associated partial wave amplitudes; the {pi}{sup 0} {yields} {gamma}{gamma} decay width; and the charged pion form factor, F{sub {pi}}(q{sup 2}). Since this approach provides a straightforward, microscopic description of dynamical chiral symmetry breaking (D{sub X}SB) and confinement, the calculation of pion observables is a simple and elegant illustrative example of its power and efficacy. The relevant DSEs are discussed in the calculation of pion observables and concluding remarks are presented.

  9. Hadronic Resonances from Lattice QCD

    SciTech Connect

    Lichtl, Adam C.; Bulava, John; Morningstar, Colin; Edwards, Robert; Mathur, Nilmani; Richards, David; Fleming, George; Juge, K. Jimmy; Wallace, Stephen J.

    2007-10-26

    The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.

  10. Hadronic Resonances from Lattice QCD

    SciTech Connect

    John Bulava; Robert Edwards; George Fleming; K. Jimmy Juge; Adam C. Lichtl; Nilmani Mathur; Colin Morningstar; David Richards; Stephen J. Wallace

    2007-06-16

    The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.

  11. Diphoton signals in theories with large extra dimensions to NLO QCD at hadron colliders

    NASA Astrophysics Data System (ADS)

    Kumar, M. C.; Mathews, Prakash; Ravindran, V.; Tripathi, Anurag

    2009-02-01

    We present a full next-to-leading order (NLO) QCD corrections to diphoton production at the hadron colliders in both standard model and ADD model. The invariant mass and rapidity distributions of the diphotons are obtained using a semi-analytical two cut-off phase space slicing method which allows for a successful numerical implementation of various kinematical cuts used in the experiments. The fragmentation photons are systematically removed using smooth-cone-isolation cuts on the photons. The NLO QCD corrections not only stabilise the perturbative predictions but also enhance the production cross section significantly.

  12. Unparticles in diphoton production to next-to-leading order in QCD at the LHC

    NASA Astrophysics Data System (ADS)

    Kumar, M. C.; Mathews, Prakash; Ravindran, V.; Tripathi, Anurag

    2009-04-01

    We compute to next-to-leading order in QCD the tensor unparticle contribution to the diphoton production at the LHC, wherein the unparticle sector is a consequence of (a) scale invariance but not full conformal invariance and (b) conformal invariance. We use the semianalytical two cutoff phase-space slicing method to handle the O(αs) corrections to the pp→γγX and show that our results are insensitive to the soft and collinear cutoffs. In order to avoid the contribution of the photons due to fragmentation, we employ the smooth cone isolation criterion. Significance of the QCD corrections to the diphoton events including unparticles is highlighted.

  13. Evolutionary loss of cone photoreception in balaenid whales reveals circuit stability in the mammalian retina.

    PubMed

    Schweikert, Lorian E; Fasick, Jeffry I; Grace, Michael S

    2016-10-01

    The classical understanding of mammalian vision is that it occurs through "duplex" retinae containing both rod and cone photoreceptors, the signals from which are processed through rod- and/or cone-specific signaling pathways. The recent discovery of rod monochromacy in some cetacean lineages provides a novel opportunity to investigate the effects of an evolutionary loss of cone photoreception on retinal organization. Sequence analysis of right whale (Eubalaena glacialis; family Balaenidae) cDNA derived from long-wavelength sensitive (LWS) cone opsin mRNA identified several mutations in the opsin coding sequence, suggesting the loss of cone cell function, but maintenance of non-photosensitive, cone opsin mRNA-expressing cells in the retina. Subsequently, we investigated the retina of the closely related bowhead whale (Balaena mysticetus; family Balaenidae) to determine how the loss of cone-mediated photoreception affects light signaling pathways in the retina. Anti-opsin immunofluorescence demonstrated the total loss of cone opsin expression in B. mysticetus, whereas light microscopy, transmission electron microscopy, and bipolar cell (protein kinase C-α [PKC-α] and recoverin) immunofluorescence revealed the maintenance of cone soma, putative cone pedicles, and both rod and cone bipolar cell types. These findings represent the first immunological and anatomical evidence of a naturally occurring rod-monochromatic mammalian retina, and suggest that despite the loss of cone-mediated photoreception, the associated cone signaling structures (i.e., cone synapses and cone bipolar cells) may be maintained for multichannel rod-based signaling in balaenid whales. J. Comp. Neurol. 524:2873-2885, 2016. © 2016 Wiley Periodicals, Inc. PMID:26972896

  14. An analytical model of the influence of cone sensitivity and numerosity on the Rayleigh match.

    PubMed

    Zhaoping, Li; Carroll, Joseph

    2016-03-01

    The Rayleigh match is defined by the range of mixtures of red and green lights that appear the same as an intensity-adjustable monochromatic yellow light. The perceptual match indicates that the red-green mixture and the yellow light have evoked the same respective cone absorptions in the L- and M-cone pathways. Going beyond the existing models, the Poisson noise in cone absorptions is proposed to make the matching proportion of red-green mixtures span a finite range because any mixture in that range evokes cone absorptions that do not differ from those by a yellow light by more than the variations in the absorption noise. We derive a mathematical formula linking the match midpoint or match range with the sensitivities and numerosities of the two cones. The noise-free, exact, matching point, close to the midpoint of the matching range, depends only on the L- and M-cone sensitivities to each of the red, green, and yellow lights [these sensitivities, in turn, depend on the preferred wavelengths (λmax) and optical densities of the cone pigments and the properties of prereceptoral light filtering]. Meanwhile, the matching range depends on both these cone sensitivities and the relative numerosity of the L and M cones. The model predicts that, in normal trichromats, all other things being equal, the match range is smallest when the ratio r between L and M cone densities is r=R(-1/2) with R as the ratio between the sensitivities of the L and M cones to the yellow light, i.e., when L and M cones are similarly abundant in typical cases, and, as r departs from R(-1/2), the match range increases. For example, when one cone type is 10 times more numerous, the match range increases two- to threefold, depending on the sensitivities of the cones. Testing these model predictions requires either a large data set to identify the effect of one factor (e.g., cone numerosity) while averaging out the effects of the other factors (e.g., cone sensitivities) or for all factors to be known

  15. Resource Letter QCD-1: Quantum chromodynamics

    NASA Astrophysics Data System (ADS)

    Kronfeld, Andreas S.; Quigg, Chris

    2010-11-01

    This Resource Letter provides a guide to the literature on quantum chromodynamics (QCD), the relativistic quantum field theory of the strong interactions. Journal articles, books, and other documents are cited for the following topics: Quarks and color, the parton model, Yang-Mills theory, experimental evidence for color, QCD as a color gauge theory, asymptotic freedom, QCD for heavy hadrons, QCD on the lattice, the QCD vacuum, pictures of quark confinement, early and modern applications of perturbative QCD, the determination of the strong coupling and quark masses, QCD and the hadron spectrum, hadron decays, the quark-gluon plasma, the strong nuclear interaction, and QCD's role in nuclear physics.

  16. Directionality of individual cone photoreceptors in the parafoveal region.

    PubMed

    Morris, Hugh J; Blanco, Leonardo; Codona, Johanan L; Li, Simone L; Choi, Stacey S; Doble, Nathan

    2015-12-01

    The pointing direction of cone photoreceptors can be inferred from the Stiles-Crawford Effect of the First Kind (SCE-I) measurement. Healthy retinas have tightly packed cones with a SCE-I function peak either centered in the pupil or with a slight nasal bias. Various retinal pathologies can change the profile of the SCE-I function implying that the arrangement or the light capturing properties of the cone photoreceptors are affected. Measuring the SCE-I may reveal early signs of photoreceptor change before actual cell apoptosis occurs. In vivo retinal imaging with adaptive optics (AO) was used to measure the pointing direction of individual cones at eight retinal locations in four control human subjects. Retinal images were acquired by translating an aperture in the light delivery arm through 19 different locations across a subject's entrance pupil. Angular tuning properties of individual cones were calculated by fitting a Gaussian to the reflected intensity profile of each cone projected onto the pupil. Results were compared to those from an accepted psychophysical SCE-I measurement technique. The maximal difference in cone directionality of an ensemble of cones, ρ¯, between the major and minor axes of the Gaussian fit was 0.05 versus 0.29mm(-2) in one subject. All four subjects were found to have a mean nasal bias of 0.81mm with a standard deviation of ±0.30mm in the peak position at all retinal locations with mean ρ¯ value decreasing by 23% with increasing retinal eccentricity. Results show that cones in the parafoveal region converge towards the center of the pupillary aperture, confirming the anterior pointing alignment hypothesis. PMID:26494187

  17. Transversity from First Principles in QCD

    SciTech Connect

    Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins

    2012-02-16

    Transversity observables, such as the T-odd Sivers single-spin asymmetry measured in deep inelastic lepton scattering on polarized protons and the distributions which are measured in deeply virtual Compton scattering, provide important constraints on the fundamental quark and gluon structure of the proton. In this talk I discuss the challenge of computing these observables from first principles; i.e.; quantum chromodynamics, itself. A key step is the determination of the frame-independent light-front wavefunctions (LFWFs) of hadrons - the QCD eigensolutions which are analogs of the Schroedinger wavefunctions of atomic physics. The lensing effects of initial-state and final-state interactions, acting on LFWFs with different orbital angular momentum, lead to T-odd transversity observables such as the Sivers, Collins, and Boer-Mulders distributions. The lensing effect also leads to leading-twist phenomena which break leading-twist factorization such as the breakdown of the Lam-Tung relation in Drell-Yan reactions. A similar rescattering mechanism also leads to diffractive deep inelastic scattering, as well as nuclear shadowing and non-universal antishadowing. It is thus important to distinguish 'static' structure functions, the probability distributions computed the target hadron's light-front wavefunctions, versus 'dynamical' structure functions which include the effects of initial- and final-state rescattering. I also discuss related effects such as the J = 0 fixed pole contribution which appears in the real part of the virtual Compton amplitude. AdS/QCD, together with 'Light-Front Holography', provides a simple Lorentz-invariant color-confining approximation to QCD which is successful in accounting for light-quark meson and baryon spectroscopy as well as hadronic LFWFs.

  18. Progressive cone dystrophies.

    PubMed

    François, J; De Rouck, A; De Laey, J J

    1976-01-01

    Patients with progressive generalized cone dystrophy often present nystagmus (or strabism) and complain of photophobia, decrease in visual acuity or disturbances in colour perception. The most classic fundus abnormality is the bull's eye maculopathy or a pallor of the optic disc. Minimal macular changes are sometimes seen, which may progress to a bull's eye type of macular degeneration. The photopic ERG is always very affected, whereas at first the scotopic ERG seems normal. Progressive deterioration of the visual functions is accompanied by increasing fundus lesions and rod involvement, as suggested by the modifications of the dark adaptation curve and the scotopic ERG. However, the progression of typical generalized cone dysfunction is very slow. On the contrary, in some cases of so-called Stargardt's disease with peripheral participation, a very rapid progression has been observed. In such cases a normal ERG does not necessarily mean that the disease will remain localized to the macular area. No definite prognosis can be made on one single ERG. In 3 cases with sector pigmentary retinopathy the photopic ERG was more affected than the scotopic ERG. However, these cases are probably primary cone-rod dystrophies. Although there is no electrophysiological control, our clinical impression is that the evolution, if possible, is very slow. PMID:1066593

  19. Electromagnetic polarizabilities: Lattice QCD in background fields

    SciTech Connect

    W. Detmold, B.C. Tiburzi, A. Walker-Loud

    2012-04-01

    Chiral perturbation theory makes definitive predictions for the extrinsic behavior of hadrons in external electric and magnetic fields. Near the chiral limit, the electric and magnetic polarizabilities of pions, kaons, and nucleons are determined in terms of a few well-known parameters. In this limit, hadrons become quantum mechanically diffuse as polarizabilities scale with the inverse square-root of the quark mass. In some cases, however, such predictions from chiral perturbation theory have not compared well with experimental data. Ultimately we must turn to first principles numerical simulations of QCD to determine properties of hadrons, and confront the predictions of chiral perturbation theory. To address the electromagnetic polarizabilities, we utilize the background field technique. Restricting our attention to calculations in background electric fields, we demonstrate new techniques to determine electric polarizabilities and baryon magnetic moments for both charged and neutral states. As we can study the quark mass dependence of observables with lattice QCD, the lattice will provide a crucial test of our understanding of low-energy QCD, which will be timely in light of ongoing experiments, such as at COMPASS and HI gamma S.

  20. AGK Rules in Perturbative QCD

    NASA Astrophysics Data System (ADS)

    Bartels, Jochen

    2006-06-01

    I summarize the present status of the AGK cutting rules in perturbative QCD. Particular attention is given to the application of the AGK analysis to diffraction and multiple scattering in DIS at HERA and to pp collisions at the LHC. I also discuss the bootstrap conditions which appear in pQCD.

  1. QCD: Questions, challenges, and dilemmas

    SciTech Connect

    Bjorken, J.

    1996-11-01

    An introduction to some outstanding issues in QCD is presented, with emphasis on work by Diakonov and co-workers on the influence of the instanton vacuum on low-energy QCD observables. This includes the calculation of input valence-parton distributions for deep-inelastic scattering. 35 refs., 3 figs.

  2. QCD coupling constants and VDM

    SciTech Connect

    Erkol, G.; Ozpineci, A.; Zamiralov, V. S.

    2012-10-23

    QCD sum rules for coupling constants of vector mesons with baryons are constructed. The corresponding QCD sum rules for electric charges and magnetic moments are also derived and with the use of vector-meson-dominance model related to the coupling constants. The VDM role as the criterium of reciprocal validity of the sum rules is considered.

  3. Shatter cones: Diagnostic impact signatures

    NASA Technical Reports Server (NTRS)

    Mchone, J. F.; Dietz, R. S.

    1988-01-01

    Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures).

  4. The Symmetries of QCD

    ScienceCinema

    Sekhar Chivukula

    2010-01-08

    The symmetries of a quantum field theory can be realized in a variety of ways. Symmetries can be realized explicitly, approximately, through spontaneous symmetry breaking or, via an anomaly, quantum effects can dynamically eliminate a symmetry of the theory that was present at the classical level.  Quantum Chromodynamics (QCD), the modern theory of the strong interactions, exemplify each of these possibilities. The interplay of these effects determine the spectrum of particles that we observe and, ultimately, account for 99% of the mass of ordinary matter. 

  5. QCD and strings

    SciTech Connect

    Sakai, Tadakatsu; Sugimoto, Shigeki

    2005-12-02

    We propose a holographic dual of QCD with massless flavors on the basis of a D4/D8-brane configuration within a probe approximation. We are led to a five-dimensional Yang-Mills theory on a curved space-time along with a Chern-Simons five-form on it, both of which provide us with a unifying framework to study the massless pion and an infinite number of massive vector mesons. We make sample computations of the physical quantities that involve the mesons and compare them with the experimental data. It is found that most of the results of this model are compatible with the experiments.

  6. QCD and strings

    NASA Astrophysics Data System (ADS)

    Sakai, Tadakatsu; Sugimoto, Shigeki

    2005-12-01

    We propose a holographic dual of QCD with massless flavors on the basis of a D4/D8-brane configuration within a probe approximation. We are led to a five-dimensional Yang-Mills theory on a curved space-time along with a Chern-Simons five-form on it, both of which provide us with a unifying framework to study the massless pion and an infinite number of massive vector mesons. We make sample computations of the physical quantities that involve the mesons and compare them with the experimental data. It is found that most of the results of this model are compatible with the experiments.

  7. Spectral Tuning of Deep Red Cone Pigments†

    PubMed Central

    Amora, Tabitha L.; Ramos, Lavoisier S.; Galan, Jhenny F.; Birge, Robert R.

    2008-01-01

    Visual pigments are G-protein-coupled receptors that provide a critical interface between organisms and their external environment. Natural selection has generated vertebrate pigments that absorb light from the far-UV (360 nm) to the deep red (630 nm) while using a single chromophore, in either the A1 (11-cis-retinal) or A2 (11-cis-3,4-dehydroretinal) form. The fact that a single chromophore can be manipulated to have an absorption maximum across such an extended spectral region is remarkable. The mechanisms of wavelength regulation remain to be fully revealed, and one of the least well-understood mechanisms is that associated with the deep red pigments. We investigate theoretically the hypothesis that deep red cone pigments select a 6-s-trans conformation of the retinal chromophore ring geometry. This conformation is in contrast to the 6-s-cis ring geometry observed in rhodopsin and, through model chromophore studies, the vast majority of visual pigments. Nomographic spectral analysis of 294 A1 and A2 cone pigment literature absorption maxima indicates that the selection of a 6-s-trans geometry red shifts M/LWS A1 pigments by ~1500 cm−1 (~50 nm) and A2 pigments by ~2700 cm−1 (~100 nm). The homology models of seven cone pigments indicate that the deep red cone pigments select 6-s-trans chromophore conformations primarily via electrostatic steering. Our results reveal that the generation of a 6-s-trans conformation not only achieves a significant red shift but also provides enhanced stability of the chromophore within the deep red cone pigment binding sites. PMID:18370404

  8. Beauty vector meson decay constants from QCD sum rules

    NASA Astrophysics Data System (ADS)

    Lucha, Wolfgang; Melikhov, Dmitri; Simula, Silvano

    2016-01-01

    We present the outcomes of a very recent investigation of the decay constants of nonstrange and strange heavy-light beauty vector mesons, with special emphasis on the ratio of any such decay constant to the decay constant of the corresponding pseudoscalar meson, by means of Borel-transformed QCD sum rules. Our results suggest that both these ratios are below unity.

  9. Chiral symmetry, axial anomaly and the structure of hot QCD

    SciTech Connect

    Hatsuda, Tetsuo.

    1991-10-01

    This lecture is composed of three parts. (1) Heavy quark and gluon contents of light hadrons, (II) anomalous gluon content of the nucleon, and (III) hot and dense QCD. Non-valence structures of nucleon due to the OZI violation are extensively discussed in (I) and (II), and non-perturbative aspects of the quark-gluon plasma are reviewed in (III). 41 refs.

  10. Chiral symmetry, axial anomaly and the structure of hot QCD

    SciTech Connect

    Hatsuda, Tetsuo

    1991-10-01

    This lecture is composed of three parts. [1] Heavy quark and gluon contents of light hadrons, [II] anomalous gluon content of the nucleon, and [III] hot and dense QCD. Non-valence structures of nucleon due to the OZI violation are extensively discussed in [I] and [II], and non-perturbative aspects of the quark-gluon plasma are reviewed in [III]. 41 refs.

  11. Radon Transform and Light-Cone Distributions

    NASA Astrophysics Data System (ADS)

    Teryaev, O. V.

    2016-08-01

    The relevance of Radon transform for generalized and transverse momentum dependent parton distributions is discussed. The new application for conditional (fracture) parton distributions and dihadron fragmentation functions is suggested.

  12. Radon Transform and Light-Cone Distributions

    NASA Astrophysics Data System (ADS)

    Teryaev, O. V.

    2016-05-01

    The relevance of Radon transform for generalized and transverse momentum dependent parton distributions is discussed. The new application for conditional (fracture) parton distributions and dihadron fragmentation functions is suggested.

  13. Cool QCD: Hadronic Physics and QCD in Nuclei

    NASA Astrophysics Data System (ADS)

    Cates, Gordon

    2015-10-01

    QCD is the only strongly-coupled theory given to us by Nature, and it gives rise to a host of striking phenomena. Two examples in hadronic physics include the dynamic generation of mass and the confinement of quarks. Indeed, the vast majority of the mass of visible matter is due to the kinetic and potential energy of the massless gluons and the essentially massless quarks. QCD also gives rise to the force that binds protons and neutrons into nuclei, including subtle effects that have historically been difficult to understand. Describing these phenomena in terms of QCD has represented a daunting task, but remarkable progress has been achieved in both theory and experiment. Both CEBAF at Jefferson Lab and RHIC at Brookhaven National Lab have provided unprecedented experimental tools for investigating QCD, and upgrades at both facilities promise even greater opportunities in the future. Also important are programs at FermiLab as well as the LHC at CERN. Looking further ahead, an electron ion collider (EIC) has the potential to answer whole new sets of questions regarding the role of gluons in nuclear matter, an issue that lies at the heart of the generation of mass. On the theoretical side, rapid progress in supercomputers is enabling stunning progress in Lattice QCD calculations, and approximate forms of QCD are also providing deep new physical insight. In this talk I will describe both recent advances in Cool QCD as well as the exciting scientific opportunities that exist for the future.

  14. Bottomonium above Deconfinement in Lattice Nonrelativistic QCD

    SciTech Connect

    Aarts, G.; Kim, S.; Lombardo, M. P.; Oktay, M. B.; Ryan, S. M.; Sinclair, D. K.; Skullerud, J.-I.

    2011-02-11

    We study the temperature dependence of bottomonium for temperatures in the range 0.4T{sub c}QCD simulations for N{sub f}=2 light flavors on a highly anisotropic lattice. We find that the {Upsilon} is insensitive to the temperature in this range, while the {chi}{sub b} propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behavior consistent with nearly free dynamics at T{approx_equal}2T{sub c}.

  15. Nuclear correlation functions in lattice QCD

    SciTech Connect

    Detmold, William; Orginos, Konstantinos

    2013-06-01

    We consider the problem of calculating the large number of Wick contractions necessary to compute states with the quantum numbers of many baryons in lattice QCD. We consider a constructive approach and a determinant-based approach and show that these methods allow the required contractions to be performed for certain choices of interpolating operators. Examples of correlation functions computed using these techniques are shown for the quantum numbers of the light nuclei, $^4$He, $^8$Be, $^{12}$C, $^{16}$O and $^{28}$Si.

  16. Massively Parallel QCD

    SciTech Connect

    Soltz, R; Vranas, P; Blumrich, M; Chen, D; Gara, A; Giampap, M; Heidelberger, P; Salapura, V; Sexton, J; Bhanot, G

    2007-04-11

    The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results.

  17. Nonperturbative QCD Calculations

    NASA Astrophysics Data System (ADS)

    Dellby, Niklas

    1995-01-01

    The research described in this thesis is an exact transformation of the Yang-Mills quantum chromodynamics (QCD) Lagrangrian into a form that is suitable for nonperturbative calculations. The conventional Yang-Mills Lagrangian has proven to be an excellent basis for perturbative calculations, but in nonperturbative calculations it is difficult to separate gauge problems from physical properties. To mitigate this problem, I develop a new equivalent Lagrangian that is not only expressed completely in terms of the field strengths ofthe gauge field but is also manifestly Lorentz and gauge invariant. The new Lagrangian is quadratic in derivatives, with non-linear local couplings, thus it is ideally suited for a numerical calculation. The field-strength Lagrangian is of such a form that it is possible to do a straightforward numerical stationary path expansion and find the fundamental QCD properties. This thesis examines several approximations analytically, investigating different ways to utilize the new Lagrangian. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).

  18. Hybrid baryons in QCD

    DOE PAGESBeta

    Dudek, Jozef J.; Edwards, Robert G.

    2012-03-21

    In this study, we present the first comprehensive study of hybrid baryons using lattice QCD methods. Using a large basis of composite QCD interpolating fields we extract an extensive spectrum of baryon states and isolate those of hybrid character using their relatively large overlap onto operators which sample gluonic excitations. We consider the spectrum of Nucleon and Delta states at several quark masses finding a set of positive parity hybrid baryons with quantum numbersmore » $$N_{1/2^+},\\,N_{1/2^+},\\,N_{3/2^+},\\, N_{3/2^+},\\,N_{5/2^+},\\,$$ and $$\\Delta_{1/2^+},\\, \\Delta_{3/2^+}$$ at an energy scale above the first band of `conventional' excited positive parity baryons. This pattern of states is compatible with a color octet gluonic excitation having $$J^{P}=1^{+}$$ as previously reported in the hybrid meson sector and with a comparable energy scale for the excitation, suggesting a common bound-state construction for hybrid mesons and baryons.« less

  19. QCD for Postgraduates (1/5)

    ScienceCinema

    None

    2011-10-06

    Modern QCD - Lecture 1 Starting from the QCD Lagrangian we will revisit some basic QCD concepts and derive fundamental properties like gauge invariance and isospin symmetry and will discuss the Feynman rules of the theory. We will then focus on the gauge group of QCD and derive the Casimirs CF and CA and some useful color identities.

  20. The uniqueness of the solution of cone-like inversion models for halo CMEs

    NASA Astrophysics Data System (ADS)

    Zhao, X. P.

    2006-12-01

    Most of elliptic halo CMEs are believed to be formed by the Thompson scattering of the photospheric light by the 3-D cone-like shell of the CME plasma. To obtain the real propagation direction and angular width of the halo CMEs, such cone-like inversion models as the circular cone, the elliptic cone and the ice-cream cone models have been suggested recently. Because the number of given parameters that are used to characterize 2-D elliptic halo CMEs observed by one spacecraft are less than the number of unknown parameters that are used to characterize the 3-D elliptic cone model, the solution of the elliptic cone model is not unique. Since it is difficult to determine whether or not an observed halo CME is formed by an circular cone or elliptic cone shell, the solution of circular cone model may often be not unique too. To fix the problem of the uniqueness of the solution of various 3-D cone-like inversion models, this work tries to develop the algorithm for using the data from multi-spacecraft, such as the STEREO A and B, and the Solar Sentinels.

  1. QCD Factorization and PDFs from Lattice QCD Calculation

    NASA Astrophysics Data System (ADS)

    Ma, Yan-Qing; Qiu, Jian-Wei

    2015-02-01

    In this talk, we review a QCD factorization based approach to extract parton distribution and correlation functions from lattice QCD calculation of single hadron matrix elements of quark-gluon operators. We argue that although the lattice QCD calculations are done in the Euclidean space, the nonperturbative collinear behavior of the matrix elements are the same as that in the Minkowski space, and could be systematically factorized into parton distribution functions with infrared safe matching coefficients. The matching coefficients can be calculated perturbatively by applying the factorization formalism on to asymptotic partonic states.

  2. Threefold Complementary Approach to Holographic QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; Dosch, Hans Gunter

    2013-12-27

    A complementary approach, derived from (a) higher-dimensional anti-de Sitter (AdS) space, (b) light-front quantization and (c) the invariance properties of the full conformal group in one dimension leads to a nonperturbative relativistic light-front wave equation which incorporates essential spectroscopic and dynamical features of hadron physics. The fundamental conformal symmetry of the classical QCD Lagrangian in the limit of massless quarks is encoded in the resulting effective theory. The mass scale for confinement emerges from the isomorphism between the conformal group andSO(2,1). This scale appears in the light-front Hamiltonian by mapping to the evolution operator in the formalism of de Alfaro, Fubini and Furlan, which retains the conformal invariance of the action. Remarkably, the specific form of the confinement interaction and the corresponding modification of AdS space are uniquely determined in this procedure.

  3. Calculation of hadronic matrix elements using lattice QCD

    SciTech Connect

    Gupta, R.

    1993-08-01

    The author gives a brief introduction to the scope of lattice QCD calculations in his effort to extract the fundamental parameters of the standard model. This goal is illustrated by two examples. First the author discusses the extraction of CKM matrix elements from measurements of form factors for semileptonic decays of heavy-light pseudoscalar mesons such as D {yields} Ke{nu}. Second, he presents the status of results for the kaon B parameter relevant to CP violation. He concludes the talk with a short outline of his experiences with optimizing QCD codes on the CM5.

  4. QCD dynamics in mesons at soft and hard scales

    SciTech Connect

    Nguyen, T.; Souchlas, N. A.; Tandy, P. C.

    2010-07-27

    Using a ladder-rainbow kernel previously established for the soft scale of light quark hadrons, we explore, within a Dyson-Schwinger approach, phenomena that mix soft and hard scales of QCD. The difference between vector and axial vector current correlators is examined to estimate the four quark chiral condensate and the leading distance scale for the onset of non-perturbative phenomena in QCD. The valence quark distributions, in the pion and kaon, defined in deep inelastic scattering, and measured in the Drell Yan process, are investigated with the same ladder-rainbow truncation of the Dyson-Schwinger and Bethe-Salpeter equations.

  5. Migraine photophobia originating in cone-driven retinal pathways.

    PubMed

    Noseda, Rodrigo; Bernstein, Carolyn A; Nir, Rony-Reuven; Lee, Alice J; Fulton, Anne B; Bertisch, Suzanne M; Hovaguimian, Alexandra; Cestari, Dean M; Saavedra-Walker, Rodrigo; Borsook, David; Doran, Bruce L; Buettner, Catherine; Burstein, Rami

    2016-07-01

    Migraine headache is uniquely exacerbated by light. Using psychophysical assessments in patients with normal eyesight we found that green light exacerbates migraine headache significantly less than white, blue, amber or red lights. To delineate mechanisms, we used electroretinography and visual evoked potential recording in patients, and multi-unit recording of dura- and light-sensitive thalamic neurons in rats to show that green activates cone-driven retinal pathways to a lesser extent than white, blue and red; that thalamic neurons are most responsive to blue and least responsive to green; and that cortical responses to green are significantly smaller than those generated by blue, amber and red lights. These findings suggest that patients' experience with colour and migraine photophobia could originate in cone-driven retinal pathways, fine-tuned in relay thalamic neurons outside the main visual pathway, and preserved by the cortex. Additionally, the findings provide substrate for the soothing effects of green light. PMID:27190022

  6. QCD structure of nuclear interactions

    NASA Astrophysics Data System (ADS)

    Granados, Carlos G.

    The research presented in this dissertation investigated selected processes involving baryons and nuclei in hard scattering reactions. These processes are characterized by the production of particles with large energies and transverse momenta. Through these processes, this work explored both, the constituent (quark) structure of baryons (specifically nucleons and Delta-Isobars), and the mechanisms through which the interactions between these constituents ultimately control the selected reactions. The first of such reactions is the hard nucleon-nucleon elastic scattering, which was studied here considering the quark exchange between the nucleons to be the dominant mechanism of interaction in the constituent picture. In particular, it was found that an angular asymmetry exhibited by proton-neutron elastic scattering data is explained within this framework if a quark-diquark picture dominates the nucleon's structure instead of a more traditional SU(6) three quarks picture. The latter yields an asymmetry around 90o center of mass scattering with a sign opposite to what is experimentally observed. The second process is the hard breakup by a photon of a nucleon-nucleon system in light nuclei. Proton-proton (pp) and proton-neutron (pn) breakup in 3He, and DeltaDelta-isobars production in deuteron breakup were analyzed in the hard rescattering model (HRM), which in conjunction with the quark interchange mechanism provides a Quantum Chromodynamics (QCD) description of the reaction. Through the HRM, cross sections for both channels in 3He photodisintegration were computed without the need of a fitting parameter. The results presented here for pp breakup show excellent agreement with recent experimental data. In DeltaDelta-isobars production in deuteron breakup, HRM angular distributions for the two DeltaDelta channels were compared to the pn channel and to each other. An important prediction fromthis study is that the Delta++Delta- channel consistently dominates Delta+Delta0

  7. Lattice QCD and Nuclear Physics

    SciTech Connect

    Konstantinos Orginos

    2007-03-01

    A steady stream of developments in Lattice QCD have made it possible today to begin to address the question of how nuclear physics emerges from the underlying theory of strong interactions. Central role in this understanding play both the effective field theory description of nuclear forces and the ability to perform accurate non-perturbative calculations in lo w energy QCD. Here I present some recent results that attempt to extract important low energy constants of the effective field theory of nuclear forces from lattice QCD.

  8. Hadron physics in holographic QCD

    NASA Astrophysics Data System (ADS)

    Santra, A. B.; Lombardo, U.; Bonanno, A.

    2012-07-01

    Hadron physics deals with the study of strongly interacting subatomic particles such as neutrons, protons, pions and others, collectively known as baryons and mesons. Physics of strong interaction is difficult. There are several approaches to understand it. However, in the recent years, an approach called, holographic QCD, based on string theory (or gauge-gravity duality) is becoming popular providing an alternative description of strong interaction physics. In this article, we aim to discuss development of strong interaction physics through QCD and string theory, leading to holographic QCD.

  9. QCD THERMODYNAMICS AT ZERO AND NON-ZERO DENSITY.

    SciTech Connect

    SCHMIDT, C.

    2007-07-03

    We present recent results on thermodynamics of QCD with almost physical light quark masses and a physical strange quark mass value. These calculations have been performed with an improved staggered action especially designed for finite temperature lattice QCD. In detail we present a calculation of the transition temperature, using a combined chiral and continuum extrapolation. Furthermore we present preliminary results on the interaction measure and energy density at almost realistic quark masses. Finally we discuss the response of the pressure to a finite quark chemical potential. Within the Taylor expansion formalism we calculate quark number susceptibilities and leading order corrections to finite chemical potential. This is particularly useful for mapping out the critical region in the QCD phase diagram.

  10. Hadronic Spectrum of a Holographic Dual of QCD

    SciTech Connect

    Teramond, Guy F. de; Brodsky, Stanley J.

    2005-05-27

    We compute the spectrum of light hadrons in a holographic dual of QCD defined on AdS{sub 5}xS{sup 5} which has conformal behavior at short distances and confinement at large interquark separation. Specific hadrons are identified by the correspondence of string modes with the dimension of the interpolating operator of the hadron's valence Fock state. Higher orbital excitations are matched quanta to quanta with fluctuations about the AdS background. Since only one parameter, the QCD scale {lambda}{sub QCD}, is used, the agreement with the pattern of physical states is remarkable. In particular, the ratio of delta to nucleon trajectories is determined by the ratio of zeros of Bessel functions.

  11. Nearly Conformal QCD and AdS/CFT

    SciTech Connect

    de Teramond, Guy F.; Brodsky, Stanley J.; /Costa Rica U. /SLAC

    2005-08-08

    The AdS/CFT correspondence is a powerful tool to study the properties of conformal QCD at strong coupling in terms of a higher dimensional dual gravity theory. The power-law falloff of scattering amplitudes in the non-perturbative regime and calculable hadron spectra follow from holographic models dual to QCD with conformal behavior at short distances and confinement at large distances. String modes and fluctuations about the AdS background are identified with QCD degrees of freedom and orbital excitations at the AdS boundary limit. A description of form factors in space and time-like regions and the behavior of light-front wave functions can also be understood in terms of a dual gravity description in the interior of AdS.

  12. Cone on Olympus Mons

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03078 Cone on Olympus Mons

    This image shows just a small part of the eastern flank of Olympus Mons. On the far left side of the image a small volcanic cone can be seen. The shadow helps to identify this feature.

    Image information: VIS instrument. Latitude 15.7N, Longitude 229.7E. 18 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  13. The Holographic Entropy Cone

    SciTech Connect

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.

  14. The Holographic Entropy Cone

    DOE PAGESBeta

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phasemore » space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.« less

  15. The holographic entropy cone

    NASA Astrophysics Data System (ADS)

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-01

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.

  16. Double Cones as a Basis for Polarization Sensitivity in Vertebrates

    NASA Astrophysics Data System (ADS)

    Rowe, Manoel

    1995-01-01

    Over the course of the past 50 years there has been an increasing number of claims that certain vertebrates are sensitive to the linear polarization state of visible radiation. However, the mechanism(s) that mediates this polarization sensitivity remains elusive at the present time. The retinas of most vertebrates contain anatomical structures loosely referred to as double cones--composite entities constituted by the apposition of two independently developed, diurnally active photoreceptors. The significance of this apposition for visual function also remains elusive. It is possible that double cones mediate polarization sensitivity as a consequence of geometric birefringence; light polarized parallel to the axis joining the centers of the two halves of a double cone can potentially stimulate the receptors more strongly than light polarized in the direction perpendicular to both that axis and the normal axis of light propagation down the length of the double cone. The feasibility of this mechanism for polarization sensitivity has been examined here with specific reference to the retina of a representative animal, the green sunfish (Lepomis cyanellus). Transmission electron micrographs of thin sections from a sunfish retina were analyzed in order to develop simple models of waveguiding down the long axis of a sunfish double cone. The results of the computations indicate that the mechanism is feasible only if there are refractive index gradients in the photoreceptors of sunfish. Isolated receptors were thus examined with scanning microinterferometry to demonstrate the presence of such gradients. In the course of the investigation, the literature pertaining to vertebrate polarization sensitivity and retinal anatomy were reviewed to delimit the generality of the conclusions drawn from sunfish photoreceptors. As a result of this analysis, it should be concluded that much future research is needed to clarify what (if any) role optical polarization plays in the sensory

  17. Connections between chiral Lagrangians and QCD sum-rules

    NASA Astrophysics Data System (ADS)

    Fariborz, Amir H.; Pokraka, A.; Steele, T. G.

    2016-01-01

    In this paper, it is shown how a chiral Lagrangian framework can be used to derive relationships connecting quark-level QCD correlation functions to mesonic-level two-point functions. Crucial ingredients of this connection are scale factor matrices relating each distinct quark-level substructure (e.g. quark-antiquark, four-quark) to its mesonic counterpart. The scale factors and mixing angles are combined into a projection matrix to obtain the physical (hadronic) projection of the QCD correlation function matrix. Such relationships provide a powerful bridge between chiral Lagrangians and QCD sum-rules that are particularly effective in studies of the substructure of light scalar mesons with multiple complicated resonance shapes and substantial underlying mixings. The validity of these connections is demonstrated for the example of the isotriplet a0(980)-a0(1450) system, resulting in an unambiguous determination of the scale factors from the combined inputs of QCD sum-rules and chiral Lagrangians. These scale factors lead to a remarkable agreement between the quark condensates in QCD and the mesonic vacuum expectation values that induce spontaneous chiral symmetry breaking in chiral Lagrangians. This concrete example shows a clear sensitivity to the underlying a0-system mixing angle, illustrating the value of this methodology in extensions to more complicated mesonic systems.

  18. Comparative Study of Algorithms for the Numerical Simulation of Lattice QCD

    SciTech Connect

    Luz, Fernando H. P.; Mendes, Tereza

    2010-11-12

    Large-scale numerical simulations are the prime method for a nonperturbative study of QCD from first principles. Although the lattice simulation of the pure-gauge (or quenched-QCD) case may be performed very efficiently on parallel machines, there are several additional difficulties in the simulation of the full-QCD case, i.e. when dynamical quark effects are taken into account. We discuss the main aspects of full-QCD simulations, describing the most common algorithms. We present a comparative analysis of performance for two versions of the hybrid Monte Carlo method (the so-called R and RHMC algorithms), as provided in the MILC software package. We consider two degenerate flavors of light quarks in the staggered formulation, having in mind the case of finite-temperature QCD.

  19. Making An Impact: Shatter Cones

    ERIC Educational Resources Information Center

    Blank, Lisa M.; Plautz, Michael R.; Crews, Jeffrey W.

    2004-01-01

    In 1990, a group of geologists discovered a large number of shatter cones in southwestern Montana. Shatter cones are a type of metamorphosed rock often found in impact structures (the remains of a crater after a meteor impact and years of Earth activity). Scientists have discovered only 168 impact craters around the world. If rocks could talk,…

  20. Aerodynamic Rear Cone for Trucks

    NASA Technical Reports Server (NTRS)

    Bullman, J.

    1985-01-01

    Wind-inflated cone reduces turbulence that ordinarily occurs in air just behind square-back truck traveling at high speed. Wind around truck would enter slits in folded cone and automatically deploy it. Energy lost to air turbulence greatly reduced, and fuel consumed by truck reduced accordingly. In addition, less air turbulence means less disturbance to nearby vehicles on highway.

  1. QCD analogy for quantum gravity

    NASA Astrophysics Data System (ADS)

    Holdom, Bob; Ren, Jing

    2016-06-01

    Quadratic gravity presents us with a renormalizable, asymptotically free theory of quantum gravity. When its couplings grow strong at some scale, as in QCD, then this strong scale sets the Planck mass. QCD has a gluon that does not appear in the physical spectrum. Quadratic gravity has a spin-2 ghost that we conjecture does not appear in the physical spectrum. We discuss how the QCD analogy leads to this conjecture and to the possible emergence of general relativity. Certain aspects of the QCD path integral and its measure are also similar for quadratic gravity. With the addition of the Einstein-Hilbert term, quadratic gravity has a dimensionful parameter that seems to control a quantum phase transition and the size of a mass gap in the strong phase.

  2. Geological constraints on the dynamic emplacement of cone-sheets - The Ardnamurchan cone-sheet swarm, NW Scotland

    NASA Astrophysics Data System (ADS)

    Mathieu, Lucie; Burchardt, Steffi; Troll, Valentin R.; Krumbholz, Michael; Delcamp, Audray

    2015-11-01

    Cone-sheets are a significant constituent of many central volcanoes, where they contribute to volcano growth by intrusion and through flank eruptions, although the exact emplacement mechanisms are still controversially discussed. In particular, it is not yet fully resolved whether cone-sheets propagate as magma-driven, opening-mode fractures or as shear fractures, and to what extent pre-existing host-rock structures and different stress fields influence cone-sheet emplacement. To shed further light on the role of these parameters in cone-sheet emplacement, we use detailed field and remote sensing data of the classic Ardnamurchan cone-sheet swarm in NW-Scotland, and we show that the cone-sheets primarily propagated as opening-mode fractures in the σ1-σ2 plane of the volcanic stress field. In addition, more than one third of the Ardnamurchan cone-sheet segments are parallel to lineaments that form a conjugate set of NNW and WNW striking fractures and probably reflect the regional NW-SE orientation of σ1 during emplacement in the Palaeogene. Cone-sheets exploit these lineaments within the NE and SW sectors of the Ardnamurchan central complex, which indicates that the local volcanic stress field dominated during sheet propagation and only allowed exploitation of host-rock discontinuities that were approximately parallel to the sheet propagation path. In addition, outcrop-scale deflections of cone-sheets into sills and back into cone-sheets (also referred to as "staircase" geometry) are explained by the interaction of stresses at the propagating sheet tip with variations in host-rock strength, as well as the influence of sheet-induced strain. As a consequence, cone-sheets associated with sill-like segments propagate as mixed-mode I/II fractures. Hence, cone-sheet emplacement requires a dynamic model that takes into account stress fields at various scales and the way propagating magma interacts with the host rock and its inherent variations in rock strength.

  3. Imaging modal content of cone photoreceptors using adaptive optics optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Liu, Zhuolin; Kocaoglu, Omer P.; Turner, Timothy L.; Miller, Donald T.

    2015-03-01

    It has been long established that photoreceptors capture light based on the principles of optical waveguiding. Yet after decades of experimental and theoretical investigations considerable uncertainty remains, even for the most basic prediction as to whether photoreceptors support more than a single waveguide mode. To test for modal behavior in human cone photoreceptors, we took advantage of adaptive-optics optical coherence tomography (AO-OCT, λc=785 nm) to noninvasively image in three dimensions the reflectance profiles generated in the inner and outer segments (IS, OS) of cones. Mode content was examined over a range of cone diameters by imaging cones from 0.6° to 10° retinal eccentricity (n = 1802). Fundamental to the method was extraction of reflections at the cone IS/OS junction and cone outer segment tip (COST). Modal content properties of size, circularity and orientation were quantified using second moment analysis. Analysis of the cone reflections indicates waveguide properties of cone IS and OS depend on segment diameter. Cone IS was found to support a single mode near the fovea (<=3°) and multiple modes further away (<4°). In contrast, no evidence of multiple modes was found in the cone OSs. The IS/OS and COST reflections share a common optical aperture, are most circular near the fovea, and show no orientation preference.

  4. Kinetic-structural analysis of neuronal growth cone veil motility.

    PubMed

    Mongiu, Anne K; Weitzke, Elizabeth L; Chaga, Oleg Y; Borisy, Gary G

    2007-03-15

    Neuronal growth cone advance was investigated by correlative light and electron microscopy carried out on chick dorsal root ganglion cells. Advance was analyzed in terms of the two principal organelles responsible for protrusive motility in the growth cone - namely, veils and filopodia. Veils alternated between rapid phases of protrusion and retraction. Electron microscopy revealed characteristic structural differences between the phases. Our results provide a significant advance in three respects: first, protruding veils are comprised of a densely branched network of actin filaments that is lamellipodial in appearance and includes the Arp2/3 complex. On the basis of this structural and biomarker evidence, we infer that the dendritic nucleation and/or array-treadmilling mechanism of protrusive motility is conserved in veil protrusion of growth cones as in the motility of fibroblasts; second, retracting veils lack dendritic organization but contain a sparse network of long filaments; and third, growth cone filopodia have the capacity to nucleate dendritic networks along their length, a property consistent with veil formation seen at the light microscopic level but not previously understood in supramolecular terms. These elements of veil and filopodial organization, when taken together, provide a conceptual framework for understanding the structural basis of growth cone advance. PMID:17327278

  5. Response properties of cones from the retina of the tiger salamander.

    PubMed Central

    Perry, R J; McNaughton, P A

    1991-01-01

    1. Spectral sensitivity measurements using the suction electrode technique reveal three types of cone in the retina of the tiger salamander, showing maximum sensitivity at wavelengths 610 nm (red-sensitive cone), 444 nm (blue-sensitive cone) and below 400 nm (UV-sensitive cone). 2. The absolute sensitivities of red- and blue-sensitive cones to flashes of optimal wavelength are 0.022 and 0.33 pA photon-1 micron 2 respectively. 3. The time-to-peak of the dim flash response and the recovery of membrane current after a flash of any intensity are fastest in red-sensitive and slowest in blue-sensitive cones. 4. In blue- and UV-sensitive cones the flash response peaks progressively earlier as the flash strength is increased, as in rods. In red-sensitive cones, however, bright flash responses take longer to peak than dim flash responses. 5. In all three cone types, voltage clamping at -40 mV reduces the time-to-peak of the response to a bright flash, showing that the rising phase of the bright flash response is normally limited by the time constant of the cell. Under voltage clamp, all cones show a decrease in time-to-peak with increasing flash intensity. 6. Voltage clamping red-sensitive cones reveals two components of the rising phase of the response to a bright flash. Most of the current is rapidly suppressed by a bright flash, and represents the closure of light-sensitive channels. The residual current decays with a mean time constant of 20 ms, and is probably attributable to the decline of electrogenic Na(+)-Ca2+, K+ exchange. The amplitude of this exchange current suggests that the proportion of the dark current carried by calcium ions is greater in red-sensitive cones than in rods of the same species. 7. In UV-sensitive cones, a prominent oscillation of light-sensitive current is observed during the recovery from flashes of intermediate intensity. A similar, but slower and less prominent oscillation is usually seen in blue-sensitive cones. 8. When a red

  6. Transonic Flow Past Cone Cylinders

    NASA Technical Reports Server (NTRS)

    Solomon, George E

    1955-01-01

    Experimental results are presented for transonic flow post cone-cylinder, axially symmetric bodies. The drag coefficient and surface Mach number are studied as the free-stream Mach number is varied and, wherever possible, the experimental results are compared with theoretical predictions. Interferometric results for several typical flow configurations are shown and an example of shock-free supersonic-to-subsonic compression is experimentally demonstrated. The theoretical problem of transonic flow past finite cones is discussed briefly and an approximate solution of the axially symmetric transonic equations, valid for a semi-infinite cone, is presented.

  7. QCD measurements at the Tevatron

    SciTech Connect

    Bandurin, Dmitry; /Florida State U.

    2011-12-01

    Selected quantum chromodynamics (QCD) measurements performed at the Fermilab Run II Tevatron p{bar p} collider running at {radical}s = 1.96 TeV by CDF and D0 Collaborations are presented. The inclusive jet, dijet production and three-jet cross section measurements are used to test perturbative QCD calculations, constrain parton distribution function (PDF) determinations, and extract a precise value of the strong coupling constant, {alpha}{sub s}(m{sub Z}) = 0.1161{sub -0.0048}{sup +0.0041}. Inclusive photon production cross-section measurements reveal an inability of next-to-leading-order (NLO) perturbative QCD (pQCD) calculations to describe low-energy photons arising directly in the hard scatter. The diphoton production cross-sections check the validity of the NLO pQCD predictions, soft-gluon resummation methods implemented in theoretical calculations, and contributions from the parton-to-photon fragmentation diagrams. Events with W/Z+jets productions are used to measure many kinematic distributions allowing extensive tests and tunes of predictions from pQCD NLO and Monte-Carlo (MC) event generators. The charged-particle transverse momenta (p{sub T}) and multiplicity distributions in the inclusive minimum bias events are used to tune non-perturbative QCD models, including those describing the multiple parton interactions (MPI). Events with inclusive production of {gamma} and 2 or 3 jets are used to study increasingly important MPI phenomenon at high p{sub T}, measure an effective interaction cross section, {sigma}{sub eff} = 16.4 {+-} 2.3 mb, and limit existing MPI models.

  8. QCD trace anomaly

    SciTech Connect

    Andersen, Jens O.; Leganger, Lars E.; Strickland, Michael; Su, Nan

    2011-10-15

    In this brief report we compare the predictions of a recent next-to-next-to-leading order hard-thermal-loop perturbation theory (HTLpt) calculation of the QCD trace anomaly to available lattice data. We focus on the trace anomaly scaled by T{sup 2} in two cases: N{sub f}=0 and N{sub f}=3. When using the canonical value of {mu}=2{pi}T for the renormalization scale, we find that for Yang-Mills theory (N{sub f}=0) agreement between HTLpt and lattice data for the T{sup 2}-scaled trace anomaly begins at temperatures on the order of 8T{sub c}, while treating the subtracted piece as an interaction term when including quarks (N{sub f}=3) agreement begins already at temperatures above 2T{sub c}. In both cases we find that at very high temperatures the T{sup 2}-scaled trace anomaly increases with temperature in accordance with the predictions of HTLpt.

  9. New Perspectives for QCD Physics at the LHC

    SciTech Connect

    Brodsky, Stanley J.; /SLAC /Stanford U. /Southern Denmark U., CP3-Origins

    2011-02-07

    I review a number of topics where conventional wisdom relevant to hadron physics at the LHC has been challenged. For example, the initial-state and final-state interactions of the quarks and gluons entering perturbative QCD hard-scattering subprocesses lead to the breakdown of traditional concepts of factorization and universality for transverse-momentum-dependent observables at leading twist. These soft-gluon rescattering effect produce single-spin asymmetries, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as diffractive deep inelastic scattering, The antishadowing of nuclear structure functions is predicted to depend on the flavor quantum numbers of each quark and antiquark. Isolated hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation, even at the LHC. Such 'direct' processes can explain the observed deviations from pQCD predictions of the power-law fall-off of inclusive hadron cross sections as well as the 'baryon anomaly' seen in high-centrality heavy-ion collisions at RHIC. The intrinsic charm contribution to the proton structure function at high x can explain the large rate for high p{sub T} photon plus charm-jet events observed at the Tevatron and imply a large production rate for charm and bottom jets at high p{sub T} at the LHC, as well as a novel mechanism for Higgs and Z{sup 0} production at high x{sub F}. The light-front wavefunctions derived in AdS/QCD can be used to calculate jet hadronization at the amplitude level. The elimination of the renormalization scale ambiguity for the QCD coupling using the scheme-independent BLM method will increase the sensitivity of searches for new physics at the LHC. The implications of 'in-hadron condensates' for the QCD contribution to the cosmological constant are also discussed.

  10. Feedback-induced glutamate spillover enhances negative feedback from horizontal cells to cones

    PubMed Central

    Vroman, Rozan; Kamermans, Maarten

    2015-01-01

    Key points In the retina, horizontal cells feed back negatively to cone photoreceptors. Glutamate released from cones can spill over to neighbouring cones. Here we show that cone glutamate release induced by negative feedback can also spill over to neighbouring cones. This glutamate activates the glutamate transporter-associated chloride current in these neighbouring cones, which leads to a change in their membrane potential and thus modulates their output. In this way, feedback-induced glutamate spillover enhances negative feedback from horizontal cells to cones, thus forming an additional feedback pathway. This effect will be particularly prominent in cones that are strongly hyperpolarized by light. Abstract Inhibition in the outer retina functions via an unusual mechanism. When horizontal cells hyperpolarize the activation potential of the Ca2+ current of cones shifts to more negative potentials. The underlying mechanism consists of an ephaptic component and a Panx1/ATP-mediated component. Here we identified a third feedback component, which remains active outside the operating range of the Ca2+ current. We show that the glutamate transporters of cones can be activated by glutamate released from their neighbours. This pathway can be triggered by negative feedback from horizontal cells to cones, thus providing an additional feedback pathway. This additional pathway is mediated by a Cl− current, can be blocked by either removing the gradient of K+ or by adding the glutamate transporter blocker TBOA, or low concentrations of Zn2+. These features point to a glutamate transporter-associated Cl− current. The pathway has a delay of 4.7 ± 1.7 ms. The effectiveness of this pathway in modulating the cone output depends on the equilibrium potential of Cl− (ECl) and the membrane potential of the cone. Because estimates of ECl show that it is around the dark resting membrane potential of cones, the activation of the glutamate transporter-associated Cl− current

  11. Origins of Small Volcanic Cones on Mars

    NASA Technical Reports Server (NTRS)

    Fagents, S. A.; Pace, K.; Greeley, R.

    2002-01-01

    Studies of volcanic cones identified in the MGS data indicate a range of possible origins, from primary vent constructs (cinder cones, tuff cones) to rootless cones formed by lava-ice interaction. Additional information is contained in the original extended abstract.

  12. RECENT LATTICE RESULTS ON FINITE TEMPERATURE AND DENSITY QCD, PART 1.

    SciTech Connect

    KARSCH,F.

    2007-07-09

    We discuss recent progress made studies of bulk thermodynamics of strongly interacting matter through lattice simulations of QCD with an almost physical light and strange quark mass spectrum. We present results on the QCD equation of state at vanishing and non-vanishing quark chemical potential and show first results on baryon number and strangeness fluctuations, which might be measured in event-by-event fluctuations in low energy runs at RHIC as well as at FAIR.

  13. Spectral and temporal sensitivity of cone-mediated responses in mouse retinal ganglion cells

    PubMed Central

    Wang, Yanbin V.; Weick, Michael; Demb, Jonathan B.

    2011-01-01

    The retina uses two photoreceptor types to encode the wide range of light intensities in the natural environment. Rods mediate vision in dim light, whereas cones mediate vision in bright light. Mouse photoreceptors include only 3% cones, and the majority of these co-express two opsins (S, M), with peak sensitivity to either ultraviolet (360 nm) or green light (508 nm). The M:S opsin ratio varies across the retina but has not been characterized functionally, preventing quantitative study of cone-mediated vision. Furthermore, physiological and behavioral measurements suggested that mouse retina supports relatively slow temporal processing (peak sensitivity, ~2–5 Hz), compared to primates; however, past studies used visible wavelengths that are inefficient at stimulating mouse S opsin. Here, we measured the M:S opsin expression ratio across the mouse retina, as reflected by ganglion cell responses, in vitro, and probed cone-mediated ganglion cell temporal properties using ultraviolet light stimulation and linear systems analysis. From recordings in mice lacking rod function (Gnat1−/−, Rho−/−), we estimate ~70% M-opsin expression in far dorsal retina, dropping to <5% M-opsin expression throughout ventral retina. In mice lacking cone function (Gnat2cpfl3), light-adapted rod-mediated responses peaked at ~5–7 Hz. In wild-type mice, cone-mediated responses peaked at ~10 Hz, with substantial responsiveness up to ~30 Hz. Therefore, despite the small percentage of cones, cone-mediated responses in mouse ganglion cells are fast and robust, similar to those in primates. These measurements enable quantitative analysis of cone-mediated responses at all levels of the visual system. PMID:21613480

  14. Recent QCD results from the Tevatron

    SciTech Connect

    Pickarz, Henryk; CDF and DO collaboration

    1997-02-01

    Recent QCD results from the CDF and D0 detectors at the Tevatron proton-antiproton collider are presented. An outlook for future QCD tests at the Tevatron collider is also breifly discussed. 27 refs., 11 figs.

  15. Kenneth Wilson and Lattice QCD

    NASA Astrophysics Data System (ADS)

    Ukawa, Akira

    2015-09-01

    We discuss the physics and computation of lattice QCD, a space-time lattice formulation of quantum chromodynamics, and Kenneth Wilson's seminal role in its development. We start with the fundamental issue of confinement of quarks in the theory of the strong interactions, and discuss how lattice QCD provides a framework for understanding this phenomenon. A conceptual issue with lattice QCD is a conflict of space-time lattice with chiral symmetry of quarks. We discuss how this problem is resolved. Since lattice QCD is a non-linear quantum dynamical system with infinite degrees of freedom, quantities which are analytically calculable are limited. On the other hand, it provides an ideal case of massively parallel numerical computations. We review the long and distinguished history of parallel-architecture supercomputers designed and built for lattice QCD. We discuss algorithmic developments, in particular the difficulties posed by the fermionic nature of quarks, and their resolution. The triad of efforts toward better understanding of physics, better algorithms, and more powerful supercomputers have produced major breakthroughs in our understanding of the strong interactions. We review the salient results of this effort in understanding the hadron spectrum, the Cabibbo-Kobayashi-Maskawa matrix elements and CP violation, and quark-gluon plasma at high temperatures. We conclude with a brief summary and a future perspective.

  16. Functional significance of the taper of vertebrate cone photoreceptors

    PubMed Central

    Hárosi, Ferenc I.

    2012-01-01

    Vertebrate photoreceptors are commonly distinguished based on the shape of their outer segments: those of cones taper, whereas the ones from rods do not. The functional advantages of cone taper, a common occurrence in vertebrate retinas, remain elusive. In this study, we investigate this topic using theoretical analyses aimed at revealing structure–function relationships in photoreceptors. Geometrical optics combined with spectrophotometric and morphological data are used to support the analyses and to test predictions. Three functions are considered for correlations between taper and functionality. The first function proposes that outer segment taper serves to compensate for self-screening of the visual pigment contained within. The second function links outer segment taper to compensation for a signal-to-noise ratio decline along the longitudinal dimension. Both functions are supported by the data: real cones taper more than required for these compensatory roles. The third function relates outer segment taper to the optical properties of the inner compartment whereby the primary determinant is the inner segment’s ability to concentrate light via its ellipsoid. In support of this idea, the rod/cone ratios of primarily diurnal animals are predicted based on a principle of equal light flux gathering between photoreceptors. In addition, ellipsoid concentration factor, a measure of ellipsoid ability to concentrate light onto the outer segment, correlates positively with outer segment taper expressed as a ratio of characteristic lengths, where critical taper is the yardstick. Depending on a light-funneling property and the presence of focusing organelles such as oil droplets, cone outer segments can be reduced in size to various degrees. We conclude that outer segment taper is but one component of a miniaturization process that reduces metabolic costs while improving signal detection. Compromise solutions in the various retinas and retinal regions occur between

  17. QCD vacuum: nuclear forces, nucleons, pions …

    NASA Astrophysics Data System (ADS)

    Robilotta, M. R.

    2011-08-01

    This contribution contains six sections, namely: 1. from QCD to chiral perturbation theory - QCD is widely accepted as the theory of strong interactions, but direct applications to low-energy hadronic processes are difficult. In this regime, the light quarks u and d prevail, and one can employ a rigorously equivalent effective theory, known a chiral perturbation theory, based on hadronic degrees of freedom. 2. strong vacuum and the pion - Chiral symmetry is not exact in the real world. Nevertheless, the absence of of parity multiplets and the smallness of the pion mass suggest that it is a good approximate symmetry, realized in the Nambu-Goldstone mode. Its ground state, the vacuum, is filled with a condensate, made of quark-antiquark pairs. In sections 1-3, instances are presented of observables strongly influenced by the QCD vacuum. 3. nuclear forces - In the last few years, chiral perturbation theory has produced a very reliable picture of both two- and three-nucleon forces. In particular, the important isospin independent central potential VC+ is well understood and known to be dominated by the scalar form factor of the nucleon, a function that describes the disturbance it produces over the vacuum. 4. nucleon scalar form factor - The spatial integration of the nucleon scalar form factor gives rise to σN, the nucleon σ-term. The value of this quantity can be extracted from experiment and the empirical value accepted presently is 45±8 MeV. A simple model, based on the idea that the pion cloud of the nucleon is constructed at the expenses of the surrounding condensate, produces a σN in the range 43-49 MeV, with no free parameters. 5. scalar radius of the pion - The value of this radius can be extracted from pion-pion scattering data and the most reliable estimate is Sπ = 0.61±0.04 fm2. The extension of the model described in section 4 to the pion gives rise to a picture in which it is embedded into the condensate. As one moves towards its center, the

  18. Meson Electro-/Photo-Production from QCD

    NASA Astrophysics Data System (ADS)

    Briceño, Raúl A.

    2016-07-01

    Recent results of meson photo-production at the existing electron machines with polarized real photon beams and the measurement of polarization observables of the final state baryons have provided high precision data that led to the discovery of new excited nucleon and Δ states using multi-channel partial wave analyses procedures. The internal structure of several prominent excited states has been revealed employing meson electroproduction processes. On the theoretical front, lattice QCD is now predicting the baryon spectrum with very similar characteristics as the constituent quark model, and continuum QCD, such as is represented in the Dyson-Schwinger equations approach and in light front relativistic quark models, describes the non-perturbative behavior of resonance excitations at photon virtuality of Q^2 > 1.5 GeV^2 . In this talk I discuss the need to continue a vigorous program of nucleon spectroscopy and the study of the internal structure of excited states as a way to reveal the effective degrees of freedom underlying the excited states and their dependence on the distance scale probed.

  19. LATTICE QCD AT FINITE TEMPERATURE AND DENSITY.

    SciTech Connect

    BLUM,T.; CREUTZ,M.; PETRECZKY,P.

    2004-02-24

    With the operation of the RHIC heavy ion program, the theoretical understanding of QCD at finite temperature and density has become increasingly important. Though QCD at finite temperature has been extensively studied using lattice Monte-Carlo simulations over the past twenty years, most physical questions relevant for RHIC (and future) heavy ion experiments remain open. In lattice QCD at finite temperature and density there have been at least two major advances in recent years. First, for the first time calculations of real time quantities, like meson spectral functions have become available. Second, the lattice study of the QCD phase diagram and equation of state have been extended to finite baryon density by several groups. Both issues were extensively discussed in the course of the workshop. A real highlight was the study of the QCD phase diagram in (T, {mu})-plane by Z. Fodor and S. Katz and the determination of the critical end-point for the physical value of the pion mass. This was the first time such lattice calculations at, the physical pion mass have been performed. Results by Z Fodor and S. Katz were obtained using a multi-parameter re-weighting method. Other determinations of the critical end point were also presented, in particular using a Taylor expansion around {mu} = 0 (Bielefeld group, Ejiri et al.) and using analytic continuation from imaginary chemical potential (Ph. de Forcrand and O. Philipsen). The result based on Taylor expansion agrees within errors with the new prediction of Z. Fodor and S. Katz, while methods based on analytic continuation still predict a higher value for the critical baryon density. Most of the thermodynamics studies in full QCD (including those presented at this workshop) have been performed using quite coarse lattices, a = 0.2-0.3 fm. Therefore one may worry about cutoff effects in different thermodynamic quantities, like the transition temperature T{sub tr}. At the workshop U. Heller presented a study of the transition

  20. Quarkonium-nucleus bound states from lattice QCD

    SciTech Connect

    Beane, S.  R.; Chang, E.; Cohen, S.  D.; Detmold, W.; Lin, H. -W.; Orginos, K.; Parreño, A.; Savage, M.  J.

    2015-06-11

    Quarkonium-nucleus systems are composed of two interacting hadronic states without common valence quarks, which interact primarily through multi-gluon exchanges, realizing a color van der Waals force. We present lattice QCD calculations of the interactions of strange and charm quarkonia with light nuclei. Both the strangeonium-nucleus and charmonium-nucleus systems are found to be relatively deeply bound when the masses of the three light quarks are set equal to that of the physical strange quark. Extrapolation of these results to the physical light-quark masses suggests that the binding energy of charmonium to nuclear matter is B < 40 MeV.

  1. LATTICE QCD THERMODYNAMICS WITH WILSON QUARKS.

    SciTech Connect

    EJIRI,S.

    2007-11-20

    We review studies of QCD thermodynamics by lattice QCD simulations with dynamical Wilson quarks. After explaining the basic properties of QCD with Wilson quarks at finite temperature including the phase structure and the scaling properties around the chiral phase transition, we discuss the critical temperature, the equation of state and heavy-quark free energies.

  2. Bs→Kℓν form factors from lattice QCD

    NASA Astrophysics Data System (ADS)

    Bouchard, C. M.; Lepage, G. Peter; Monahan, Christopher; Na, Heechang; Shigemitsu, Junko

    2014-09-01

    We report the first lattice QCD calculation of the form factors for the standard model tree-level decay Bs→K ℓν. In combination with future measurement, this calculation will provide an alternative exclusive semileptonic determination of |Vub|. We compare our results with previous model calculations, make predictions for differential decay rates and branching fractions, and predict the ratio of differential branching fractions between Bs→Kτν and Bs→Kμν. We also present standard model predictions for differential decay rate forward-backward asymmetries and polarization fractions and calculate potentially useful ratios of Bs→K form factors with those of the fictitious Bs→ηs decay. Our lattice simulations utilize nonrelativistic QCD b and highly improved staggered light quarks on a subset of the MILC Collaboration 2+1 asqtad gauge configurations, including two lattice spacings and a range of light quark masses.

  3. Neutron star structure from QCD

    NASA Astrophysics Data System (ADS)

    Fraga, Eduardo S.; Kurkela, Aleksi; Vuorinen, Aleksi

    2016-03-01

    In this review article, we argue that our current understanding of the thermodynamic properties of cold QCD matter, originating from first principles calculations at high and low densities, can be used to efficiently constrain the macroscopic properties of neutron stars. In particular, we demonstrate that combining state-of-the-art results from Chiral Effective Theory and perturbative QCD with the current bounds on neutron star masses, the Equation of State of neutron star matter can be obtained to an accuracy better than 30% at all densities.

  4. The supercritical pomeron in QCD.

    SciTech Connect

    White, A. R.

    1998-06-29

    Deep-inelastic diffractive scaling violations have provided fundamental insight into the QCD pomeron, suggesting a single gluon inner structure rather than that of a perturbative two-gluon bound state. This talk outlines a derivation of a high-energy, transverse momentum cut-off, confining solution of QCD. The pomeron, in first approximation, is a single reggeized gluon plus a ''wee parton'' component that compensates for the color and particle properties of the gluon. This solution corresponds to a super-critical phase of Reggeon Field Theory.

  5. QCD inequalities for hadron interactions.

    PubMed

    Detmold, William

    2015-06-01

    We derive generalizations of the Weingarten-Witten QCD mass inequalities for particular multihadron systems. For systems of any number of identical pseudoscalar mesons of maximal isospin, these inequalities prove that near threshold interactions between the constituent mesons must be repulsive and that no bound states can form in these channels. Similar constraints in less symmetric systems are also extracted. These results are compatible with experimental results (where known) and recent lattice QCD calculations, and also lead to a more stringent bound on the nucleon mass than previously derived, m_{N}≥3/2m_{π}. PMID:26196617

  6. Recent QCD results from CDF

    SciTech Connect

    Yun, J.C.

    1990-10-10

    In this paper we report recent QCD analysis with the new data taken from CDF detector. CDF recorded an integrated luminosity of 4.4 nb{sup {minus}1} during the 1988--1989 run at center of mass system (CMS) energy of 1.8 TeV. The major topics of this report are inclusive jet, dijet, trijet and direct photon analysis. These measurements are compared of QCD predictions. For the inclusive jet an dijet analysis, tests of quark compositeness are emphasized. 11 refs., 6 figs.

  7. QCD corrections to triboson production

    NASA Astrophysics Data System (ADS)

    Lazopoulos, Achilleas; Melnikov, Kirill; Petriello, Frank

    2007-07-01

    We present a computation of the next-to-leading order QCD corrections to the production of three Z bosons at the Large Hadron Collider. We calculate these corrections using a completely numerical method that combines sector decomposition to extract infrared singularities with contour deformation of the Feynman parameter integrals to avoid internal loop thresholds. The NLO QCD corrections to pp→ZZZ are approximately 50% and are badly underestimated by the leading order scale dependence. However, the kinematic dependence of the corrections is minimal in phase space regions accessible at leading order.

  8. Lattice QCD clusters at Fermilab

    SciTech Connect

    Holmgren, D.; Mackenzie, Paul B.; Singh, Anitoj; Simone, Jim; /Fermilab

    2004-12-01

    As part of the DOE SciDAC ''National Infrastructure for Lattice Gauge Computing'' project, Fermilab builds and operates production clusters for lattice QCD simulations. This paper will describe these clusters. The design of lattice QCD clusters requires careful attention to balancing memory bandwidth, floating point throughput, and network performance. We will discuss our investigations of various commodity processors, including Pentium 4E, Xeon, Opteron, and PPC970. We will also discuss our early experiences with the emerging Infiniband and PCI Express architectures. Finally, we will present our predictions and plans for future clusters.

  9. QCD: Challenges for the future

    SciTech Connect

    Burrows, P.; Dawson, S.; Orr, L.; Smith, W.H.

    1997-01-13

    Despite many experimental verifications of the correctness of our basic understanding of QCD, there remain numerous open questions in strong interaction physics and we focus on the role of future colliders in addressing these questions. We discuss possible advances in the measurement of {alpha}{sub s}, in the study of parton distribution functions, and in the understanding of low x physics at present colliders and potential new facilities. We also touch briefly on the role of spin physics in advancing our understanding of QCD.

  10. Nucleon Structure from Lattice QCD

    SciTech Connect

    David Richards

    2007-09-05

    Recent advances in lattice field theory, in computer technology and in chiral perturbation theory have enabled lattice QCD to emerge as a powerful quantitative tool in understanding hadron structure. I describe recent progress in the computation of the nucleon form factors and moments of parton distribution functions, before proceeding to describe lattice studies of the Generalized Parton Distributions (GPDs). In particular, I show how lattice studies of GPDs contribute to building a three-dimensional picture of the proton, I conclude by describing the prospects for studying the structure of resonances from lattice QCD.

  11. Lighting

    SciTech Connect

    Audin, L.

    1994-12-31

    EPAct covers a vast territory beyond lighting and, like all legislation, also contains numerous {open_quotes}favors,{close_quotes} compromises, and even some sleight-of-hand. Tucked away under Title XIX, for example, is an increase from 20% to 28% tax on gambling winnings, effective January 1, 1993 - apparently as a way to help pay for new spending listed elsewhere in the bill. Overall, it is a landmark piece of legislation, about a decade overdue. It remains to be seen how the Federal Government will enforce upgrading of state (or even their own) energy codes. There is no mention of funding for {open_quotes}energy police{close_quotes} in EPAct. Merely creating such a national standard, however, provides a target for those who sincerely wish to create an energy-efficient future.

  12. The nucleon axial charge in full lattice QCD

    SciTech Connect

    Robert Edwards; George Fleming; P Hagler; John Negele; Konstantinos Orginos; Andrew Pochinsky; Dru Renner; David Richards; Wolfram Schroers

    2005-10-13

    The nucleon axial charge is calculated as a function of the pion mass in full QCD. Using domain wall valence quarks and improved staggered sea quarks, we present the first calculation with pion masses as light as 354 MeV and volumes as large as (3.5 fm)3. We show that finite volume effects are small for our volumes and that a constrained fit based on finite volume chiral perturbation theory agrees with experiment within 5% statistical errors.

  13. QCD Phase Diagram and the Constant Mass Approximation

    NASA Astrophysics Data System (ADS)

    Ahmad, A.; Ayala, A.; Bashir, A.; Gutiérrez, E.; Raya, A.

    2015-11-01

    Dynamical generation of quark masses in the infrared region of QCD plays an important role to understand the peculiar nature of the physics of hadrons. As it is known, the solution of QCD gap equation for the quark mass function is flat for low momentum, but smoothly evolves to the perturbative behavior at high momentum. In this work, we use an effective truncation of QCD gap equation valid up to 1 GeV, and implement it at finite temperature and chemical potential to understand the QCD phase diagram for chiral symmetry breaking-chiral symmetry restoration, and confinement-deconfinement phase transitions from the Schwinger-Dysin equations point of view. Our effective kernel contains a gluon dressing function with two light quark flavors Nf = 2, with current quark mass 0.0035 GeV. An effective coupling, adjusted to reproduce the behavior of the chiral condensate at finite T complements our truncation. We find the critical end point of the phase diagram located at the temperature TE = 0.1245 GeV and the baryonic chemical potential μEB = 0.211 GeV.

  14. QCD Corrections and New Physics - Proceedings of the International Symposium

    NASA Astrophysics Data System (ADS)

    Kodaira, Jiro; Onogi, Tetsuya; Sasaki, Ken

    1998-09-01

    The Table of Contents for the full book PDF is as follows: * Preface * Opening Address * Top Quark Physics * Threshold Resummation of Soft Gluons in Hadronic Reactions - An Introduction * Recent Results from CDF * Top Quark Physics: Overview * Complete Description of Polarization Effects in Top Quark Decays Including Higher Order QCD Corrections * Top Pair Production in e+e- and γγ Processes * Structure Functions I * Highlights of Physics at HERA * Some Aspects of the BFKL Evolution * Structure Functions II * New Result from SMC on g_{1}^ρ * Studies of the Nucleon Spin Structure by HERMES * Recent Developments in Perturbative QCD: Q2 Evolution of Chiral-Odd Distributions h1(x,Q2) and hL(x,Q2) * The Small x Behavior of g1 in the Resummed Approach * Jet Physics * QCD Results from LEP1 and LEP2 * Twenty Years of Jet Physics : Old and New * Multi-Parton Loop Amplitudes and Next-to-Leading Order Jet Cross-Sections * Heavy Meson * PQCD Analysis of Inclusive Heavy Hadrons Decays * Strong Coupling Constant from Lattice QCD * Heavy-Light Decay Constant from Lattice NRQCD * Concluding Remarks * Program * Organizing Committee * List of Participants

  15. Molecular mechanism of spontaneous pigment activation in retinal cones.

    PubMed

    Sampath, Alapakkam P; Baylor, Denis A

    2002-07-01

    Spontaneous current and voltage fluctuations (dark noise) in the photoreceptor cells of the retina limit the ability of the visual system to detect dim light. We recorded the dark current noise of individual salamander L cones. Previous work showed that the dark noise in these cells arises from thermal activation of the visual pigment. From the temperature dependence of the rate of occurrence of elementary noise events, we found an Arrhenius activation energy E(a) of 25 +/- 7 kcal/mol (mean +/- SD). This E(a) is similar to that reported for the thermal isomerization of 11-cis retinal in solution, suggesting that the cone pigment noise results from isomerization of the retinal chromophore. E(a) for the cone noise is similar to that previously reported for the "photon-like" noise of rods, but the preexponential factor is five orders of magnitude higher. To test the hypothesis that thermal isomerization can only occur in molecules whose Schiff base linkage is unprotonated, we changed the pH of the solution bathing the cone outer segment. This had little effect on the rate of occurrence of elementary noise events. The rate was also unchanged when the cone was exposed to Ringer solution made up from heavy water, whose solvent isotope effect should reduce the probability, that the Schiff base nitrogen is naked. PMID:12080111

  16. Coherent backscattering cone shape depends on the beam size.

    PubMed

    Bi, Renzhe; Dong, Jing; Lee, Kijoon

    2012-09-10

    Coherent backscattering (CBS) is a beautiful physical phenomenon that takes place in a highly scattering medium, which has potential application in noninvasive optical property measurement. The current model that explains the CBS cone shape, however, assumes the incoming beam diameter is infinitely large compared to the transport length. In this paper, we evaluate the effect of a finite scalar light illumination area on the CBS cone, both theoretically and experimentally. The quantitative relationship between laser beam size and the CBS cone shape is established by using two different finite beam models (uniform top hat and Gaussian distribution). A series of experimental data with varying beam diameters is obtained for comparison with the theory. Our study shows the CBS cone shape begins to show distortion when beam size becomes submillimeter, and this effect should not be ignored in general. In biological tissue where a normal large beam CBS cone is too narrow for detection, this small beam CBS may be more advantageous for more accurate and higher resolution tissue characterization. PMID:22968267

  17. Expression of the functional cone phototransduction cascade in retinoblastoma.

    PubMed Central

    Hurwitz, R L; Bogenmann, E; Font, R L; Holcombe, V; Clark, D

    1990-01-01

    Retinoblastoma is a malignant intraocular tumor that primarily affects small children. These tumors are primitive neuroectodermal malignancies, however some of them show morphologic evidence of differentiation into photoreceptors. Phototransduction cascades are a series of biochemical reactions that convert a photon of light into a neural impulse in rods and cones. The components of these cascades are uniquely expressed in photoreceptors and, although functionally similar, distinct components of these cascades are expressed in rods and cones. Using HPLC anion exchange chromatography, Western blot analysis, and specific monoclonal and polyclonal antibodies, we found that the cone but not the rod cGMP phosphodiesterase is functionally expressed in all six primary retinoblastomas examined and in three continuous retinoblastoma cell lines. Morphologic evidence of differentiation did not correlate with the expression of the enzyme. Furthermore, GTP analogues could activate the phosphodiesterase activity suggesting that an intact phototransduction cascade is present in the tumors. The presence of the cone phototransduction cascade in retinoblastoma confirms that this tumor has biochemically differentiated along the cone cell lineage. Images PMID:2161431

  18. Two-color QCD at high density

    NASA Astrophysics Data System (ADS)

    Boz, Tamer; Giudice, Pietro; Hands, Simon; Skullerud, Jon-Ivar; Williams, Anthony G.

    2016-01-01

    QCD at high chemical potential has interesting properties such as deconfinement of quarks. Two-color QCD, which enables numerical simulations on the lattice, constitutes a laboratory to study QCD at high chemical potential. Among the interesting properties of two-color QCD at high density is the diquark condensation, for which we present recent results obtained on a finer lattice compared to previous studies. The quark propagator in two-color QCD at non-zero chemical potential is referred to as the Gor'kov propagator. We express the Gor'kov propagator in terms of form factors and present recent lattice simulation results.

  19. Tests of QCD with polarized electrons

    SciTech Connect

    Pavel, T.J.; SLD Collaboration

    1996-08-01

    We present three measurements that exploit the highly-polarized incident electrons of the SLC facility to probe QCD and the hadronization process. We observe preliminary evidence for leading particle production in hadronic decays of the Zo to light-quark pairs. In a high-purity sample of quark jets, the momentum spectra of p, A0, and K(-) are harder than those of p(bar), A(bar)0, and K(+), supporting the hypothesis that faster particles in jets are more likely to carry the primary quark or antiquark of the jet. Second, we present an improved limit on jet handedness, which seeks to measure the transport of quark spin through the hadronization process. Finally, we search for a correlation of the three jet event orientation with the Zo spin direction, which would indicate new physics beyond the Standard model.

  20. Magnetic susceptibility of the QCD vacuum

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Chul; Musakhanov, M.; Siddikov, M.

    2005-02-01

    We investigate the magnetic susceptibility of the QCD vacuum, based on the instanton vacuum. Starting from the instanton liquid model for the instanton vacuum, we derive the light-quark partition function Z [ V, T,mˆ ] in the presence of the current quark mass mˆ as well as the external Abelian vector and tensor fields. We calculate a two-point correlation function relevant for the magnetic susceptibility and derive it beyond the chiral limit. We obtain for the different flavors the following magnetic susceptibility: χu, d< i ψu,d†ψu,d > 0 ∼ 40- 45MeV, while χs0 ≃ 6- 10MeV with the quark condensate < iψ† ψ > 0.

  1. Marginal breaking of conformal SUSY QCD

    NASA Astrophysics Data System (ADS)

    Cleary, Kevin F.; Terning, John

    2016-07-01

    We provide an example of a 4D theory that exhibits the Contino-Pomarol-Rattazzi mechanism, where breaking conformal symmetry by an almost marginal operator leads to a light pseudo-Goldstone boson, the dilaton, and a parametrically suppressed contribution to vacuum energy. We consider SUSY QCD at the edge of the conformal window and break conformal symmetry by weakly gauging a subgroup of the flavor symmetry. Using Seiberg duality we show that for a range of parameters the singlet meson in the dual theory reaches the unitarity bound, however, this theory does not have a stable vacuum. We stabilize the vacuum with soft breaking terms, compute the mass of the dilaton, and determine the range of parameters where the leading contribution to the dilaton mass is from the almost marginal coupling.

  2. QCD spectrum with three quark flavors

    SciTech Connect

    Bernard, Claude; Burch, Tom; Orginos, Kostas; Toussaint, Doug; DeGrand, Thomas A.; DeTar, Carleton; Datta, Saumen; Gottlieb, Steven; Heller, Urs M.; Sugar, Robert

    2001-09-01

    We present results from a lattice hadron spectrum calculation using three flavors of dynamical quarks -- two light and one strange -- and quenched simulations for comparison. These simulations were done using a one-loop Symanzik improved gauge action and an improved Kogut-Susskind quark action. The lattice spacings, and hence also the physical volumes, were tuned to be the same in all the runs to better expose differences due to flavor number. Lattice spacings were tuned using the static quark potential, so as a by-product we obtain updated results for the effect of sea quarks on the static quark potential. We find indications that the full QCD meson spectrum is in better agreement with experiment than the quenched spectrum. For the 0{sup ++} (a{sub 0}) meson we see a coupling to two pseudoscalar mesons, or a meson decay on the lattice.

  3. Renormalization in Coulomb gauge QCD

    NASA Astrophysics Data System (ADS)

    Andraši, A.; Taylor, John C.

    2011-04-01

    In the Coulomb gauge of QCD, the Hamiltonian contains a non-linear Christ-Lee term, which may alternatively be derived from a careful treatment of ambiguous Feynman integrals at 2-loop order. We investigate how and if UV divergences from higher order graphs can be consistently absorbed by renormalization of the Christ-Lee term. We find that they cannot.

  4. Nuclear reactions from lattice QCD

    SciTech Connect

    Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.

    2015-01-13

    In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.

  5. Nuclear reactions from lattice QCD

    DOE PAGESBeta

    Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.

    2015-01-13

    In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculationsmore » of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.« less

  6. QCD Phase Transitions, Volume 15

    SciTech Connect

    Schaefer, T.; Shuryak, E.

    1999-03-20

    The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.

  7. Lattice QCD in Background Fields

    SciTech Connect

    William Detmold, Brian Tiburzi, Andre Walker-Loud

    2009-06-01

    Electromagnetic properties of hadrons can be computed by lattice simulations of QCD in background fields. We demonstrate new techniques for the investigation of charged hadron properties in electric fields. Our current calculations employ large electric fields, motivating us to analyze chiral dynamics in strong QED backgrounds, and subsequently uncover surprising non-perturbative effects present at finite volume.

  8. Basics of QCD perturbation theory

    SciTech Connect

    Soper, D.E.

    1997-06-01

    This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. The author also covers some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions. 31 refs., 38 figs.

  9. Experimenting with Langevin lattice QCD

    SciTech Connect

    Gavai, R.V.; Potvin, J.; Sanielevici, S.

    1987-05-01

    We report on the status of our investigations of the effects of systematic errors upon the practical merits of Langevin updating in full lattice QCD. We formulate some rules for the safe use of this updating procedure and some observations on problems which may be common to all approximate fermion algorithms.

  10. Seven topics in perturbative QCD

    SciTech Connect

    Buras, A.J.

    1980-09-01

    The following topics of perturbative QCD are discussed: (1) deep inelastic scattering; (2) higher order corrections to e/sup +/e/sup -/ annihilation, to photon structure functions and to quarkonia decays; (3) higher order corrections to fragmentation functions and to various semi-inclusive processes; (4) higher twist contributions; (5) exclusive processes; (6) transverse momentum effects; (7) jet and photon physics.

  11. Multiple cone pathways are involved in photic regulation of retinal dopamine

    PubMed Central

    Qiao, Sheng-Nan; Zhang, Zhijing; Ribelayga, Christophe P.; Zhong, Yong-Mei; Zhang, Dao-Qi

    2016-01-01

    Dopamine is a key neurotransmitter in the retina and plays a central role in the light adaptive processes of the visual system. The sole source of retinal dopamine is dopaminergic amacrine cells (DACs). We and others have previously demonstrated that DACs are activated by rods, cones, and intrinsically photosensitive retinal ganglion cells (ipRGCs) upon illumination. However, it is still not clear how each class of photosensitive cells generates light responses in DACs. We genetically isolated cone function in mice to specifically examine the cone-mediated responses of DACs and their neural pathways. In addition to the reported excitatory input to DACs from light-increment (ON) bipolar cells, we found that cones alternatively signal to DACs via a retrograde signalling pathway from ipRGCs. Cones also produce ON and light-decrement (OFF) inhibitory responses in DACs, which are mediated by other amacrine cells, likely driven by type 1 and type 2/3a OFF bipolar cells, respectively. Dye injections indicated that DACs had similar morphological profiles with or without ON/OFF inhibition. Our data demonstrate that cones utilize specific parallel excitatory and inhibitory circuits to modulate DAC activity and efficiently regulate dopamine release and the light-adaptive state of the retina. PMID:27356880

  12. Twenty-first Century Lattice Gauge Theory: Results from the QCD Lagrangian

    SciTech Connect

    Kronfeld, Andreas S.; /Fermilab

    2012-03-01

    Quantum chromodynamics (QCD) reduces the strong interactions, in all their variety, to an elegant nonabelian gauge theory. It clearly and elegantly explains hadrons at short distances, which has led to its universal acceptance. Since its advent, however, many of its long-distance, emergent properties have been believed to be true, without having been demonstrated to be true. This paper reviews a variety of results in this regime that have been established with lattice gauge theory, directly from the QCD Lagrangian. This body of work sheds light on the origin of hadron masses, its interplay with dynamical symmetry breaking, as well as on other intriguing features such as the phase structure of QCD. In addition, nonperturbative QCD is quantitatively important to many aspects of particle physics (especially the quark flavor sector), nuclear physics, and astrophysics. This review also surveys some of the most interesting connections to those subjects.

  13. The p110α Isoform of Phosphoinositide 3-Kinase is Essential for Cone Photoreceptor Survival

    PubMed Central

    Rajala, Raju V.S.; Ranjo-Bishop, Michelle; Wang, Yuhong; Rajala, Ammaji; Anderson, Robert E.

    2015-01-01

    Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that phosphorylates the 3'OH of the inositol ring of phosphoinositides (PIs). They are responsible for coordinating a diverse range of cellular functions. Class IA PI3K is a heterodimeric protein composed of a regulatory p85 and a catalytic p110 subunit. In this study, we conditionally deleted the p110α-subunit of PI3K in cone photoreceptor cells using the Cre-loxP system. Cone photoreceptors allow for color vision in bright light (daylight vision). Cone-specific deletion of p110α resulted in cone degeneration. Our studies suggest that PI3K signaling is essential for cone photoreceptor functions. PMID:25742742

  14. Shatter cones: (Mis)understood?

    PubMed

    Osinski, Gordon R; Ferrière, Ludovic

    2016-08-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and "double" cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship D sc = 0.4 D a, where D sc is the maximum spatial extent of in situ shatter cones, and D a is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact. PMID:27532050

  15. Shatter cones: (Mis)understood?

    PubMed Central

    Osinski, Gordon R.; Ferrière, Ludovic

    2016-01-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and “double” cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship Dsc = 0.4 Da, where Dsc is the maximum spatial extent of in situ shatter cones, and Da is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact. PMID:27532050

  16. Alcohol intoxication impairs mesopic rod and cone temporal processing in social drinkers

    PubMed Central

    Zhuang, Xiaohua; Kang, Para; King, Andrea; Cao, Dingcai

    2015-01-01

    Background Alcohol-related driving accidents and fatalities occur most frequently at nighttime and at dawn, i.e. a mesopic lighting condition in which visual processing depends on both rod and cone photoreceptors. The temporal functions of the rod and cone pathways are critical for driving in this lighting condition. However, how alcohol influences the temporal functions in the rod and cone pathways at mesopic light levels is inconclusive. To address this, the present study investigated whether an acute intoxicating dose of alcohol impairs rod- and/or cone-mediated critical fusion frequency (CFF, the lowest frequency of which an intermittent or flickering light stimulus is perceived as steady). Methods In Experiment I, we measured the CFFs for three types of visual stimuli (rod stimulus alone, cone stimulus alone, and the mixture of both stimuli types), under three illuminant light levels (dim illuminance: 2Td; low illuminance: 20Td; and medium illuminance 80Td) in moderate-heavy social drinkers before and after they consumed an intoxicating dose of alcohol (0.8g/kg) compared with a placebo beverage. In Experiment II, we examined if the illuminance level (dark versus light) of the visual area surrounding the test stimuli alters alcohol’s effect on the temporal processing of rods and cones. Results The results showed that compared with placebo, alcohol significantly reduced CFFs of all stimulus types at all illuminance levels. Furthermore, alcohol intoxication produced a larger impairment on rod-pathway-mediated CFFs under light versus dark surround. Conclusions These results indicate that alcohol intake slows down rod and cone-pathway-mediated temporal processing. Further research may elucidate if this effect may play a role in alcohol-related injury and accidents, which often occur under low light conditions. PMID:26247196

  17. Scatter corrections for cone beam optical CT

    NASA Astrophysics Data System (ADS)

    Olding, Tim; Holmes, Oliver; Schreiner, L. John

    2009-05-01

    Cone beam optical computed tomography (OptCT) employing the VISTA scanner (Modus Medical, London, ON) has been shown to have significant promise for fast, three dimensional imaging of polymer gel dosimeters. One distinct challenge with this approach arises from the combination of the cone beam geometry, a diffuse light source, and the scattering polymer gel media, which all contribute scatter signal that perturbs the accuracy of the scanner. Beam stop array (BSA), beam pass array (BPA) and anti-scatter polarizer correction methodologies have been employed to remove scatter signal from OptCT data. These approaches are investigated through the use of well-characterized phantom scattering solutions and irradiated polymer gel dosimeters. BSA corrected scatter solutions show good agreement in attenuation coefficient with the optically absorbing dye solutions, with considerable reduction of scatter-induced cupping artifact at high scattering concentrations. The application of BSA scatter corrections to a polymer gel dosimeter lead to an overall improvement in the number of pixel satisfying the (3%, 3mm) gamma value criteria from 7.8% to 0.15%.

  18. Calculation of the nucleon axial charge in lattice QCD

    SciTech Connect

    D. B. Renner; R. G. Edwards; G. Fleming; Ph. Hagler; J. W. Negele; K. Orginos; A. V. Pochinsky; D. G. Richards; W. Schroers

    2006-09-01

    Protons and neutrons have a rich structure in terms of their constituents, the quarks and gluons. Understanding this structure requires solving Quantum Chromodynamics (QCD). However QCD is extremely complicated, so we must numerically solve the equations of QCD using a method known as lattice QCD. Here we describe a typical lattice QCD calculation by examining our recent computation of the nucleon axial charge.

  19. Selective Stimulation of Penumbral Cones Reveals Perception in the Shadow of Retinal Blood Vessels

    PubMed Central

    Spitschan, Manuel; Aguirre, Geoffrey K.; Brainard, David H.

    2015-01-01

    In 1819, Johann Purkinje described how a moving light source that displaces the shadow of the retinal blood vessels to adjacent cones can produce the entopic percept of a branching tree. Here, we describe a novel method for producing a similar percept. We used a device that mixes 56 narrowband primaries under computer control, in conjunction with the method of silent substitution, to present observers with a spectral modulation that selectively targeted penumbral cones in the shadow of the retinal blood vessels. Such a modulation elicits a clear Purkinje-tree percept. We show that the percept is specific to penumbral L and M cone stimulation and is not produced by selective penumbral S cone stimulation. The Purkinje-tree percept was strongest at 16 Hz and fell off at lower (8 Hz) and higher (32 Hz) temporal frequencies. Selective stimulation of open-field cones that are not in shadow, with penumbral cones silenced, also produced the percept, but it was not seen when penumbral and open-field cones were modulated together. This indicates the need for spatial contrast between penumbral and open-field cones to create the Purkinje-tree percept. Our observation provides a new means for studying the response of retinally stabilized images and demonstrates that penumbral cones can support spatial vision. Further, the result illustrates a way in which silent substitution techniques can fail to be silent. We show that inadvertent penumbral cone stimulation can accompany melanopsin-directed modulations that are designed only to silence open-field cones. This in turn can result in visual responses that might be mistaken as melanopsin-driven. PMID:25897842

  20. Unparticles in diphoton production to next-to-leading order in QCD at the LHC

    SciTech Connect

    Kumar, M. C.; Mathews, Prakash

    2009-04-01

    We compute to next-to-leading order in QCD the tensor unparticle contribution to the diphoton production at the LHC, wherein the unparticle sector is a consequence of (a) scale invariance but not full conformal invariance and (b) conformal invariance. We use the semianalytical two cutoff phase-space slicing method to handle the O({alpha}{sub s}) corrections to the pp{yields}{gamma}{gamma}X and show that our results are insensitive to the soft and collinear cutoffs. In order to avoid the contribution of the photons due to fragmentation, we employ the smooth cone isolation criterion. Significance of the QCD corrections to the diphoton events including unparticles is highlighted.

  1. Strange Light Nuclei

    SciTech Connect

    Nakamura, Satoshi N.

    2014-04-01

    "Strange" means 1) unusual or surprising, especially in a way that is difficult to explain or understand or 2) having strangeness degree of freedom. Light nuclear systems with strangeness, light hypernuclei, are perfect playground to study baryon force which would be a bridge between well established nuclear force in low energy region and QCD, the first principle of the strong interaction. Overview of study of light hypernuclei is given and recent experimental findings are reviewed.

  2. Cone Penetrometer N Factor Determination Testing Results

    SciTech Connect

    Follett, Jordan R.

    2014-03-05

    This document contains the results of testing activities to determine the empirical 'N Factor' for the cone penetrometer in kaolin clay simulant. The N Factor is used to releate resistance measurements taken with the cone penetrometer to shear strength.

  3. Soft and Hard Scale QCD Dynamics in Mesons

    NASA Astrophysics Data System (ADS)

    Nguyen, T.; Souchlas, N. A.; Tandy, P. C.

    2011-09-01

    Using a ladder-rainbow kernel previously established for light quark hadron physics, we explore the extension to masses and electroweak decay constants of ground state pseudoscalar and vector quarkonia and heavy-light mesons in the c- and b-quark regions. We make a systematic study of the effectiveness of a constituent mass concept as a replacement for a heavy quark dressed propagator for such states. The difference between vector and axial vector current correlators is explored within the same model to provide an estimate of the four quark chiral condensate and the leading distance scale for the onset of non-perturbative phenomena in QCD.

  4. Non-perturbative QCD Modeling and Meson Physics

    NASA Astrophysics Data System (ADS)

    Nguyen, T.; Souchlas, N. A.; Tandy, P. C.

    2009-04-01

    Using a ladder-rainbow kernel previously established for light quark hadron physics, we explore the extension to masses and electroweak decay constants of ground state pseudoscalar and vector quarkonia and heavy-light mesons in the c- and b-quark regions. We make a systematic study of the effectiveness of a constituent mass concept as a replacement for a heavy quark dressed propagator for such states. The difference between vector and axial vector current correlators is explored within the same model to provide an estimate of the four quark chiral condensate and the leading distance scale for the onset of non-perturbative phenomena in QCD.

  5. Non-perturbative QCD Modeling and Meson Physics

    SciTech Connect

    Nguyen, T.; Souchlas, N. A.; Tandy, P. C.

    2009-04-20

    Using a ladder-rainbow kernel previously established for light quark hadron physics, we explore the extension to masses and electroweak decay constants of ground state pseudoscalar and vector quarkonia and heavy-light mesons in the c- and b-quark regions. We make a systematic study of the effectiveness of a constituent mass concept as a replacement for a heavy quark dressed propagator for such states. The difference between vector and axial vector current correlators is explored within the same model to provide an estimate of the four quark chiral condensate and the leading distance scale for the onset of non-perturbative phenomena in QCD.

  6. Cone outer segment shedding in the goldfish retina characterized with the /sup 3/H-fucose technique

    SciTech Connect

    Balkema, G.W. Jr.; Bunt-Milam, A.H.

    1982-09-01

    After an intravitreal injection of /sup 3/H-fucose, red- and blue-sensitive cone outer segments (OSs) in the goldfish retina became heavily labeled, green-sensitive cone OSs showed light labeling, and rod OSs showed virtually no labeling. Fish were maintained in white light (light/dark: 12 hr/12 hr; 6 to 10 weeks) and were injected with /sup 3/H-fucose 24 hr before sacrifice. After light onset, only phagosomes with no label were found in the retinal pigment epithelium (RPE); after light offset, phagosomes with heavy, light, or no label were found in the RPE. A broad peak of cone OS shedding derived from all cone types was found beginning 2 hr after light offset and returning to baseline levels after 12 hr, with a maximum at 4 to 6 hr. When the white light was replaced with red light during the final 24 hr (irradiance matched to the white light at 625 nm), the green cones showed a reduction in shedding by 62%, the rods showed a 48% reduction in shedding, and the number of heavily labeled phagosomes was reduced by 24% (a value that may reflect normal and red cone shedding and a reduction in blue cone shedding). The results suggest that chromatic stimulation during the light period may influence the shedding response of a given class of cone OS. Finally, the /sup 3/H-fucose technique is useful for determination of the photoreceptor OS from which a given phagosome in the RPE originates in this species.

  7. In Vivo Two-Photon Fluorescence Kinetics of Primate Rods and Cones

    PubMed Central

    Sharma, Robin; Schwarz, Christina; Williams, David R.; Palczewska, Grazyna; Palczewski, Krzysztof; Hunter, Jennifer J.

    2016-01-01

    Purpose The retinoid cycle maintains vision by regenerating bleached visual pigment through metabolic events, the kinetics of which have been difficult to characterize in vivo. Two-photon fluorescence excitation has been used previously to track autofluorescence directly from retinoids and pyridines in the visual cycle in mouse and frog retinas, but the mechanisms of the retinoid cycle are not well understood in primates. Methods We developed a two-photon fluorescence adaptive optics scanning light ophthalmoscope dedicated to in vivo imaging in anesthetized macaques. Using pulsed light at 730 nm, two-photon fluorescence was captured from rods and cones during light and dark adaptation through the eye's pupil. Results The fluorescence from rods and cones increased with light exposure but at different rates. During dark adaptation, autofluorescence declined, with cone autofluorescence decreasing approximately 4 times faster than from rods. Rates of autofluorescence decrease in rods and cones were approximately 4 times faster than their respective rates of photopigment regeneration. Also, subsets of sparsely distributed cones were less fluorescent than their neighbors immediately following bleach at 565 nm and they were comparable with the S cone mosaic in density and distribution. Conclusions Although other molecules could be contributing, we posit that these fluorescence changes are mediated by products of the retinoid cycle. In vivo two-photon ophthalmoscopy provides a way to monitor noninvasively stages of the retinoid cycle that were previously inaccessible in the living primate eye. This can be used to assess objectively photoreceptor function in normal and diseased retinas. PMID:26903225

  8. The current state of knowledge about shatter cones: Introduction to the special issue

    NASA Astrophysics Data System (ADS)

    Baratoux, David; Reimold, Wolf Uwe

    2016-08-01

    Shatter cones are a fracture phenomenon that is exclusively associated with shock metamorphism and has also been produced in the laboratory in several shock experiments. The occurrence of shatter cones is the only accepted meso- to macroscopic recognition criterion for impact structures. Shatter cones exhibit a number of geometric characteristics (orientation, apical angles, striation angles, sizes) that can be best described as varied, from case to case. Possible links between geometric properties with impact or crater parameters have remained controversial and the lack of understanding of the mechanism of formation of shatter cones does not offer a physical framework to discuss or understand them. A database of shatter cone occurrences has been produced for this introduction paper to the special issue of Meteoritics and Planetary Science on shatter cones. Distribution of shatter cones with respect to crater size and lithology suggests that shatter cones do not occur in impact craters less than a few kilometers in diameter, with a few, currently questionable exceptions. All pertinent hypotheses of formation are presented and discussed. Several may be discarded in light of the most recent observations. The branching fracture mechanism and the interference models proposed, respectively, by Sagy et al. (2002) and Baratoux and Melosh (2003) require further evaluation. New observations, experiments, or theoretical considerations presented in this special issue promise an important step forward, based on a renewed effort to resolve the enigmatic origin of these important features.

  9. The current state of knowledge about shatter cones: Introduction to the special issue

    NASA Astrophysics Data System (ADS)

    Baratoux, David; Reimold, Wolf Uwe

    2016-07-01

    Shatter cones are a fracture phenomenon that is exclusively associated with shock metamorphism and has also been produced in the laboratory in several shock experiments. The occurrence of shatter cones is the only accepted meso- to macroscopic recognition criterion for impact structures. Shatter cones exhibit a number of geometric characteristics (orientation, apical angles, striation angles, sizes) that can be best described as varied, from case to case. Possible links between geometric properties with impact or crater parameters have remained controversial and the lack of understanding of the mechanism of formation of shatter cones does not offer a physical framework to discuss or understand them. A database of shatter cone occurrences has been produced for this introduction paper to the special issue of Meteoritics and Planetary Science on shatter cones. Distribution of shatter cones with respect to crater size and lithology suggests that shatter cones do not occur in impact craters less than a few kilometers in diameter, with a few, currently questionable exceptions. All pertinent hypotheses of formation are presented and discussed. Several may be discarded in light of the most recent observations. The branching fracture mechanism and the interference models proposed, respectively, by Sagy et al. (2002) and Baratoux and Melosh (2003) require further evaluation. New observations, experiments, or theoretical considerations presented in this special issue promise an important step forward, based on a renewed effort to resolve the enigmatic origin of these important features.

  10. Direct rod input to cone BCs and direct cone input to rod BCs challenge the traditional view of mammalian BC circuitry

    PubMed Central

    Pang, Ji-Jie; Gao, Fan; Lem, Janis; Bramblett, Debra E.; Paul, David L.; Wu, Samuel M.

    2009-01-01

    Bipolar cells are the central neurons of the retina that transmit visual signals from rod and cone photoreceptors to third-order neurons in the inner retina and the brain. A dogma set forth by early anatomical studies is that bipolar cells in mammalian retinas receive segregated rod/cone synaptic inputs (either from rods or from cones), and here, we present evidence that challenges this traditional view. By analyzing light-evoked cation currents from morphologically identified depolarizing bipolar cells (DBCs) in the wild-type and three pathway-specific knockout mice (rod transducin knockout [Trα−/−], connexin36 knockout [Cx36−/−], and transcription factor beta4 knockout [Bhlhb4−/−]), we show that a subpopulation of rod DBCs (DBCR2s) receives substantial input directly from cones and a subpopulation of cone DBCs (DBCC1s) receives substantial input directly from rods. These results provide evidence of the existence of functional rod-DBCC and cone-DBCR synaptic pathways in the mouse retina as well as the previously proposed rod hyperpolarizing bipolar-cells pathway. This is grounds for revising the mammalian rod/cone bipolar cell dogma. PMID:20018684

  11. Evolutionary transformation of rod photoreceptors in the all-cone retina of a diurnal garter snake

    PubMed Central

    Schott, Ryan K.; Müller, Johannes; Yang, Clement G. Y.; Bhattacharyya, Nihar; Chan, Natalie; Xu, Mengshu; Morrow, James M.; Ghenu, Ana-Hermina; Loew, Ellis R.; Tropepe, Vincent; Chang, Belinda S. W.

    2016-01-01

    Vertebrate retinas are generally composed of rod (dim-light) and cone (bright-light) photoreceptors with distinct morphologies that evolved as adaptations to nocturnal/crepuscular and diurnal light environments. Over 70 years ago, the “transmutation” theory was proposed to explain some of the rare exceptions in which a photoreceptor type is missing, suggesting that photoreceptors could evolutionarily transition between cell types. Although studies have shown support for this theory in nocturnal geckos, the origins of all-cone retinas, such as those found in diurnal colubrid snakes, remain a mystery. Here we investigate the evolutionary fate of the rods in a diurnal garter snake and test two competing hypotheses: (i) that the rods, and their corresponding molecular machinery, were lost or (ii) that the rods were evolutionarily modified to resemble, and function, as cones. Using multiple approaches, we find evidence for a functional and unusually blue-shifted rhodopsin that is expressed in small single “cones.” Moreover, these cones express rod transducin and have rod ultrastructural features, providing strong support for the hypothesis that they are not true cones, as previously thought, but rather are modified rods. Several intriguing features of garter snake rhodopsin are suggestive of a more cone-like function. We propose that these cone-like rods may have evolved to regain spectral sensitivity and chromatic discrimination as a result of ancestral losses of middle-wavelength cone opsins in early snake evolution. This study illustrates how sensory evolution can be shaped not only by environmental constraints but also by historical contingency in forming new cell types with convergent functionality. PMID:26715746

  12. Evolutionary transformation of rod photoreceptors in the all-cone retina of a diurnal garter snake.

    PubMed

    Schott, Ryan K; Müller, Johannes; Yang, Clement G Y; Bhattacharyya, Nihar; Chan, Natalie; Xu, Mengshu; Morrow, James M; Ghenu, Ana-Hermina; Loew, Ellis R; Tropepe, Vincent; Chang, Belinda S W

    2016-01-12

    Vertebrate retinas are generally composed of rod (dim-light) and cone (bright-light) photoreceptors with distinct morphologies that evolved as adaptations to nocturnal/crepuscular and diurnal light environments. Over 70 years ago, the "transmutation" theory was proposed to explain some of the rare exceptions in which a photoreceptor type is missing, suggesting that photoreceptors could evolutionarily transition between cell types. Although studies have shown support for this theory in nocturnal geckos, the origins of all-cone retinas, such as those found in diurnal colubrid snakes, remain a mystery. Here we investigate the evolutionary fate of the rods in a diurnal garter snake and test two competing hypotheses: (i) that the rods, and their corresponding molecular machinery, were lost or (ii) that the rods were evolutionarily modified to resemble, and function, as cones. Using multiple approaches, we find evidence for a functional and unusually blue-shifted rhodopsin that is expressed in small single "cones." Moreover, these cones express rod transducin and have rod ultrastructural features, providing strong support for the hypothesis that they are not true cones, as previously thought, but rather are modified rods. Several intriguing features of garter snake rhodopsin are suggestive of a more cone-like function. We propose that these cone-like rods may have evolved to regain spectral sensitivity and chromatic discrimination as a result of ancestral losses of middle-wavelength cone opsins in early snake evolution. This study illustrates how sensory evolution can be shaped not only by environmental constraints but also by historical contingency in forming new cell types with convergent functionality. PMID:26715746

  13. Perfect Actions and Operators for Lattice QCD

    NASA Astrophysics Data System (ADS)

    Wiese, Uwe-Jens

    1996-05-01

    Wilson's renormalization group implies that lattice actions located on a renormalized trajectory emanating from a fixed point represent perfect discretizations of continuum physics. With a perfect action the spectrum of a lattice theory is identical with the one of the continuum theory even at finite lattice spacing. Similarly, perfect operators yield cut-off independent matrix elements. Hence, continuum QCD can in principle be reconstructed from a lattice with finite spacing. In practice it is difficult to construct perfect actions and perfect operators explicitly. Here perturbation theory is used to derive perfect actions for quarks and gluons by performing a block renormalization group transformation directly from the continuum. The renormalized trajectory for free massive quarks is identified and a parameter in the renormalization group transformation is tuned such that for 1-d configurations the perfect action reduces to the nearest neighbor Wilson fermion action. Then the 4-d perfect action turns out to be extremely local as well, which is vital for numerical simulations. The fixed point action for free gluons is also obtained by blocking from the continuum. For 2-d configurations it reduces to the standard plaquette action, and for 4-d configurations it is still very local. With interactions between quarks and gluons switched on the perfect quark-gluon and 3-gluon vertex functions are computed analytically. In particular, a perfect clover term can be extracted from the quark-gluon vertex. The perturbatively perfect action is directly applicable to heavy quark physics. The construction of a perfect QCD action for light quarks should include nonperturbative effects, which is possible using numerical methods. Classically perfect quark and gluon fields are constructed as well. They allow to interpolate the continuum fields from the lattice data. In this way one can obtain information about space-time regions between lattice points. The classically perfect fields

  14. Small Molecules in the Cone Snail Arsenal.

    PubMed

    Neves, Jorge L B; Lin, Zhenjian; Imperial, Julita S; Antunes, Agostinho; Vasconcelos, Vitor; Olivera, Baldomero M; Schmidt, Eric W

    2015-10-16

    Cone snails are renowned for producing peptide-based venom, containing conopeptides and conotoxins, to capture their prey. A novel small-molecule guanine derivative with unprecedented features, genuanine, was isolated from the venom of two cone snail species. Genuanine causes paralysis in mice, indicating that small molecules and not just polypeptides may contribute to the activity of cone snail venom. PMID:26421741

  15. anQCD: Fortran programs for couplings at complex momenta in various analytic QCD models

    NASA Astrophysics Data System (ADS)

    Ayala, César; Cvetič, Gorazd

    2016-02-01

    We provide three Fortran programs which evaluate the QCD analytic (holomorphic) couplings Aν(Q2) for complex or real squared momenta Q2. These couplings are holomorphic analogs of the powers a(Q2)ν of the underlying perturbative QCD (pQCD) coupling a(Q2) ≡αs(Q2) / π, in three analytic QCD models (anQCD): Fractional Analytic Perturbation Theory (FAPT), Two-delta analytic QCD (2 δanQCD), and Massive Perturbation Theory (MPT). The index ν can be noninteger. The provided programs do basically the same job as the Mathematica package anQCD.m published by us previously (Ayala and Cvetič, 2015), but are now written in Fortran.

  16. The nature of surround-induced depolarizing responses in goldfish cones.

    PubMed

    Kraaij, D A; Spekreijse, H; Kamermans, M

    2000-01-01

    Cones in the vertebrate retina project to horizontal and bipolar cells and the horizontal cells feedback negatively to cones. This organization forms the basis for the center/surround organization of the bipolar cells, a fundamental step in the visual signal processing. Although the surround responses of bipolar cells have been recorded on many occasions, surprisingly, the underlying surround-induced responses in cones are not easily detected. In this paper, the nature of the surround-induced responses in cones is studied. Horizontal cells feed back to cones by shifting the activation function of the calcium current in cones to more negative potentials. This shift increases the calcium influx, which increases the neurotransmitter release of the cone. In this paper, we will show that under certain conditions, in addition to this increase of neurotransmitter release, a calcium-dependent chloride current will be activated, which polarizes the cone membrane potential. The question is, whether the modulation of the calcium current or the polarization of the cone membrane potential is the major determinant for feedback-mediated responses in second-order neurons. Depolarizing light responses of biphasic horizontal cells are generated by feedback from monophasic horizontal cells to cones. It was found that niflumic acid blocks the feedback-induced depolarizing responses in cones, while the shift of the calcium current activation function and the depolarizing biphasic horizontal cell responses remain intact. This shows that horizontal cells can feed back to cones, without inducing major changes in the cone membrane potential. This makes the feedback synapse from horizontal cells to cones a unique synapse. Polarization of the presynaptic (horizontal) cell leads to calcium influx in the postsynaptic cell (cone), but due to the combined activity of the calcium current and the calcium-dependent chloride current, the membrane potential of the postsynaptic cell will be hardly

  17. Towards a Theoretical Understanding of the XYZ Mesons from QCD

    NASA Astrophysics Data System (ADS)

    Braaten, Eric

    2016-03-01

    The XYZ mesons are mesons that contain a heavy quark and antiquark but have properties that seem to require additional constituents. Some of them are electrically charged, so they must be tetraquark mesons whose additional constituents are a light quark and antiquark. The list of XYZ mesons has grown to about two dozen over the last decade. A promising approach to understanding these mesons within QCD is the Born-Oppenheimer approximation, which reduces the problem to the solution of the Schrödinger equation in potentials that can be calculated using lattice QCD. The Born-Oppenheimer approximation has not yet revealed the pattern of the XYZ mesons, but it provides a compelling framework for understanding them from the fundamental theory.

  18. Duality between QCD perturbative series and power corrections

    NASA Astrophysics Data System (ADS)

    Narison, S.; Zakharov, V. I.

    2009-08-01

    We elaborate on the relation between perturbative and power-like corrections to short-distance sensitive QCD observables. We confront theoretical expectations with explicit perturbative calculations existing in literature. As is expected, the quadratic correction is dual to a long perturbative series and one should use one of them but not both. However, this might be true only for very long perturbative series, with number of terms needed in most cases exceeding the number of terms available. What has not been foreseen, the quartic corrections might also be dual to the perturbative series. If confirmed, this would imply a crucial modification of the dogma. We confront this quadratic correction against existing phenomenology (QCD (spectral) sum rules scales, determinations of light quark masses and of αs from τ-decay). We find no contradiction and (to some extent) better agreement with the data and with recent lattice calculations.

  19. Baryon Spectroscopy and Operator Construction in Lattice QCD

    SciTech Connect

    S. Basak; I. Sato; S. Wallace; R. Edwards; D. Richards; R. Fiebig; G. Fleming; U. Heller; C. Morningstar

    2004-07-01

    This talk describes progress at understanding the properties of the nucleon and its excitations from lattice QCD. I begin with a review of recent lattice results for the lowest-lying states of the excited baryon spectrum. The need to approach physical values of the light quark masses is emphasized, enabling the effects of the pion cloud to be revealed. I then outline the development of techniques that will enable the extraction of the masses of the higher resonances. I will describe how such calculations provide insight into the structure of the hadrons, and enable comparison both with experiment, and with QCD-inspired pictures of hadron structure, such as calculations in the limit of large N{sub c}.

  20. The QCD equation of state with charm quarks from lattice QCD

    NASA Astrophysics Data System (ADS)

    Cheng, Michael

    Recently, there have been several calculations of the QCD equation of state (EoS) on the lattice. These calculations take into account the two light quarks and the strange quark, but have ignored the effects of the charm quark, assuming that the charm mass (mc ≈ 1300 MeV) is exponentially suppressed at the temperatures which are explored. However, future heavy ion collisions, such as those planned at the LHC, may well probe temperature regimes where the charm quarks play an important role in the dynamics of the QGP. We present a calculation of the charm quark contribution to the QCD EoS using p4-improved staggered fermions at Nt = 4, 6, 8. This calculation is done with a quenched charm quark, i.e. the relevant operators are measured using a valence charm quark mass on a 2+1 flavor gauge field background. The charm quark masses are determined by calculating charmonium masses (metac and mJ/Psi) and fixing these mesons to their physical masses. The interaction measure, pressure, energy density, and entropy density are calculated. We find that the charm contribution makes a significant contribution, even down to temperatures as low as the pseudo-critical temperature, Tc. However, there are significant scaling corrections at the lattice spacings that we use, preventing a reliable continuum extrapolation.

  1. Form factors from lattice QCD

    SciTech Connect

    Dru Renner

    2012-04-01

    Precision computation of hadronic physics with lattice QCD is becoming feasible. The last decade has seen precent-level calculations of many simple properties of mesons, and the last few years have seen calculations of baryon masses, including the nucleon mass, accurate to a few percent. As computational power increases and algorithms advance, the precise calculation of a variety of more demanding hadronic properties will become realistic. With this in mind, I discuss the current lattice QCD calculations of generalized parton distributions with an emphasis on the prospects for well-controlled calculations for these observables as well. I will do this by way of several examples: the pion and nucleon form factors and moments of the nucleon parton and generalized-parton distributions.

  2. Quark eigenmodes and lattice QCD

    NASA Astrophysics Data System (ADS)

    Liu, Guofeng

    In this thesis, we study a number of topics in lattice QCD through the low-lying quark eigenmodes in the domain wall fermion (DWF) formulation in the quenched approximation. Specifically, we present results for the chiral condensate measured from these eigenmodes; we investigate the QCD vacuum structure by looking at the correlation between the magnitude of the chirality density, |psi†(x)gamma5psi( x)|, and the normal density, psi†( x)psi(x), for these states; we study the behavior of DWF formulation at large quark masses by investigating the mass dependence of the eigenvalues of the physical four dimensional-states as well as the bulk, five-dimensional states.

  3. LATTICE QCD AT FINITE DENSITY.

    SciTech Connect

    SCHMIDT, C.

    2006-07-23

    I discuss different approaches to finite density lattice QCD. In particular, I focus on the structure of the phase diagram and discuss attempts to determine the location of the critical end-point. Recent results on the transition line as function of the chemical potential (T{sub c}({mu}{sub q})) are reviewed. Along the transition line, hadronic fluctuations have been calculated; which can be used to characterize properties of the Quark Gluon plasma and eventually can also help to identify the location of the critical end-point in the QCD phase diagram on the lattice and in heavy ion experiments. Furthermore, I comment on the structure of the phase diagram at large {mu}{sub q}.

  4. Innovations in Lattice QCD Algorithms

    SciTech Connect

    Konstantinos Orginos

    2006-06-25

    Lattice QCD calculations demand a substantial amount of computing power in order to achieve the high precision results needed to better understand the nature of strong interactions, assist experiment to discover new physics, and predict the behavior of a diverse set of physical systems ranging from the proton itself to astrophysical objects such as neutron stars. However, computer power alone is clearly not enough to tackle the calculations we need to be doing today. A steady stream of recent algorithmic developments has made an important impact on the kinds of calculations we can currently perform. In this talk I am reviewing these algorithms and their impact on the nature of lattice QCD calculations performed today.

  5. Sudakov safety in perturbative QCD

    NASA Astrophysics Data System (ADS)

    Larkoski, Andrew J.; Marzani, Simone; Thaler, Jesse

    2015-06-01

    Traditional calculations in perturbative quantum chromodynamics (pQCD) are based on an order-by-order expansion in the strong coupling αs. Observables that are calculable in this way are known as "safe." Recently, a class of unsafe observables was discovered that do not have a valid αs expansion but are nevertheless calculable in pQCD using all-orders resummation. These observables are called "Sudakov safe" since singularities at each αs order are regulated by an all-orders Sudakov form factor. In this paper, we give a concrete definition of Sudakov safety based on conditional probability distributions, and we study a one-parameter family of momentum sharing observables that interpolate between the safe and unsafe regimes. The boundary between these regimes is particularly interesting, as the resulting distribution can be understood as the ultraviolet fixed point of a generalized fragmentation function, yielding a leading behavior that is independent of αs.

  6. Chromatic adaptation in red-green cone-opponent retinal ganglion cells of the macaque.

    PubMed

    Lee, Barry B; Smith, Vivianne C; Pokorny, Joel; Sun, Hao

    2008-11-01

    The degree of chromatic adaptation of midget ganglion cells of the parvocellular (PC) pathway was studied by measuring long-(L) to middle-wavelength (M) cone weighting at different mean chromaticities in the mid-photopic range. Cone weighting was measured using a protocol involving changing the relative phase of modulated lights, which provided an estimate independent of the level of maintained activity. The degree of adaptation at 2500 td was found to be less than complete (i.e., sub-Weberian), with the M- and L-cone contributions having slopes averaging 0.89 rather than 1.0. This is broadly consistent with the degree of light adaptation present in this cell class. The changes in maintained activity following a step change in chromaticity took tens of seconds to return toward a baseline level, but changes in cone weighting appeared much faster. PMID:18281074

  7. On the interface between perturbative and nonperturbative QCD

    NASA Astrophysics Data System (ADS)

    Deur, Alexandre; Brodsky, Stanley J.; de Téramond, Guy F.

    2016-06-01

    The QCD running coupling αs (Q2) sets the strength of the interactions of quarks and gluons as a function of the momentum transfer Q. The Q2 dependence of the coupling is required to describe hadronic interactions at both large and short distances. In this article we adopt the light-front holographic approach to strongly-coupled QCD, a formalism which incorporates confinement, predicts the spectroscopy of hadrons composed of light quarks, and describes the low-Q2 analytic behavior of the strong coupling αs (Q2). The high-Q2 dependence of the coupling αs (Q2) is specified by perturbative QCD and its renormalization group equation. The matching of the high and low Q2 regimes of αs (Q2) then determines the scale Q0 which sets the interface between perturbative and nonperturbative hadron dynamics. The value of Q0 can be used to set the factorization scale for DGLAP evolution of hadronic structure functions and the ERBL evolution of distribution amplitudes. We discuss the scheme-dependence of the value of Q0 and the infrared fixed-point of the QCD coupling. Our analysis is carried out for the MS ‾, g1, MOM and V renormalization schemes. Our results show that the discrepancies on the value of αs at large distance seen in the literature can be explained by different choices of renormalization schemes. We also provide the formulae to compute αs (Q2) over the entire range of space-like momentum transfer for the different renormalization schemes discussed in this article.

  8. Recent QCD results from CDF

    SciTech Connect

    Huston, J. |; CDF Collaboration

    1994-01-01

    CDF has recently concluded a very successful 1992--93 data run in which an integrated luminosity of 21.3 pb {sup {minus}1} was written to tape. The large data sample allows for a greater discovery potential for new phenomena and for better statistical and systematic precision in analysis of conventional physics. This paper summarizes some of the new results from QCD analyses for this run.

  9. Berry Phase in Lattice QCD.

    PubMed

    Yamamoto, Arata

    2016-07-29

    We propose the lattice QCD calculation of the Berry phase, which is defined by the ground state of a single fermion. We perform the ground-state projection of a single-fermion propagator, construct the Berry link variable on a momentum-space lattice, and calculate the Berry phase. As the first application, the first Chern number of the (2+1)-dimensional Wilson fermion is calculated by the Monte Carlo simulation. PMID:27517766

  10. Lattice gauge theory for QCD

    SciTech Connect

    DeGrand, T.

    1997-06-01

    These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and {alpha}{sub s} (M{sub z}), and B-{anti B} mixing. 67 refs., 36 figs.

  11. Light-Front Holography and the Light-Front Schrodinger Equation

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy

    2012-08-15

    One of the most important nonperturbative methods for solving QCD is quantization at fixed light-front time {tau} = t+z=c - Dirac's 'Front Form'. The eigenvalues of the light-front QCD Hamiltonian predict the hadron spectrum and the eigensolutions provide the light-front wavefunctions which describe hadron structure. More generally, we show that the valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrodinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. We outline a method for computing the required potential from first principles in QCD. The holographic mapping of gravity in AdS space to QCD, quantized at fixed light-front time, yields the same light front Schrodinger equation; in fact, the soft-wall AdS/QCD approach provides a model for the light-front potential which is color-confining and reproduces well the light-hadron spectrum. One also derives via light-front holography a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The light-front AdS/QCD holographic approach thus gives a frame-independent first approximation of the color-confining dynamics, spectroscopy, and excitation spectra of relativistic light-quark bound states in QCD.

  12. FermiQCD: A tool kit for parallel lattice QCD applications

    SciTech Connect

    Di Pierro, M.

    2002-03-01

    We present here the most recent version of FermiQCD, a collection of C++ classes, functions and parallel algorithms for lattice QCD, based on Matrix Distributed Processing. FermiQCD allows fast development of parallel lattice applications and includes some SSE2 optimizations for clusters of Pentium 4 PCs.

  13. Achromatic vector vortex beams from a glass cone

    PubMed Central

    Radwell, N.; Hawley, R. D.; Götte, J. B.; Franke-Arnold, S.

    2016-01-01

    The reflection of light is governed by the laws first described by Augustin-Jean Fresnel: on internal reflection, light acquires a phase shift, which depends on its polarization direction with respect to the plane of incidence. For a conical reflector, the cylindrical symmetry is echoed in an angular variation of this phase shift, allowing us to create light modes with phase and polarization singularities. Here we observe the phase and polarization profiles of light that is back reflected from a solid glass cone and, in the case of circular input light, discover that not only does the beam contain orbital angular momentum but can trivially be converted to a radially polarized beam. Importantly, the Fresnel coefficients are reasonably stable across the visible spectrum, which we demonstrate by measuring white light polarization profiles. This discovery provides a highly cost-effective technique for the generation of broadband orbital angular momentum and radially polarized beams. PMID:26861191

  14. QCD for Postgraduates (2/5)

    ScienceCinema

    None

    2011-10-06

    Modern QCD - Lecture 2 We will start discussing the matter content of the theory and revisit the experimental measurements that led to the discovery of quarks. We will then consider a classic QCD observable, the R-ratio, and use it to illustrate the appearance of UV divergences and the need to renormalize the coupling constant of QCD. We will then discuss asymptotic freedom and confinement. Finally, we will examine a case where soft and collinear infrared divergences appear, will discuss the soft approximation in QCD and will introduce the concept of infrared safe jets.

  15. Differentiation of human embryonic stem cells into cone photoreceptors through simultaneous inhibition of BMP, TGFβ and Wnt signaling.

    PubMed

    Zhou, Shufeng; Flamier, Anthony; Abdouh, Mohamed; Tétreault, Nicolas; Barabino, Andrea; Wadhwa, Shashi; Bernier, Gilbert

    2015-10-01

    Cone photoreceptors are required for color discrimination and high-resolution central vision and are lost in macular degenerations, cone and cone/rod dystrophies. Cone transplantation could represent a therapeutic solution. However, an abundant source of human cones remains difficult to obtain. Work performed in model organisms suggests that anterior neural cell fate is induced 'by default' if BMP, TGFβ and Wnt activities are blocked, and that photoreceptor genesis operates through an S-cone default pathway. We report here that Coco (Dand5), a member of the Cerberus gene family, is expressed in the developing and adult mouse retina. Upon exposure to recombinant COCO, human embryonic stem cells (hESCs) differentiated into S-cone photoreceptors, developed an inner segment-like protrusion, and could degrade cGMP when exposed to light. Addition of thyroid hormone resulted in a transition from a unique S-cone population toward a mixed M/S-cone population. When cultured at confluence for a prolonged period of time, COCO-exposed hESCs spontaneously developed into a cellular sheet composed of polarized cone photoreceptors. COCO showed dose-dependent and synergistic activity with IGF1 at blocking BMP/TGFβ/Wnt signaling, while its cone-inducing activity was blocked in a dose-dependent manner by exposure to BMP, TGFβ or Wnt-related proteins. Our work thus provides a unique platform to produce human cones for developmental, biochemical and therapeutic studies and supports the hypothesis that photoreceptor differentiation operates through an S-cone default pathway during human retinal development. PMID:26443633

  16. Domain wall QCD with physical quark masses

    NASA Astrophysics Data System (ADS)

    Blum, T.; Boyle, P. A.; Christ, N. H.; Frison, J.; Garron, N.; Hudspith, R. J.; Izubuchi, T.; Janowski, T.; Jung, C.; Jüttner, A.; Kelly, C.; Kenway, R. D.; Lehner, C.; Marinkovic, M.; Mawhinney, R. D.; McGlynn, G.; Murphy, D. J.; Ohta, S.; Portelli, A.; Sachrajda, C. T.; Soni, A.; Rbc; Ukqcd Collaborations

    2016-04-01

    We present results for several light hadronic quantities (fπ , fK, BK, mu d, ms, t01 /2, w0) obtained from simulations of 2 +1 flavor domain wall lattice QCD with large physical volumes and nearly physical pion masses at two lattice spacings. We perform a short, O (3 )%, extrapolation in pion mass to the physical values by combining our new data in a simultaneous chiral/continuum "global fit" with a number of other ensembles with heavier pion masses. We use the physical values of mπ, mK and mΩ to determine the two quark masses and the scale—all other quantities are outputs from our simulations. We obtain results with subpercent statistical errors and negligible chiral and finite-volume systematics for these light hadronic quantities, including fπ=130.2 (9 ) MeV ; fK=155.5 (8 ) MeV ; the average up/down quark mass and strange quark mass in the MS ¯ scheme at 3 GeV, 2.997(49) and 81.64(1.17) MeV respectively; and the neutral kaon mixing parameter, BK, in the renormalization group invariant scheme, 0.750(15) and the MS ¯ scheme at 3 GeV, 0.530(11).

  17. Journey of water in pine cones

    PubMed Central

    Song, Kahye; Yeom, Eunseop; Seo, Seung-Jun; Kim, Kiwoong; Kim, Hyejeong; Lim, Jae-Hong; Joon Lee, Sang

    2015-01-01

    Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system. PMID:25944117

  18. Quark-mass dependence of the three-flavor QCD phase diagram at zero and imaginary chemical potential: Model prediction

    SciTech Connect

    Sasaki, Takahiro; Sakai, Yuji; Yahiro, Masanobu; Kouno, Hiroaki

    2011-11-01

    We draw the three-flavor phase diagram as a function of light- and strange-quark masses for both zero and imaginary quark-number chemical potential, using the Polyakov-loop extended Nambu-Jona-Lasinio model with an effective four-quark vertex depending on the Polyakov loop. The model prediction is qualitatively consistent with 2+1 flavor lattice QCD prediction at zero chemical potential and with degenerate three-flavor lattice QCD prediction at imaginary chemical potential.

  19. Inside the cone of protection

    SciTech Connect

    Stahmann, J.R.

    1983-01-01

    Although lightning cones of protection and cones of attraction have been used for over 100 years, much confusion still remains as to their effectiveness, particularly as applied to personnel protection. At Kennedy Space Center, a 1:1 cone of protection with a straight side is standard for structure or equipment protection. However, at the launch pad, where a 400-foot lightning lightning rod on top of an insulating mast is used for pad lightning protection, the idea developed that personnel within a 400-foot radius of this mast would be safe from lightning and those outside it would not. Since it is obvious that a person 395 feet (120.4 m.) from the mast is only slightly safer than one at 405 feet (123.5 m.), an investigation was initiated to calculate the probabilities of a person being struck by lightning as he moves closer to the mast inside the cone of protection. Since the risk does not go to zero outside the structure, the risk level can then be estimated. To arrive at the expected strike frequency, it was necessary to measure the strike frequencies at KSC. Krider and others have found a mean area density of cloud-to-ground lightning at KSC of about 4.6 + or - 3.1 flashes per sq km per month in the summer. An overall frequency is estimated as about 20 flashes per sq km per year. With these data, the risk of exposure at various distances from the lightning mast can be calculated. Assuming continuous exposure during thunderstorms, this risk varies from about one strike per person in 1,400 years near the tower to one stroke per person in 300 years at about 400 foot (122 m.).

  20. Cardiac cone-beam CT

    SciTech Connect

    Manzke, Robert . E-mail: robert.manzke@philips.com

    2005-10-15

    This doctoral thesis addresses imaging of the heart with retrospectively gated helical cone-beam computed tomography (CT). A thorough review of the CT reconstruction literature is presented in combination with a historic overview of cardiac CT imaging and a brief introduction to other cardiac imaging modalities. The thesis includes a comprehensive chapter about the theory of CT reconstruction, familiarizing the reader with the problem of cone-beam reconstruction. The anatomic and dynamic properties of the heart are outlined and techniques to derive the gating information are reviewed. With the extended cardiac reconstruction (ECR) framework, a new approach is presented for the heart-rate-adaptive gated helical cardiac cone-beam CT reconstruction. Reconstruction assessment criteria such as the temporal resolution, the homogeneity in terms of the cardiac phase, and the smoothness at cycle-to-cycle transitions are developed. Several reconstruction optimization approaches are described: An approach for the heart-rate-adaptive optimization of the temporal resolution is presented. Streak artifacts at cycle-to-cycle transitions can be minimized by using an improved cardiac weighting scheme. The optimal quiescent cardiac phase for the reconstruction can be determined automatically with the motion map technique. Results for all optimization procedures applied to ECR are presented and discussed based on patient and phantom data. The ECR algorithm is analyzed for larger detector arrays of future cone-beam systems throughout an extensive simulation study based on a four-dimensional cardiac CT phantom. The results of the scientific work are summarized and an outlook proposing future directions is given. The presented thesis is available for public download at www.cardiac-ct.net.

  1. Bursting the Taylor cone bubble

    NASA Astrophysics Data System (ADS)

    Pan, Zhao; Truscott, Tadd

    2014-11-01

    A soap bubble fixed on a surface and placed in an electric field will take on the shape of a cone rather than constant curvature (dome) when the electrical field is not present. The phenomenon was introduced by J. Zeleny (1917) and studied extensively by C.T. Wilson & G.I. Taylor (1925). We revisit the Taylor cone problem by studying the deformation and bursting of soap bubbles in a point charge electric field. A single bubble takes on the shape of a cone in the electric field and a high-speed camera equipped with a micro-lens is used to observe the unsteady dynamics at the tip. Rupture occurs as a very small piece of the tip is torn away from the bubble toward the point charge. Based on experiments, a theoretical model is developed that predicts when rupture should occur. This study may help in the design of foam-removal techniques in engineering and provide a better understanding of an electrified air-liquid interface.

  2. Lattice QCD at the physical point: simulation and analysis details

    NASA Astrophysics Data System (ADS)

    Dürr, S.; Fodor, Z.; Hoelbling, C.; Katz, S. D.; Krieg, S.; Kurth, T.; Lellouch, L.; Lippert, T.; Szabó, K. K.; Vulvert, G.

    2011-08-01

    We give details of our precise determination of the light quark masses m ud = ( m u + m d )/2 and m s in 2 + 1 flavor QCD, with simulated pion masses down to 120 MeV, at five lattice spacings, and in large volumes. The details concern the action and algorithm employed, the HMC force with HEX smeared clover fermions, the choice of the scale setting procedure and of the input masses. After an overview of the simulation parameters, extensive checks of algorithmic stability, autocorrelation and (practical) ergodicity are reported. To corroborate the good scaling properties of our action, explicit tests of the scaling of hadron masses in N f = 3 QCD are carried out. Details of how we control finite volume effects through dedicated finite volume scaling runs are reported. To check consistency with SU(2) Chiral Perturbation Theory the behavior of M π 2 /m ud and F π as a function of m ud is investigated. Details of how we use the RI/MOM procedure with a separate continuum limit of the running of the scalar density R S ( μ, μ') are given. This procedure is shown to reproduce the known value of r 0 m s in quenched QCD. Input from dispersion theory is used to split our value of m ud into separate values of m u and m d . Finally, our procedure to quantify both systematic and statistical uncertainties is discussed.

  3. Color Confinement and Screening in the θ Vacuum of QCD.

    PubMed

    Kharzeev, Dmitri E; Levin, Eugene M

    2015-06-19

    QCD perturbation theory ignores the compact nature of the SU(3) gauge group that gives rise to the periodic θ vacuum of the theory. We propose to modify the gluon propagator to reconcile perturbation theory with the anomalous Ward identities for the topological current in the θ vacuum. As a result, the gluon couples to the Veneziano ghost describing the tunneling transitions between different Chern-Simons sectors of the vacuum; we call the emerging gluon dressed by ghost loops a "glost." We evaluate the glost propagator and find that it has the form G(p)=(p(2)+χ(top)/p(2))(-1) where χ(top) is the Yang-Mills topological susceptibility related to the η' mass by the Witten-Veneziano relation; this propagator describes the confinement of gluons at distances ∼χ(top)(-1/4)≃1  fm. The same functional form of the propagator was originally proposed by Gribov as a solution to the gauge copies problem that plagues perturbation theory. The resulting running coupling coincides with the perturbative one at p(2)≫√[χ(top)], but in the infrared region either freezes (in pure Yang-Mills theory) or vanishes (in full QCD with light quarks), in accord with experimental evidence. Our scenario makes explicit the connection between confinement and topology of the QCD vacuum; we discuss the implications for spin physics, high energy scattering, and the physics of quark-gluon plasma. PMID:26196971

  4. Color Confinement and Screening in the θ Vacuum of QCD

    NASA Astrophysics Data System (ADS)

    Kharzeev, Dmitri E.; Levin, Eugene M.

    2015-06-01

    QCD perturbation theory ignores the compact nature of the S U (3 ) gauge group that gives rise to the periodic θ vacuum of the theory. We propose to modify the gluon propagator to reconcile perturbation theory with the anomalous Ward identities for the topological current in the θ vacuum. As a result, the gluon couples to the Veneziano ghost describing the tunneling transitions between different Chern-Simons sectors of the vacuum; we call the emerging gluon dressed by ghost loops a "glost." We evaluate the glost propagator and find that it has the form G (p )=(p2+χtop/p2)-1 where χtop is the Yang-Mills topological susceptibility related to the η' mass by the Witten-Veneziano relation; this propagator describes the confinement of gluons at distances ˜χtop-1 /4≃1 fm . The same functional form of the propagator was originally proposed by Gribov as a solution to the gauge copies problem that plagues perturbation theory. The resulting running coupling coincides with the perturbative one at p2≫√{χtop } , but in the infrared region either freezes (in pure Yang-Mills theory) or vanishes (in full QCD with light quarks), in accord with experimental evidence. Our scenario makes explicit the connection between confinement and topology of the QCD vacuum; we discuss the implications for spin physics, high energy scattering, and the physics of quark-gluon plasma.

  5. Cone visual pigments of aquatic mammals.

    PubMed

    Newman, Lucy A; Robinson, Phyllis R

    2005-01-01

    It has long been hypothesized that the visual systems of animals are evolutionarily adapted to their visual environment. The entrance many millions of years ago of mammals into the sea gave these new aquatic mammals completely novel visual surroundings with respect to light availability and predominant wavelengths. This study examines the cone opsins of marine mammals, hypothesizing, based on previous studies [Fasick et al. (1998) and Levenson & Dizon (2003)], that the deep-dwelling marine mammals would not have color vision because the pressure to maintain color vision in the dark monochromatic ocean environment has been relaxed. Short-wavelength-sensitive (SWS) and long-wavelength-sensitive (LWS) cone opsin genes from two orders (Cetacea and Sirenia) and an additional suborder (Pinnipedia) of aquatic mammals were amplified from genomic DNA (for SWS) and cDNA (for LWS) by PCR, cloned, and sequenced. All animals studied from the order Cetacea have SWS pseudogenes, whereas a representative from the order Sirenia has an intact SWS gene, for which the corresponding mRNA was found in the retina. One of the pinnipeds studied (harp seal) has an SWS pseudogene, while another species (harbor seal) appeared to have an intact SWS gene. However, no SWS cone opsin mRNA was found in the harbor seal retina, suggesting a promoter or splice site mutation preventing transcription of the gene. The LWS opsins from the different species were expressed in mammalian cells and reconstituted with the 11-cis-retinal chromophore in order to determine maximal absorption wavelengths (lambda(max)) for each. The deeper dwelling Cetacean species had blue shifted lambda(max) values compared to shallower-dwelling aquatic species. Taken together, these findings support the hypothesis that in the monochromatic oceanic habitat, the pressure to maintain color vision has been relaxed and mutations are retained in the SWS genes, resulting in pseudogenes. Additionally, LWS opsins are retained in the

  6. QCD tests in electron-positron scattering

    SciTech Connect

    Maruyama, T.

    1995-11-01

    Recent results on QCD tests at the Z{sup o} resonance are described. Measurements of Color factor ratios, and studies of final state photon radiation are performed by the LEP experiments. QCD tests using a longitudinally polarized beam are reported by the SLD experiment.

  7. Lattice QCD and High Baryon Density State

    SciTech Connect

    Nagata, Keitaro; Nakamura, Atsushi; Motoki, Shinji; Nakagawa, Yoshiyuki; Saito, Takuya

    2011-10-21

    We report our recent studies on the finite density QCD obtained from lattice QCD simulation with clover-improved Wilson fermions of two flavor and RG-improved gauge action. We approach the subject from two paths, i.e., the imaginary and chemical potentials.

  8. Solvable models and hidden symmetries in QCD

    SciTech Connect

    Yepez-Martinez, Tochtli; Hess, P. O.; Civitarese, O.; Lerma H., S.

    2010-12-23

    We show that QCD Hamiltonians at low energy exhibit an SU(2) structure, when only few orbital levels are considered. In case many orbital levels are taken into account we also find a semi-analytic solution for the energy levels of the dominant part of the QCD Hamiltonian. The findings are important to propose the structure of phenomenological models.

  9. Consistent Perturbative Fixed Point Calculations in QCD and Supersymmetric QCD

    NASA Astrophysics Data System (ADS)

    Ryttov, Thomas A.

    2016-08-01

    We suggest how to consistently calculate the anomalous dimension γ* of the ψ ¯ ψ operator in finite order perturbation theory at an infrared fixed point for asymptotically free theories. If the n +1 loop beta function and n loop anomalous dimension are known, then γ* can be calculated exactly and fully scheme independently in a Banks-Zaks expansion through O (Δfn) , where Δf=N¯ f-Nf , Nf is the number of flavors, and N¯f is the number of flavors above which asymptotic freedom is lost. For a supersymmetric theory, the calculation preserves supersymmetry order by order in Δf. We then compute γ* through O (Δf2) for supersymmetric QCD in the dimensional reduction scheme and find that it matches the exact known result. We find that γ* is astonishingly well described in perturbation theory already at the few loops level throughout the entire conformal window. We finally compute γ* through O (Δf3) for QCD and a variety of other nonsupersymmetric fermionic gauge theories. Small values of γ* are observed for a large range of flavors.

  10. Consistent Perturbative Fixed Point Calculations in QCD and Supersymmetric QCD.

    PubMed

    Ryttov, Thomas A

    2016-08-12

    We suggest how to consistently calculate the anomalous dimension γ_{*} of the ψ[over ¯]ψ operator in finite order perturbation theory at an infrared fixed point for asymptotically free theories. If the n+1 loop beta function and n loop anomalous dimension are known, then γ_{*} can be calculated exactly and fully scheme independently in a Banks-Zaks expansion through O(Δ_{f}^{n}), where Δ_{f}=N[over ¯]_{f}-N_{f}, N_{f} is the number of flavors, and N[over ¯]_{f} is the number of flavors above which asymptotic freedom is lost. For a supersymmetric theory, the calculation preserves supersymmetry order by order in Δ_{f}. We then compute γ_{*} through O(Δ_{f}^{2}) for supersymmetric QCD in the dimensional reduction scheme and find that it matches the exact known result. We find that γ_{*} is astonishingly well described in perturbation theory already at the few loops level throughout the entire conformal window. We finally compute γ_{*} through O(Δ_{f}^{3}) for QCD and a variety of other nonsupersymmetric fermionic gauge theories. Small values of γ_{*} are observed for a large range of flavors. PMID:27563948

  11. A neuronal circuit for colour vision based on rod-cone opponency.

    PubMed

    Joesch, Maximilian; Meister, Markus

    2016-04-14

    In bright light, cone-photoreceptors are active and colour vision derives from a comparison of signals in cones with different visual pigments. This comparison begins in the retina, where certain retinal ganglion cells have 'colour-opponent' visual responses-excited by light of one colour and suppressed by another colour. In dim light, rod-photoreceptors are active, but colour vision is impossible because they all use the same visual pigment. Instead, the rod signals are thought to splice into retinal circuits at various points, in synergy with the cone signals. Here we report a new circuit for colour vision that challenges these expectations. A genetically identified type of mouse retinal ganglion cell called JAMB (J-RGC), was found to have colour-opponent responses, OFF to ultraviolet (UV) light and ON to green light. Although the mouse retina contains a green-sensitive cone, the ON response instead originates in rods. Rods and cones both contribute to the response over several decades of light intensity. Remarkably, the rod signal in this circuit is antagonistic to that from cones. For rodents, this UV-green channel may play a role in social communication, as suggested by spectral measurements from the environment. In the human retina, all of the components for this circuit exist as well, and its function can explain certain experiences of colour in dim lights, such as a 'blue shift' in twilight. The discovery of this genetically defined pathway will enable new targeted studies of colour processing in the brain. PMID:27049951

  12. Imaging Ca2+ dynamics in cone photoreceptor axon terminals of the mouse retina.

    PubMed

    Kulkarni, Manoj; Schubert, Timm; Baden, Tom; Wissinger, Bernd; Euler, Thomas; Paquet-Durand, Francois

    2015-01-01

    Retinal cone photoreceptors (cones) serve daylight vision and are the basis of color discrimination. They are subject to degeneration, often leading to blindness in many retinal diseases. Calcium (Ca(2+)), a key second messenger in photoreceptor signaling and metabolism, has been proposed to be indirectly linked with photoreceptor degeneration in various animal models. Systematically studying these aspects of cone physiology and pathophysiology has been hampered by the difficulties of electrically recording from these small cells, in particular in the mouse where the retina is dominated by rod photoreceptors. To circumvent this issue, we established a two-photon Ca(2+) imaging protocol using a transgenic mouse line that expresses the genetically encoded Ca(2+) biosensor TN-XL exclusively in cones and can be crossbred with mouse models for photoreceptor degeneration. The protocol described here involves preparing vertical sections ("slices") of retinas from mice and optical imaging of light stimulus-evoked changes in cone Ca(2+) level. The protocol also allows "in-slice measurement" of absolute Ca(2+) concentrations; as the recordings can be followed by calibration. This protocol enables studies into functional cone properties and is expected to contribute to the understanding of cone Ca(2+) signaling as well as the potential involvement of Ca(2+) in photoreceptor death and retinal degeneration. PMID:25993489

  13. Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years.

    PubMed

    Mariotti, Letizia; Devaney, Nicholas; Lombardo, Giuseppe; Lombardo, Marco

    2016-07-01

    Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation. PMID:27446708

  14. Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years

    PubMed Central

    Mariotti, Letizia; Devaney, Nicholas; Lombardo, Giuseppe; Lombardo, Marco

    2016-01-01

    Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation. PMID:27446708

  15. Imaging Ca2+ Dynamics in Cone Photoreceptor Axon Terminals of the Mouse Retina

    PubMed Central

    Kulkarni, Manoj; Schubert, Timm; Baden, Tom; Wissinger, Bernd; Euler, Thomas; Paquet-Durand, Francois

    2015-01-01

    Retinal cone photoreceptors (cones) serve daylight vision and are the basis of color discrimination. They are subject to degeneration, often leading to blindness in many retinal diseases. Calcium (Ca2+), a key second messenger in photoreceptor signaling and metabolism, has been proposed to be indirectly linked with photoreceptor degeneration in various animal models. Systematically studying these aspects of cone physiology and pathophysiology has been hampered by the difficulties of electrically recording from these small cells, in particular in the mouse where the retina is dominated by rod photoreceptors. To circumvent this issue, we established a two-photon Ca2+ imaging protocol using a transgenic mouse line that expresses the genetically encoded Ca2+ biosensor TN-XL exclusively in cones and can be crossbred with mouse models for photoreceptor degeneration. The protocol described here involves preparing vertical sections (“slices”) of retinas from mice and optical imaging of light stimulus-evoked changes in cone Ca2+ level. The protocol also allows “in-slice measurement” of absolute Ca2+ concentrations; as the recordings can be followed by calibration. This protocol enables studies into functional cone properties and is expected to contribute to the understanding of cone Ca2+ signaling as well as the potential involvement of Ca2+ in photoreceptor death and retinal degeneration. PMID:25993489

  16. QCD Collisional Energy Loss Reexamined

    NASA Astrophysics Data System (ADS)

    Peshier, A.

    2006-11-01

    It is shown that at a large temperature and E→∞ the QCD collisional energy loss reads dE/dx˜α(mD2)T2. Compared to previous approaches, which led to dEB/dx˜α2T2ln⁡(ET/mD2) similar to the Bethe-Bloch formula in QED, we take into account the running of the strong coupling. As one significant consequence, due to asymptotic freedom, dE/dx becomes E independent for large parton energies. Some implications with regard to heavy ion collisions are pointed out.

  17. QCD collisional energy loss reexamined.

    PubMed

    Peshier, A

    2006-11-24

    It is shown that at a large temperature and E --> infinity the QCD collisional energy loss reads dE/dx approximately alpha(m(D)2)T2. Compared to previous approaches, which led to dE(B)/dx approximately alpha2 T2 ln(ET/m(D)2) similar to the Bethe-Bloch formula in QED, we take into account the running of the strong coupling. As one significant consequence, due to asymptotic freedom, dE/dx becomes E independent for large parton energies. Some implications with regard to heavy ion collisions are pointed out. PMID:17155739

  18. "Quantum Field Theory and QCD"

    SciTech Connect

    Jaffe, Arthur M.

    2006-02-25

    This grant partially funded a meeting, "QFT & QCD: Past, Present and Future" held at Harvard University, Cambridge, MA on March 18-19, 2005. The participants ranged from senior scientists (including at least 9 Nobel Prize winners, and 1 Fields medalist) to graduate students and undergraduates. There were several hundred persons in attendance at each lecture. The lectures ranged from superlative reviews of past progress, lists of important, unsolved questions, to provocative hypotheses for future discovery. The project generated a great deal of interest on the internet, raising awareness and interest in the open questions of theoretical physics.

  19. Nucleon Structure from Lattice QCD

    SciTech Connect

    Haegler, Philipp

    2011-10-24

    Hadron structure calculations in lattice QCD have seen substantial progress during recent years. We illustrate the achievements that have been made by discussing latest lattice results for a limited number of important observables related to nucleon form factors and generalized parton distributions. A particular focus is placed on the decomposition of the nucleon spin 1/2 in terms of quark spin and orbital angular momentum contributions. Results and limitations of the necessary chiral extrapolations based on ChPT will be briefly discussed.

  20. Nuclear Physics from Lattice QCD

    SciTech Connect

    William Detmold, Silas Beane, Konstantinos Orginos, Martin Savage

    2011-01-01

    We review recent progress toward establishing lattice Quantum Chromodynamics as a predictive calculational framework for nuclear physics. A survey of the current techniques that are used to extract low-energy hadronic scattering amplitudes and interactions is followed by a review of recent two-body and few-body calculations by the NPLQCD collaboration and others. An outline of the nuclear physics that is expected to be accomplished with Lattice QCD in the next decade, along with estimates of the required computational resources, is presented.