Shuryak, E.V.
1990-04-01
Excited hadronic matter in the temperature interval T = 100--200 MeV is not an ideal pion gas, but rather a liquid, in which attractive interaction among particles plays an important role. Pion dispersion curve is in this case essentially modified by a kind of collective momentum-dependent potential, which becomes important as the quasipion'' comes to the boundary of the system. We show that effects can provide and explanation for a number of recent experimental puzzles, in particular, for the observed copious production of soft pions and soft photons in high energy hadronic reactions. 31 refs., 13 figs.
Selected problems in pion physics
Weise, W.
1987-12-01
In this talk I will discuss two seperate topics which can in principle be investigated with a high quality pion beam in the momentum range p/sub b//sub e//sub a//sub m/approx.1GeV/c up to several GeV/c: a) The structure of the nucleon resonances (other than the ..delta..(1232) and their properties in nuclei; b) the electric polarizabilitiy of the pion. The first subject can be seen as a continuation of earlier systematic explorations using the pion as a probe to investigate the properties of the ..delta..(1232) in a nuclear environment. The second topic concerns the intrinsic structure of the pion itself.
Nucleon polarisabilities at and beyond physical pion masses
NASA Astrophysics Data System (ADS)
Grießhammer, Harald W.; McGovern, Judith A.; Phillips, Daniel R.
2016-05-01
We examine the results of Chiral Effective Field Theory ( χ EFT) for the scalar- and spin-dipole polarisabilities of the proton and neutron, both for the physical pion mass and as a function of {m_{π}}. This provides chiral extrapolations for lattice QCD polarisability computations. We include both the leading and subleading effects of the nucleon's pion cloud, as well as the leading ones of the Δ(1232)-resonance and its pion cloud. The analytic results are complete at N2LO in the δ counting for pion masses close to the physical value, and at leading order for pion masses similar to the Delta-nucleon mass splitting. In order to quantify the truncation error of our predictions and fits as 68% degree-of-belief intervals, we use a Bayesian procedure recently adapted to EFT expansions. At the physical point, our predictions for the spin polarisabilities are, within respective errors, in good agreement with alternative extractions using experiments and dispersion-relation theory. At larger pion masses we find that the chiral expansion of all polarisabilities becomes intrinsically unreliable as {m_{π}} approaches about 300 MeV -as has already been seen in other observables. χ EFT also predicts a substantial isospin splitting above the physical point for both the electric and magnetic scalar polarisabilities; and we speculate on the impact this has on the stability of nucleons. Our results agree very well with emerging lattice computations in the realm where χ EFT converges. Curiously, for the central values of some of our predictions, this agreement persists to much higher pion masses. We speculate on whether this might be more than a fortuitous coincidence.
The user's view for the future of LAMPF, 1989: Reports from the pion physics working group
Burleson, G.R.; Ernst, D.J.
1990-01-01
This report contains a collection of papers on pion-nucleus interactions that were written as part of the long-range planning process of LAMPF that took place in spring, 1989. These papers served as the basis of the pion portion of a report to the Nuclear Science Advisory Committee (NSAC) for its Long Range Plan. They were read and discussed in some detail by the pion physics community and represent the views of the present and the future of pion physics by the authors and to a great extent by the pion physics community as a whole.
PILAC: A Pion Linac facility for 1-GeV pion physics at LAMPF
Thiessen, H.A.
1991-12-31
A design study for a Pion Linac (PILAC) at LAMPF is underway at Los Alamos. We present here a reference design for a system of pion source, linac, and high-resolution beam line and spectrometer that will provide 10{sup 9} pions per second on target and 200-keV resolution for the ({pi} {sup +}, K{sup +}) reaction at 0.92 GeV. A general-purpose beam line that delivers both positive and negative pions in the energy range 0.4--1.1 GeV is included, thus opening up the possibility of a broad experimental program as is discussed in this report. A kicker-based beam sharing system allows delivery of beam to both beamlines simultaneously with independent sign and energy control. Because the pion linac acts like and rf particle separator, all beams produced by PILAC will be free of electron (or positron) and proton contamination.
PILAC: A pion linac facility for 1-GeV pion physics at LAMPF
Thiessen, H.A.
1991-01-01
A design study or a Pion Linac (PILAC) at LAMPF is underway at Los Alamos. We present here a reference design for a system of pion sources, linac, and high-resolution beam line and spectrometer that will provide 10{sup 9} pions per second on target and 200-keV resolution for the ({pi}{sup +}, K{sup +}) reaction at 0.92 GeV. A general-purpose beam line that delivers both positive and negative pions in the energy range 0.4--1.1 GeV is included, thus opening up the possibility of a broad experimental program as is discussed in this report. A kicker-based beam sharing system allows delivery of beam to both beamlines simultaneously with independent sign and energy control. Because the pionlinac acts like an rf particle separator, all beams produced by PILAC will be free of electron (or positron) and proton contamination. 4 refs., 6 figs.
Status of PILAC: A pion linac facility for 1-GeV pion physics at LAMPF
Thiessen, H.A.
1990-01-01
A Pion Linac (PILAC) is being designed for LAMPF. Together with its high resolution beam line and spectrometer, the system is optimized to provide 10{sup 9} pions per second on target and 200-keV resolution for the ({pi}{sup +},K{sup +}) reaction at 920, MeV. There will also be an achromatic beam line capable of utilizing the maximum energy available, thus opening up the possibility of a broad experimental program as is being discussed at this workshop. 12 figs.
Nucleon Structure from 2+1 Flavor Domain Wall QCD at Nearly Physical Pion Mass
NASA Astrophysics Data System (ADS)
Ohta, Shigemi
2011-05-01
The RBC and UKQCD collaborations have been investigating hadron physics in numerical lattice quantum chromodynamics (QCD) with (2+1) flavors of dynamical domain wall fermions (DWF) quarks that preserves continuum-like chiral and flavor symmetries. The strange quark mass is adjusted to physical value via reweighting and degenerate up and down quark masses are set as light as possible. In a recent study of nucleon structure we found a strong dependence on pion mass and lattice spatial extent in isovector axialvector-current form factors. This is likely the first credible evidence for the pion cloud surrounding nucleon. Here we report the status of nucleon structure calculations with a new (2+1)-flavor dynamical DWF ensembles with much lighter pion mass of 180 and 250 MeV and a much larger lattice spatial exent of 4.6 fm. A combination of the Iwasaki and dislocation-suppressing-determinant-ratio (I+DSDR) gauge action and DWF fermion action allows us to generate these ensembles at cutoff of about 1.4 GeV while keeping the residual breaking of chiral symmetry sufficiently small. Nucleon source Gaussian smearing has been optimized. Preliminary nucleon mass estimates are 0.98 and 1.05 GeV.
Nucleon Structure from 2+1 Flavor Domain Wall QCD at Nearly Physical Pion Mass
Ohta, Shigemi
2011-05-24
The RBC and UKQCD collaborations have been investigating hadron physics in numerical lattice quantum chromodynamics (QCD) with (2+1) flavors of dynamical domain wall fermions (DWF) quarks that preserves continuum-like chiral and flavor symmetries. The strange quark mass is adjusted to physical value via reweighting and degenerate up and down quark masses are set as light as possible. In a recent study of nucleon structure we found a strong dependence on pion mass and lattice spatial extent in isovector axialvector-current form factors. This is likely the first credible evidence for the pion cloud surrounding nucleon. Here we report the status of nucleon structure calculations with a new (2+1)-flavor dynamical DWF ensembles with much lighter pion mass of 180 and 250 MeV and a much larger lattice spatial exent of 4.6 fm. A combination of the Iwasaki and dislocation-suppressing-determinant-ratio (I+DSDR) gauge action and DWF fermion action allows us to generate these ensembles at cutoff of about 1.4 GeV while keeping the residual breaking of chiral symmetry sufficiently small. Nucleon source Gaussian smearing has been optimized. Preliminary nucleon mass estimates are 0.98 and 1.05 GeV.
Nucleon electromagnetic form factors from lattice QCD using a nearly physical pion mass
NASA Astrophysics Data System (ADS)
Green, J. R.; Negele, J. W.; Pochinsky, A. V.; Syritsyn, S. N.; Engelhardt, M.; Krieg, S.
2014-10-01
We present lattice QCD calculations of nucleon electromagnetic form factors using pion masses mπ=149, 202, and 254 MeV and an action with clover-improved Wilson quarks coupled to smeared gauge fields, as used by the Budapest-Marseille-Wuppertal Collaboration. Particular attention is given to the removal of the effects of excited-state contamination by calculations at three source-sink separations and the use of the summation and generalized pencil-of-function methods. The combination of a calculation at the nearly physical mass mπ=149 MeV in a large spatial volume (mπLs=4.2) and the removal of excited-state effects yields agreement with experiment for the electric and magnetic form factors GE(Q2) and GM(Q2) up to Q2=0.5 GeV2.
NASA Technical Reports Server (NTRS)
1974-01-01
The survey of negative pion absorption reactions on light and medium nuclei was continued. Muon spin precession was studied using an iron target. An impulse approximation model of the pion absorption process implied that the ion will absorb almost exclusively on nucleon pairs, single nucleon absorption being suppressed by energy and momentum conservation requirements. For measurements on both paramagnetic and ferromagnetic iron, the external magnetic field was supplied by a large C-type electromagnet carrying a current of about 100 amperes.
Johnson, M.B.; Matthews, J.L.
1995-07-01
The LAMPF accelerator, with its high-intensity teams of pions and array of high-resolution spectrometers, provides opportunities for investigations of nuclear structure as well as of strong-interaction hadron dynamics. During operation of LAMPF as a national users facility, Nuclear Physics has undergone an evolution in the way it pictures nuclei: from a system of nucleons interacting through potentials to a system of mutually coupled nucleons, {Delta}(1232)`s, and mesons. While nuclear physics is in the midst of yet another shift of paradigm, with quarks and gluons playing a central role, the traditional picture still has great predictive power, and LAMPF has new opportunities to contribute to solving problems of current interest. At the same time, LAMPF is poised to make important contributions to the evolving area of nonperturbative QCD, where we will be learning how to connect phenomena at large momentum transfer to those at lower momentum scales. where the physically observable hadrons are the natural degrees of freedom. Within the traditional area, exploration of nuclei having extreme ratios of neutron/proton number is of growing interest in a variety of contexts, including astrophysics. Pion double charge exchange (the ({pi}{sup {plus_minus}}, {pi}{sup {plus_minus}}) processes) can produce proton-rich nuclei such as {sup 9}C, {sup 10}C, and {sup 11}N as well as neutron-rich nuclei such as {sup 10}He, {sup 11}Li, {sup 14}Be, and {sup 17}B. With spectrometers available for analyzing the outgoing pion spectra, one can study interesting and controversial modes of motion (soft-dipole modes) and obtain angular distributions that explore the spatial extent of neutron halos.
Direct determinations of the nucleon and pion σ terms at nearly physical quark masses
NASA Astrophysics Data System (ADS)
Bali, Gunnar S.; Collins, Sara; Richtmann, Daniel; Schäfer, Andreas; Söldner, Wolfgang; Sternbeck, André; RQCD Collaboration
2016-05-01
We present a high statistics study of the pion and nucleon light and strange quark sigma terms using Nf=2 dynamical nonperturbatively improved clover fermions with a range of pion masses down to mπ˜150 MeV and several volumes, L mπ=3.4 up to 6.7, and lattice spacings, a =0.06 - 0.08 fm , enabling a study of finite volume and discretization effects for mπ≳260 MeV . Systematics are found to be reasonably under control. For the nucleon we obtain σπ N=35 (6 ) MeV and σs=35 (12 ) MeV , or equivalently in terms of the quark fractions, fTu=0.021 (4 ) , fTd=0.016 (4 ) and fTs=0.037 (13 ) , where the errors include estimates of both the systematic and statistical uncertainties. These values, together with perturbative matching in the heavy quark limit, lead to fTc=0.075(4 ), fT b=0.072 (2 ) and fT t=0.070 (1 ). In addition, through the use of the (inverse) Feynman-Hellmann theorem our results for σπ N are shown to be consistent with the nucleon masses determined in the analysis. For the pion we implement a method which greatly reduces excited state contamination to the scalar matrix elements from states traveling across the temporal boundary. This enables us to demonstrate the Gell-Mann-Oakes-Renner expectation σπ=mπ/2 over our range of pion masses.
Pion loop contribution to the electromagnetic pion charge radius
Roberts, C.D.; Bender, A.; Alkofer, R.
1995-08-01
There is a widely held misconception, based on a misrepresentation of the application of chiral perturbation theory, that the electromagnetic structure of the pion is dominated by the pion`s own pion-cloud. To clarify this the Global Color-symmetry Model (GCM), was used to calculate the electromagnetic charge radius of the pion. In this calculation the contributions from the quark core and pion loop were identified and compared. It was shown explicitly that the divergence of the charge radius in the chiral limit is due solely to the pion loop and that, at the physical value of the pion mass, this loop contributes less than 15% {l_angle}r{sub {pi}}{sup 2}{r_angle}; i.e. the quark core is the dominant determining characteristic for the pion. This suggests that quark-based models that fail to reproduce the m{sub {pi}} divergence of {l_angle}{sub {pi}}{sup 2}{r_angle} nevertheless incorporate the dominant characteristic of the pion: its quark core. The result`s studylend further support to the contention that, away from resonances, the dominant determining characteristic of kinematic and dynamical properties of hadrons is their quark core. A paper describing this work was submitted for publication.
ERIC Educational Resources Information Center
Dunne, Peter
2002-01-01
The origins of the pion exchange model of nuclear forces are described and the exchange process is reinterpreted in the light of current views on the quark-gluon structure of nucleons. It is suggested that the reinterpretation might provide a picture of cohesive nuclear forces that is more intellectually satisfying than that produced by the…
Strangeness production with protons and pions
Dover, C.B.
1993-04-01
We discuss the spectrum of physics questions related to strangeness which could be addressed with intense beams of protons and pions in the few GeV region. We focus on various aspects of strangeness production, including hyperon production in pp collisions, studies of hyperon-nucleon scattering, production of hypernuclei in proton and pion-nucleus collisions, and spin phenomena in hypernuclei.
Strangeness production with protons and pions
Dover, C.B.
1993-01-01
We discuss the spectrum of physics questions related to strangeness which could be addressed with intense beams of protons and pions in the few GeV region. We focus on various aspects of strangeness production, including hyperon production in pp collisions, studies of hyperon-nucleon scattering, production of hypernuclei in proton and pion-nucleus collisions, and spin phenomena in hypernuclei.
Neutrino-induced coherent pion production off nuclei reexamined
Leitner, T.; Mosel, U.; Winkelmann, S.
2009-05-15
It is pointed out that so far all theoretical estimates of coherent pion production off nuclei induced by neutrinos rely on the ''local approximation'' well known in photonuclear physics. The effects of dropping this approximation are discussed. It is found that in a plane wave approximation for the pion, the local approximation overestimates the coherent neutrino-induced pion production on nuclei.
Beavis, D.; Fung, S.Y.; Gorn, W.; Keane, D.; Liu, Y.M.; Poe, R.T.; VanDalen, G.; Vient, M.
1984-01-01
Preliminary analysis of pion production in 1.2 GeV/nucleon Kr-RbBr collisions is presented. The negative pion multiplicity is consistent with a convolution of Poisson distributions and a freeze-out density between 1/3 and 1/2 normal nuclear density is extracted. Global negative pion kinematic variables are used to search for possible structure in the multi-pion emission. No evidence for structured emission or conservation constraints is found. Pion interferometry analysis gives a source radius of 5.4 +- 1.2 Fermi and a freeze-out density of .3 +- .2 times normal nuclear density. 10 refs., 5 figs.
DOE R&D Accomplishments Database
Nambu, Y.
1968-01-01
My talk is concerned with a review, not necessarily of the latest theoretical developments, but rather of an old idea which has contributed to recent theoretical activities. By soft pion processes I mean processes in which low energy pions are emitted or absorbed or scattered, just as we use the word soft photon in a similar context. Speaking more quantitatively, we may call a pion soft if its energy is small compared to a natural scale in the reaction. This scale is determined by the particular dynamics of pion interaction, and one may roughly say that a pion is soft if its energy is small compared to the energies of the other individual particles that participate in the reaction. It is important to note at this point that pion is by far the lightest member of all the hadrons, and much of the success of the soft pion formulas depends on this fact.
NASA Astrophysics Data System (ADS)
Lu, Egang; Moore, Guy D.
2011-04-01
We compute the bulk viscosity of a gas of pions at temperatures below the QCD crossover temperature, for the physical value of mπ, to lowest order in chiral perturbation theory. Bulk viscosity is controlled by number-changing processes which become exponentially slow at low temperatures when the pions become exponentially dilute, leading to an exponentially large bulk viscosity ζ~(F08/mπ5)exp(2mπ/T), where F0≃93MeV is the pion decay constant.
NASA Astrophysics Data System (ADS)
Brown, Laurie Mark; Dresden, Max; Hoddeson, Lillian
2009-01-01
Part I. Introduction; 1. Pions to quarks: particle physics in the 1950s Laurie M Brown, Max Dresden and Lillian Hoddeson; 2. Particle physics in the early 1950s Chen Ning Yang; 3. An historian's interest in particle physics J. L. Heilbron; Part II. Particle discoveries in cosmic rays; 4. Cosmic-ray cloud-chamber contributions to the discovery of the strange particles in the decade 1947-1957 George D. Rochester; 5. Cosmic-ray work with emulsions in the 1940s and 1950s Donald H. Perkins; Part III. High-energy nuclear physics; Learning about nucleon resonances with pion photoproduction Robert L. Walker; 7. A personal view of nucleon structure as revealed by electron scattering Robert Hofstadter; 8. Comments on electromagnetic form factors of the nucleon Robert G. Sachs and Kameshwar C. Wali; Part IV. The new laboratory; 9. The making of an accelerator physicist Matthew Sands; 10. Accelerator design and construction in the 1950s John P. Blewett; 11. Early history of the Cosmotron and AGS Ernest D. Courant; 12. Panel on accelerators and detectors in the 1950s Lawrence W. Jones, Luis W. Alvarez, Ugo Amaldi, Robert Hofstadter, Donald W. Kerst, Robert R. Wilson; 13. Accelerators and the Midwestern Universities Research Association in the 1950s Donald W. Kerst; 14. Bubbles, sparks and the postwar laboratory Peter Galison; 15. Development of the discharge (spark) chamber in Japan in the 1950s Shuji Fukui; 16. Early work at the Bevatron: a personal account Gerson Goldhaber; 17. The discovery of the antiproton Owen Chamberlain; 18. On the antiproton discovery Oreste Piccioni; Part V. The Strange Particles; 19. The hydrogen bubble chamber and the strange resonances Luis W. Alvarez; 20. A particular view of particle physics in the fifties Jack Steinberger; 21. Strange particles William Chinowsky; 22. Strange particles: production by Cosmotron beams as observed in diffusion cloud chambers William B. Fowler; 23. From the 1940s into the 1950s Abraham Pais; Part VI. Detection of the
Electromagnetic structure of pion
Mello, Clayton S.; Cruz Filho, Jose P.; Da Silva, Edson O.; El-Bennich, Bruno; De Melo, J. P.; Filho, Victo S.
2013-03-25
In this work, we analyze the electromagnetic structure of the pion, an elementary particle composed by a quark-antiquark bound state, by considering the calculation of its electromagnetic radius and its electromagnetic form factor in low and intermediate energy range. Such observables are determined by means of a theoretical model that takes into account the constituent quark and antiquark of the pion, in the formalism of the light-front field theory. In particular, it is considered a nonsymmetrical vertex for such a model, in which we have calculated the electromagnetic form factor of the pion in an optimized way, by varying its regulator mass, so that we can obtain the best value for the pion electromagnetic radius when compared with the experimental one. The theoretical calculations are also compared with the most recent experimental data involving the pion electromagnetic form factor and the results show very good agreement.
NASA Astrophysics Data System (ADS)
Garcilazo, H.; Mathelitsch, L.
1994-03-01
We investigate the continuum three-pion problem within a relativistic three-body model that takes into account the ππ S and P waves. The dynamical input of the two-body subsystem is given by separable potentials, which yield a good fit to the ππ scattering data and resonance parameters up to a two-body invariant mass of 900MeV. We introduce a parameter ν expressing the ambiguity in the reduction of a fully relativistic theory to a three-dimensional one. The masses and widths of the ω, a 1(1260), and π(1300) mesons, which decay predominantly into three pions, are reasonably well described by our model. The h 1(1170) meson, however, which also decays into three pions, cannot be explained as a three-pion resonance. Some πρ Argand diagrams are shown in those channels where resonances exist.
Pion treatment procedures and verification techniques
Zink, S.R.; Bush, S.E.; Gilman, C.J.; Hilko, R.H.; Justice, R.K.; Osborne, E.C.; Smith, A.R.; Berardo, P.A.
1984-05-01
Procedures and techniques developed for the negative pi-meson (pion) radiotherapy program at the Los Alamos Meson Physics Facility, Los Alamos, NM, are reviewed and described. A particular pion patient is followed through the entire planning and treatment sequence to describe CT scanning procedures, bolus and collimator and treatment techniques developed to minimize positioning errors (less than 5 mm). Comparison of 2-D and 3-d isodose calculation developed at Los Alamos showed differences of less than 10% attributable to multiple scattering effects and the computational models used. Treatment verification methods using in vivo ion chamber dosimetry generally confirmed the prescribed dose delivery within 10% and using TLD within 18%.
The pion: an enigma within the Standard Model
NASA Astrophysics Data System (ADS)
Horn, Tanja; Roberts, Craig D.
2016-07-01
Quantum chromodynamics (QCDs) is the strongly interacting part of the Standard Model. It is supposed to describe all of nuclear physics; and yet, almost 50 years after the discovery of gluons and quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: neutrons and protons, and the pions that bind them together. QCD is characterised by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB). They have far-reaching consequences, expressed with great force in the character of the pion; and pion properties, in turn, suggest that confinement and DCSB are intimately connected. Indeed, since the pion is both a Nambu–Goldstone boson and a quark–antiquark bound-state, it holds a unique position in nature and, consequently, developing an understanding of its properties is critical to revealing some very basic features of the Standard Model. We describe experimental progress toward meeting this challenge that has been made using electromagnetic probes, highlighting both dramatic improvements in the precision of charged-pion form factor data that have been achieved in the past decade and new results on the neutral-pion transition form factor, both of which challenge existing notions of pion structure. We also provide a theoretical context for these empirical advances, which begins with an explanation of how DCSB works to guarantee that the pion is un-naturally light; but also, nevertheless, ensures that the pion is the best object to study in order to reveal the mechanisms that generate nearly all the mass of hadrons. In canvassing advances in these areas, our discussion unifies many aspects of pion structure and interactions, connecting the charged-pion elastic form factor, the neutral-pion transition form factor and the pion's leading-twist parton distribution amplitude. It also sketches novel ways in which experimental and theoretical studies of the charged-kaon electromagnetic form factor can provide
Charged pion production in $$\
Eberly, B.; et al.
2015-11-23
Charged pion production via charged-current νμ interactions on plastic scintillator (CH) is studied using the MINERvA detector exposed to the NuMI wideband neutrino beam at Fermilab. Events with hadronic invariant mass W < 1.4 GeV and W < 1.8 GeV are selected in separate analyses: the lower W cut isolates single pion production, which is expected to occur primarily through the Δ(1232) resonance, while results from the higher cut include the effects of higher resonances. Cross sections as functions of pion angle and kinetic energy are compared to predictions from theoretical calculations and generator-based models for neutrinos ranging in energymore » from 1.5–10 GeV. The data are best described by calculations which include significant contributions from pion intranuclear rescattering. As a result, these measurements constrain the primary interaction rate and the role of final state interactions in pion production, both of which need to be well understood by neutrino oscillation experiments.« less
Eberly, B.; et al.
2015-11-23
Charged pion production via charged-current νμ interactions on plastic scintillator (CH) is studied using the MINERvA detector exposed to the NuMI wideband neutrino beam at Fermilab. Events with hadronic invariant mass W < 1.4 GeV and W < 1.8 GeV are selected in separate analyses: the lower W cut isolates single pion production, which is expected to occur primarily through the Δ(1232) resonance, while results from the higher cut include the effects of higher resonances. Cross sections as functions of pion angle and kinetic energy are compared to predictions from theoretical calculations and generator-based models for neutrinos ranging in energy from 1.5–10 GeV. The data are best described by calculations which include significant contributions from pion intranuclear rescattering. As a result, these measurements constrain the primary interaction rate and the role of final state interactions in pion production, both of which need to be well understood by neutrino oscillation experiments.
Battye, Richard A.; Sutcliffe, Paul M.
2006-05-15
In the Skyrme model with massless pions, the minimal energy multi-Skyrmions are shell-like, with the baryon density localized on the edges of a polyhedron that is approximately spherical and generically of the fullerene-type. In this paper we show that in the Skyrme model with massive pions these configurations are unstable for sufficiently large baryon number. Using numerical simulations of the full nonlinear field theory, we show that these structures collapse to form qualitatively different stable Skyrmion solutions. These new Skyrmions have a flat structure and display a clustering phenomenon into lower charge components, particularly components of baryon numbers three and four. These new qualitative features of Skyrmions with massive pions are encouraging in comparison with the expectations based on real nuclei.
Experimental studies of pion-nucleus interactions at intermediate energies
Not Available
1991-12-31
This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting {pi}{sup 0} mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized {sup 3}He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure.
Remarks on the pion-nucleon σ-term
NASA Astrophysics Data System (ADS)
Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.
2016-09-01
The pion-nucleon σ-term can be stringently constrained by the combination of analyticity, unitarity, and crossing symmetry with phenomenological information on the pion-nucleon scattering lengths. Recently, lattice calculations at the physical point have been reported that find lower values by about 3σ with respect to the phenomenological determination. We point out that a lattice measurement of the pion-nucleon scattering lengths could help resolve the situation by testing the values extracted from spectroscopy measurements in pionic atoms.
Sugimitsu, T.; Swenson, D.A.
1980-05-01
For the treatment of tumors with pi-minus mesons (pions), a pion channel with a large solid angle is essential. A parallel beam of uniform density and reasonable size at the patient position is favored from the practical point of view. A new pion channel with sixty toroidal current sheets and some solenoids is shown to meet these requirements. It would also be useful for some physics experiments using low-energy pion and muon beam.
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.
Pion exchange at high energies
Jones, L.M.
1980-07-01
The state of Regge pion exchange calculations for high-energy reactions is reviewed. Experimental evidence is summarized to show that (i) the pion trajectory has a slope similar to that of other trajectories; (ii) the pion exchange contribution can dominate contributions of higher trajectories up to quite a large energy; (iii) many two-body cross sections with large pion contributions can be fit only by models which allow for kinematical conspiracy at t=0. The theory of kinematic conspiracy is reviewed for two-body amplitudes, and calculations of the conspiring pion--Pomeron cut discussed. The author then summarizes recent work on pion exchange in Reggeized Deck models for multiparticle final states, with emphasis on the predictions of various models (with and without resonances) for phases of the partial wave amplitudes.
NASA Astrophysics Data System (ADS)
Bhattacharyya, S.; De, B.; Guptaroy, P.
2001-08-01
The pion densities and the nature of kaon-pion ratios offer two very prominent and crucial physical observables on which sufficient data for heavy nucleus collisions, to date, are available. In the light of two models - one purely phenomenological and the other with a sound dynamical basis - we would try to examine here the state of agreement between calculations and experimental results obtainable from the past and the latest measurements. Impact and implications of all these would also finally be spelt out.
Isospin violation in pion-kaon scattering
NASA Astrophysics Data System (ADS)
Kubis, Bastian; Meißner, Ulf-G.
2002-03-01
We consider strong and electromagnetic isospin violation in near-threshold pion-kaon scattering. At tree level, such effects are small for all physical channels. We work out the complete one-loop corrections to the process π-K +→ π0K 0. They come out rather small. We also show that the corresponding radiative cross section is highly suppressed at threshold.
Radiobiology of pions at LAMPF.
Raju, M R; Tokita, N
1982-12-01
Recent radiobiology data for pion beams used in therapy are presented. The biological systems used were cultured cells suspended in gelatin and intestinal crypt assay. The importance of fast neutrons from pion stars in large treatment volumes is discussed. The data for compensating the depth dose distribution to produce uniform cell killing across the peak region are presented. The changes in biological effectiveness with peak width for pion beams (unlike heavy ions) are small because of fast neutron contribution from pion stars. The need for innovative radiobiology programs to guide high-LET radiotherapy is discussed. PMID:7161165
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
NASA Astrophysics Data System (ADS)
Miller, Jack
We have measured charged pion production in the reaction ^{139}La + ^{139}Latopi ^{+/-} + X at three beam energies (246, 183 and 138 MeV/nucleon) below the nucleon-nucleon threshold. Associated multiplicity for charged participants was obtained using a 110-element scintillator multiplicity array. Data were taken over the angular range of 21 ^circ-67^circ in the laboratory (equivalent to 30^ circ-90^circ in the center of mass). Dependence of the spectra upon pion charge, energy and angle, beam energy, system mass and associated multiplicity was investigated. Based on the isotropic angular distributions and the associated multiplicities for pion production, it apprears that subthreshold pions in the range of our experiment are produced predominantly from a source at rest in the center of mass and involving a large number of nucleons. The general character of the subthreshold pion spectra is comparable to previous results above threshold. However, the scaling of the subthreshold pion yield with system mass deviates from the dependence observed in light systems, to an extent which cannot be explained by a simple nucleon-nucleon model. We also found charge dependent structure in the pion spectra, which we analysed in the framework of both Coulomb distortion and clustering models. We conclude that while we did not clear evidence of collective effects in subthreshold pion production, it would be very worthwhile to conduct a systematic investigation of pion production for all charge states and over a range of angles, system masses and beam energies, below threshold.
Low-energy pion-nucleon scattering
Gibbs, W.R.; Ai, L.; Kaufmann, W.B.
1998-02-01
An analysis of low-energy charged pion-nucleon data from recent {pi}{sup {plus_minus}}p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f{sup 2}=0.0756{plus_minus}0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P{sub 31} and P{sub 13} partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the {Sigma} term. Off-shell amplitudes are also provided. {copyright} {ital 1998} {ital The American Physical Society}
Adams, J.; Adler, C.; Ahammed, Z.; Allgower, C.; Amonett, J.; Anderson, B.D.; Anderson, M.; Arkhipkin, D.; Averichev, G.S.; Balewski, J.; Barannikova, O.; Barnby, L.S.; Baudot, J.; Bekele, S.; Belaga, V.V.; Bellwied, R.; Berger, J.; Bichsel, H.; Billmeier, A.; Bland, L.C.; Blyth, C.O.; Bonner, B.E.; Botje, M.; Boucham, A.; Brandin, A.; Bravar, A.; Cadman, R.V.; Cai, X.Z.; Caines, H.; Calderon de la Barca Sanchez, M.; Cardenas, A.; Carroll, J.; Castillo, J.; Castro, M.; Cebra, D.; Chaloupka, P.; Chattopadhyay, S.; Chen, Y.; Chernenko, S.P.; Cherney, M.; Chikanian, A.; Choi, B.; Christie, W.; Coffin, J.P.; Cormier, T.M.; Corral, Mora M.; Cramer, J.G.; Crawford, H.J.; Derevschikov, A.A.; Didenko, L.; Dietel, T.; Draper, J.E.; Dunin, V.B.; Dunlop, J.C.; Eckardt, V.; Efimov, L.G.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Fachini, P.; Faine, V.; Faivre, J.; Fatemi, R.; Filimonov, K.; Finch, E.; Fisyak, Y.; Flierl, D.; Foley, K.J.; Fu, J.; Gagliardi, C.A.; Gagunashvili, N.; Gans, J.; Gaudichet, L.; Germain, M.; Geurts, F.; Ghazikhanian, V.; Grachov, O.; Guedon, M.; Guertin, S.M.; Gushin, E.; Gutierrez, T.D.; Hallman, T.J.; Hardtke, D.; Harris, J.W.; Heinz, M.; Henry, T.W.; Heppelmann, S.; Herston, T.; Hippolyte, B.; Hirsch, A.; Hjort, E.; Hoffmann, G.W.; Horsley, M.; Huang, H.Z.; Humanic, T.J.; Igo, G.; Ishihara, A.; Jacobs, P.; Jacobs, W.W.; Janik, M.; Johnson, I.; Jones, P.G.; Judd, E.G.; Kabana, S.; Kaneta, M.; Kaplan, M.; Keane, D.; Kiryluk, J.; Kisiel, A.; Klay, J.; Klein, S.R.; Klyachko, A.; Kollegger, T.; Konstantinov, A.S.; Kopytine, M.; Kotchenda, L.; Kovalenko, A.D.; Kramer, M.; Kravtsov, P.; Krueger, K.; Kuhn, C.; Kulikov, A.I.; Kunde, G.J.; Kunz, C.L.; Kutuev, R.Kh.; Kuznetsov, A.A.; Lamont, M.A.C.; Landgraf, J.M.; Lange, S.; Lansdell, C.P.; Lasiuk, B.; Laue, F.; Lauret, J.; Lebedev, A.; Lednicky, R.; Leontiev, V.M.; LeVine, M.J.; Li, Q.; Lindenbaum, S.J.; Lisa, M.A.; Liu, F.; Liu, L.; Liu, Q.J.; Liu, Z.; et al.
2003-06-19
Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory, Au+Au collisions at {radical}s{sub NN} = 130 GeV, have been analyzed by the STAR Collaboration using three-pion correlations with charged pions to study whether pions are emitted independently at freezeout. We have made a high-statistics measurement of the three-pion correlation function and calculated the normalized three-particle correlator to obtain a quantitative measurement of the degree of chaoticity of the pion source. It is found that the degree of chaoticity seems to increase with increasing particle multiplicity.
Pions from and about heavy ions
Rasmussen, J.O.
1982-09-01
A review is presented of the possibilities of pion production with heavy ion reactions. Major headings include: pion thermometry; hills and valleys in pion spectra; pionic orbits of nuclear size; pion confinement in the fireball; anomalons; and Schroedinger equation solutions for pionic atoms. 47 references, 9 figures. (GHT)
Haiyan Gao, Wei Chen
2009-12-01
We extracted the differential cross section for the gn --> pi-p process from a deuterium target using the CLAS detector at Jefferson Lab in Hall B for photon energies between 1.0 and 3.5 GeV and pion center-of-mass (c.m.) angles (theta c.m.) between 50 deg. and 115 deg. We confirm a previous indication of a broad enhancement around a c.m. energy (sqrt s) of 2.1 GeV at theta c.m. =90 deg. in the scaled differential cross section, s^7 ds/dt and a rapid fall-off in a center-of-mass energy region of about 400 MeV following the enhancement. Our data show an angular dependence of this enhancement as the suggested scaling region is approached for theta c.m. from 70 deg. to 10 deg.
Sibirtsev, A; Haidenbauer, J; Huang, F; Krewald, S; Meissner, U -G
2009-04-01
We present a systematic analysis of backward pion photoproduction for the reactions $ \\gamma$ p $ \\rightarrow$ $ \\pi^{0}_{}$ p and $ \\gamma$ p $ \\rightarrow$ $ \\pi^{+}_{}$ n . Regge phenomenology is applied at invariant collision energies above 3GeV in order to fix the reaction amplitude. A comparision with older data on $ \\pi^{0}_{}$ - and $ \\pi^{+}_{}$ -photoproduction at $ \\vartheta$ = 180° indicates that the high-energy limit as given by the Regge calculation could be reached possibly at energies of around $ \\sqrt{{s}}$ ≃ 3 GeV. In the energy region of $ \\sqrt{{s}}$ $ \\le$2.5 GeV, covered by the new measurements of $ \\gamma$ p $ \\rightarrow$ $ \\pi^{0}_{}$ p differential cross-sections at large angles at ELSA, JLab, and LEPS, we see no clear signal for a convergence towards the Regge results. The baryon trajectories obtained in our analysis are in good agreement with those given by the spectrum of excited baryons.
Ryong Ji, C.; Pang, A.; Szczepaniak, A.
1994-04-01
It is pointed out that the correct criterion to define the legal PQCD contribution to the exclusive processes in the lightcone perturbative expansion should be based on the large off-shellness of the lightcone energy in the intermediate states. In the lightcone perturbative QCD calculation of the pion form factor, the authors find that the legal PQCD contribution defined by the lightcone energy cut saturates in the smaller Q{sup 2} region compared to that defined by the gluon four-momentum square cut. This is due to the contribution by the highly off-energy-shell gluons in the end point regions of the phase space, indicating that the gluon four-momentum-square cut may have cut too much to define the legal PQCD.
Neutrino pion production off deuteron
NASA Astrophysics Data System (ADS)
Myhrer, F.; Pastore, S.
2016-03-01
Experimental investigations of neutrino properties, using neutrino beams generated at accelerators facilities, necessitate a detailed and precise knowledge of neutrinonucleus reaction mechanisms. In the energy region of nuclear quasi-elastic scattering, pion-production reactions constitute an important background process. A theoretical understanding of these processes is then required in order to correctly determine the produced neutrino energy spectrum. In the first stage of our research project, we study neutrino induced pion-production off deuterons. The choice of the deuteron minimizes the complications of the nuclear dynamics associated with larger nuclear systems. We evaluate the pion-production reaction near threshold using heavy baryon chiral perturbation theory.
Critique of a pion exchange model for interquark forces
Isgur, Nathan
2000-09-01
I describe four serious defects of a widely discussed pion exchange model for interquark forces: it does not solve the ''spin-orbit problem'' as advertised, it fails to describe the internal structure of baryon resonances, it leads to disastrous conclusions when extended to mesons, and it is not reasonably connected to the physics of heavy-light systems. While extensions of the original pion exchange model may be able to correct these defects, this catalogue of criticisms defines some of the most formidable problems such elaborations must address. (c) 2000 The American Physical Society.
Neutrino induced coherent pion production
Hernandez, E.; Nieves, J.; Valverde, M.; Vicente-Vacas, M. J.
2010-03-30
We discuss different parameterizations of the C{sub 5}{sup A}(q{sup 2}) NDELTA form factor, fitted to the old Argonne bubble chamber data for pion production by neutrinos, and we use coherent pion production to test their low q{sup 2} behavior. We find moderate effects that will be difficult to observe with the accuracy of present experiments. We also discuss the use of the Rein-Sehgal model for low energy coherent pion production. By comparison to a microscopic calculation, we show the weaknesses some of the approximations in that model that lead to very large cross sections as well as to the wrong shapes for differential ones. Finally we show that models based on the partial conservation of the axial current hypothesis are not fully reliable for differential cross sections that depend on the angle formed by the pion and the incident neutrino.
Shape of Pion Distribution Amplitude
Radyushkin, Anatoly
2009-11-01
A scenario is investigated in which the leading-twist pion distribution amplitude $\\varphi_\\pi (x)$ is approximated by the pion decay constant $f_\\pi$ for all essential values of the light-cone fraction $x$. A model for the light-front wave function $\\Psi (x, k_\\perp)$ is proposed that produces such a distribution amplitude and has a rapidly decreasing (exponential for definiteness) dependence on the light-front energy combination $ k_\\perp^2/x(1-x)$. It is shown that this model easily reproduces the fit of recent large-$Q^2$ BaBar data on the photon-pion transition form factor. Some aspects of scenario with flat pion distribution amplitude are discussed.
Pion condensation in holographic QCD
Albrecht, Dylan; Erlich, Joshua
2010-11-01
We study pion condensation at zero temperature in a hard-wall holographic model of hadrons with isospin chemical potential. We find that the transition from the hadronic phase to the pion condensate phase is first order except in a certain limit of model parameters. Our analysis suggests that immediately across the phase boundary the condensate acts as a stiff medium approaching the Zel'dovich limit of equal energy density and pressure.
NASA Astrophysics Data System (ADS)
Lin, Guoji
Electro-magnetic (E&M) probes such as direct photons and muons (mu) are important tools to study the properties of the extremely hot and dense matter created in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC). In this thesis, several topics of E&M physics will be addressed, including neutral pion (pi0) production, direct photon HBT, and photon elliptic flow (v2) in Au+Au collisions at sNN = 200 GeV. A discussion on the simulation study of the new Muon Telescope Detector (MTD) will also be presented. The pi0 production is a fundamental measurement of hadron production and prerequisite for the background study of direct photons. Neutral pions are reconstructed using the photons detected by the STAR Barrel Electro-magnetic Calorimeter (BEMC) and the Time Projection Chamber (TPC). Spectra of pi 0 are measured at transverse momentum 1 < pT < 12 GeV/c near mid-rapidity (0 < eta < 0.8) in 200 GeV Au+Au collisions. The spectra and nuclear modification factors RCP and RAA are compared to earlier pi+/- and pi0 results. Direct photon Hanbury-Brown and Twiss (HBT) correlations can reveal information of the system size throughout the whole collision. A first attempt of direct photon HBT study at RHIC in 200 GeV Au+Au collisions is done using photons detected by the STAR BEMC and TPC. All unknown correlation at small Qinv is observed, whose magnitude is much larger than the expected HBT signal, and possible causes of the correlation will be discussed. Direct photon elliptic flow (v2) at intermediate to high pT is sensitive to the source of direct photon production. Results of inclusive photon v2 in 200 GeV Au+Au collisions are presented. The v2 of pi0 decay photons is calculated from the previously published pi results. The comparison between inclusive and decay photon v 2 indicates that direct photon v2 is small. A new large-area Muon Telescope Detector at mid-rapidity at RHIC is proposed and under investigation, using the Long-strip Multi-Gap Resistive Plate
Electromagnetic pion form factor
Roberts, C.D.
1995-08-01
A phenomenological Dyson-Schwinger/Bethe-Salpeter equation approach to QCD, formalized in terms of a QCD-based model field theory, the Global Color-symmetry Model (GCM), was used to calculate the generalized impulse approximation contribution to the electromagnetic pion form factor at space-like q{sup 2} on the domain [0,10] GeV{sup 2}. In effective field theories this form factor is sometimes understood as simply being due to Vector Meson Dominance (VMD) but this does not allow for a simple connection with QCD where the VMD contribution is of higher order than that of the quark core. In the GCM the pion is treated as a composite bound state of a confined quark and antiquark interacting via the exchange of colored vector-bosons. A direct study of the quark core contribution is made, using a quark propagator that manifests the large space-like-q{sup 2} properties of QCD, parameterizes the infrared behavior and incorporates confinement. It is shown that the few parameters which characterize the infrared form of the quark propagator may be chosen so as to yield excellent agreement with the available data. In doing this one directly relates experimental observables to properties of QCD at small space-like-q{sup 2}. The incorporation of confinement eliminates endpoint and pinch singularities in the calculation of F{sub {pi}}(q{sup 2}). With asymptotic freedom manifest in the dressed quark propagator the calculation yields q{sup 4}F{sub {pi}}(q{sup 2}) = constant, up to [q{sup 2}]- corrections, for space-like-q{sup 2} {approx_gt} 35 GeV{sup 2}, which indicates that soft, nonperturbative contributions dominate the form factor at presently accessible q{sup 2}. This means that the often-used factorization Ansatz fails in this exclusive process. A paper describing this work was submitted for publication. In addition, these results formed the basis for an invited presentation at a workshop on chiral dynamics and will be published in the proceedings.
The pion distribution amplitude from SDE-BSE
NASA Astrophysics Data System (ADS)
Cobos-Martínez, J. J.
2015-11-01
A brief exposition of the Schwinger-Dyson-Bethe-Salpeter equations of Quantum Chromodynamics and their application to hadron physics is given. Results for the rainbow- ladder trucantion scheme are presented. The Pion distribution amplitude is calculated in the SDE-BSE approach to hadron physics employing a novel method of computation [28]. The SDE-BSE is a well founded continuum approach to nonperturbative hadron physics that unifies a range of hadron observables.
Pion and kaon valence-quark parton distribution functions.
Nguyen, T.; Bashir, A.; Roberts, C. D.; Tandy, P. C.
2011-06-16
A rainbow-ladder truncation of QCD's Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to {pi}-N Drell-Yan data for the pion's u-quark distribution and to Drell-Yan data for the ratio u{sub K}(x)/u{sub {pi}}(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
Pion and kaon valence-quark parton distribution functions
Nguyen, Trang; Bashir, Adnan; Roberts, Craig D.; Tandy, Peter C.
2011-06-15
A rainbow-ladder truncation of QCD's Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to {pi}-N Drell-Yan data for the pion's u-quark distribution and to Drell-Yan data for the ratio u{sub K}(x)/u{sub {pi}}(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
The Pion Charge Form Factor Through Pion Electroproduction
Horn, Tanja
2006-04-01
The goal of Jefferson Lab experiment E01-004 (F?-2) was the measurement of the longitudinal and transverse cross sections via pion electroproduction from hydrogen and deuterium for the purpose of extracting the charged pion form factor using pole dominance. The data were taken at two values of Q2 (1.60 and 2.45 GeV/c)2. In order to attain full coverage in R?, charged pions were detected in parallel kinematics (along the direction of momentum transfer, q), and at Â±3 degrees off the direction of momentum transfer. For each Q2 data were taken for two values of the virtual photon polarization, ?, respectively. All data were taken at a fixed center of mass energy, W=2.22 GeV. The longitudinal and transverse pieces of the cross section were separated using the Rosenbluth separation method.
Tilted pion sources from azimuthally sensitive HBT interferometry
NASA Astrophysics Data System (ADS)
Lisa, M. A.; Heinz, U.; Wiedemann, U. A.
2000-09-01
Intensity interferometry in noncentral heavy ion collisions provides access to novel information on the geometry of the effective pion-emitting source. We demonstrate analytically that, even for vanishing pair momentum, the cross terms Rol2 and Rsl2 of the HBT correlation function in general show a strong first harmonic in their azimuthal dependence. The strength of this oscillation characterizes the tilt of the major axis of the spatial emission ellipsoid away from the direction of the beam. Event generator studies indicate that this tilt can be large (/>20°) at AGS energies which makes it by far the most significant azimuthally sensitive HBT signal at these energies. Moreover, transport models suggest that for pions this spatial tilt is directed opposite to the tilt of the directed flow ellipsoid in momentum space. A measurement of the azimuthal dependence of the HBT cross terms Rol2 and Rsl2 thus probes directly the physical origin of directed pion flow.
Four-nucleon potential due to exchange of pions
Robilotta, M.R.
1985-03-01
A four-body force due to the exchange of pions has been derived by means of It includes effects corresponding to pion-pion scattering, pion production, and pion-nucleon rescattering. The strength parameters of this four-body potential are typically one order of magnitude smaller than those of the two-pion-exchange three-body force.
Single Pion production from Nuclei
Singh, S. K.; Athar, M. Sajjad; Ahmed, S.
2007-12-21
We have studied charged current one pion production induced by {nu}{sub {mu}}({nu}-bar{sub {mu}}) from some nuclei. The calculations have been done for the incoherent pion production processes from these nuclear targets in the {delta} dominance model and take into account the effect of Pauli blocking, Fermi motion and renormalization of {delta} properties in the nuclear medium. The effect of final state interactions of pions has also been taken into account. The numerical results have been compared with the recent results from the MiniBooNE experiment for the charged current 1{pi} production, and also with some of the older experiments in Freon and Freon-Propane from CERN.
Investigation of pion-nucleus interactions. [295 MeV
Moore, C.F.
1992-09-01
This report summarizes the work carried out by personnel from the University of Texas at Austin at the Los Alamos Clinton P. Anderson Meson Physics Facility (LAMPF). The research activities involved experiments done with the Energetic Pion Channel and Spectrometer (EPICS), the Low Energy Pion Channel (LEP), the Pion and Particle Physics Channel (P[sup 3]), the High Resolution Spectrometer (HRS), and planning a new experimental program associated with the new high-resolution Neutral Meson Spectrometer (NMS) at LAMPF. A brief overview of work supported by this grant is given followed by an account of the study of the double giant resonances in pion double charge exchange on [sup 51]V, [sup 115]In, and [sup 197]Au. This report contains a list of published papers and preprints, abstracts, and invited talks. These papers summarize experiments involving participants supported by this grant and indicate the work accomplished by these participants in this program of medium energy nuclear physics research. Lists of the most recent proposals on which we have participation at LAMPF, proposals which have been approved this past year to run as experiments, personnel who have participated in this research program are included. The research cited in this report is, in many cases, the collaborative effort of many groups associated with research at LAMPF.
Broemmel, D.; Diehl, M.; Goeckeler, M.; Schaefer, A.; Haegler, Ph.; Horsley, R.; Zanotti, J. M.; Nakamura, Y.; Pleiter, D.; Schierholz, G.
2008-09-19
We present the first calculation of the transverse spin structure of the pion in lattice QCD. Our simulations are based on two flavors of nonperturbatively improved Wilson fermions, with pion masses as low as 400 MeV in volumes up to (2.1 fm){sup 3} and lattice spacings below 0.1 fm. We find a characteristic asymmetry in the spatial distribution of transversely polarized quarks. This asymmetry is very similar in magnitude to the analogous asymmetry we previously obtained for quarks in the nucleon. Our results support the hypothesis that all Boer-Mulders functions are alike.
Experimental studies of pion-nucleus interactions at intermediate energies. Annual progress report
Not Available
1991-12-31
This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting {pi}{sup 0} mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized {sup 3}He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure.
Pion shadowing as a tool to study the topology of heavy-ion collisions at intermediate energies
Badala, A.; Barbera, R.; Palmeri, A.; Pappalardo, G.S.; Riggi, F.; Russo, A.C.; Turrisi, R.; Barbera, R.; Riggi, F.; Russo, G.; Turrisi, R.; Russo, G.
1997-05-01
The pion reabsorption effect has been exploited, through a new analysis technique, to study the topological distribution of nuclear matter in the course of a heavy-ion collision at intermediate energies. The azimuthal angular distribution of pions with respect to the reaction plane and the angular correlations between pions and projectilelike fragments have been investigated. Quantitative estimations of the pion production time scale and of the impact parameter range involved are provided. The experimental results are successfully compared with the predictions of a microscopic theoretical model based on the solution of the Boltzmann-Nordheim-Vlasov transport equation. {copyright} {ital 1997} {ital The American Physical Society}
Neutron star cooling and pion condensation
NASA Technical Reports Server (NTRS)
Umeda, Hideyuki; Nomoto, Ken'ichi; Tsuruta, Sachiko; Muto, Takumi; Tatsumi, Toshitaka
1994-01-01
The nonstandard cooling of a neutron star with the central pion core is explored. By adopting the latest results from the pion condensation theory, neutrino emissivity is calulated for both pure charged pions and a mixture of charged and neutral pions, and the equations of state are constructed for the pion condensate. The effect of superfluidity on cooling is investigated, adopting methods more realistic than in previous studies. Our theoretical models are compared with the currently updated observational data, and possible implications are explored.
Pauli Principle and Pion Scattering
DOE R&D Accomplishments Database
Bethe, H. A.
1972-10-01
It is pointed out that if the Pauli principle is taken into account in the discussion of pion scattering by complex nuclei (as it ought, of course, to be) some rather implausible consequences of some earlier treatments of this problem can be avoided. (auth)
Pion inelastic scattering from sup 20 Ne
Burlein, M. . Dept. of Physics)
1989-12-01
Angular distributions for {sup 20}Ne({pi}{sup {plus minus}}, {pi}{sup {plus minus}}{prime}) were measured on the Energetic Pion Channel and Spectrometer (EPICS) at the Clinton P. Anderson Meson Physics Facility (LAMPF). Data were taken with both {pi}{sup {plus}} and {pi}{sup {minus}} over an angular range of 12{degree} to 90{degree} for T{sub {pi}}=180 MeV and with {pi}{sup +} from 15{degree} to 90{degree} for T{sub {pi}}=120 MeV. The data were analyzed using both the distorted-wave impulse approximation (DWIA) and the coupled-channels impulse approximation (CCIA) with collective transition densities. In addition, microscopic transition densities were used in the DWIA analysis for states in the lowest rotational bands. The transitions to the 6.73-MeV 0{sup +} and several 1{sup {minus}} states, including the states at 5.79 MeV and 8.71 MeV, were studied using several models for the transition density. Strong evidence for the importance of two-step routes in pion inelastic scattering was seen in several angular distributions, including the 5.79-MeV 1{sup {minus}}, the first three 4{sup +} states, and the 8.78-MeV 6{sup +}. 100 refs., 81 figs., 33 tabs.
Study of the two pion final state photoproduction on deuterium
Lewis Graham, Kijun Park, Ralf Gothe, Elton Smith
2010-08-01
Understanding the structure of baryons in terms of the fundamental interaction of the constituent quarks and gluons is one of the challenges in strong interaction physics. This interaction is governed by Quantum Chromodynamics (QCD). However, solutions of this theory in the non-perturbative domain of the interaction are extremely difficult to achieve. In inelastic electron scattering, very little is known about exclusive hadron production purely contributed to a lack of knowledge. The gammaN interaction is recognized for being a powerful method for investigating hadrons and the mysteries that still exist within the strong interaction. From reactions with the nucleon, the strong interaction can be tested through the amplitudes of the N and Delta resonances. More specifically, if an electromagnetic interaction is well known then the intermediate resonance states may be evaluated through pion photoproduction. To gain more detailed insight into this interaction, we look to probe the baryon structure of Delta and the meson structure of the pion through photon scattering off a deuteron producing two pions in the final state. The photoproduction processes on the deuteron will be used to investigate known baryon resonances in the proton-pion channel. The two pion final state will be investigated for unraveling new information in to the rho decay at threshold. We want to explore both final states interactions to search for “missing” states that are predicted by quark models but have not yet been found experimentally. Using the CEBAF Large Acceptance Spectrometer (CLAS), the hadronic products are detected in coincidence with the scattered photon. This makes it possible to measure the differential cross section and the decay angular distribution for the production of two and three pion final states. The measured cross sections will contribute significantly and push the knowledge of the strong interaction to the next level. We propose to use the CEBAF Large Acceptance
Study of the two pion final state photoproduction on deuterium
Graham, Lewis; Gothe, Ralf; Park, Kijun; Smith, Elton
2010-08-05
Understanding the structure of baryons in terms of the fundamental interaction of the constituent quarks and gluons is one of the challenges in strong interaction physics. This interaction is governed by Quantum Chromodynamics (QCD). However, solutions of this theory in the non-perturbative domain of the interaction are extremely difficult to achieve. In inelastic electron scattering, very little is known about exclusive hadron production purely contributed to a lack of knowledge. The {gamma}N interaction is recognized for being a powerful method for investigating hadrons and the mysteries that still exist within the strong interaction. From reactions with the nucleon, the strong interaction can be tested through the amplitudes of the N and {Delta} resonances. More specifically, if an electromagnetic interaction is well known then the intermediate resonance states may be evaluated through pion photoproduction. To gain more detailed insight into this interaction, we look to probe the baryon structure of {Delta} and the meson structure of the pion through photon scattering off a deuteron producing two pions in the final state. The photoproduction processes on the deuteron will be used to investigate known baryon resonances in the proton-pion channel. The two pion final state will be investigated for unraveling new information in to the rho decay at threshold. We want to explore both final states interactions to search for ''missing'' states that are predicted by quark models but have not yet been found experimentally. Using the CEBAF Large Acceptance Spectrometer (CLAS), the hadronic products are detected in coincidence with the scattered photon. This makes it possible to measure the differential cross section and the decay angular distribution for the production of two and three pion final states. The measured cross sections will contribute significantly and push the knowledge of the strong interaction to the next level. We propose to use the CEBAF Large Acceptance
Muon neutrino charged current inclusive charged pion (CCπ{sup ±}) production in MINERνA
Eberly, B.
2015-05-15
The production of charged pions by neutrinos interacting on nuclei is of great interest in nuclear physics and neutrino oscillation experiments. The MINERνA experiment is working towards releasing the world’s first high statistics neutrino pion production measurements in a few-GeV neutrino beam. We describe MINERνA’s CCπ{sup ±} analysis event selection in both the neutrino and antineutrino beams, noting reconstruction resolutions and kinematic limits. We also show area-normalized data-simulation comparisons of the reconstructed muon and charged pion kinetic energy distributions.
Dmitri Diakonov
2004-05-01
I overview the physical picture of QCD at low energies that has led to the prediction of a narrow exotic baryon Theta{sup +} which cannot be made of three quarks. The very narrow width of the Theta{sup +} and a possible reason why it is seen in low- but not in high-energy experiments are briefly discussed.
Measuring pion beta decay with high-energy pion beams
McFarlane, W.K. Temple Univ., Philadelphia, PA ); Hoffman, C.M. )
1993-01-01
Improved measurements of the pion beta decay rate are possible with an intense high-energy pion beam. The rate for the decay [pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon] is predicted by the Standard Model (SM) to be R([pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon]) = 0.3999[plus minus]0.0005 s[sup [minus]1]. The best experimental number, obtained using in-flight decays, is R([pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon]) = 0.394 [plus minus] 0.015 s[sup [minus]1]. A precise measurement would test the SM by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix for which one analysis of the nuclear beta decay data has shown a 0.4% discrepancy. Several nuclear correction factors, needed for nuclear decay, are not present for pion beta decay, so that an experiment at the 0.2% level would be a significant one. Detailed study of possible designs will be needed, as well as extensive testing of components. The reduction of systematic errors to the 0.1% level can only be done over a period of years with a highly stable apparatus and beam. At a minimum, three years of occupancy of a beam line, with 800 hours per year, would be required.
Measuring pion beta decay with high-energy pion beams
McFarlane, W.K. |; Hoffman, C.M.
1993-02-01
Improved measurements of the pion beta decay rate are possible with an intense high-energy pion beam. The rate for the decay {pi}{sup +} {yields} {pi}{sup 0}e{sup +}v{epsilon} is predicted by the Standard Model (SM) to be R({pi}{sup +} {yields} {pi}{sup 0}e{sup +}v{epsilon}) = 0.3999{plus_minus}0.0005 s{sup {minus}1}. The best experimental number, obtained using in-flight decays, is R({pi}{sup +} {yields} {pi}{sup 0}e{sup +}v{epsilon}) = 0.394 {plus_minus} 0.015 s{sup {minus}1}. A precise measurement would test the SM by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix for which one analysis of the nuclear beta decay data has shown a 0.4% discrepancy. Several nuclear correction factors, needed for nuclear decay, are not present for pion beta decay, so that an experiment at the 0.2% level would be a significant one. Detailed study of possible designs will be needed, as well as extensive testing of components. The reduction of systematic errors to the 0.1% level can only be done over a period of years with a highly stable apparatus and beam. At a minimum, three years of occupancy of a beam line, with 800 hours per year, would be required.
Tavakoli, Mohammad Bagher; Mohammadi, Mohammad Mehdi; Reiazi, Reza; Jabbari, Keyvan
2015-01-01
Geant4 is an open source simulation toolkit based on C++, which its advantages progressively lead to applications in research domains especially modeling the biological effects of ionizing radiation at the sub-cellular scale. However, it was shown that Geant4 does not give a reasonable result in the prediction of antiproton dose especially in Bragg peak. One of the reasons could be lack of reliable physic model to predict the final states of annihilation products like pions. Considering the fact that most of the antiproton deposited dose is resulted from high-LET nuclear fragments following pion interaction in surrounding nucleons, we reproduced depth dose curves of most probable energy range of pions and neutron particle using Geant4. We consider this work one of the steps to understand the origin of the error and finally verification of Geant4 for antiproton tracking. Geant4 toolkit version 9.4.6.p01 and Fluka version 2006.3 were used to reproduce the depth dose curves of 220 MeV pions (both negative and positive) and 70 MeV neutrons. The geometry applied in the simulations consist a 20 × 20 × 20 cm3 water tank, similar to that used in CERN for antiproton relative dose measurements. Different physic lists including Quark-Gluon String Precompound (QGSP)_Binary Cascade (BIC)_HP, the recommended setting for hadron therapy, were used. In the case of pions, Geant4 resulted in at least 5% dose discrepancy between different physic lists at depth close to the entrance point. Even up to 15% discrepancy was found in some cases like QBBC compared to QGSP_BIC_HP. A significant difference was observed in dose profiles of different Geant4 physic list at small depths for a beam of pions. In the case of neutrons, large dose discrepancy was observed when LHEP or LHEP_EMV lists were applied. The magnitude of this dose discrepancy could be even 50% greater than the dose calculated by LHEP (or LHEP_EMV) at larger depths. We found that effect different Geant4 physic list in
Tavakoli, Mohammad Bagher; Mohammadi, Mohammad Mehdi; Reiazi, Reza; Jabbari, Keyvan
2015-01-01
Geant4 is an open source simulation toolkit based on C++, which its advantages progressively lead to applications in research domains especially modeling the biological effects of ionizing radiation at the sub-cellular scale. However, it was shown that Geant4 does not give a reasonable result in the prediction of antiproton dose especially in Bragg peak. One of the reasons could be lack of reliable physic model to predict the final states of annihilation products like pions. Considering the fact that most of the antiproton deposited dose is resulted from high-LET nuclear fragments following pion interaction in surrounding nucleons, we reproduced depth dose curves of most probable energy range of pions and neutron particle using Geant4. We consider this work one of the steps to understand the origin of the error and finally verification of Geant4 for antiproton tracking. Geant4 toolkit version 9.4.6.p01 and Fluka version 2006.3 were used to reproduce the depth dose curves of 220 MeV pions (both negative and positive) and 70 MeV neutrons. The geometry applied in the simulations consist a 20 × 20 × 20 cm(3) water tank, similar to that used in CERN for antiproton relative dose measurements. Different physic lists including Quark-Gluon String Precompound (QGSP)_Binary Cascade (BIC)_HP, the recommended setting for hadron therapy, were used. In the case of pions, Geant4 resulted in at least 5% dose discrepancy between different physic lists at depth close to the entrance point. Even up to 15% discrepancy was found in some cases like QBBC compared to QGSP_BIC_HP. A significant difference was observed in dose profiles of different Geant4 physic list at small depths for a beam of pions. In the case of neutrons, large dose discrepancy was observed when LHEP or LHEP_EMV lists were applied. The magnitude of this dose discrepancy could be even 50% greater than the dose calculated by LHEP (or LHEP_EMV) at larger depths. We found that effect different Geant4 physic list in
Pion scattering and nuclear dynamics
Johnson, M.B.
1988-01-01
A phenomenological optical-model analysis of pion elastic scattering and single- and double-charge-exchange scattering to isobaric-analog states is reviewed. Interpretation of the optical-model parameters is briefly discussed, and several applications and extensions are considered. The applications include the study of various nuclear properties, including neutron deformation and surface-fluctuation contributions to the density. One promising extension for the near future would be to develop a microscopic approach based on powerful momentum-space methods brought to existence over the last decade. In this, the lowest-order optical potential as well as specific higher-order pieces would be worked out in terms of microscopic pion-nucleon and delta-nucleon interactions that can be determined within modern meson-theoretical frameworks. A second extension, of a more phenomenological nature, would use coupled-channel methods and shell-model wave functions to study dynamical nuclear correlations in pion double charge exchange. 35 refs., 11 figs., 1 tab.
How strange is pion electroproduction?
NASA Astrophysics Data System (ADS)
Gorchtein, Mikhail; Spiesberger, Hubert; Zhang, Xilin
2016-01-01
We consider pion production in parity-violating electron scattering (PVES) in the presence of nucleon strangeness in the framework of partial wave analysis with unitarity. Using the experimental bounds on the strange form factors obtained in elastic PVES, we study the sensitivity of the parity-violating asymmetry to strange nucleon form factors. For forward kinematics and electron energies above 1 GeV, we observe that this sensitivity may reach about 20% in the threshold region. With parity-violating asymmetries being as large as tens p.p.m., this study suggests that threshold pion production in PVES can be used as a promising way to better constrain strangeness contributions. Using this model for the neutral current pion production, we update the estimate for the dispersive γZ-box correction to the weak charge of the proton. In the kinematics of the Qweak experiment, our new prediction reads Re □γZV (E = 1.165 GeV) = (5.58 ± 1.41) ×10-3, an improvement over the previous uncertainty estimate of ± 2.0 ×10-3. Our new prediction in the kinematics of the upcoming MESA/P2 experiment reads Re □γZV (E = 0.155 GeV) = (1.1 ± 0.2) ×10-3.
Radiation quality of beams of negative pions
Dicello, J.F.; Brenner, D.J.
1981-01-01
As a negative pion stops in tissue, it attaches itself to an adjacent atom to form a mesonic atom. Subsequently, the wave function of the pion interacts with that of the nucleus and the pion is absorbed. Because the energy associated with the rest mass of the pion is greater than the separation energy of the nuclear particles, the nucleus disintegrates (pion star). In tissue, approximately 40 MeV goes into overcoming the binding energies; 20 MeV goes into kinetic energy of charged particles; 80 MeV goes into kinetic energy of neutrons. In cases where biological studies are performed with beams of negative pions, as much as 20% of the total absorbed dose in the treatment volume and about 50% of the high-LET dose (> 100 keV/..mu..m) can result from neutrons. The degree of biological response and the variation of that response throughout the treatment volume can be altered by the neutron dose.
Photon annd pion production in heavy ion collisions
Blann, M.
1989-05-01
In this paper we describe different formulations for treating the nucleon-nucleon transport physics. These will all be semi-classical treatments; however considerable work has been done considering the relationship between quantal and semi-classical formulations. We discuss additional input specific to calculation of pion and photon yields, and present comparisons between calculated and experimental results, mostly for high energy photons. Conclusions and suggestions for future work are presented in the last section. 65 refs., 7 figs.
Pion single charge exchange in three body nuclei at intermediate energies
Dowell, M.L.
1994-01-01
The purpose of this thesis is to present new experimental information about modifications to the pion-nucleon single charge exchange interaction, {pi}{sup +}n {yields}{pi}{sup 0} p or {pi}{sup {minus}} p {yields} {pi}{sup 0}n, due to the presence of other nucleons. The results of two experimental studies of pion single charge exchange in the three nucleon system near the {triangle}-resonance are presented. Both of these experiments were performed at the Clinton P. Anderson Meson Physics Facility (LAMPF), a division of the Los Alamos National Laboratory. Each explored different aspects of pion single charge exchange in three body nuclei--{sup 3}He and {sup 3}H. Since the nuclear wavefunctions of the three nucleon systems are believed to be well understood, it should be possible to perform theoretical calculations of pion interactions with this system and compare their predictions with the experimental results.
Pion correlations in relativistic heavy ion collisions at Heavy Ion Spectrometer Systems (HISS)
Christie, W.B. Jr.
1990-05-01
This thesis contains the setup, analysis and results of experiment E684H Multi-Pion Correlations in Relativistic Heavy Ion Collisions''. The goals of the original proposal were: (1) To initiate the use of the HISS facility in the study of central Relativistic Heavy Ion Collisions (RHIC). (2) To perform a second generation experiment for the detailed study of the pion source in RHIC. The first generation experiments, implied by the second goal above, refer to pion correlation studies which the Riverside group had performed at the LBL streamer chamber. The major advantage offered by moving the pion correlation studies to HISS is that, being an electronic detector system, as opposed to the Streamer Chamber which is a visual detector, one can greatly increase the statistics for a study of this sort. An additional advantage is that once one has written the necessary detector and physics analysis code to do a particular type of study, the study may be extended to investigate the systematics, with much less effort and in a relatively short time. This paper discusses the Physics motivation for this experiment, the experimental setup and detectors used, the pion correlation analysis, the results, and the conclusions possible future directions for pion studies at HISS. If one is not interested in all the details of the experiment, I believe that by reading the sections on intensity interferometry, the section the fitting of the correlation function and the systematic corrections applied, and the results section, one will get a fairly complete synopsis of the experiment.
Pion interference correlations in pion-nucleus collisions at 10. 5 GeV/c
Wong, R.
1983-01-01
Inclusive reactions of pion, Ne collisions at 10.5 GeV/c have been studied. The pion intensity interference effect has been observed in identical pion (..pi../sup +/, ..pi../sup -/, and ..pi../sup -/, ..pi../sup -/) as well as non-identical (..pi../sup +/, ..pi../sup -/) pion pair correlations. A momentum dependence is observed in the interference correlation function at small momentum differences. Previously only the identical pion interference correlations have been reported. In this thesis, the non-identical pion pair correlation is also studied. The momentum dependence is also new. For (..pi../sup -/,..pi../sup +/) and (..pi../sup -/,..pi../sup -/) pairs, the enhancement is due mostly to pions with mom/sup */>600 MeV/c. However for (..pi../sup +/, ..pi../sup +/) pairs, the peak is due primarily to pions with mom<200 MeV/c. Using the method of Kopylov and Podgoretsky the identical pion source region is determined to be 4.1 +/- 2.3 fermis. Also the influence on the final state correlations by the Bose statistics, Coulomb, and nuclear forces is observed. The possibility of using the (..pi../sup +/,..pi../sup -/) pion pair correlations to examine the pions produced in the quark-gluon perturbative vacuum of high-energy nucleus-nucleus collisions is suggested.
Pion in deep inelastic scattering
Povh, B.
2008-10-13
The forward neutron production in the ep collisions at 300 GeV measured by the H1 and ZEUS Collaborations at DESY has been used to estimate the total probability for the proton fluctuation into n{pi}{sup +} and p{pi}{sup 0}. The probability found is on the order of the 30%. This number is compared with the numbers of obtained for the probability of quark fluctuation into {pi}{sup +} from several alternative DIS processes (Gottfried sum rule, polarized structure function) and the axial-vector coupling constant, where the pion fluctuation is believed to play an important role.
Summary of the pion production sessions
Dytman, S. A.
2015-05-15
This is a short summary of the 10 talks given in the Pion Production Sessions at NUINT12. There were 2 very interesting themes that spanned talks - problems with data for single nucleons and pion absorption in the nuclear medium. In addition, a number of interesting new efforts were described.
Heavy ion pion production: spectral irregularities
Rasmussen, J.O.
1982-09-01
Data on ..pi../sup -//..pi../sup +/ ratios and on hills and valleys in spectra from heavy ion collisions are reviewed. Theoretical studies to handle Coulomb effects on pion spectra are examined. The possible role of strongly-bound pion orbitals of nuclear size is discussed.
Production of Pions in pA-collisions
NASA Technical Reports Server (NTRS)
Moskalenko, I. V.; Mashnik, S. G.
2003-01-01
Accurate knowledge of pion production cross section in PA-collisions is of interest for astrophysics, CR physics, and space radiation studies. Meanwhile, pion production in pA-reactions is often accounted for by simple scaling of that for pp-collisions, which is not enough for many real applications. We evaluate the quality of existing parameterizations using the data and simulations with the Los Alamos version of the Quark-Gluon String Model code LAQGSM and the improved Cascade-Exciton Model code CEM2k. The LAQGSM and CEM2k models have been shown to reproduce well nuclear reactions and hadronic data in the range 0.01-800 GeV/nucleon.
Study of the Two-pion Photoproduction on the Deuteron
Graham, Lewis P.
2012-12-01
Understanding the structure of baryons in terms of the fundamental interaction of the constituent quarks and gluons is one of the primary challenges in strong interaction physics. This interaction is governed by Quantum Chromodynamics (QCD), which is a theory for understanding the dynamics of strong. QCD displays the asymptotic freedom of hadrons at very short distances and also the confinement of quarks and gluons inside hadrons. However, solutions of this QCD theory in the non-perturbative domain of the interaction are extremely difficult to achieve, mainly because confinement happens on the hadronic scale on which the coupling constant is large and prevents any perturbative approach. Thus leaving us with strategies such as lattice QCD or formulating QCD sum rules to get around this problem. In exclusive hadron production the yN interaction is recognized for being a powerful method for investigating hadrons and the mysteries that still exist within the strong interaction. From reactions with the nucleon, the strong interaction can be investigated through the transition amplitudes to the N and Delta resonances. More specifically, if an electromagnetic interaction is well known then the intermediate resonance states may be evaluated through meson photoproduction. To gain more detailed insight into this interaction, we look to probe the baryon structure of the nucleon and the photo-excited resonance decays through photon scattering off a deuteron producing two pions in the final state. This photoproduction process off the deuteron will be used to investigate known baryon resonances in the two pion channel. The two pion final state will be investigated for unraveling new information into the photo-coupling strengths. We want to explore final state interactions, search for properties of known resonances, and to explore the possibility of seeing missing states that are predicted by quark models but have not yet been found experimentally. Using the CEBAF Large
Threshold pion production in proton-proton collisions at NNLO in chiral EFT
NASA Astrophysics Data System (ADS)
Baru, V.; Epelbaum, E.; Filin, A. A.; Hanhart, C.; Krebs, H.; Myhrer, F.
2016-05-01
The reaction NN → NN π offers a good testing ground for chiral effective field theory at intermediate energies. It challenges our understanding of the first inelastic channel in nucleon-nucleon scattering and of the charge symmetry breaking pattern in hadronic reactions. In our previous studies, we presented a complete calculation of the pion production operator for s -wave pions up-to-and-including next-to-next-to-leading order (NNLO) in the formulation of chiral effective field theory, which includes pions, nucleons and Δ(1232) degrees of freedom. In this paper we calculate the near-threshold cross section for the pp → d π+ reaction by performing the convolution of the obtained operators with nuclear wave functions based on modern phenomenological and chiral potentials. The available chiral NN wave functions are constructed with a cutoff comparable with the momentum transfer scale inherent in pion production reactions. Hence, a significant portion of the dynamical intermediate-range physics is thereby cut off by them. On the other hand, the NNLO amplitudes evaluated with phenomenological wave functions appear to be largely independent of the NN model used and give corrections to the dominant leading-order contributions as expected from dimensional analysis. The result gives support to the counting scheme used to classify the pion production operators, which is a precondition for a reliable investigation of the chirally suppressed neutral pion production. The explicit inclusion of the Δ(1232) is found to be important but smaller than expected due to cancellations.
CERBEROS: A tracking system for secondary pion beams at the HADES spectrometer
NASA Astrophysics Data System (ADS)
Wirth, J.; Fabbietti, L.; Lalik, R.; Maier, L.; Scordo, A.
2016-07-01
In 2014 the HADES collaboration performed two successful physics production runs with secondary pion beams. Since secondary pion beams are strongly defocussed in position and momentum, two fast tracking stations were installed along the pion beam chicane following the pion production target providing the momentum measurement of each individual pion. The momentum is reconstructed using the position information of every hit detected by the tracking stations and the beam optics transport calculation with a resolution below 0.5% playing an important role in terms of the exclusive analysis of investigated reactions. Both tracking stations consist of a double-sided silicon strip sensor with a large active area (10 × 10cm2). To guarantee fast tracking, the sensors are read out with the n-XYTER ASIC chip. Due to its self-triggering architecture and local storage capability, the chip enables on-line tracking at high rates (dN / dt >106 part / s). The TRB3 read out board on which the trigger logic is implemented integrates the system into the HADES DAQ. In this report we are showing the results obtained during the calibration experiment with a monochromatic proton beam set at seven different momenta centred around 2.68 GeV/c. Also the excellent performance achieved during the production campaign with a pion beam are presented.
Pion- and proton-nucleus interactions at intermediate energy
Dehnhard, D.
1992-02-01
{pi}-meson and proton beams from the Los Alamos Meson Physics Facility (LAMPF) and the Indiana University Cyclotron Facility (IUCF) were used in scattering and reaction experiments on atomic nuclei. The experimental data allow tests of models of the reaction mechanism and of nuclear structure. For example, the asymmetries observed in a pion scattering experiment on polarized {sup 13}C nuclei were found to contain unique information on the isoscalar spin density. However, further experiments on polarized nuclei of simpler structure are needed to provide the data for a thorough analysis of the reaction mechanism. For this reason a pion scattering experiment on a polarized {sup 3}He target is planned and a high-resolution study on {sup 6}Li({pi},{pi}{prime}) will be done. An analysis of {pi}-triton coincidence events from the {sup 4}He({pi},{pi}{prime}t)p reaction yielded evidence for direct triton knock-out from {sup 4}He. This work will be continued at higher incident pion energies. Additional work on the {sup 4}He(p,n) reaction at IUCF is planned to determine the isovector strength in mass-4 nuclei and the level parameters of {sup 4}Li.
Backward pion-nucleon scattering
F. Huang; Sibirtsev, Alex; Haidenbauer, Johann; Meissner, Ulf-G.
2010-02-01
A global analysis of the world data on differential cross sections and polarization asymmetries of backward pion-nucleon scattering for invariant collision energies above 3 GeV is performed in a Regge model. Including the $N_\\alpha$, $N_\\gamma$, $\\Delta_\\delta$ and $\\Delta_\\beta$ trajectories, we reproduce both angular distributions and polarization data for small values of the Mandelstam variable $u$, in contrast to previous analyses. The model amplitude is used to obtain evidence for baryon resonances with mass below 3 GeV. Our analysis suggests a $G_{39}$ resonance with a mass of 2.83 GeV as member of the $\\Delta_{\\beta}$ trajectory from the corresponding Chew-Frautschi plot.
Pions in and out of equilibrium
Gavin, S.
1991-12-01
Can final state scattering wrestle the secondaries in nucleus-nucleus collisions into a fluid state near local thermal equilibrium What do the pion p{sub T} spectra measured in pp, pA and SPS light ion experiments already tell us about the approach to equilibrium To begin to address these questions, we must face the nonequilibrium nature of hadronic evolution in the late stages of these collisions. I will outline efforts to apply transport theory to the nonequilibrium pion fluid at midrapidity focusing on two phenomena: partial thermalization and pion conservation.
Pions in and out of equilibrium
Gavin, S.
1991-12-01
Can final state scattering wrestle the secondaries in nucleus-nucleus collisions into a fluid state near local thermal equilibrium? What do the pion p{sub T} spectra measured in pp, pA and SPS light ion experiments already tell us about the approach to equilibrium? To begin to address these questions, we must face the nonequilibrium nature of hadronic evolution in the late stages of these collisions. I will outline efforts to apply transport theory to the nonequilibrium pion fluid at midrapidity focusing on two phenomena: partial thermalization and pion conservation.
Radiative pion capture by C12.
NASA Technical Reports Server (NTRS)
Lam, W. C.; Gotow, K.; Macdonald, B.; Trower, W. P.; Anderson, D. K.
1972-01-01
The energy spectrum of neutrons from radiative pion capture by carbon is investigated. Radiative pion capture is identified by coincidence of a stop signal and a signal from one of six lead-glass gamma detectors when negative pions traverse a beam telescope and are stopped in a carbon target. The energy of the neutrons is measured using the time interval between a stop signal coincident with a gamma-counter signal and a signal from a liquid-oscillator neutron counter. Asymmetry in the neutron-photon angular correlation increases with neutron energy and is accounted for by direct neutron emission.
Cross-Section Parameterizations for Pion and Nucleon Production From Negative Pion-Proton Collisions
NASA Technical Reports Server (NTRS)
Norbury, John W.; Blattnig, Steve R.; Norman, Ryan; Tripathi, R. K.
2002-01-01
Ranft has provided parameterizations of Lorentz invariant differential cross sections for pion and nucleon production in pion-proton collisions that are compared to some recent data. The Ranft parameterizations are then numerically integrated to form spectral and total cross sections. These numerical integrations are further parameterized to provide formula for spectral and total cross sections suitable for use in radiation transport codes. The reactions analyzed are for charged pions in the initial state and both charged and neutral pions in the final state.
PION PRODUCTION MODELS AND NEUTRINO FACTORIES
COLLOT,J.; KIRK,H.G.; MOKHOV,N.V.
2000-02-11
Scenarios for the building of muon colliders or storage rings suitable for the generation of robust neutrino beams call for the generation of a prodigious quantity of pions. These pions are then conducted into a decay channel where the resulting muon decay products can be collected for cooling and subsequent acceleration. Central to this concept is the design and construction of a target which will be highly efficient in producing pions of both signs while mitigating the absorption of these pions before they decay. This design effort is being facilitated by using two computer codes FLUKA and MARS. The authors present comparisons of the two computer codes and also present a comparison of these codes with available data.
Neutrino-induced coherent pion production
Alvarez-Ruso, L.; Geng, L. S.; Vacas, M. J. Vicente; Hirenzaki, S.; Leitner, T.; Mosel, U.
2007-12-21
We have investigated the neutrino induced coherent pion production reaction at the energies of interest for recent experiments like K2K and MiniBooNE. The model includes pion, nucleon and the {delta}(1232) resonance. Medium effects in the production mechanism and the distortion of the pion wave function are taken into account. We find a strong reduction of the cross section due to these effects and also substantial modifications in the energy distributions of the final pion. The sensitivity of the results on the axial N-{delta} coupling C{sub 5}{sup A}(0) and the coherent fraction in neutral-current {pi}{sup 0} production are discussed.
Pion valence-quark parton distribution function
NASA Astrophysics Data System (ADS)
Chang, Lei; Thomas, Anthony W.
2015-10-01
Within the Dyson-Schwinger equation formulation of QCD, a rainbow ladder truncation is used to calculate the pion valence-quark distribution function (PDF). The gap equation is renormalized at a typical hadronic scale, of order 0.5 GeV, which is also set as the default initial scale for the pion PDF. We implement a corrected leading-order expression for the PDF which ensures that the valence-quarks carry all of the pion's light-front momentum at the initial scale. The scaling behavior of the pion PDF at a typical partonic scale of order 5.2 GeV is found to be (1 - x) ν, with ν ≃ 1.6, as x approaches one.
Exclusive Reactions Involving Pions and Nucleons
NASA Technical Reports Server (NTRS)
Norbury, John W.; Blattnig, Steve R.; Tripathi, R. K.
2002-01-01
The HZETRN code requires inclusive cross sections as input. One of the methods used to calculate these cross sections requires knowledge of all exclusive processes contributing to the inclusive reaction. Conservation laws are used to determine all possible exclusive reactions involving strong interactions between pions and nucleons. Inclusive particle masses are subsequently determined and are needed in cross-section calculations for inclusive pion production.
Pion Cloud Contributions to the Proton Sea
NASA Astrophysics Data System (ADS)
Furukawa, Kayla; Aldahlawi, Feras; Merfeld, Kara
2012-10-01
A proton may split into a meson and a baryon as allowed by the Heisenberg uncertainty principle. This process and the possible meson-baryon combinations have been studied by several theoretical models. In this study, we investigate the proton and its constituents through the pion cloud model. The pion cloud model depends on the splitting function, fπB(y), which represents the probability of a proton splitting into a pion and a baryon, and the pion parton distribution function, qπ(z). The goal of our research is to examine the way the proton antiquark distributions depend on qπ(z) and the form factors and cutoffs of fπB(y). We have studied functional forms for the dbar and ubar quarks given by the Durham HepData Project, compared their difference and ratio to the E866 experimental data from FermiLab and have studied a simplified pion cloud model. For Henley and Miller's fπN(y) we show how different qπ(z) affect the proton antiquark distribution. We consider the pion parton distribution function of Sutton et al., as well as Aicher et al., and other forms of qπ(z).
Pion Production Data Needed for Space Radiation
NASA Technical Reports Server (NTRS)
Norbury, John W.
2010-01-01
A recent discovery concerning the importance of hadron production in space radiation is that pions can contribute up to twenty percent of the dose from galactic cosmic ray interactions (S. Aghara, S. Blattnig, J. Norbury, R. Singleterry, Nuclear Instruments and Methods, Vol. 267, 2009, p. 1115). Although the contribution for dose equivalent will be smaller, the dose contribution could be important for fluence based radiation models. Pion production cross sections will be an essential ingredient to such models, and it is of interest to investigate the adequacy of the pion production experimental data base for energies relevant to space radiation. The pion production threshold in nucleon - nucleon reactions is at 280 MeV and, in an interesting accident of nature, this lies near the peak of the galactic cosmic ray proton spectrum. Therefore, pion production data are needed from threshold up to energies around 50 GeV/nucleon, where the galactic cosmic ray fluence is of decreasing importance. Total and differential cross section data for pion production in this energy range will be reviewed. The availability and accuracy of theoretical models will also be discussed. It will be shown that there are a significant lack of data in this important energy range and that theoretical models still need improvement.
Two-Pion Correlations in Au+Au Collisions at 10.8GeV/{ital c} per Nucleon
David, G.; Ludlam, T.; McCorkle, S.; OBrien, E.; Woody, C.; Herrmann, N.; Cole, J.; Drigert, M.; Barrette, J.; Gilbert, S.; Lacasse, R.; Mark, S.; Rosati, M.; Wang, G.; Bersch, R.; Braun-Munzinger, P.; Chang, W.; Dee, J.; Hemmick, T.; Hong, B.; Jiang, C.; Johnson, S.; Kwon, Y.; Miskowiec, D.; Panitkin, S.; Piazza, T.; Pollack, M.; Rao, M.; Sedykh, S.; Stachel, J.; Trzaska, M.; Vongpaseuth, T.; Wessels, J.; Xu, N.; Zhang, Y.; Zou, C.; Cleland, W.; Sonnadara, U.; Voloshin, S.; Dietzsch, O.; daSilva, N.; Takagui, E.; Bellwied, R.; Bennett, S.; Cormier, T.; Hall, J.; Lukaszew, A.; Li, Q.; Matheus, R.; Pruneau, C.
1997-04-01
Two-particle correlation functions for positive and negative pions have been measured in Au+Au collisions at 10.8GeV/{ital c} per nucleon. The data were analyzed using one- and three-dimensional correlation functions. From the results of the three-dimensional fit the phase space density of pions was calculated. It is consistent with local thermal equilibrium. {copyright} {ital 1997} {ital The American Physical Society}
Pion and kaon valence-quark parton distribution functions
NASA Astrophysics Data System (ADS)
Nguyen, Trang; Bashir, Adnan; Roberts, Craig D.; Tandy, Peter C.
2011-06-01
A rainbow-ladder truncation of QCD’s Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to π-N Drell-Yan data for the pion’s u-quark distribution and to Drell-Yan data for the ratio uK(x)/uπ(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
Pion absorption in nuclei: The (. pi. /sup + -/,p) reactions
Mishra, C.S.
1987-05-01
Reported here is the first experiment to measure the excitation of discrete final states following the (..pi../sup -/,p) reaction. The Energetic Pion Channel and Spectrometer (EPICS) at the Los Alamos National Laboratory and the High Resolution Pion Channel and Spectrometer (..pi..M1-SUSI) at the Swiss Institute for Nuclear Physics were used for this high resolution study of (..pi../sup + -/,p) reactions. An average energy resolution of 500 KeV and 700 KeV was achieved at EPICS and ..pi..M1-SUSI respectively. At EPICS these reactions were measured at T/sub ..pi../ = 120 MeV and theta/sub lab/ = 25/sup 0/ on /sup 24/Mg, /sup 27/Al, /sup 40/Ca and /sup 58/Ni; /sup 12/C(..pi../sup -/,p) was measured at T/sub ..pi../ = 145 MeV. At ..pi..M1-SUSI these reactions were measured at T/sub ..pi../ = 90 MeV and at theta/sub lab/ = 20/sup 0/ on /sup 23/Na and /sup 24/Mg. The measurement includes both the differential cross sections and continuum up to an excitation energy of 40 MeV. In /sup 23/Na, /sup 24/Mg, and /sup 27/Al there are peaks in the low excitation region. The shape of the continuum in an excitation energy range of 10 to 40 MeV was found to be independent of pion charge and target mass. The magnitude of proton yield from all the targets at T/sub ..pi../ = 120 MeV is more than twenty four times larger for ..pi../sup +/ than for ..pi../sup -/. Also, the cross sections for both reactions on /sup 24/Mg is slightly enhanced compared to other nuclei. At T/sub ..pi../ = 90 MeV the ratio of the proton yield for ..pi../sup +/ to ..pi../sup -/ absorption drops down to fourteen. This high ratio and its energy dependence supports the idea of a two nucleon pion absorption model. Pion absorption in the context of both the reaction mechanism and nuclear structure is discussed. 99 refs., 64 figs., 11 tabs.
Scholberg, Kate
2006-02-01
Rates of coherent neutrino-nucleus elastic scattering at a high-intensity stopped-pion neutrino source in various detector materials (relevant for novel low-threshold detectors) are calculated. Sensitivity of a coherent neutrino-nucleus elastic scattering experiment to new physics is also explored.
Polarimetry with inclusive charged pions at U-70 accelerator of IHEP
NASA Astrophysics Data System (ADS)
Rykov, V. L.; Abramov, V. V.; Bogdanov, A. A.; Mochalov, V. V.; Nurushev, S. B.; Semenov, P. A.; Strikhanov, M. N.; Vasiliev, A. N.
2016-02-01
A feasibility of the proton beam polarimetry based on exploiting the observed large single-spin asymmetry AN in inclusive charged pion production is evaluated for the SPASCHARM experiment at IHEP, Protvino, Russia. It is shown that, for a few hours of beam exposition time, the beam polarization could be measured at the statistical errors of ∼3-5%. The inclusive pion polarimetry at SPASCHARM does not require construction of a special polarimeter. The polarimetry will be carried out entirely by the main SPASCHARM spectrometer simultaneously with physics data taking.
Diffractive Pion Dissociation into {pi}{sup -{pi}+{pi}-{pi}+{pi}-} at COMPASS
Neubert, S.
2010-08-05
At the COMPASS experiment a sample of {approx}380000 exclusive events of diffractive pion dissociation on a lead target into a {pi}{sup -{pi}+{pi}-{pi}+{pi}-} final state has been recorded in 2004. The 5{pi} invariant mass spectrum shows a momentum transfer dependent structure peaking around 1.8 GeV/c{sup 2}. In the (4{pi}){sup 0} subsystem there is a clear signal for the f{sub 1}(1285) resonance decaying into 4 pions. In this note we describe the data sample and explore the physics potential of this final state.
NASA Astrophysics Data System (ADS)
Guptaroy, P.; de, Bh.; Bhattacharyya, S.; Bhattacharyya, D. P.
The pion and kaon rapidity densities and the nature of kaon-pion ratios offer two very prominent and crucial physical observables on which modestly sufficient data for heavy nucleus collisions are available to date. In the light of two sets of models - one purely phenomenological and the other with a modest degree of a dynamical basis - we try to examine the state of agreement between calculations and experimental results obtainable from the past and the latest measurements. Impact and implications of all these would also finally be spelt out.
Two-pion-exchange potential and the {pi}{ital N} amplitude
Pena, M.T.; Gross, F.; Surya, Y.
1996-11-01
We discuss the two-pion-exchange (TPE) potential which emerges from a box diagram with one nucleon (the spectator) restricted to its mass shell, and the other nucleon line replaced by a subtracted, covariant {pi}{ital N} scattering amplitude which includes {Delta}, Roper, and {ital D}{sub 13} isobars, as well as contact terms and off-shell (nonpole) dressed nucleon terms. The {pi}{ital N} amplitude satisfies chiral symmetry constraints and fits {pi}{ital N} data below {approximately} 700 MeV pion energy. We find that this TPE potential can be well approximated by the exchange of an effective sigma and delta meson, with parameters close to the ones used in one-boson-exchange models that fit {ital NN} data below the pion production threshold. {copyright} {ital 1996 The American Physical Society.}
NASA Astrophysics Data System (ADS)
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
2016-06-01
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are ni,f ∼104-105. We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one can infer the decay width in more realistic magnetic fields of 1015 G, where ni,f ∼1012-1013, from the results for ni,f ∼104-105. The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed.
NASA Astrophysics Data System (ADS)
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
2016-06-01
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are ni,f ∼104-105. We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one can infer the decay width in more realistic magnetic fields of 1015 G, where ni,f ∼1012-1013, from the results for ni,f ∼104-105. The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed.
Measurement of the charged-pion polarizability.
Adolph, C; Akhunzyanov, R; Alexeev, M G; Alexeev, G D; Amoroso, A; Andrieux, V; Anosov, V; Austregesilo, A; Badełek, B; Balestra, F; Barth, J; Baum, G; Beck, R; Bedfer, Y; Berlin, A; Bernhard, J; Bicker, K; Bieling, J; Birsa, R; Bisplinghoff, J; Bodlak, M; Boer, M; Bordalo, P; Bradamante, F; Braun, C; Bressan, A; Büchele, M; Burtin, E; Capozza, L; Chiosso, M; Chung, S U; Cicuttin, A; Colantoni, M; Crespo, M L; Curiel, Q; Dalla Torre, S; Dasgupta, S S; Dasgupta, S; Denisov, O Yu; Dinkelbach, A M; Donskov, S V; Doshita, N; Duic, V; Dünnweber, W; Dziewiecki, M; Efremov, A; Elia, C; Eversheim, P D; Eyrich, W; Faessler, M; Ferrero, A; Filin, A; Finger, M; Finger, M; Fischer, H; Franco, C; du Fresne von Hohenesche, N; Friedrich, J M; Frolov, V; Gautheron, F; Gavrichtchouk, O P; Gerassimov, S; Geyer, R; Gnesi, I; Gobbo, B; Goertz, S; Gorzellik, M; Grabmüller, S; Grasso, A; Grube, B; Grussenmeyer, T; Guskov, A; Guthörl, T; Haas, F; von Harrach, D; Hahne, D; Hashimoto, R; Heinsius, F H; Herrmann, F; Hinterberger, F; Höppner, Ch; Horikawa, N; d'Hose, N; Huber, S; Ishimoto, S; Ivanov, A; Ivanshin, Yu; Iwata, T; Jahn, R; Jary, V; Jasinski, P; Jörg, P; Joosten, R; Kabuss, E; Ketzer, B; Khaustov, G V; Khokhlov, Yu A; Kisselev, Yu; Klein, F; Klimaszewski, K; Koivuniemi, J H; Kolosov, V N; Kondo, K; Königsmann, K; Konorov, I; Konstantinov, V F; Kotzinian, A M; Kouznetsov, O; Krämer, M; Kroumchtein, Z V; Kuchinski, N; Kuhn, R; Kunne, F; Kurek, K; Kurjata, R P; Lednev, A A; Lehmann, A; Levillain, M; Levorato, S; Lichtenstadt, J; Maggiora, A; Magnon, A; Makke, N; Mallot, G K; Marchand, C; Martin, A; Marzec, J; Matousek, J; Matsuda, H; Matsuda, T; Meshcheryakov, G; Meyer, W; Michigami, T; Mikhailov, Yu V; Miyachi, Y; Moinester, M A; Nagaytsev, A; Nagel, T; Nerling, F; Neubert, S; Neyret, D; Nikolaenko, V I; Novy, J; Nowak, W-D; Nunes, A S; Olshevsky, A G; Orlov, I; Ostrick, M; Panknin, R; Panzieri, D; Parsamyan, B; Paul, S; Peshekhonov, D; Platchkov, S; Pochodzalla, J; Polyakov, V A; Pretz, J; Quaresma, M; Quintans, C; Ramos, S; Regali, C; Reicherz, G; Rocco, E; Rossiyskaya, N S; Ryabchikov, D I; Rychter, A; Samoylenko, V D; Sandacz, A; Sarkar, S; Savin, I A; Sbrizzai, G; Schiavon, P; Schill, C; Schlüter, T; Schmidt, K; Schmieden, H; Schönning, K; Schopferer, S; Schott, M; Shevchenko, O Yu; Silva, L; Sinha, L; Sirtl, S; Slunecka, M; Sosio, S; Sozzi, F; Srnka, A; Steiger, L; Stolarski, M; Sulc, M; Sulej, R; Suzuki, H; Szabelski, A; Szameitat, T; Sznajder, P; Takekawa, S; ter Wolbeek, J; Tessaro, S; Tessarotto, F; Thibaud, F; Uhl, S; Uman, I; Virius, M; Wang, L; Weisrock, T; Wilfert, M; Windmolders, R; Wollny, H; Zaremba, K; Zavertyaev, M; Zemlyanichkina, E; Ziembicki, M; Zink, A
2015-02-13
The COMPASS collaboration at CERN has investigated pion Compton scattering, π(-)γ→π(-)γ, at center-of-mass energy below 3.5 pion masses. The process is embedded in the reaction π(-)Ni→π(-)γNi, which is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, Q(2)<0.0015 (GeV/c)(2). From a sample of 63,000 events, the pion electric polarizability is determined to be α(π)=(2.0±0.6(stat)±0.7(syst))×10(-4) fm(3) under the assumption α(π)=-β(π), which relates the electric and magnetic dipole polarizabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambiguously known, was performed for an independent estimate of the systematic uncertainty. PMID:25723208
Measurement of the Charged-Pion Polarizability
NASA Astrophysics Data System (ADS)
Adolph, C.; Akhunzyanov, R.; Alexeev, M. G.; Alexeev, G. D.; Amoroso, A.; Andrieux, V.; Anosov, V.; Austregesilo, A.; Badełek, B.; Balestra, F.; Barth, J.; Baum, G.; Beck, R.; Bedfer, Y.; Berlin, A.; Bernhard, J.; Bicker, K.; Bieling, J.; Birsa, R.; Bisplinghoff, J.; Bodlak, M.; Boer, M.; Bordalo, P.; Bradamante, F.; Braun, C.; Bressan, A.; Büchele, M.; Burtin, E.; Capozza, L.; Chiosso, M.; Chung, S. U.; Cicuttin, A.; Colantoni, M.; Crespo, M. L.; Curiel, Q.; Dalla Torre, S.; Dasgupta, S. S.; Dasgupta, S.; Denisov, O. Yu.; Dinkelbach, A. M.; Donskov, S. V.; Doshita, N.; Duic, V.; Dünnweber, W.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P. D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Filin, A.; Finger, M.; Finger, M.; Fischer, H.; Franco, C.; Du Fresne von Hohenesche, N.; Friedrich, J. M.; Frolov, V.; Gautheron, F.; Gavrichtchouk, O. P.; Gerassimov, S.; Geyer, R.; Gnesi, I.; Gobbo, B.; Goertz, S.; Gorzellik, M.; Grabmüller, S.; Grasso, A.; Grube, B.; Grussenmeyer, T.; Guskov, A.; Guthörl, T.; Haas, F.; von Harrach, D.; Hahne, D.; Hashimoto, R.; Heinsius, F. H.; Herrmann, F.; Hinterberger, F.; Höppner, Ch.; Horikawa, N.; D'Hose, N.; Huber, S.; Ishimoto, S.; Ivanov, A.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jasinski, P.; Jörg, P.; Joosten, R.; Kabuß, E.; Ketzer, B.; Khaustov, G. V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koivuniemi, J. H.; Kolosov, V. N.; Kondo, K.; Königsmann, K.; Konorov, I.; Konstantinov, V. F.; Kotzinian, A. M.; Kouznetsov, O.; Krämer, M.; Kroumchtein, Z. V.; Kuchinski, N.; Kuhn, R.; Kunne, F.; Kurek, K.; Kurjata, R. P.; Lednev, A. A.; Lehmann, A.; Levillain, M.; Levorato, S.; Lichtenstadt, J.; Maggiora, A.; Magnon, A.; Makke, N.; Mallot, G. K.; Marchand, C.; Martin, A.; Marzec, J.; Matousek, J.; Matsuda, H.; Matsuda, T.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu. V.; Miyachi, Y.; Moinester, M. A.; Nagaytsev, A.; Nagel, T.; Nerling, F.; Neubert, S.; Neyret, D.; Nikolaenko, V. I.; Novy, J.; Nowak, W.-D.; Nunes, A. S.; Olshevsky, A. G.; Orlov, I.; Ostrick, M.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Peshekhonov, D.; Platchkov, S.; Pochodzalla, J.; Polyakov, V. A.; Pretz, J.; Quaresma, M.; Quintans, C.; Ramos, S.; Regali, C.; Reicherz, G.; Rocco, E.; Rossiyskaya, N. S.; Ryabchikov, D. I.; Rychter, A.; Samoylenko, V. D.; Sandacz, A.; Sarkar, S.; Savin, I. A.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schlüter, T.; Schmidt, K.; Schmieden, H.; Schönning, K.; Schopferer, S.; Schott, M.; Shevchenko, O. Yu.; Silva, L.; Sinha, L.; Sirtl, S.; Slunecka, M.; Sosio, S.; Sozzi, F.; Srnka, A.; Steiger, L.; Stolarski, M.; Sulc, M.; Sulej, R.; Suzuki, H.; Szabelski, A.; Szameitat, T.; Sznajder, P.; Takekawa, S.; Ter Wolbeek, J.; Tessaro, S.; Tessarotto, F.; Thibaud, F.; Uhl, S.; Uman, I.; Virius, M.; Wang, L.; Weisrock, T.; Wilfert, M.; Windmolders, R.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zink, A.; Compass Collaboration
2015-02-01
The COMPASS collaboration at CERN has investigated pion Compton scattering, π-γ →π-γ , at center-of-mass energy below 3.5 pion masses. The process is embedded in the reaction π-Ni →π-γ Ni , which is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, Q2<0.0015 (GeV /c )2 . From a sample of 63 000 events, the pion electric polarizability is determined to be απ=(2.0 ±0. 6stat±0. 7syst)×1 0-4 fm3 under the assumption απ=-βπ, which relates the electric and magnetic dipole polarizabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambiguously known, was performed for an independent estimate of the systematic uncertainty.
Investigation of pion-nucleus interactions. Progress report, April 1, 1991--March 31, 1992
Moore, C.F.
1992-09-01
This report summarizes the work carried out by personnel from the University of Texas at Austin at the Los Alamos Clinton P. Anderson Meson Physics Facility (LAMPF). The research activities involved experiments done with the Energetic Pion Channel and Spectrometer (EPICS), the Low Energy Pion Channel (LEP), the Pion and Particle Physics Channel (P{sup 3}), the High Resolution Spectrometer (HRS), and planning a new experimental program associated with the new high-resolution Neutral Meson Spectrometer (NMS) at LAMPF. A brief overview of work supported by this grant is given followed by an account of the study of the double giant resonances in pion double charge exchange on {sup 51}V, {sup 115}In, and {sup 197}Au. This report contains a list of published papers and preprints, abstracts, and invited talks. These papers summarize experiments involving participants supported by this grant and indicate the work accomplished by these participants in this program of medium energy nuclear physics research. Lists of the most recent proposals on which we have participation at LAMPF, proposals which have been approved this past year to run as experiments, personnel who have participated in this research program are included. The research cited in this report is, in many cases, the collaborative effort of many groups associated with research at LAMPF.
NASA Astrophysics Data System (ADS)
Wilson, P.; Williams, A.; Nagasawa, H.; Peng, Y.; Chatterjee, A.; Bedford, J.
To determine whether shielding materials that might be utilized for radiation protection of astronauts would affect the RBE of HZE particles such as those of concern for deep space missions we irradiated non cycling G0 monolayer cultures of contact inhibited normal human fibroblasts with 1 Gev amu iron ions with and without filtration with various thicknesses of Aluminum Al or polyethylene CH 2 and then measured the frequencies of chromosome-type aberrations dicentrics and excess fragments in the first post-irradiation mitosis Irradiations were carried out at the NRSL facility at Brookhaven National Laboratory For doses ranging up to 4 to 6 Gy the dose response for the total of these aberrations per cell was not significantly affected by beam filtrations up to 5 4 cm Al or up to 11 cm polyethylene relative to the unfiltered beam Neither was the dose response significantly different for unfiltered beams of 300 or 600 Mev amu iron ions relative to the 1 Gev amu iron ions The studies with 1 Gev amu iron ions were repeated four different times over a period of four years in each case with coded samples so the individual scoring aberrations would not know the irradiation conditions employed Comparison of the same effects in parallel experiments using 137 Cs gamma-rays allowed us to estimate that the RBE for aberration induction by these HZE iron ions for these acute high dose-rate exposures was approximately
Pion form factor from a contact interaction
Gutierrez-Guerrero, L. X.; Bashir, A.; Cloeet, I. C.; Roberts, C. D.
2010-06-15
In a Poincare-covariant vector-boson-exchange theory, the pion possesses components of pseudovector origin, which materially influence its observable properties. For a range of such quantities, we explore the consequences of a momentum-independent interaction, regularized in a symmetry-preserving manner. The contact interaction, while capable of describing pion static properties, produces a form factor whose evolution for Q{sup 2}>0.17 GeV{sup 2} disagrees markedly with experiment and whose asymptotic power-law behavior conflicts strongly with perturbative QCD.
Pion form factor from a contact interaction.
Gutierrez-Guerrero, L. X.; Bashir, A.; Cloet, I. C.; Roberts, C. D.
2010-01-01
In a Poincare-covariant vector-boson-exchange theory, the pion possesses components of pseudovector origin, which materially influence its observable properties. For a range of such quantities, we explore the consequences of a momentum-independent interaction, regularized in a symmetry-preserving manner. The contact interaction, while capable of describing pion static properties, produces a form factor whose evolution for Q{sup 2} > 0.17 GeV{sup 2} disagrees markedly with experiment and whose asymptotic power-law behavior conflicts strongly with perturbative QCD.
Beam dynamics design of a pion linac
Nath, S; Swain, G.; Garnett, R.; Wangler, T.P.
1990-01-01
We have conducted a study of a superconducting linac to accelerate pions produced at LAMPF from 400 or 500 MeV to 925 MeV kinetic energy. For such a linac, it is necessary to keep the machine as short as practical in order to minimize the loss of beam due to particle decay, and to tailor the beam to achieve the maximum flux within the desired momentum bite at the exit. The interplay of these and other considerations with the transverse and longitudinal beam dynamics is discussed, and is illustrated with the simulated performance of reference pion-linac designs.
Low energy pion-pion elastic scattering in the Sakai-Sugimoto model
Parthasarathy, R.; Viswanathan, K. S.
2008-06-01
We have considered the holographic large N{sub c} QCD model proposed by Sakai and Sugimoto and evaluated the non-Abelian DBI-action on the D8-brane up to ({alpha}{sup '}){sup 4} terms. Restricting to the pion sector, these corrections give rise to four derivative contact terms for the pion field. We derive the Weinberg's phenemenological Lagrangian. The coefficients of the four derivative terms are determined in terms of g{sub YM}{sup 2}. The low energy pion-pion scattering amplitudes are evaluated. Numerical results are presented with the choice of M{sub KK}=0.94 GeV and N{sub c}=11. The results are compared with the amplitudes calculated using the experimental phase shifts. The agreement with the experimental data is found to be satisfactory.
Experimental studies of nucleon-nucleon and pion-nucleus interactions at intermediate energies
Not Available
1990-10-01
This report summarizes the work on experimental research in intermediate energy nuclear and particle physics carried out by New Mexico State University in 1988--91. Most of these studies have involved investigations of neutron-proton and pion-nucleus interactions. The neutron-proton research is part of a program of studies of interactions between polarized nucleons that we have been involved with for more than ten years. Its purpose has been to help complete the determination of the full set of ten complex nucleon-nucleon amplitudes at energies up to 800 MeV, as well as to continue investigating the possibility of the existence of dibaryon resonances. The give complex isospin-one amplitudes have been fairly well determined, partly as a result of this work. Our work in this period has involved measurements and analysis of data on elastic scattering and total cross sections for polarized neutrons on polarized protons. The pion-nucleus research continues our studies of this interaction in regions where it has not been well explored. One set of experiments includes studies of pion elastic and double-charge-exchange scattering at energies between 300 and 550 MeV, where our data is unique. Another involves elastic and single-charge-exchange scattering of pions from polarized nuclear targets, a new field of research which will give the first extensive set of information on spin-dependent pion-nucleus amplitudes. Still another involves the first set of detailed studies of the kinematic correlations among particles emitted following pion absorption in nuclei.
Parameterizations of Pion Energy Spectrum in Nucleon-Nucleon Collisions
NASA Technical Reports Server (NTRS)
Cucinotta, Franics A.; Wilson, John W.; Norbury, John W.
1998-01-01
The effects of pion (PI) production are expected to play an important role in radiation exposures in the upper atmosphere or on the Martian surface. Nuclear databases for describing pion production are developed for radiation transport codes to support these studies. We analyze the secondary energy spectrum of pions produced in nucleon-nucleon (NN) collisions in the relativistic one-pion exchange model. Parametric formulas of the isospin cross sections for one-pion production channels are discussed and are used to renormalize the model spectrum. Energy spectra for the deuteron related channels (NN yields dPi) are also described.
Quark-Hadron Duality for the Pion: a Phenomenological Study
Wally Melnitchouk
2002-08-01
We explore the relationship between exclusive and inclusive electromagnetic scattering from the pion, focusing on the transition region at intermediate Q{sup 2}. Combining Drell-Yan data on the leading twist quark distribution in the pion with a model for the resonance region at large x, we calculate QCD moments of the pion structure function over a range of Q{sup 2}, and quantify the role of higher twist corrections. Using a parameterization of the pion elastic form factor and phenomenological models for the pi --> p transition form factor, we test the extent to which local duality may be valid for the pion.
The Pion cloud: Insights into hadron structure
A.W. Thomas
2007-11-01
Modern nuclear theory presents a fascinating study in contrasting approaches to the structure of hadrons and nuclei. Nowhere is this more apparent than in the treatment of the pion cloud. As this discussion really begins with Yukawa, it is entirely appropriate that this invited lecture at the Yukawa Institute in Kyoto should deal with the issue.
High Purity Pion Beam at TRIUMF
Kettell, S.; Kettell, S.; Aguilar-Arevalo, A.; Blecher, M.; Bryman, D.A.; Comfort, J.; Doornbos, J.; Doria, L.; Hussein, A.; Ito, N.; et al.
2009-10-11
An extension of the TRIUMF M13 low-energy pion channel designed to suppress positrons based on an energy-loss technique is described. A source of beam channel momentum calibration from the decay {pi}{sup +} {yields} e{sup +}{nu} is also described.
Probing neutron-proton dynamics by pions
NASA Astrophysics Data System (ADS)
Ikeno, Natsumi; Ono, Akira; Nara, Yasushi; Ohnishi, Akira
2016-04-01
In order to investigate the nuclear symmetry energy at high density, we study the pion production in central collisions of neutron-rich nuclei 132Sn+124Sn at 300 MeV/nucleon using a new approach that combines antisymmetrized molecular dynamics (AMD) and a hadronic cascade model (JAM). The dynamics of neutrons and protons is solved by AMD, and then pions and Δ resonances in the reaction process are handled by JAM. We see the mechanism by which the Δ resonance and pions are produced, reflecting the dynamics of neutrons and protons. We also investigate the impacts of cluster correlations as well as of the high-density symmetry energy on the nucleon dynamics and consequently on the pion ratio. We find that the Δ-/Δ++ production ratio agrees very well with the neutron-proton squared ratio (N/Z ) 2 in the high-density and high-momentum region. We show quantitatively that the Δ production ratio, and therefore (N/Z ) 2, are directly reflected in the π-/π+ ratio, with modification in the final stage of the reaction.
Pion double charge exchange and hadron dynamics
Johnson, M.B.
1991-01-01
This paper will review theoretical results to show how pion double charge exchange is contributing to our understanding of hadron dynamics in nuclei. The exploitation of the nucleus as a filter is shown to be essential in facilitating the comparison between theory and experiment. 23 refs., 3 figs., 2 tabs.
Low energy scattering with a nontrivial pion
Fariborz, Amir H.
2007-12-01
An earlier calculation in a generalized linear sigma model showed that the well-known current algebra formula for low energy pion-pion scattering held even though the massless Nambu Goldstone pion contained a small admixture of a two-quark two-antiquark field. Here we turn on the pion mass and note that the current algebra formula no longer holds exactly. We discuss this small deviation and also study the effects of a SU(3) symmetric quark mass type term on the masses and mixings of the eight SU(3) multiplets in the model. We calculate the s-wave scattering lengths, including the beyond current algebra theorem corrections due to the scalar mesons, and observe that the effect of the scalar mesons is to improve the agreement with experiment. In the process, we uncover the way in which linear sigma models give controlled corrections (due to the presence of scalar mesons) to the current algebra scattering formula. Such a feature is commonly thought to exist only in the nonlinear sigma model approach.
Abelian anomaly and neutral pion production
Roberts, H. L. L.; Roberts, C. D.; Bashir, A.; Gutierrez-Guerrero, L. X.; Tandy, P. C.
2010-12-15
We show that in fully self-consistent treatments of the pion, namely, its static properties and elastic and transition form factors, the asymptotic limit of the product Q{sup 2}G{sub {gamma}}{sup *}{sub {gamma}{pi}}{sup 0}(Q{sup 2}), determined a priori by the interaction employed, is not exceeded at any finite value of spacelike momentum transfer. Furthermore, in such a treatment of a vector-vector contact-interaction one obtains a {gamma}{sup *{gamma}{yields}{pi}0} transition form factor that disagrees markedly with all available data. We explain that the contact interaction produces a pion distribution amplitude that is flat and nonvanishing at the endpoints. This amplitude characterizes a pointlike pion bound state. Such a state has the hardest possible form factors (i.e., form factors that become constant at large momentum transfers and hence are in striking disagreement with completed experiments). However, interactions with QCD-like behavior produce soft pions, a valence-quark distribution amplitude that vanishes as {approx}(1-x){sup 2} for x{approx}1, and results that agree with the bulk of existing data. Our analysis supports a view that the large-Q{sup 2} data obtained by the BaBar Collaboration is not an accurate measure of the {gamma}*{gamma}{yields}{pi}{sup 0} form factor.
Benchmark Analysis of Pion Contribution from Galactic Cosmic Rays
NASA Technical Reports Server (NTRS)
Aghara, Sukesh K.; Blattnig, Steve R.; Norbury, John W.; Singleterry, Robert C., Jr.
2008-01-01
Shielding strategies for extended stays in space must include a comprehensive resolution of the secondary radiation environment inside the spacecraft induced by the primary, external radiation. The distribution of absorbed dose and dose equivalent is a function of the type, energy and population of these secondary products. A systematic verification and validation effort is underway for HZETRN, which is a space radiation transport code currently used by NASA. It performs neutron, proton and heavy ion transport explicitly, but it does not take into account the production and transport of mesons, photons and leptons. The question naturally arises as to what is the contribution of these particles to space radiation. The pion has a production kinetic energy threshold of about 280 MeV. The Galactic cosmic ray (GCR) spectra, coincidentally, reaches flux maxima in the hundreds of MeV range, corresponding to the pion production threshold. We present results from the Monte Carlo code MCNPX, showing the effect of lepton and meson physics when produced and transported explicitly in a GCR environment.
Do Pions Pull or Push the Nucleons Apart?
NASA Astrophysics Data System (ADS)
Goradia, Shantilal
2004-10-01
My derivation of the strong force coupling constant, a conventional calculation, my optical probing, direction of string theory, some observations, Einstein's view and more [1], [2] give compelling reasons for the existence of strong gravity, raising a question about the Nature's purpose of pions. Could pions be pushing the nucleons apart to stop gravitational collapse of the nucleus? Its observed range limited to the size of nuclei is logically consistent with this possibility. Since the spin-dependent nuclear force could be negative or positive, its tiny long-range effects can add an indistinguishable negative component to gravitation. Repulsive gravity in expanding universe implies negative gravity at cosmic scale too. Since graviton is based on positive gravity, a second question rises if photons, theorized to mediate both, positive and negative forces, could be the particles mediating gravity. These questions lie at the heart of our understanding of other important issues. References: [1] Gravity and Nuclear Forces: A Potential Link, arXiv.org/pdf/physics/0210040 by Shantilal G. Goradia [2] http://www.gravityresearchinstitute.org
Biomedical program leading to therapeutic trials on pion radiation at Los Alamos.
Kligerman, M M; Knapp, E A; Petersen, D F
1975-11-01
Hypoxia and variations in cell cycle phase protect tumor cells being treated with x rays or gamma rays (cobalt). Heavy particles can overcome these protective effects, because of the dense ionization they deposit in tissues. Pions (negative pi mesons) can be directed to and stopped in a specific area, where they are captured by the nuclei of atoms, rendering the nuclei unstable. The nuclei disintegrate, releasing densely ionizing radiation. By confining the dense ionization to the tumor-bearing volume, pions have the potential of increasing the tolerance of the area under treatment to radiation, thus increasing the probability of destroying the tumor. A special channel at the proton factory at the Los Alamos Scientific Laboratory is producing pions for biomedical research. Considerable physical dosimetry has been completed. Cellular studies are underway to provide depth-dose-biological-effect curves. Animal studies will provide information on acute and late effects, which will permit the safe application of pions to a series of anatomical sites established by protocols for radiotherapy clinical trials. PMID:1192358
Low-energy pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Gibbs, W. R.; Ai, Li; Kaufmann, W. B.
1998-02-01
An analysis of low-energy charged pion-nucleon data from recent π+/-p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f2=0.0756+/-0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P31 and P13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided.
Pion and kaon freezeout in NA44
NA44 Collaboration
1994-12-01
The NA44 spectrometer is optimized for the study of single and two-particle particle spectra near mid-rapidity for transverse momenta below {approx} 1 GeV/c. A large fraction of all pairs in the spectrometer`s acceptance are at low relative momenta, resulting in small statistical uncertainties on the extracted size parameters. In addition, the spectrometer`s clean particle identification allows the authors to measure correlation functions for pions, kaons, and protons. This contribution will concentrate on the source size parameters determined from pion and kaon correlation functions. These size parameters will be compared to calculations from the RQMD event generator and also interpreted in the context of a hydrodynamic model. Finally, the measured single particle spectra will be examined from the viewpoint of hydrodynamics.
Entanglement of Quasielastic Scattering and Pion Production
Mosel, Ulrich; Lalakulich, Olga; Leitner, Tina
2011-11-23
The extraction of neutrino oscillation parameters requires the determination of the neutrino energy from observations of the hadronic final state. Here we discuss the difficulties connected with this energy reconstruction for the ongoing experiments MiniBooNE and T2K. We point out that a lower limit to the uncertainty in the reconstructed energy from Fermi motion alone amounts to about 15%. The entanglement of very different elementary processes, in this case quasielastic scattering and pion production, in the actual observables leads to considerably larger errors. We discuss the sensitivity of the energy reconstruction to detection techniques and experimental acceptances. We also calculate the misidentification cross section for electron appearance in the T2K experiment due to neutral pion production.
Pion contamination in the MICE muon beam
NASA Astrophysics Data System (ADS)
Adams, D.; Alekou, A.; Apollonio, M.; Asfandiyarov, R.; Barber, G.; Barclay, P.; de Bari, A.; Bayes, R.; Bayliss, V.; Bertoni, R.; Blackmore, V. J.; Blondel, A.; Blot, S.; Bogomilov, M.; Bonesini, M.; Booth, C. N.; Bowring, D.; Boyd, S.; Brashaw, T. W.; Bravar, U.; Bross, A. D.; Capponi, M.; Carlisle, T.; Cecchet, G.; Charnley, C.; Chignoli, F.; Cline, D.; Cobb, J. H.; Colling, G.; Collomb, N.; Coney, L.; Cooke, P.; Courthold, M.; Cremaldi, L. M.; DeMello, A.; Dick, A.; Dobbs, A.; Dornan, P.; Drews, M.; Drielsma, F.; Filthaut, F.; Fitzpatrick, T.; Franchini, P.; Francis, V.; Fry, L.; Gallagher, A.; Gamet, R.; Gardener, R.; Gourlay, S.; Grant, A.; Greis, J. R.; Griffiths, S.; Hanlet, P.; Hansen, O. M.; Hanson, G. G.; Hart, T. L.; Hartnett, T.; Hayler, T.; Heidt, C.; Hills, M.; Hodgson, P.; Hunt, C.; Iaciofano, A.; Ishimoto, S.; Kafka, G.; Kaplan, D. M.; Karadzhov, Y.; Kim, Y. K.; Kuno, Y.; Kyberd, P.; Lagrange, J.-B.; Langlands, J.; Lau, W.; Leonova, M.; Li, D.; Lintern, A.; Littlefield, M.; Long, K.; Luo, T.; Macwaters, C.; Martlew, B.; Martyniak, J.; Mazza, R.; Middleton, S.; Moretti, A.; Moss, A.; Muir, A.; Mullacrane, I.; Nebrensky, J. J.; Neuffer, D.; Nichols, A.; Nicholson, R.; Nugent, J. C.; Oates, A.; Onel, Y.; Orestano, D.; Overton, E.; Owens, P.; Palladino, V.; Pasternak, J.; Pastore, F.; Pidcott, C.; Popovic, M.; Preece, R.; Prestemon, S.; Rajaram, D.; Ramberger, S.; Rayner, M. A.; Ricciardi, S.; Roberts, T. J.; Robinson, M.; Rogers, C.; Ronald, K.; Rubinov, P.; Rucinski, P.; Sakamato, H.; Sanders, D. A.; Santos, E.; Savidge, T.; Smith, P. J.; Snopok, P.; Soler, F. J. P.; Speirs, D.; Stanley, T.; Stokes, G.; Summers, D. J.; Tarrant, J.; Taylor, I.; Tortora, L.; Torun, Y.; Tsenov, R.; Tunnell, C. D.; Uchida, M. A.; Vankova-Kirilova, G.; Virostek, S.; Vretenar, M.; Warburton, P.; Watson, S.; White, C.; Whyte, C. G.; Wilson, A.; Winter, M.; Yang, X.; Young, A.; Zisman, M.
2016-03-01
The international Muon Ionization Cooling Experiment (MICE) will perform a systematic investigation of ionization cooling with muon beams of momentum between 140 and 240 MeV/c at the Rutherford Appleton Laboratory ISIS facility. The measurement of ionization cooling in MICE relies on the selection of a pure sample of muons that traverse the experiment. To make this selection, the MICE Muon Beam is designed to deliver a beam of muons with less than ~1% contamination. To make the final muon selection, MICE employs a particle-identification (PID) system upstream and downstream of the cooling cell. The PID system includes time-of-flight hodoscopes, threshold-Cherenkov counters and calorimetry. The upper limit for the pion contamination measured in this paper is fπ < 1.4% at 90% C.L., including systematic uncertainties. Therefore, the MICE Muon Beam is able to meet the stringent pion-contamination requirements of the study of ionization cooling.
Two Photon Exchange for Exclusive Pion Electroproduction
Afanaciev, Andrei V.; Aleksejevs, Aleksandrs G.; Barkanova, Svetlana G.
2013-09-01
We perform detailed calculations of two-photon-exchange QED corrections to the cross section of pion electroproduction. The results are obtained with and without the soft-photon approximation; analytic expressions for the radiative corrections are derived. The relative importance of the two-photon correction is analyzed for the kinematics of several experiments at Jefferson Lab. A significant, over 20%, effect due to two-photon exchange is predicted for the backward angles of electron scattering at large transferred momenta.
Modeling the Pion Generalized Parton Distribution
NASA Astrophysics Data System (ADS)
Mezrag, C.
2016-02-01
We compute the pion Generalized Parton Distribution (GPD) in a valence dressed quarks approach. We model the Mellin moments of the GPD using Ansätze for Green functions inspired by the numerical solutions of the Dyson-Schwinger Equations (DSE) and the Bethe-Salpeter Equation (BSE). Then, the GPD is reconstructed from its Mellin moment using the Double Distribution (DD) formalism. The agreement with available experimental data is very good.
Parameterized Cross Sections for Pion Production in Proton-Proton Collisions
NASA Technical Reports Server (NTRS)
Blattnig, Steve R.; Swaminathan, Sudha R.; Kruger, Adam T.; Ngom, Moussa; Norbury, John W.; Tripathi, R. K.
2000-01-01
An accurate knowledge of cross sections for pion production in proton-proton collisions finds wide application in particle physics, astrophysics, cosmic ray physics, and space radiation problems, especially in situations where an incident proton is transported through some medium and knowledge of the output particle spectrum is required when given the input spectrum. In these cases, accurate parameterizations of the cross sections are desired. In this paper much of the experimental data are reviewed and compared with a wide variety of different cross section parameterizations. Therefore, parameterizations of neutral and charged pion cross sections are provided that give a very accurate description of the experimental data. Lorentz invariant differential cross sections, spectral distributions, and total cross section parameterizations are presented.
Covariant density functional theory: The role of the pion
Lalazissis, G. A.; Karatzikos, S.; Serra, M.; Otsuka, T.; Ring, P.
2009-10-15
We investigate the role of the pion in covariant density functional theory. Starting from conventional relativistic mean field (RMF) theory with a nonlinear coupling of the {sigma} meson and without exchange terms we add pions with a pseudovector coupling to the nucleons in relativistic Hartree-Fock approximation. In order to take into account the change of the pion field in the nuclear medium the effective coupling constant of the pion is treated as a free parameter. It is found that the inclusion of the pion to this sort of density functionals does not destroy the overall description of the bulk properties by RMF. On the other hand, the noncentral contribution of the pion (tensor coupling) does have effects on single particle energies and on binding energies of certain nuclei.
Pion momentum distributions in the nucleon in chiral effective theory
Burkardt, Matthias R.; Hendricks, K. S.; Ji, Cheung Ryong; Melnitchouk, Wally; Thomas, Anthony W.
2013-03-01
We compute the light-cone momentum distributions of pions in the nucleon in chiral effective theory using both pseudovector and pseudoscalar pion--nucleon couplings. For the pseudovector coupling we identify $\\delta$-function contributions associated with end-point singularities arising from the pion-nucleon rainbow diagrams, as well as from pion tadpole diagrams which are not present in the pseudoscalar model. Gauge invariance is demonstrated, to all orders in the pion mass, with the inclusion of Weinberg-Tomozawa couplings involving operator insertions at the $\\pi NN$ vertex. The results pave the way for phenomenological applications of pion cloud models that are manifestly consistent with the chiral symmetry properties of QCD.
Pion condensation and instabilities: current theory and experiment
Gyulassy, M.
1980-05-01
Current calculations of pion condensation phenomena in symmetric nuclear matter are reviewed. The RPA and MFA methods are compared. Latest results (LBL-10572) with a relativistic MFA theory constrained by bulk nuclear properties are presented. The differences between equilibrium (condensation) and nonequilibrium (dynamic) instabilities are discussed. Finally, two-proton correlation experiments aimed at looking for critical scattering phenomena and two-pion correlation experiments aimed at looking for pion field coherence are analyzed. 10 figures, 2 tables.
Hormuzdiar, J.N.; Hsu, S.D.
1999-02-01
We describe a class of pionic breather solutions (PBS) which appear in the chiral Lagrangian description of low-energy QCD. These configurations are long lived, with lifetimes greater than 10{sup 3} fm/c, and could arise as remnants of disoriented chiral condensate (DCC) formation at RHIC. We show that the chiral Lagrangian equations of motion for a uniformly isospin-polarized domain reduce to those of the sine-Gordon model. Consequently, our solutions are directly related to the breather solutions of sine-Gordon theory in 3+1 dimensions. We investigate the possibility of PBS formation from multiple domains of DCC, and show that the probability of formation is non-negligible. {copyright} {ital 1999} {ital The American Physical Society}
NASA Astrophysics Data System (ADS)
Kunne, Fabienne
2016-02-01
We present preliminary COMPASS results on pion and kaon multiplicities produced in semi inclusive deep inelastic scattering of 160GeV muons off an isoscalar (6LiD) target. The results constitute an impressive data set of more than 400 points in p and 400 in K, covering a large x,Q2 and z domain in a fine binning, which will be used in future QCD fits at next to leading order to extract quark fragmentation functions. We show results of a first leading order fit performed to extract the favored and unfavored quark fragmentation functions into pions Dfavπ and Dunfavπ.
Design and Simulation of the nuSTORM Pion Beamline
Liu, A.; Neuffer, D.; Bross, A.
2015-08-15
The nuSTORM (neutrinos from STORed Muons) proposal presents a detailed design for a neutrino facility based on a muon storage ring, with muon decay in the production straight section of the ring providing well defined neutrino beams. The facility includes a primary high-energy proton beam line, a target station with pion production and collection, and a pion beamline for pion transportation and injection into a muon decay ring. The nuSTORM design uses “stochastic injection”, in which pions are directed by a chicane, referred to as the Orbit Combination Section (OCS), into the production straight section of the storage ring. Pions that decay within that straight section provide muons within the circulating acceptance of the ring. Furthermore, the design enables injection without kickers or a separate pion decay transport line. The beam line that the pions traverse before being extracted from the decay ring is referred to as the pion beamline. Our paper describes the design and simulation of the pion beamline, and includes full beam dynamics simulations of the system.
Joint Resummation for TMD Wave Function of Pion
NASA Astrophysics Data System (ADS)
Wang, Yu-Ming
2015-02-01
QCD corrections to transverse-momentum-dependent pion wave function develop the mixed double logarithm ln x ln(ζ P2/k_T^2), when the gluon emission is collinear to the energetic pion. The fist scheme-independent kT factorization formula for γ*π → γ transition form factor is achieved by resumming all the enhanced logarithms for both pion wave function and short-distance coefficient function. High-order QCD corrections and transfer momentum √ {Q2} dependence of pion form factor are found to be distinct from those predicted by the conventional resummation approach.
A dynamical model for pion electroproduction on the nucleon
George L. Caia; Louis E. Wright; Vladimir Pascalutsa
2005-06-01
We develop a Lorenz- and gauge-invariant dynamical model for pion electroproduction in the resonance region. The model is based on solving of the Salpeter (instantaneous) equation for the pion-nucleon interaction with a hadron-exchange potential. We find that the one-particle-exchange kernel of the Salpeter equation for pion electroproduction develops an unphysical singularity for a finite value of Q{sup 2}. We analyze two methods of dealing with this problem. Results of our model are compared with recent single-polarization data for pion electroproduction.
Matrix elements of the electromagnetic operator between kaon and pion states
Baum, I.; Lubicz, V.; Martinelli, G.; Orifici, L.; Simula, S.
2011-10-01
We compute the matrix elements of the electromagnetic operator sF{sub {mu}{nu}}{sigma}{sup {mu}{nu}}d between kaon and pion states, using lattice QCD with maximally twisted-mass fermions and two flavors of dynamical quarks (N{sub f}=2). The operator is renormalized nonperturbatively in the RI'/MOM scheme and our simulations cover pion masses as light as 270 MeV and three values of the lattice spacing from {approx_equal}0.07 up to {approx_equal}0.1 fm. At the physical point our result for the corresponding tensor form factor at zero-momentum transfer is f{sub T}{sup K{pi}}(0)=0.417(14{sub stat})(5{sub syst}), where the systematic error does not include the effect of quenching the strange and charm quarks. Our result differs significantly from the old quenched result f{sub T}{sup K{pi}}(0)=0.78(6) obtained by the SPQ{sub cd}R Collaboration with pion masses above 500 MeV. We investigate the source of this difference and conclude that it is mainly related to the chiral extrapolation. We also study the tensor charge of the pion and obtain the value f{sub T}{sup {pi}{pi}}(0)=0.195(8{sub stat})(6{sub syst}) in good agreement with, but more accurate than the result f{sub T}{sup {pi}{pi}}(0)=0.216(34) obtained by the QCDSF Collaboration using higher pion masses.
Pion scattering to 8/sup -/ stretched states in /sup 60/Ni
Clausen, B.L.
1988-03-01
Using the Energetic Pion Channel and Spectrometer at the Los Alamos Meson Physics Facility, differential cross sections for pion scattering were measured for ten previously known J/sup ..pi../ = 8/sup /minus// stretched states in /sup 60/Ni. A possible new pure isoscalar stretched state was also found. The data were taken near the /DELTA//sub 3,3/-resonance using 162 MeV incident pions and scattering angles of 65/degree/, 80/degree/, and 90/degree/ for ..pi../sup +/ and 65/degree/ and 80/degree/ for ..pi../sup /minus//. The analysis of the /sup 60/Ni data found that the use of Woods-Saxon wave functions in the theoretical calculations gave much better agreement with data than the use of the usual harmonic oscillator wave functions. The WS theory gave better predictions of: the angle at which the ..pi../sup /minus// and ..pi../sup +/ angular distributions are maximum, the ratios of ..pi../sup /minus// to ..pi../sup +/ cross sections for pure isovector states (which were much larger than unity), and the absolute size of the cross sections for all states (so that the normalization factor necessary to arrive at agreement of theory with data was closer to unity). The theoretical calculations used the distorted wave impulse approximation, including new methods for unbound states. The sensitivities of the calculations to input parameters were investigated. This analysis using WS wave functions was extended to five other nuclei (/sup 12/C, /sup 14/C, /sup 16/O, /sup 28/Si, and /sup 54/Fe) on which both pion scattering and electron scattering have been done. A significant improvement in arriving at a normalization factor close to unity was found when WS wave functions were consistently used for analyzing both pion and electron inelastic scattering data. 101 refs., 26 figs., 13 tabs.
Lattice QCD study of the Boer-Mulders effect in a pion
NASA Astrophysics Data System (ADS)
Engelhardt, M.; Hägler, P.; Musch, B.; Negele, J.; Schäfer, A.
2016-03-01
The three-dimensional momenta of quarks inside a hadron are encoded in transverse momentum-dependent parton distribution functions (TMDs). This work presents an exploratory lattice QCD study of a TMD observable in the pion describing the Boer-Mulders effect, which is related to polarized quark transverse momentum in an unpolarized hadron. The primary goal is to gain insight into the behavior of TMDs as a function of a Collins-Soper evolution parameter, ζ ^, which quantifies the rapidity difference between the hadron momentum and a vector describing the trajectory of the struck quark, e.g., in a semi-inclusive deep-inelastic scattering (SIDIS) process. The lattice calculation, performed at the pion mass mπ=518 MeV , utilizes a definition of TMDs via hadronic matrix elements of a quark bilocal operator with a staple-shaped gauge connection; in this context, the evolution parameter is related to the staple direction. By parametrizing the aforementioned matrix elements in terms of invariant amplitudes, the problem can be cast in a Lorentz frame suited for the lattice calculation. Aided by the lower mass of the pion, compared to the nucleon studied previously, the present investigation of pion TMD observables constitutes an important step towards the quantitative study of the physically important regime of large relative rapidity where the dependence on ζ ^ appears to approach a limit. Although matching to perturbative evolution equations in ζ ^ is not yet available, extrapolations based on Ansätze containing inverse powers of ζ ^ yield stable results with an uncertainty as low as 20%, and both upper and lower bounds for the asymptotics are obtained. In passing, the similarity between the Boer-Mulders effects extracted in the pion and the nucleon is noted.
Experiments on the nuclear interactions of pion and electrons. Final progress report
Minehart, R.C.
1998-05-01
The work in this report is grouped into four categories. (1) The experiments in pion nucleus physics were primarily studies of pion absorption and scattering in light nuclei, carried out at the Los Alamos Meson Physics Facility (LAMPF). (2) The experiments on fundamental particle properties were carried out at LAMPF and at the Paul Scherrer Institute (PSI) in Switzerland, the pion-beta decay experiment is still under construction and will begin taking data in 1999. (3) The experiments in electro-nuclear physics were performed at the Stanford Linear Electron Accelerator (SLAC), at the Saclay Laboratory in France, at the LEGS facility at the Brookhaven National Laboratory, and at the Continuous Electron Beam Accelerator Facility (CEBAF) at the Jefferson Laboratory. These experiments relate mainly to the question of the role of longitudinal and transverse strength for inelastic scattering from nuclei, measurements of fundamental nuclear properties with tagged polarized photons, and to the quark structure of the nucleon and its excited states. (4) Experiments on absorption of antiprotons in heavy nuclei, were carried out by K. Ziock primarily while on a sabbatical leave in Munich, Germany.
Form factors and the s-wave component of the two-pion-exchange three-nucleon potential
Robilotta, M.R.; Isidro Filho, M.P.; Coelho, H.T.; Das, T.K.
1985-02-01
We argue that the straightforward introduction of ..pi..N form factors into the s-wave component of the two-pion-exchange three-nucleon potential based on chiral symmetry is not free of problems. These can be avoided by means of a redefinition of the potential which considers its physical content.
Constantia Alexandrou; Bojan Bistrovic; Robert Edwards; P de Forcrand; George Fleming; Philipp Haegler; John Negele; Konstantinos Orginos; Andrew Pochinsky; Dru Renner; David Richards; Wolfram Schroers; Antonios Tsapalis
2005-10-01
Lattice QCD is an essential complement to the current and anticipated DOE-supported experimental program in hadronic physics. In this poster we address several key questions central to our understanding of the building blocks of nuclear matter, nucleons and pions. Firstly, we describe progress at computing the electromagnetic form factors of the nucleon, describing the distribution of charge and current, before considering the role played by the strange quarks. We then describe the study of transition form factors to the Delta resonance. Finally, we present recent work to determine the pion form factor, complementary to the current JLab experimental determination and providing insight into the approach to asymptotic freedom.
A Study of Charged Current Single Charged Pion Productions on Carbon in a Few-GeV Neutrino Beam
Hiraide, Katsuki
2009-01-01
current coherent pion production to the total charged current cross section at 0.67 x 10^{-2} at mean neutrino energy 1.1 GeV and 1.36 x 10^{-2} at mean neutrino energy 2.2 GeV. We reveal that the Rein-Sehgal model widely used in neutrino oscillation experiments breaks down at the neutrino energy region of a few GeV. This creates active controversies on the model of coherent pion production, and the understanding of coherent pion production is being progressed. In addition, future prospects of measurements of charged current single charged pion production in SciBooNE are discussed.
Charged-pion electroproduction above the resonance region
NASA Astrophysics Data System (ADS)
Vrancx, Tom; Ryckebusch, Jan
2014-02-01
Background: Above the nucleon resonance region, the N(e ,e'π±)N' data cannot be explained by conventional hadronic models. For example, the observed magnitude of the transverse cross section is significantly underestimated in a framework with Reggeized background amplitudes. Purpose: Develop a phenomenological framework for the N(e ,e'π±)N' reaction at high invariant mass W and deep photon virtuality Q2. Method: Building on the work of Kaskulov and Mosel [Phys. Rev. C 81, 045202 (2010), 10.1103/PhysRevC.81.045202], a gauged pion-exchange current is introduced with a running cutoff energy for the proton electromagnetic transition form factor. A new transition form factor is proposed. It respects the correct on-shell limit, has a simple physical interpretation, and reduces the number of free parameters by one. Results: A study of the W dependence of the N(e ,e'π±)N' lends support for the newly proposed transition form factor. In addition, an improved description of the separated and unseparated cross sections at -t≲0.5GeV2 is obtained. The predictions overshoot the measured unseparated cross sections for -t>0.5GeV2. Introducing a strong hadronic form factor in the Reggeized background amplitudes brings the calculations considerably closer to the high -t data. Conclusions: Hadronic models corrected for resonance-parton duality describe the separated pion electroproduction cross sections above the resonance region reasonably well at low -t. In order to validate the applicability of these models at high -t, separated cross sections are needed. These are expected to provide a more profound insight into the relevant reaction mechanisms.
Pion production in neutrino interactions with nuclei
Leitner, T.; Lalakulich, O.; Buss, O.; Mosel, U.; Alvarez-Ruso, L.
2010-03-30
Neutrino-induced pion production on nuclear targets is the major inelastic channel in all present-day neutrino-oscillation experiments. It has to be understood quantitatively in order to be able to reconstruct the neutrino-energy at experiments such as MiniBooNE or K2K and T2K. We report here results of cross section calculations for both this channel and for quasielastic scattering within the semiclassical GiBUU method. This method contains scattering, both elastic and inelastic, absorption and side-feeding of channels all in a unitary, common theoretical framework and code. We find that charged current quasielastic scattering (CCQE) and 1 pi production are closely entangled in actual experiments, due to final state interactions of the scattered nucleons on one hand and of the DELTA resonances and pions, on the other hand. We discuss the uncertainties in the elementary pion production cross sections from ANL and BNL. We find the surprising result that the recent 1 pi production cross section data from MiniBooNE are well described by calculations without any FSI. For higher energies we study the validity of the Bloom-Gilman quark-hadron duality for both electron- and neutrino-induced reactions. While this duality holds quite well for nucleon targets, for nuclear targets the average resonance contributions to the structure function F{sub 2} are always lower than the DIS values. This result indicates a significant impact of nuclear effects on observables, reducing the cross section and structure functions by at least 30-40% and changing the form of various distributions.
Unitary constraints on neutral pion electroproduction
Laget, J. -M.
2010-11-10
At large virtuality $Q^2$, the coupling to the vector meson production channels provides us with a natural explanation of the surprisingly large cross section of the neutral pion electroproduction recently measured at Jefferson Laboratory, without destroying the good agreement between the Regge pole model and the data at the real photon point. Lastly, elastic rescattering of the $\\pi^0$ provides us with a way to explain why the node, that appears at $t\\sim -0.5$~GeV$^2$ at the real photon point, disappears as soon as $Q^2$ differs from zero.
Unitary constraints on neutral pion electroproduction
Laget, J. -M.
2010-11-10
At large virtualitymore » $Q^2$, the coupling to the vector meson production channels provides us with a natural explanation of the surprisingly large cross section of the neutral pion electroproduction recently measured at Jefferson Laboratory, without destroying the good agreement between the Regge pole model and the data at the real photon point. Lastly, elastic rescattering of the $$\\pi^0$$ provides us with a way to explain why the node, that appears at $$t\\sim -0.5$$~GeV$^2$ at the real photon point, disappears as soon as $Q^2$ differs from zero.« less
Nuclear transparencies from photoinduced pion production
W. Cosyn; M.C. Martinez; J. Ryckebusch; B. Van Overmeire
2006-12-01
We present a relativistic and cross-section factorized framework for computing nuclear transparencies extracted from A({gamma}, {pi} N) reactions at intermediate energies. The proposed quantum mechanical model adopts a relativistic extension to the multiple-scattering Glauber approximation to account for the final state interactions of the ejected nucleon and pion. The theoretical predictions are compared against the experimental {sup 4}He({gamma},p {pi}{sup -}) data from Jefferson Lab. For those data, our results show no conclusive evidence for the onset of mechanisms related to color transparency.
Study of the radiative pion decay
Chen, Chuan-Hung; Geng, Chao-Qiang; Lih, Chong-Chung
2011-04-01
We study the radiative pion decay of {pi}{sup +}{yields}e{sup +}{nu}{sub e}{gamma} in the light-front quark model. We also summarize the result in the chiral perturbation theory. The vector and axial-vector hadronic form factors (F{sub V,A}) for the {pi}{yields}{gamma} transition are evaluated in the whole allowed momentum transfer. In terms of these momentum dependent form factors, we calculate the decay branching ratio and compare our results with the experimental data and other theoretical predictions in the literature. We also constrain the possible size of the tensor interaction in the light-front quark model.
Rare kaon, muon, and pion decay
Littenberg, L.
1998-12-01
The author discusses the status of and prospects for the study of rare decays of kaons, muons, and pions. Studies of rare kaon decays are entering an interesting new phase wherein they can deliver important short-distance information. It should be possible to construct an alternative unitarity triangle to that determined in the B sector, and thus perform a critical check of the Standard Model by comparing the two. Rare muon decays are beginning to constrain supersymmetric models in a significant way, and future experiments should reach sensitivities which this kind of model must show effects, or become far less appealing.
End point behaviour of the pion distribution amplitude
NASA Astrophysics Data System (ADS)
Szcepaniak, Adam; Mankiewicz, Lech
1991-08-01
We study the end point structure of the pion distribution amplitude and reexamine the perturbative analysis of the high-Q2 pion form factor in the factorization approach. Permanent address: Nicolaus Copernicus Astronomical Centre, Bartycka 18, PL-00-716 Warsaw, Poland.
Design and Simulation of the nuSTORM Pion Beamline
Liu, A.; Neuffer, D.; Bross, A.
2015-08-15
The nuSTORM (neutrinos from STORed Muons) proposal presents a detailed design for a neutrino facility based on a muon storage ring, with muon decay in the production straight section of the ring providing well defined neutrino beams. The facility includes a primary high-energy proton beam line, a target station with pion production and collection, and a pion beamline for pion transportation and injection into a muon decay ring. The nuSTORM design uses “stochastic injection”, in which pions are directed by a chicane, referred to as the Orbit Combination Section (OCS), into the production straight section of the storage ring. Pionsmore » that decay within that straight section provide muons within the circulating acceptance of the ring. Furthermore, the design enables injection without kickers or a separate pion decay transport line. The beam line that the pions traverse before being extracted from the decay ring is referred to as the pion beamline. Our paper describes the design and simulation of the pion beamline, and includes full beam dynamics simulations of the system.« less
High lying N* studies in electromagnetic double charged pion production
V. I. Mokeev; M. Ripani; M. Anghinolfi; M. Battaglieri; R. De Vita; G. V. Fedotov; E. N. Golovach; B. S. Ishkhanov; M. V. Osipenko; G. Ricco; V. Sapunenko; M. Taiuti
2002-06-07
A phenomenological model for double charged pion production is presented, aimed to exact N* electromagnetic form factors from measured observables (differential cross-sections, asymmetries). The preliminary results of CLAS data analysis on double charged pion production by virtual photons are discussed, focusing on high lying N* electromagnetic excitation and signals from possible ''missing'' baryon states.
Pion Cloud and the Sea of the Nucleon
Wally Melnitchouk
2009-05-01
I review recent progress in understanding the structure of the nucleon sea and the role of the nucleon's pion cloud. In particular, I discuss the consequences of the pion cloud for the d-bar - u-bar asymmetry in the proton, the neutron's electric form factor, and the proton's electric to magnetic form factor ratio.
Pion transverse charge density and the edge of hadrons
NASA Astrophysics Data System (ADS)
Carmignotto, Marco; Horn, Tanja; Miller, Gerald A.
2014-08-01
We use the world data on the pion form factor for space-like kinematics and a technique previously used to extract the proton transverse densities to extract the transverse pion charge density and its uncertainty due the incomplete knowledge of the pion form factor at large values of Q2 and the experimental uncertainties. The pion charge density at small values of impact parameter b < 0.1 fm is dominated by this incompleteness error while the range between 0.1-0.3 fm is relatively well constrained. A comparison of pion and proton transverse charge densities shows that the pion is denser than the proton for values of b <0.2fm. The pion and proton transverse charge densities seem to be the same for values of b =0.3-0.6 fm. Future data from Thomas Jefferson National Accelerator Facility (JLab) 12 GeV and the Electron-Ion Collider (EIC) will increase the dynamic extent of the form factor data to higher values of Q2 and thus reduce the uncertainties in the extracted pion transverse charge density.
Pion Electromagnetic Form Factor in Virtuality Distribution Formalism
Radyushkin, Anatoly V.
2016-01-01
We discuss two applications of the {\\it Virtuality Distribution Amplitudes} (VDA) formalism developed in our recent papers. We start with an overview of the main properties of the pion distribution amplitude emphasizing the quantitative measures of its width, and possibility to access them through the pion transition form factor studies. We formulate the basic concepts of the VDA approach and introduce the pion {\\it transverse momentum distribution amplitude} (TMDA) which plays, in a covariant Lagrangian formulation, a role similar to that of the pion wave function in the 3-dimensional Hamiltonian light-front approach. We propose simple factorized models for soft TMDAs, and use them to describe existing data on the pion transition form factor, thus fixing the scale determining the size of the transverse-momentum effects. Finally, we apply the VDA approach to the one-gluon exchange contribution for the pion electromagnetic form factor. We observe a very late $Q^2 \\gtrsim 20$ GeV$^2$ onset of transition to the asymptotic pQCD predictions and show that in the $Q^2 \\lesssim 10$ GeV$^2$ region there is essentially no sensitivity to the shape of the pion distribution amplitude. Furthermore, the magnitude of the one-gluon exchange contribution in this region is estimated to be an order of magnitude below the Jefferson Lab data, thus leaving the Feynman mechanism as the only one relevant to the pion electromagnetic form factor behavior for accessible $Q^2$.
Pion transverse charge density and the edge of hadrons
Carmignotto, Marco; Horn, Tanja; Miller, Gerald A.
2014-08-01
We use the world data on the pion form factor for space-like kinematics and a technique used to extract the proton transverse densities, to extract the transverse pion charge density and its uncertainty due to experimental uncertainties and incomplete knowledge of the pion form factor at large values of Q2. The pion charge density at small values of b<0.1 fm is dominated by this incompleteness error while the range between 0.1-0.3 fm is relatively well constrained. A comparison of pion and proton charge densities shows that the pion is denser than the proton for values of b<0.2 fm. The pion and proton distributions seem to be the same for values of b=0.2-0.6 fm. Future data from Jlab 12 GeV and the EIC will increase the dynamic extent of the data to higher values of Q2 and thus reduce the uncertainties in the extracted pion charge density.
Neutrino-induced coherent pion production off nuclei
Leitner, T.; Mosel, U.; Winkelmann, S.
2009-11-25
All available theoretical estimates of neutrino-induced coherent pion production rely on the 'local approximation' for the Delta propagator. The validity of this approximation is scrutinized. It is found that the local approximation overestimates the neutrino-induced coherent pion production on nuclei significantly, by up to 100%.
Research program in nuclear and solid state physics
NASA Technical Reports Server (NTRS)
Stronach, C. E.
1973-01-01
The spectra of prompt gamma rays emitted following nuclear pion absorption were studied to determine the states of excited daughter nuclei, and the branching ratios for these states. Studies discussed include the negative pion absorption of C-12, S-32, and N-14; and the positive pion absorption on 0-16. Abstracts of papers submitted to the conference of the American Physical Society are included.
RATHKE,J.; SCHULTHEISS,T.; ROSE,J.; KIRK,H.
2001-06-18
A conceptual design for a pion bunch rotator cavity has been performed. The cavity is an integral part of a pion production target and capture system envisioned as an experiment on the AGS at Brookhaven National Laboratory in support of the Muon Collider Collaboration [1]. The design specification calls for a single gap cavity operating at peak fields of 6 MV/m, limited by available RF, and an RF frequency of approximately 71 MHz, a harmonic of AGS. The cavity is located directly following the capture and matching solenoids and must accommodate the decay solenoids within the reentrant noses of the cavity. These requirements place severe restrictions upon the physical structure of the cavity. This paper will present the engineering design and supporting RF, thermal, and structural analysis to achieve a mechanically stable cavity with good steady state and transient thermal and RF performance. In addition, design details and the approach to fabrication will be discussed.
Equation of state of an interacting pion gas with realistic {pi}-{pi} interactions
Rapp, R.; Wambach, J.
1996-06-01
Within the finite-temperature Green{close_quote}s-function formalism we study the equation of state of a hot interacting pion gas at zero chemical potential. Employing realistic {pi}{pi} meson-exchange interactions, we self-consistently calculate the in-medium single-pion self-energy and the {pi}{pi} scattering amplitude in the quasiparticle approximation. These quantities are then used to evaluate the thermodynamic potential {Omega}{sub {pi}}({ital T}) from which the state variables of pressure, entropy, and energy density can be derived. In contrast to earlier calculations based on the low-energy Weinberg Lagrangian we find an overall increase as compared to the free-gas results. We also consider the possibility of a dropping {rho}-meson mass as suggested by the {open_quote}{open_quote}Brown-Rho scaling{close_quote}{close_quote} law. {copyright} {ital 1996 The American Physical Society.}
{delta}-mediated pion production in nuclei
Praet, C.; Lalakulich, O.; Jachowicz, N.; Ryckebusch, J.
2009-04-15
We present a fully relativistic formalism for describing neutrino-induced {delta}-mediated single-pion production in nuclei. We assess the ambiguities stemming from the {delta} interactions and quantify the uncertainties in the axial form-factor parameters by comparing with the available bubble-chamber neutrino-scattering data. To include nuclear effects, we turn to a relativistic plane-wave impulse approximation (RPWIA) using realistic bound-state wave functions derived in the Hartree approximation to the {sigma}-{omega} Walecka model. For neutrino energies larger than 1 GeV, we show that a relativistic Fermi-gas model with appropriate binding-energy correction produces results that are comparable to the RPWIA that naturally includes Fermi motion, nuclear-binding effects, and the Pauli exclusion principle. Including {delta} medium modifications roughly halves the RPWIA cross section. Calculations for primary (prior to undergoing final-state interactions) pion production are presented for both electron- and neutrino-induced processes, and a comparison with electron-scattering data and other theoretical approaches is included. We infer that the total {delta}-production strength is underestimated by about 20 to 25%, a fraction that is due to the pionless decay modes of the {delta} in a medium. The model presented in this work can be naturally extended to include the effect of final-state interactions in a relativistic and quantum-mechanical way.
Multiplicity dependence of two-pion correlations
Soltz, R.A.; E802 Collaboration
1993-12-31
Experiment E859 has measured two-pion correlations for 14.6 A{center_dot}GeV/c {sup 28}Si + Au and {sup 28}Si + Al systems as a function of total charged particle multiplicity. The data have been divided into three multiplicity regions for each system, and fits to two-dimensional Gaussian sources have been performed. The extracted source parameters R{sub l} and {tau} show little or no multiplicity dependence while the parameters R{sub t} and R show a slight dependence. Two-pion correlations were also measured for the 11.6 A{center_dot}GeV/c {sup 197}Au + Au system as part of experiment E866. The rms radius (R{sub rms}) for this system was found to be 7.03 {plus_minus} 0.53 fm, consistent with a scaling of R{sub rms} = 1.2A{sub p}{sup 1/3}, where A{sub p} is the number of projectile nucleons.
Pion contamination in the MICE muon beam
Adams, D.; Alekou, A.; Apollonio, M.; Asfandiyarov, R.; Barber, G.; Barclay, P.; de Bari, A.; Bayes, R.; Bayliss, V.; Bertoni, R.; et al
2016-03-01
Here, the international Muon Ionization Cooling Experiment (MICE) will perform a systematic investigation of ionization cooling with muon beams of momentum between 140 and 240\\,MeV/c at the Rutherford Appleton Laboratory ISIS facility. The measurement of ionization cooling in MICE relies on the selection of a pure sample of muons that traverse the experiment. To make this selection, the MICE Muon Beam is designed to deliver a beam of muons with less thanmore » $$\\sim$$1% contamination. To make the final muon selection, MICE employs a particle-identification (PID) system upstream and downstream of the cooling cell. The PID system includes time-of-flight hodoscopes, threshold-Cherenkov counters and calorimetry. The upper limit for the pion contamination measured in this paper is $$f_\\pi < 1.4\\%$$ at 90% C.L., including systematic uncertainties. Therefore, the MICE Muon Beam is able to meet the stringent pion-contamination requirements of the study of ionization cooling.« less
NASA Astrophysics Data System (ADS)
Kim, Changhoan
We report the results of a calculation of the K → pipi matrix elements of the DeltaI = 3/2 operators. Relying on the 3-flavor effective Hamiltonian, we calculate the low energy contribution to the matrix elements in quenched lattice QCD with the DBW2 action using domain wall fermions, while the high energy contribution is included in the Wilson coefficients. In order to generate interacting pipi states with non-zero relative momentum in lattice, we apply anti-periodic boundary conditions on pions. Since only the magnitude of the overlap of our interpolating operators with the initial and final state is determined, we can calculate only the magnitude of the matrix elements. From the comparison with the experimental result, however, we find some degree of discrepancy. This discrepancy might be ascribed to the unphysical kinematics we choose in this report.
Activities report in nuclear and high energy physics
NASA Astrophysics Data System (ADS)
High energy physics research using particle accelerators is summarized. Electron scattering; experiments concerning pions, muons, and antiprotons; theoretical physics; radiochemistry; and technical aspects of the accelerators and associated equipment are discussed.
Measurement of Charged Pion Photoproduction at ELPH
NASA Astrophysics Data System (ADS)
Kanda, Hiroki; Beckford, Brian; Fujibayashi, Takeji; Fujii, Takao; Fujii, Yu; Futatsukawa, Kenta; Gogami, Toshiyuki; Han, Yun-Cheng; Hashimoto, Osamu; Hirose, Kentaro; Hosomi, Kenji; Honda, Ryotaro; Iguchi, Alan; Ishikawa, Takatsugu; Kaneta, Masashi; Kaneko, Yusuke; Kasai, Yuma; Kawasaki, Taito; Kimura, Chigusa; Kiyokawa, Shogo; Koike, Takeshi; Maeda, Kazushige; Maruyama, Nayuta; Matsubara, Masao; Miwa, Koji; Miyagi, Yohei; Nagao, Sho; Nakamura, Satoshi N.; Nishizawa, Takashi; Okuyama, Akira; Shimizu, Hajime; Suzuki, Kotaku; Tamae, Tadaaki; Tamura, Hirokazu; Tsukada, Kyo; Terada, Nobu; Ukai, Mifuyu; Wang, Tie-Shan; Yamamoto, Fumiya; Yamazaki, Hirohito
We investigated the charged pion photoproductions on the deuteron in the photon energy region of 0.65 to 1.1 GeV at Research Center for Electron Photon Science, Tohoku University. The objective is to explore the π+π- photoproduction process which dominates at Eγ > 0.8 GeV. We measured the charged particles from the photoreaction on the deuteron with the Neutral Kaon Spectrometer-2 (NKS2). The analyses both for quasi-free and non-quasi-free processes are underway. As one of the non-quasi-free processes, γd → π+π-d was separated by requiring π+, π- and d. The relative yield and the π+π- invariant mass spectra are presented. We are also proceeding with the development of the new photon tagger to be ready in 2014.
Incoherent neutral pion photoproduction on 12C.
Tarbert, C M; Watts, D P; Aguar, P; Ahrens, J; Annand, J R M; Arends, H J; Beck, R; Bekrenev, V; Boillat, B; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Codling, R; Downie, E J; Föhl, K; Glazier, D I; Grabmayr, P; Gregor, R; Heid, E; Hornidge, D; Jahn, O; Kashevarov, V L; Knezevic, A; Kondratiev, R; Korolija, M; Kotulla, M; Krambrich, D; Krusche, B; Lang, M; Lisin, V; Livingston, K; Lugert, S; Macgregor, I J D; Manley, D M; Martinez, M; McGeorge, J C; Mekterovic, D; Metag, V; Nefkens, B M K; Nikolaev, A; Novotny, R; Owens, R O; Pedroni, P; Polonski, A; Prakhov, S N; Price, J W; Rosner, G; Rost, M; Rostomyan, T; Schadmand, S; Schumann, S; Sober, D; Starostin, A; Supek, I; Thomas, A; Unverzagt, M; Walcher, Th; Zehr, F
2008-04-01
We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The 12C(gamma,pi(0))(12)C*(4.4 MeV) reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a pi(0) spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the Delta in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a Delta-hole model. PMID:18517938
Charge symmetry breaking two-pion exchange
Niskanen, J.A. )
1992-06-01
Two-pion exchange (TPE) contribution to the charge symmetry breaking class IV neutron-proton interaction is examined in a potential and coupled channels approach. Based on nonrelativistic {pi}{ital NN} and {pi}{ital N}{Delta} vertices, a TPE interaction is treated in two ways, as a potential or as a part calculable by the coupled channels method plus a residual potential interaction. A practical parametrization of the TPE potentials is given, which can also be used in the case of class III charge symmetry breaking (CSB) forces as well as for charge symmetric interactions. The results show that below 300 MeV the TPE contribution to CSB in elastic {ital np} scattering is insignificant, whereas at higher energies it should not be neglected.
Systematics of pion double charge exchange
Gilman, R.A.
1985-10-01
Differential cross sections have been measured for pion-induced double-charge-exchange (DCX) reactions leading to double-isobaric-analog states (DIAS) and low-lying nonanalog states in the residual nuclei. A description of the experimental details and data analysis is presented. The experimentally observed systematics of reactions leading to DIAS, to nonanalog ground states, and to low-lying 2 states are described. Lowest-order optical-model calculations of DIAS DCX are compared to the data. Efforts to understand the anomalies by invoking additional reaction-mechanism amplitudes and a higher-order optical potential are described. Calculations of nonanalog DCX reactions leading to J/sup / = 0 states were performed within a distorted-wave impulse-approximation framework. The sensitivities of these calculations to input parameters are discussed. 58 refs., 41 figs., 16 tabs.
Pion Production Momentum Loss of Cosmic Ray Hadrons
NASA Astrophysics Data System (ADS)
Krakau, S.; Schlickeiser, R.
2015-04-01
We present new results on the energy loss rate of high energy protons due to pion production in proton-proton interactions. Our calculations are based on the parameterized pion flux of Kelner et al. Our new results are valid for proton energies in the range of 1 GeV \\ll E≤slant {{10}8} GeV, which enhance the valid energy range by orders of magnitude. With these results one can calculate the energy loss due to pion production for cosmic ray protons from low energies to energies between the knee and ankle.
Kaon, pion, and proton associated photofission of Bi nuclei
Song, Y.; Margaryan, A.; Acha, A.; Ahmidouch, A.; Androic, D.; Asaturyan, A.; Asaturyan, R.; Baker, O. K.; Baturin, P.; Benmokhtar, F.; Carlini, R.; Chen, X.; Christy, M.; Cole, L.; Danagoulian, S.; Daniel, A.; Dharmawardane, V.; Egiyan, K.; Elaasar, M.; Ent, R.
2010-10-15
The first measurement of proton, pion, and kaon associated fission of Bi nuclei has been performed in a photon energy range 1. 45 < E{sub {gamma}}< 1. 55 GeV. The fission probabilities are compared with an inclusive fission probabilities obtained with photons, protons and pions. The fission probability of Bi nuclei in coincidence with kaons is 0. 18 {+-} 0. 06 which is {approx}3 times larger than the proton and pion associated fission probabilities and {approx}2 times larger than inclusive ones. The kaon associated excess fission events are explained in terms of bound {Lambda} residual states and their weak nonmesonic decays.
Structure of compact stars in a pion superfluid phase
NASA Astrophysics Data System (ADS)
Mao, Shijun
2014-06-01
The gross structure of compact stars composed of pion superfluid quark matter is investigated in the frame of the Nambu-Jona-Lasinio model. Under the Pauli-Villars regularization scheme, the uncertainty of the thermodynamic functions for inhomogeneous states is cured, and the Larkin-Ovchinnikov-Fulde-Ferrel state that appeared in the hard cutoff scheme is removed from the phase diagram of the pion superfluid. Different from the unpaired quark matter and color superconductor, the strongly coupled pion superfluid is a possible candidate of compact stars with mass M ≃3M⊙ and radius R ≃14 km.
Pion electromagnetic form factor in the Covariant Spectator Theory
Biernat, Elmar P.; Gross, Franz L.; Pena, Teresa; Stadler, Alfred
2014-01-01
The pion electromagnetic form factor at spacelike momentum transfer is calculated in relativistic impulse approximation using the Covariant Spectator Theory. The same dressed quark mass function and the equation for the pion bound-state vertex function as discussed in the companion paper are used for the calculation, together with a dressed quark current that satisfies the Ward-Takahashi identity. The results obtained for the pion form factor are in agreement with experimental data, they exhibit the typical monopole behavior at high momentum transfer and they satisfy some remarkable scaling relations.
Interaction lengths of energetic pions and protons in iron.
NASA Technical Reports Server (NTRS)
Crannell, H.; Crannell, C. J.; Whiteside, H.; Ormes, J. F.; Ryan, M. J.
1973-01-01
Determination of the mean interaction lengths for 9.3-, 13.8-, and 17.8-GeV protons and 9.3- and 17.8-GeV positive pions in iron. The mean interaction length of pions is found to be approximately 20% greater than that of protons. No statistically significant variation of the mean interaction length for protons or pions as a function of energy is observed. With only two exceptions, the data obtained show a systematic 5% difference between measurements of the mean interaction length made with cosmic rays and those made with accelerator-produced protons.
BPS pion domain walls in the supersymmetric chiral Lagrangian
NASA Astrophysics Data System (ADS)
Gudnason, Sven Bjarke; Nitta, Muneto; Sasaki, Shin
2016-07-01
We construct exact solutions of BPS pion domain walls in the four-dimensional N =1 supersymmetric S U (N ) chiral Lagrangian with pion masses introduced via linear and quadratic superpotentials. The model admits N discrete vacua in the center of S U (N ) for the linear superpotential. In addition to the latter, new vacua appear for the quadratic superpotential. We find that the domain wall solutions of pions (Nambu-Goldstone bosons) that interpolate between a pair of (pion) vacua preserve half of supersymmetry. Contrary to our expectations, we have not been able to find domain walls involving the quasi-Nambu-Goldstone bosons present in the theory, which in turn has the consequence that not all vacua of the theory are connected by a BPS domain wall solution.
Pion Total Cross Section in Nucleon - Nucleon Collisions
NASA Technical Reports Server (NTRS)
Norbury, John W.
2009-01-01
Total cross section parameterizations for neutral and charged pion production in nucleon - nucleon collisions are compared to experimental data over the projectile momentum range from threshold to 300 GeV. Both proton - proton and proton - neutron reactions are considered. Overall excellent agreement between parameterizations and experiment is found, except for notable disagreements near threshold. In addition, the hypothesis that the neutral pion production cross section can be obtained from the average charged pion cross section is checked. The theoretical formulas presented in the paper obey this hypothesis for projectile momenta below 500 GeV. The results presented provide a test of engineering tools used to calculate the pion component of space radiation.
QED Radiative Corrections in Processes of Exclusive Pion Electroproduction
Andrei Afanasev; I. Akushevich; Volker Burkert; K. Joo
2002-03-01
Formalism for radiative correction (RC) calculation in exclusive pion electroproduction on the proton is presented. A FORTRAN code EXCLURAD is developed for the RC procedure. The numerical analysis is done in the kinematics of current Jefferson Lab experiments.
QED radiative corrections in processes of exclusive pion electroproduction
NASA Astrophysics Data System (ADS)
Afanasev, A.; Akushevich, I.; Burkert, V.; Joo, K.
2002-10-01
A formalism for radiative correction (RC) calculation in exclusive pion electroproduction on the proton is presented. A FORTRAN code EXCLURAD is developed for the RC procedure. The numerical analysis is done in the kinematics of current Jefferson Lab experiments.
Hadron dynamics in high-energy pion-nucleus scattering
Johnson, M.B.
1992-12-31
It is argued that pion-nucleus scattering at high energy (above 300 MeV) is likely to be easier to interpret than it has been at lower energies where the {Delta}{sub 33} resonance dominates. We establish this by examining the relative importance of various dynamic ingredients of scattering theory for high-energy pions and comparing different versions of the theory: a ``model-exact`` microscopic optical model and an eikonal approximation. For nuclei as heavy as Ca, the eikonal theory is an excellent approximation to the full theory for the angular distribution out to the position of the second minimum in the cross section. The prospects for using high-energy pions to examine modifications of nucleons and baryon resonances in nuclei, nuclear structure, exchange currents, short-range correlations, and to characterize pion propagation are discussed.
Pion production for neutrino factories and muon colliders
Mokhov, N.V.; Guidman, K.K.; Strait, J.B.; Striganov, S.I.; /Fermilab
2009-12-01
Optimization of pion and muon production/collection for neutrino factories and muon colliders is described along with recent developments of the MARS15 code event generators and effects influencing the choice of the optimal beam energy.
Comparing pion production models to MiniBooNE data
Rodrigues, P. A.
2015-05-15
Predictions for neutrino-induced charged- and neutral-current single pion production on CH{sub 2} from theoretical models and Monte Carlo event generators are compared with the cross section measurements from the MiniBooNE experiment.
A New Pion-Nucleon Partial Wave Analysis
NASA Astrophysics Data System (ADS)
Sadler, Michael; Watson, Shon; Stahov, Jugoslav
2006-10-01
Existing determinations of the masses, widths and decay modes of low-lying excited states of the nucleon, as compiled in the Review of Particle Physics, are determined from energy-independent partial wave analyses of pion-nucleon scattering data. For the N*(1440) and most other resonances under 2 GeV, the analyses cited are the Karlsruhe-Helsinki, Carnegie Mellon-Berkeley and Kent State analyses, the latter of which used the elastic amplitudes from the other two. The data included in these analyses were published before 1980. Other analyses, notably the recent ones from George Washington University and the Pittsburgh-Argonne group, are ``not used for averages, fits, limits, etc.'' Complete sets of measurements (differential cross sections, analyzing powers and spin rotation parameters) have been measured in the N*(1440) resonance region since 1980, culminating in the Crystal Ball program at BNL to measure all-neutral final states (charge exchange, multiple pi-zero final states, and inverse photoproduction). A new partial wave analysis of the Karlsruhe-Helsinki type has been started by Abilene Christian University, University of Tuzla, and Rudjer Boskovic Institute. The analysis is constrained by fixed-t and interior hyperbolic dispersion relations. Comparisons of the new analysis to modern experimental data and to previous analyses will be presented.
Coherent and neutral pion production results from MINERνA
Palomino, J. L.; Higuera, A.
2015-05-15
MINERνA is a neutrino-nucleus scattering experiment employing multiple nuclear targets. The experiment is studying neutral pion production due to coherent, resonant and deep-inelastic processes, from both charged current and neutral current reactions. Neutral pions are detected through their two photon decay and the resultant electromagnetic showers. We will describe the analysis for the cross sections of inclusive and exclusive processes.
The Onset of Quark-Hadron Duality in Pion Electroproduction
Tigran Navasardyan; Gary Adams; Abdellah Ahmidouch; Tatiana Angelescu; John Arrington; Razmik Asaturyan; O. Baker; Nawal Benmouna; Crystal Bertoncini; Henk Blok; Werner Boeglin; Peter Bosted; Herbert Breuer; Michael Christy; Simon Connell; Yonggang Cui; Mark Dalton; Samuel Danagoulian; Donal Day; T. Dodario; James Dunne; Dipangkar Dutta; Najib Elkhayari; Rolf Ent; Howard Fenker; Valera Frolov; Liping Gan; David Gaskell; Kawtar Hafidi; Wendy Hinton; Roy Holt; Tanja Horn; Garth Huber; Ed Hungerford; Xiaodong Jiang; Mark Jones; Kyungseon Joo; Narbe Kalantarians; James Kelly; Cynthia Keppel; Edward Kinney; V. Kubarovski; Ya Li; Yongguang Liang; Simona Malace; Pete Markowitz; Erin McGrath; Daniella Mckee; David Meekins; Hamlet Mkrtchyan; Brian Moziak; Gabriel Niculescu; Maria-Ioana Niculescu; Allena Opper; Tanya Ostapenko; Paul Reimer; Joerg Reinhold; Julie Roche; Stephen Rock; Elaine Schulte; Edwin Segbefia; C. Smith; G.R. Smith; Paul Stoler; Vardan Tadevosyan; Liguang Tang; Maurizio Ungaro; Alicia Uzzle; Sandra Vidakovic; Anthony Villano; William Vulcan; Miao Wang; Glen Warren; Frank Wesselmann; Bogdan Wojtsekhowski; Stephen Wood; Chuncheng Xu; Lulin Yuan; Xiaochao Zheng; Hong Guo Zhu
2006-08-29
A large data set of charged-pion electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark-to- pion production mechanisms.
Stopping pions in high-energy nuclear cascades.
NASA Technical Reports Server (NTRS)
Jones, W. V.; Johnson, D. P.; Thompson, J. A.
1973-01-01
Results of Monte Carlo calculations for the number and energy spectra of charged pions from nuclear-electromagnetic cascades developing in rock are presented for primary hadron energies ranging from 3 to 3000 GeV. These spectra are given as functions of the longitudinal depth in the absorber and the lateral distance from the cascade axis. The number of charged pions which stop in the absorber increases with the primary energy of the hadron initiating the cascade.
Two-photon exchange corrections to the pion form factor
Peter G. Blunden; Melnitchouk, Wally; Tjon, John A.
2010-01-06
Here, we compute two-photon exchange corrections to the electromagnetic form factor of the pion, taking into account the finite size of the pion. Compared to the soft-photon approximation for the infrared divergent contribution which neglects hadron structure effects, the corrections are found to be ≲ 1% for small Q2 (Q2 < 0.1 GeV2), but increase to several percent for Q2 ≳ 1 GeV2 at extreme backward angles.
Di-photon resonance and Dark Matter as heavy pions
NASA Astrophysics Data System (ADS)
Redi, Michele; Strumia, Alessandro; Tesi, Andrea; Vigiani, Elena
2016-05-01
We analyse confining gauge theories where the 750 GeV di-photon resonance is a composite techni-pion that undergoes anomalous decays into SM vectors. These scenarios naturally contain accidentally stable techni-pions Dark Matter candidates. The di-photon resonance can acquire a larger width by decaying into Dark Matter through the CP-violating θ-term of the new gauge theory reproducing the cosmological Dark Matter density as a thermal relic.
Pion interferometry in {sup 28}Si + Pb central collisions
Xu, Nu; E814 Collaboration: BNL-GSI-McGill Univ.-Univ. of Pittsburg-SUNY Stony Brook-Univ. of Sao Paulo-Wayne State Univ.-Yale Univ.
1994-08-01
Two-pion correlation functions have been studied using the E814 apparatus in 14.6 A{center_dot}GeV/c {sup 28}Si + Pb central collisions. Results of the correlation functions for pions from the RQMD event generator are compared to the data and show that a source with RMS radius of 8.3 fm is compartable with the experimental data.
The onset of quark-hadron duality in pion electroproduction.
Navasardyan, T.; Adams, G. S.; Ahnidouch, A.; Angelescu, T.; Arrington, T.; Arrington, J.; Hafidi, K.; Holt, R. J.; Reimer, P.; Schulte, E.; Zheng, X.; Physics; Yerevan Physics Inst.; Rensselaer Polytechnic Inst.; North Carolina A & T Univ.; Bucharest Univ.
2007-01-01
A large data set of charged-pion ({pi}*) electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark {yields} pion production mechanisms.
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.
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
2016-03-26
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are n(i, f) similar to 10(4)-10(5). We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one canmore » infer the decay width in more realistic magnetic fields of 10(15) G, where n(i, f) similar to 10(12)-10(13), from the results for n(i, f) similar to 10(4)-10(5). The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).« less
Pion transverse charge density from timelike form factor data
Gerald Miller, Mark Strikman, Christian Weiss
2011-01-01
The transverse charge density in the pion can be represented as a dispersion integral of the imaginary part of the pion form factor in the timelike region. This formulation incorporates information from e+e- annihilation experiments and allows one to reconstruct the transverse density much more accurately than from the spacelike pion form factor data alone. We calculate the transverse density using an empirical parametrization of the timelike pion form factor and estimate that it is determined to an accuracy of ~10% at a distance b ~ 0.1 fm, and significantly better at larger distances. The density is found to be close to that obtained from a zero-width rho meson pole over a wide range and shows a pronounced rise at small distances. The resulting two-dimensional image of the fast-moving pion can be interpreted in terms of its partonic structure in QCD. We argue that the singular behavior of the charge density at the center requires a substantial presence of pointlike configurations in the pion's partonic wave function, which can be probed in other high-momentum transfer processes.
Neutron Radii from Low Energy Pion Scattering.
NASA Astrophysics Data System (ADS)
Gyles, William
Recent electron scattering measurements and muonic atom studies have allowed precise determinations of the charge distributions of nuclei. Measurements of the neutron distributions, however, have not progressed to this degree of sophistication, largely because of the uncertainties in the hadron-nucleus interaction. Charge distribution measurements provide good tests of nuclear structure calculations, but measurements of neutron distributions will provide independent constraints on these calculations and the potentials used. In this experiment, (pi)('-) differential cross section ratios were measured on pairs of isotopes (('36)S,('32)S), (('34)S,('32)S) with 50 MeV pions and (('26)Mg,('24)Mg) with 45 MeV pions. Absolute differential cross sections were also measured for ('32)S and ('24)Mg. Magnetic spectro -meters were used to collect the data. The cross section ratios were compared to optical model calcula-tions in which the parameters of a Fermi function representing the neutron distribution of the larger isotope of each pair were varied. The rms radius difference between the two isotopes producing the best fit was found to be independent of the details of the optical potential used, as long as the potential produced a fit to the absolute cross sections. The neutron distribution of the larger isotope was also rep-resented as a Fermi function modified by a sum of spherical Bessel functions, the coefficients of which were allowed to vary. The results for the rms radius differences were consistent with the Fermi function fits, except for ('34)S-('32)S, where the results differed by a full standard deviation. The rms radius differences found for the sulfur isotopes agreed with the results of shell-model calculations by Hodgson (Str82,Hod83). The extracted rms radius difference of the magnesium isotopes was one standard deviation less than the shell-model prediction. The results for the Fermi function fits, Fourier Bessell fits and the single particle potential (SPP
Scadron, Michael D.; Kleefeld, Frieder; Rupp, George
2007-02-27
Light constituent quark masses and the corresponding dynamical quark masses are determined by data, the quark-level linear {sigma} model, and infrared QCD. This allows to define effective nonstrange and strange current quark masses, which reproduce the experimental pion and kaon masses very accurately, by simple additivity. In contrast, the usual nonstrange and strange current quarks employed by the Particle Data Group and Chiral Perturbation Theory do not allow a straightforward quantitative explanation of the pion and kaon masses.
750 GeV diphoton excess confronted with a top-pion in the TTM model
NASA Astrophysics Data System (ADS)
Guo, Yu-Chen; Yue, Chong-Xing; Zhao, Zhen-Hua
2016-05-01
The latest LHC data suggest an intriguing excess at mγγ = 750GeV which apparently requires an explanation from the beyond standard model physics. In this paper, we explore the possibility for this signal to arise from a top-pion in the Top Triangle Moose model which can be viewed as a dimensional-deconstruction version of the top-color assisted technicolor model. We demonstrate that the observed excess can be accommodated by and has important implications for this interesting model.
Mekjian, A. Z.
1999-12-01
A general expression is discussed for pion probability distributions coming from relativistic heavy ion collisions. The general expression contains as limits (1) the disoriented chiral condensate (DCC), (2) the negative binomial distribution and Pearson type-III distribution, (3) a binomial or Gaussian result, and (4) a Poisson distribution. This general expression approximates other distributions such as a signal-to-noise laser distribution. Similarities and differences of the DCC distribution with these other distributions are studied. A connection with the theory of disordered systems will be discussed which includes spin glasses, randomly broken objects, and random and chaotic maps. (c) 1999 The American Physical Society.
ERIC Educational Resources Information Center
Bromley, D. Allan
1980-01-01
The author presents the argument that the past few years, in terms of new discoveries, insights, and questions raised, have been among the most productive in the history of physics. Selected for discussion are some of the most important new developments in physics research. (Author/SA)
Pion scattering poles and chiral symmetry restoration
Fernandez-Fraile, D.; Nicola, A. Gomez; Herruzo, E. T.
2007-10-15
Using unitarized chiral perturbation theory methods, we perform a detailed analysis of the {pi}{pi} scattering poles f{sub 0}(600) and {rho}(770) behavior when medium effects such as temperature or density drive the system towards chiral symmetry restoration. In the analysis of real poles below threshold, we show that it is crucial to extend properly the unitarized amplitudes so that they match the perturbative Adler zeros. Our results do not show threshold enhancement effects at finite temperature in the f{sub 0}(600) channel, which remains as a pole of broad nature. We also implement T=0 finite-density effects related to chiral symmetry restoration, by varying the pole position with the pion decay constant. Although this approach takes into account only a limited class of contributions, we reproduce the expected finite-density restoration behavior, which drives the poles towards the real axis, producing threshold enhancement and {pi}{pi} bound states. We compare our results with several model approaches and discuss the experimental consequences, both in relativistic heavy ion collisions and in {pi}{yields}{pi}{pi} and {gamma}{yields}{pi}{pi} reactions in nuclei.
Optimized perturbation theory: the pion form factor
Gupta, R.
1981-10-01
The order ..cap alpha../sup 2//sub s/(Q/sup 2/) corrections to the pion form-factor F/sub ..pi../(Q/sup 2/) are calculated using perturbative QCD and dimensional regularization. The result is compared in the MS and MOM subtraction schemes and plotted as a function of Q/sup 2//Q/sup 2/ where Q is the subtraction point. There is a large dependence on the scheme, the definition of the running coupling constant ..cap alpha../sub s/(Q/sup 2/) and the subtraction point Q. We find it best to invert the ..beta..-function equation for the definition of ..cap alpha../sub s/ rather than make an expansion in powers of log(Q/sup 2//..lambda../sup 2/). We study two methods to optimize the result with respect to Q: Stevenson's prescription and putting the 0(..cap alpha../sup 2//sub s/) term to zero. Both methods give almost the same value for Q/sup 2/F/sub ..pi../ and this value is scheme independent.
Asymmetry measurement for (13)C(charged pion,charged pion)(13)C* at T(pi) = 162 MeV
NASA Astrophysics Data System (ADS)
Johnson, Kevin William
1998-12-01
Left-right asymmetry measurements ( AY) were obtained for charged pion scattering of incident kinetic energy 162 MeV from polarized 13C nuclei over an angular range of 30o to 90o. The experiment was performed at the Los Alamos Meson Physics Facility with the Energetic PIon Channel and Spectrometer (EPICS). The 13C target was made up of frozen beads of toluene consisting of 93% 13C612CH8 cryogenically cooled to 0.45o K by a 3He evaporation refrigerator. Polarization was achieved with the dynamic nuclear polarization method using a 2.5 Tesla magnetic field, target material doping by the paramagnetic substance DTBN, and a polarization driving microwave field of frequency 70.060 GHz for parallel and 70.320 GHz anti-parallel alignment with the applied magnetic field. Average polarization of the 13Cl nuclei was ~17% and for the 1H nuclei was ~54% which was obtained after an initial polarization time period of about 30 minutes. AY measurements were calculated by separately obtaining the excitation yield spectra for the chosen target nuclei spin orientation of up or down with respect to [/bf k]inc×[/bf k]scat of the incident and scattered pion. The separate excitation spectra for up and down were used to derive the difference and polarization scaled sum in a channel-by- channel method to reduce effects of the spectrometer plus polarization magnet acceptance. These difference and sum spectra were statistically fitted to peak shapes calculated to account for the pion energy loss straggling. The ratio of the peak yield of the difference spectra to the sum spectra is Ay. Results of AY for the elastic scattering of π+ and πsp- from 1H are consistent with the values calculated by phase shift analysis. Measured AY for the elastic scattering from 13C are found to be in general small but to exhibit two maxima at approximately 51o and 88o CMS scattering angle of approximate values 0.26 (0.24) and 0.21 (0.41) for π+/ (/pi/sp-) scattering. AY values were also measured for states
Pion Form Factor in Chiral Limit of Hard-Wall AdS/QCD Model
Anatoly Radyushkin; Hovhannes Grigoryan
2007-12-01
We develop a formalism to calculate form factor and charge density distribution of pion in the chiral limit using the holographic dual model of QCD with hard-wall cutoff. We introduce two conjugate pion wave functions and present analytic expressions for these functions and for the pion form factor. They allow to relate such observables as the pion decay constant and the pion charge electric radius to the values of chiral condensate and hard-wall cutoff scale. The evolution of the pion form factor to large values of the momentum transfer is discussed, and results are compared to existing experimental data.
Valence-quark distribution functions in the kaon and pion
NASA Astrophysics Data System (ADS)
Chen, Chen; Chang, Lei; Roberts, Craig D.; Wan, Shaolong; Zong, Hong-Shi
2016-04-01
We describe expressions for pion and kaon dressed-quark distribution functions that incorporate contributions from gluons which bind quarks into these mesons and hence overcome a flaw of the commonly used handbag approximation. The distributions therewith obtained are purely valence in character, ensuring that dressed quarks carry all the meson's momentum at a characteristic hadronic scale and vanish as (1 -x )2 when Bjorken-x →1 . Comparing such distributions within the pion and kaon, it is apparent that the size of S U (3 ) -flavor symmetry breaking in meson parton distribution functions is modulated by the flavor dependence of dynamical chiral symmetry breaking. Corrections to these leading-order formulas may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea quarks. Working with available empirical information, we build an algebraic framework that is capable of expressing the principal impact of both classes of corrections. This enables a realistic comparison with experiment which allows us to identify and highlight basic features of measurable pion and kaon valence-quark distributions. We find that whereas roughly two thirds of the pion's light-front momentum is carried by valence dressed quarks at a characteristic hadronic scale; this fraction rises to 95% in the kaon; evolving distributions with these features to a scale typical of available Drell-Yan data produces a kaon-to-pion ratio of u -quark distributions that is in agreement with the single existing data set, and predicts a u -quark distribution within the pion that agrees with a modern reappraisal of π N Drell-Yan data. Precise new data are essential in order to validate this reappraisal and because a single modest-quality measurement of the kaon-to-pion ratio cannot be considered definitive.
NASA Astrophysics Data System (ADS)
Slaba, Tony C.; Blattnig, Steve R.; Reddell, Brandon; Bahadori, Amir; Norman, Ryan B.; Badavi, Francis F.
2013-07-01
Recent work has indicated that pion production and the associated electromagnetic (EM) cascade may be an important contribution to the total astronaut exposure in space. Recent extensions to the deterministic space radiation transport code, HZETRN, allow the production and transport of pions, muons, electrons, positrons, and photons. In this paper, the extended code is compared to the Monte Carlo codes, Geant4, PHITS, and FLUKA, in slab geometries exposed to galactic cosmic ray (GCR) boundary conditions. While improvements in the HZETRN transport formalism for the new particles are needed, it is shown that reasonable agreement on dose is found at larger shielding thicknesses commonly found on the International Space Station (ISS). Finally, the extended code is compared to ISS data on a minute-by-minute basis over a seven day period in 2001. The impact of pion/EM production on exposure estimates and validation results is clearly shown. The Badhwar-O'Neill (BO) 2004 and 2010 models are used to generate the GCR boundary condition at each time-step allowing the impact of environmental model improvements on validation results to be quantified as well. It is found that the updated BO2010 model noticeably reduces overall exposure estimates from the BO2004 model, and the additional production mechanisms in HZETRN provide some compensation. It is shown that the overestimates provided by the BO2004 GCR model in previous validation studies led to deflated uncertainty estimates for environmental, physics, and transport models, and allowed an important physical interaction (π/EM) to be overlooked in model development. Despite the additional π/EM production mechanisms in HZETRN, a systematic under-prediction of total dose is observed in comparison to Monte Carlo results and measured data.
Soft two-pion-exchange nucleon-nucleon potentials
Rijken, Th.A. )
1991-06-01
Two-pion-exchange nucleon-nucleon potentials are derived for the pseudo-vector pion-nucleon interaction, assuming strong dynamical pair-suppression. At the pion-nucleon vertices the authors include Gaussian form factors, which are incorporated into the relativistic two-body framework by using a dispersion representation for the one-pion-exchange amplitude. The Fourier transformations are performed using a factorization technique for the energy denominators. This leads to analytic expressions for the TPE-potentials containing at most one-dimensional integrals. The TPE-potentials are calculated up to orders {line integral}{sup 4} and (m/M){line integral}{sup 4}. The terms of order {line integral}{sup 4} come from the adiabatic contributions of the parallel and crossed three-dimensional momentum-space TPE-diagrams, and from the non-adiabatic contributions of the OPE-iteration. The (m/M)-corrections are due to the 1/M-terms in the non-adiabatic expansion of the nucleon energies in the intermediate states, and the 1/M-terms in the pion-nucleon vertices. The latter are typical for the PV-coupling and would be absent for the PS-coupling. The Gaussian form factors lead to soft TPE-potentials. These potentials can readily be exploited in NN-calculations in combination with, e.g., the Nijmegen soft-core OBE-model, and in nuclear (matter) calculations.
Pion- and proton-nucleus interactions at intermediate energy
Dehnhard, D.
1992-12-01
We report on scattering and reaction experiments on light nuclei using the [pi]-meson and proton beams from the Los Alamos Meson Physics Facility (LAMPF) and the Indiana University Cyclotron Facility (IUCF). Differential cross sections, cross section asymmetries, and angular correlation functions have been measured in order to test models of the reaction mechanism and of nuclear structure. At LAMPF we have measured asymmetries for pion scattering from polarized [sup 13]C which are uniquely sensitive to the isoscalar spin density. In order to determine details of the reaction mechanism, we have obtained approval for a scattering experiment on polarized [sup 3]He for which the nuclear structure is very well known. We have completed data taking for two studies of elastic scattering of [pi][sup +] from [sup 6]Li and [sup l3]C. The detailed differential cross sections from these experiments will be used to constrain theoretical analyses of previous polarization experiments done at the Pierre-Scherrer-Institute (PSI) and at LAMPF. We have analyzed [pi]-triton coincidence events from the [sup 4]He([pi],[pi][prime] t)p reaction and have found evidence for direct triton knockout from [sup 4]He. We have extended these angular correlation measurements to higher energies and to [sup 2]H and [sup 3]He targets. At IUCF we have performed the first [sup 4]He(p,n) experiment at intermediate energies, T[sub p] = 100, 147, and 200 MeV, in a search for previously reported narrow states in [sup 4]Li of widths of [approx] 1 MeV. Within the statistics of the data we have found no evidence for such narrow structures.
One-pion production in neutrino-nucleus collisions
Hernández, E.; Nieves, J.; Vicente-Vacas, J. M.
2015-05-15
We use our model for neutrino pion production on the nucleon to study pion production on a nucleus. The model is conveniently modified to include in-medium corrections and its validity is extended up to 2 GeV neutrino energies by the inclusion of new resonant contributions in the production process. Our results are compared with recent MiniBooNE data measured in mineral oil. Our total cross sections are below data for neutrino energies above ≈ 1 GeV. As with other theoretical calculations, the agreement with data improves if we neglect pion final state interaction. This is also the case for differential cross sections convoluted over the neutrino flux.
Pion-Skyrmion scattering: collective coordinates at work
Peskin, M.E.
1985-06-01
It is argued that the Skryme model, and more generally, the picture of the nucleon as a chiral soliton, can give a qualitatively correct picture of pion-nucleon scattering, considering both group-theoretic and more scheme-dependent results. The properties of the nucleon and its excited states in large-N quantum chromodynamics are discussed qualitatively. Then the pion-nucleon S-matrix is reduced. It is found that the model succeeds at the first level of calculation in producing many of the features of pion-nucleon scattering which are revealed by experiment, but that many aspects of the description need to be better understood, including the treatment of nonleading corrections near threshold and the inclusion of inelastic channels. 22 refs., 8 figs. (LEW)
Analysis of single pion electroproduction data from CLAS
Hovanes Egiyan; Inna Aznauryan; Volker Burkert; Kyungseon Joo; Lee Smith; Stepan Stepanyan
2003-07-01
Analysis of the single pion electroproduction data is one of the most powerful tools in investigating the nucleon resonances in the first and second resonance regions. Recent pion electroproduction experiments using CLAS detector at Jefferson Lab for the first time provides us with data for the cross sections and the single beam spin asymmetries for both epto e' n pi^+ and epto e' p pi^0 channels. In order to analyze this data an analysis program based on the Mainz unitary isobar model was developed at Jefferson Lab. The single pion electroproduction cross sections and the single beam asymmetry data were fitted simultaneously to obtain the resonant amplitudes for the excited states in the first two nucleon resonance regions. Preliminary results will be presented for the electroproduction amplitudes for the S_11(1535) and D_13(1520) resonances.
Internal Structure of the Pion Inspired by the AdS/QCD Correspondence
NASA Astrophysics Data System (ADS)
Bacchetta, Alessandro; Cotogno, Sabrina; Pasquini, Barbara
2016-06-01
We present a study of the pion structure in the context of the AdS/QCD soft-wall model. This approach provides the light-front wave function of the pion in terms of a set of parameters that we fit to available experimental information on the electromagnetic form factor and parton distribution of the pion. We discuss the corresponding predictions for the unpolarized transverse momentum dependent parton distribution of the pion.
Internal Structure of the Pion Inspired by the AdS/QCD Correspondence
NASA Astrophysics Data System (ADS)
Bacchetta, Alessandro; Cotogno, Sabrina; Pasquini, Barbara
2016-04-01
We present a study of the pion structure in the context of the AdS/QCD soft-wall model. This approach provides the light-front wave function of the pion in terms of a set of parameters that we fit to available experimental information on the electromagnetic form factor and parton distribution of the pion. We discuss the corresponding predictions for the unpolarized transverse momentum dependent parton distribution of the pion.
PIGMI: a design report for Pion Generator for Medical Irradiations
Hansborough, L.D.
1981-09-01
PIGMI (Pion Generator for Medical Irradiations) is an integrated linear accelerator (linac) system developed under the auspices of the National Cancer Institute for specific application to cancer treatment in a hospital environment. In its full configuration, PIGMI is a proton linac that is far smaller, less expensive, and more reliable than previous machines that produce pions. Subsets of PIGMI technology can be used with equal advantage to generate beams of other particles (such as neutrons, protons, or heavy ions) that may be of interest for radiotherapy, radioisotope production, or other applications. The dramatic performance and cost advantages of this new breed of acceleraor result from a number of improvements. In the low-energy portion of the machine, a new type of low-energy linac (the radio-frequency quadrupole(RFQ)) produces an exceptionally good quality beam, and uses a very simple 30-kV injector. In the second part of the machine (the drift-tube linac (DTL)), high accelerating gradients are now achievable with consequent reductions in machine length. Another new structure (the disk and washer (DAW)) will be used in the third and final section of the accelerator; this portion will also be relatively short and require few power amplifiers. The entire machine is designed for ease of operation and high reliability. The pion-production machine, discussed in this report, accelerates a 100-..mu..A average proton-beam current to 650 MeV; use of an efficient pion-collection channel would result in an average pion flux of over 100 rad/min in a volume of about 1 l. Pion-channel design is not treated in this report. Accelerator construction cost is estimated at $10 million (1980 dollars); site preparation and treatment facility costs would bring the cost of a complete facility to an estimated $25 million.
Scaling study of the pion electroproduction cross sections and the pion form factor
Tanja Horn; Xin Qian; John Arrington; Razmik Asaturyan; Fatiha Benmokthar; Werner Boeglin; Peter Bosted; Antje Bruell; Eric Christy; Eugene Chudakov; Ben Clasie; Mark Dalton; AJI Daniel; Donal Day; Dipangkar Dutta; Lamiaa El Fassi; Rolf Ent; Howard Fenker; J. Ferrer; Nadia Fomin; H. Gao; K Garrow; Dave Gaskell; C Gray; G. Huber; M. Jones; N Kalantarians; C. Keppel; K Kramer; Y Li; Y Liang; A. Lung; S Malace; P. Markowitz; A. Matsumura; D. Meekins; T Mertens; T Miyoshi; H. Mykrtchyan; R. Monson; T. Navasardyan; G. Niculescu; I. Niculescu; Y. Okayasu; A. Opper; C Perdrisat; V. Punjabi; A. Rauf; V. Rodriguez; D. Rohe; J Seely; E Segbefia; G. Smith; M. Sumihama; V. Tadevoyan; L Tang; V. Tvaskis; A. Villano; W. Vulcan; F. Wesselmann; S. Wood; L. Yuan; X. Zheng
2007-07-12
The $^{1}$H($e,e^\\prime \\pi^+$)n cross section was measured for a range of four-momentum transfer up to $Q^2$=3.91 GeV$^2$ at values of the invariant mass, $W$, above the resonance region. The $Q^2$-dependence of the longitudinal component is consistent with the $Q^2$-scaling prediction for hard exclusive processes. This suggests that perturbative QCD concepts are applicable at rather low values of $Q^2$. Pion form factor results, while consistent with the $Q^2$-scaling prediction, are inconsistent in magnitude with perturbative QCD calculations. The extraction of Generalized Parton Distributions from hard exclusive processes assumes the dominance of the longitudinal term. However, transverse contributions to the cross section are still significant at $Q^2$=3.91 GeV$^2$.
Centrality Dependence of Neutral Pion Production in 158A GeV {sup 208}Pb+{sup 208}Pb Collisions
Aggarwal, M.M.; Bhatia, V.S.; Agnihotri, A.; Bhalla, K.B.; Gupta, S.K.; Raniwala, R.; Raniwala, S.; Ahammed, Z.; Chattopadhyay, S.; Das, A.C.; Dutta Majumdar, M.R.; Ganti, M.S.; Mukhopadhyay, D.S.; Nayak, T.K.; Sinha, B.C.; Trivedi, M.D.; Viyogi, Y.P.; Angelis, A.L.; Donni, P.; Foka, P.; Kalechofsky, H.; Martin, M.; Naef, H.; Rosselet, L.; Rubio, J.M.; Solomey, N.; Voeroes, S.; Antonenko, V.; Cherbatchev, R.; Doubovik, I.; Fokin, S.; Ippolitov, M.; Karadjev, K.; Koutcheryaev, I.; Lebedev, A.; Manko, V.; Mgebrichvili, G.; Nianine, A.; Sibiriak, I.; Tsvetkov, A.; Vinogradov, A.; Arefiev, V.; Astakhov, V.; Avdeitchikov, V.; Baldine, A.; Barabach, L.; Batiounia, B.; Chalyshev, V.; Djordjadze, V.; Frolov, V.; Gavrishchuk, O.; Guskov, B.; Kosarev, I.; Kuzmin, N.; Maximov, A.; Mehdiyev, R.; Mikhalev, D.; Myalkovski, V.; Nikitine, V.; Nikolaev, S.; Nomokonov, P.; Parfenov, A.; Pavliouk, S.; Roufanov, I.; Shabratova, G.; Slavine, N.; Vodopianov, A.; Awes, T.C.; Kim, H.; Plasil, F.; Stankus, P.; Young, G.R.; Baba, P.V.; Badyal, S.K.; Rao, N.K.; Sambyal, S.S.; Barlag, C.; Bathe, S.; Blume, C.; Bohne, E.; Boeroecz, Z.K.; Bucher, D.; Buesching, H.; Claussen, A.; Glasow, R.; Kampert, K.; Kees, S.; Kruempel, T.; Pietzmann, T.; Reygers, K.; Santo, R.; Schlagheck, H.; Stueken, D.; Bernier, T.; Gutbrod, H.H.; Luquin, L.; Nayak, S.K.; Pinanaud, W.; Retiere, F.; Roy, C.; Bock, R.; Kolb, B.W.; Langbein, I.; Lee, Y.Y.; Neumaier, S.; and others
1998-11-01
The production of neutral pions in 158A GeV {sup 208}Pb+ {sup 208}Pb collisions has been studied in the WA98 experiment at the CERN Super Proton Synchrotron (SPS). Transverse momentum spectra are studied for the range 0.3{le}m{sub T}{minus}m{sub 0}{le}4.0 GeV /c . The results for central collisions are compared to various models. The centrality dependence of the neutral pion spectral shape and yield is investigated. An invariance of the spectral shape and a simple scaling of the yield with the number of participating nucleons is observed for centralities with greater than about 30thinspthinspparticipating nucleons. This is most naturally explained by assuming an equilibrated system. {copyright} {ital 1998} {ital The American Physical Society }
Huang, Z.; Suzuki, M.
1996-01-01
We obtain the general solutions of the nonlinear {sigma} model in 3+1 dimensions as the candidates for the disoriented chiral condensate (DCC). The nonuniformly isospin-oriented solutions are shown to be related to the uniformly oriented ones through the chiral (axial) rotations. We discuss the pion charge distribution arising from these solutions. The distribution {ital dP}/{ital d}{ital f}=1/(2 {radical}{ital f} ) holds for the uniform solutions in general and the nonuniform solutions in the 1+1 boost-invariant case. For the nonuniform solution in 1+1 without boost invariance and in higher dimensions, the distribution does not hold in the integrated form. However, it is applicable to the pions selected from a small segment in the momentum phase space. We suggest that the nonuniform DCC{close_quote}s may correspond to the mini-Centauro events. {copyright} {ital 1996 The American Physical Society.}
Neutral Pion Production from Deuterium at the Legs Facility
NASA Astrophysics Data System (ADS)
Hicks, K. H.; Ardashev, K.; Blecher, M.; Caracappa, A.; Cichocki, A.; Commeaux, C.; D'Angelo, A.; Didilez, J.-P.; Deininger, R.; Hoblit, S.; Khandaker, M.; Kistner, O.; Kuczewski, A.; Lincoln, F.; Lindgren, R.; Lehmann, A.; Lowry, M.; Lucas, M.; Meyer, H.; Miceli, L.; Opper, A.; Preedom, B. M.; Norum, B.; Sandorfi, A. M.; Schaerf, C.; Ströher, H.; Thorn, C. E.; Tonnison, J.; Wang, K.; Wei, X.; Whisnant, C. S.; Willits, D.
2002-06-01
Neutral pion photoproduction from a liquid deuterium target was measured in the energy region near 300 MeV at the LEGS facility of Brookhaven National Laboratory. The inclusive cross sections from deuterium are in agreement with measurments from Mainz, yet the exclusive cross sections and spin asymmetries for neutral pion production in coincidence with a detected nucleon are much smaller than expected from a quasi-free approximation. This may indicate that substantial final state interactions play a significant role, which will complicate the extraction of the desired amplitudes that would be measured if a free neutron target could be used.
Role of pion pole in hard exlusive meson leptoproduction
NASA Astrophysics Data System (ADS)
Goloskokov, Sergey
2016-02-01
We consider the pion pole contribution and transversity effects determined by the HT and ĒT Generalized Parton Distributions (GPDs) which are essential in hard pseudoscalar and vector meson leptoproduction. We investigate spin effects in the ω and ρ0 reactions. It is shown that the pion pole contribution is very important in the w production. Such effects in the ρ0 channel are much smaller. Our results on spin asymmetries and spin density matrix elements in these reactions were found to be in good agreement with HERMES data.
Electroproduction of pions at threshold in chiral perturbation theory
Lee, T.S.H.; Bernard, V.; Kaiser, N.; Meissner, U.G.
1995-08-01
The electroproduction of pions off protons close to threshold is studied within the framework of baryon chiral perturbation theory. The approach is based on the fundamental QCD property that at low energies the strong interactions are dictated by the spontaneously broken chiral symmetry. The calculation was done up to the 1-loop level by carrying out order-by-order renormalization procedures. A thorough study of the low-energy theorems related to electroproduction of pions was carried out. Our study showed how the axial radius of the nucleon can be related to the S-wave multipoles E{sub 0+}{sup (-)} and L{sub 0+}{sup (-)}.
Pion double charge exchange reactions leading to double pionic atoms
Nieves, J.; Oset, E.; Vincente-Vacas, M.J. ); Hirenzaki, S.; Toki, H. )
1992-10-20
In this paper, the authors study theoretically pion double charge exchange reactions leading to double pionic atoms. The reaction cross-sections with two pions in the deeper bound pionic orbits in [sup 208]Pb are calculated with realistic pionic atom wave functions and distortion effects. The cross-sections are found to be d[sup 2] [sigma]/dEd[Omega] [approx] 10[sup [minus] 3] [minus] 10[sup [minus] 4] [mu]b/srMeV, which are only a small fraction of the double charge exchange.
[ital I]=2 pion scattering amplitude with Wilson fermions
Gupta, R. ); Patel, A. ); Sharpe, S.R. )
1993-07-01
We present an exploratory calculation of the [ital I]=2 [pi][pi] scattering amplitude at threshold using Wilson fermions in the quenched approximation, including all the required contractions. We find good agreement with the predictions of chiral perturbation theory even for pions of mass 560--700 MeV. Within 10% error, we do not see the onset of the bad chiral behavior expected for Wilson fermions. We also derive rigorous inequalities that apply to two-particle correlators and as a consequence show that the interaction in the antisymmetric state of two pions has to be attractive.
Two-photon exchange corrections to the pion form factor
Peter G. Blunden; Melnitchouk, Wally; Tjon, John A.
2010-01-06
Here, we compute two-photon exchange corrections to the electromagnetic form factor of the pion, taking into account the finite size of the pion. Compared to the soft-photon approximation for the infrared divergent contribution which neglects hadron structure effects, the corrections are found to be ≲ 1% for small Q^{2} (Q^{2} < 0.1 GeV^{2}), but increase to several percent for Q^{2} ≳ 1 GeV^{2} at extreme backward angles.
Onset of Quark-Hadron Duality in Pion Electroproduction
Navasardyan, T.; Asaturyan, R.; Mkrtchyan, H.; Tadevosyan, V.; Adams, G. S.; Kubarovski, V.; Moziak, B.; Stoler, P.; Ungaro, M.; Villano, A.; Ahmidouch, A.; Danagoulian, S.; Angelescu, T.; Malace, S.; Arrington, J.; Hafidi, K.; Holt, R. J.; Reimer, P.; Schulte, E.; Zheng, X.
2007-01-12
A large data set of charged-pion ({pi}{sup {+-}}) electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark{yields}pion production mechanisms.
Multinucleon pion absorption on {sup 4}He into the pppn final state
Lehmann, A.; Backenstoss, G.; Koehler, J.; Kroedel, M.; Weyer, H.J.; Wildi, M.; Hoffart, A.; Trezeciak, R.; Ullrich, H.; Gram, P.A.; Breuer, H.; Gregory, N.K.; Mateos, A.O.; Redwine, R.P.; Rowntree, D.; Simicevic, N.; Wilson, K.E.; Kyle, G.; Wang, M.; Wang, M.H.; Dooling, T.; Klein, A.; Lehmann, A.; Doebbeling, H.; Hoffart, A.; Ingram, C.H.; Koch, K.; Kotlinski, B.; Michaelian, K.; Sennhauser, U.; Weyer, H.J.; Androic, D.; Bosnar, D.; Furic, M.; Petkovic, T.; Planinic, M.
1997-10-01
Results from a 4{pi} solid angle measurement of the reaction {pi}{sup +4}He{r_arrow}pppn at incident pion energies of T{sub {pi}{sup +}}= 70, 118, 162, 239, and 330 MeV are presented. Integrated cross sections are given for the reactions where three nucleons participate, leading to energetic (ppp) or (ppn) final states, and for states where four nucleons are involved (pppn). The two three-nucleon absorption modes were investigated in particular, and an energy dependent isospin ratio of the cross sections of {sigma}{sub ppn}/ {sigma}{sub ppp}=3.6{plus_minus}1.3, 2.6 {plus_minus}0.5, 1.8{plus_minus}0.3, 1.4{plus_minus} 0.2, and 1.8{plus_minus}0.6 was determined from 70 to 330 MeV. The differential cross sections were described by a complete set of eight independent variables and compared to simple cascade and phase space models. From this analysis the contributions from initial state interactions to the multinucleon absorption cross sections were found to be more important at higher pion energies, while those from final state interactions are stronger at lower energies. However, both mechanisms combined were found to account for not more than one-third of the total pppn multinucleon yield. The remaining strength is reasonably well reproduced by phase space models, but shows a dependence on the incident pion{close_quote}s orbital angular momentum. The isospin structure of the (ppp) and (ppn) final states is not understood, nor are some structures in their distributions. The four-nucleon yield (pppn) was found to be weak (1{endash}8{percent} of the total absorption cross section) and shows no evidence for a {open_quotes}double- {Delta}{close_quotes} excitation. {copyright} {ital 1997} {ital The American Physical Society}
Inclusive Pion Double Charge Exchange in Light P - Nuclei at Intermediate Energies.
NASA Astrophysics Data System (ADS)
Fong, Wilson
Inclusive measurements of the doubly differential cross section for the reaction pion double charge exchange (DCX) reaction were made on ^6Li, ^7Li, ^9Be and ^{12}C. The experiments were performed at the Los Alamos Physics Facility (LAMPF) using the "Little Yellow Spectrometer", LYS. The measurements were made for both pi^+ and pi^- at T_ pi = 120, 180, and 240 MeV for three to five angles between 25^circ and 130^circ. The outgoing pion kinetic energy range was observed. These are the only known measurements of inclusive DCX cross sections on the ^6Li, ^7Li and ^9Be nuclei. The DCX reaction requires at least two nucleons to be involved in order to conserve charge. The simplest reaction model for DCX is the sequential single charge exchange model, SSCX. The measurements aimed to examine the evolution of the double peaked structure seen at high incident pion energy at forward angles as the nuclear mass, A, increases. The double peaked structure is believed to be a direct consequence of the dominant p-wave nature of the SCX reaction in the Delta -region and the two step process of SSCX. Furthermore, an examination of the effects of introducing an additional neutron into an N = Z system is made. When the additional neutron is not involved in the DCX process, it functions to draw flux away from the DCX channel, thereby reducing the DCX cross section. Calculations based on theoretical models of Oset and Kinney have been performed and a comparison made with the measured DCX cross sections. The comparison between experiment and theory shows the need for further theoretical work in inclusive DCX reactions. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).
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.
Pion-nucleus interactions and the STAR experiment at RHIC. Progress report, 1990--1993
Moore, C.F.
1993-09-01
This report summarizes the work carried out by personnel from the University of Texas at Austin at the Los Alamos Clinton P. Anderson Meson Physics Facility (LAMPF) during the calendar years 1990--1993 and on the STAR experiment at RHIC under grant DE-FGO5-87ER40343 between the University of Texas at Austin and the United States Department of Energy. A brief overview of work supported by this grant is given in Section 2. An account of the study of the double giant resonances in pion double charge exchange forms Section 3. This report contains a list of published papers and preprints in Section 6, invited talks in Section 7, and abstracts in Section 8. These papers summarize experiments involving participants supported by this grant and indicate the work accomplished by these participants in this program of medium energy nuclear physics research. Section 9 contains a list of personnel who have participated in this research program.
Measurement of the pion electromagnetic form-factor in the SELEX experiment
Dirkes, Guido; /Heidelberg, Max Planck Inst.
1999-10-01
This work describes the analysis of pion-electron scattering data of the fix-trage-experiment SELEX at Fermilab with special respects to the pion charge radius. At an average rate of 150 Hz, 215 million candidates for pion-electron elastic scattering were recorded during the fix target run until September 1997. A sample of 24,000 pion-electron scattering events was extracted in the course of several data strips. Monte Carlo studies gave detailed knowledge of acceptance, which is important due to special trigger conditions. Systematics were studied and the pion mean square charge radius was determined.
Pion transfer from hydrogen to deuterium in H2+D2 gas mixtures
NASA Astrophysics Data System (ADS)
Weber, P.; Armstrong, D. S.; Measday, D. F.; Noble, A. J.; Stanislaus, S.; Harston, M. R.; Aniol, K. A.; Horváth, D.
1990-01-01
The transfer of negative pions from pionic hydrogen to deuterium has been investigated in gas mixtures of H2 and D2 as a function of the D2 concentration (C). The concentration dependence of the transfer rate was fitted using a phenomenological model with two parameters. For C-->∞ (32+/-3)% of the pions undergo transfer. The fitted parameters reflect the ratio of pion capture to pion transfer in collisions of pionic hydrogen with protons or deuterons. No pressure dependence for pion transfer was found.
Longitudinal Lelectroproduction of Charged Pions on Hydrogen, Deuterium, and Helium 3
David Gaskell
2001-05-01
Conventional pictures of nuclear interactions, in which the pion mediates the long/medium range part of the nuclear force, predict an enhancement of the virtual pion cloud in nuclei relative to that in the free nucleon. Jefferson Lab Experiment E91003 measured charged pion electroproduction from Hydrogen, Deuterium, and Helium-3. The longitudinal cross section, which in the limit of pole dominance can be viewed as the quasifree knockout of a virtual pion, was extracted via a Rosenbluth separation. The longitudinal cross sections from Deuterium and Helium-3 were compared to Hydrogen to look for signatures of the nuclear pions.
Delta: the First Pion Nucleon Resonance - Its Discovery and Applications
DOE R&D Accomplishments Database
Nagle, D. E.
1984-07-01
It is attempted to recapture some of the fun and excitement of the pion-scattering work that led to the discovery of what is now called the delta particle. How significant this discovery was became apparent only gradually. That the delta is alive today and thriving at Los Alamos (as well as other places) is described.
A microscopic, coupled-channel theory of pion scattering
Kagarlis, M.A.; Johnson, M.B.; Fortune, H.T.
1995-05-15
The authors develop a new and comprehensive coordinate-space theory of pion-nucleus scattering to facilitate disentangling the conventional aspects of pion scattering from the non-conventional ones relevant to issues of hadron dynamics. They work in coordinate space in order to both unify and extend the relatively extensive and successful analyses of exclusive pion-nucleus reactions previously made within a similar framework. They construct the optical potential microscopically in shell-model framework by summing particle-hole pair configurations, leading naturally to a coupled-channel formulation. The theory includes a complete treatment of all spin-isospin components of the pion-nucleon scattering amplitude, and Fermi averaging is done explicitly. The authors present numerical results showing the significance of Fermi motion and spin dependence on charge-exchange angular distributions: Single and double spin flip are shown to play dominant and generally unappreciated roles in charge-exchange reactions, and corrections for Fermi motion are shown to be needed in order to quantitatively separate medium effects from conventional multiple scattering. 72 refs., 11 figs.
Measurement of the pion form factor at higher energies
Mack, D.J.
1994-04-01
One of the strongest arguments for increasing the nominal CEBAF beam energy to equal or exceed 6 GeV is that one would be able to make quality high Q{sup 2} measurements of the charged pion form factor.
Multiplicity of pions from a heated interacting gas
NASA Astrophysics Data System (ADS)
Vorov, O. K.; Hussein, M. S.
2001-09-01
We consider a toy model to mimic the properties of the hot self-interacting pion system created in high-energy collisions. We show that the distribution of the multiplicities is similar to the negative binomial distribution that is typical for the squeezed states.
Energy dependence of pion inelastic scattering from sup 208 Pb
Oakley, D.S. Lewis and Clark College, Portland, Oregon ); Peterson, R.J. ); Seestrom, S.J.; Morris, C.L.; Plum, M.A. ); Zumbro, J.D. ); Williams, A.L.; Bryan, M.A.; McDonald, J.W.; Moore, C.F. )
1991-11-01
Differential cross sections were measured for pion elastic and inelastic scattering from {sup 208}Pb at {ital T}{sub {pi}}=120 and 250 MeV. Energy-dependent neutron- and proton-transition matrix elements for a range of excited states were extracted and tested for consistency, using several structure models.
Renormalization of NN Interaction with Relativistic Chiral Two Pion Exchange
Higa, R; Valderrama, M Pavon; Arriola, E Ruiz
2007-06-14
The renormalization of the NN interaction with the Chiral Two Pion Exchange Potential computed using relativistic baryon chiral perturbation theory is considered. The short distance singularity reduces the number of counter-terms to about a half as those in the heavy-baryon expansion. Phase shifts and deuteron properties are evaluated and a general overall agreement is observed.
Delta: the first pion nucleon resonance - its discovery and applications
Nagle, D.E.
1984-07-01
It is attempted to recapture some of the fun and excitement of the pion-scattering work that led to the discovery of what is now called the delta particle. How significant this discovery was became apparent only gradually. That the delta is alive today and thriving at Los Alamos (as well as other places) is described.
Pion-induced scattering above the 3,3 resonance
Oset, E. ); Strottman, D. )
1991-01-01
Results of Gluaber model calculations of elastic, inelastic, single- and double-charge exchange reactions from light nuclei of pions having energy of 300 to 1200 MeV are presented. Experimental {pi}N phase shifts including {ell}=0 through 5 were used in the calculation. 25 refs., 6 figs.
Pion production in the MiniBooNE
Lalakulich, O.; Gallmeister, K.; Leitner, T.; Mosel, U.
2011-11-23
We investigate one pion production processes within the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) coupled channel transport model. Our calculations for integrated and differential cross sections for realistic experimental neutrino fluxes are compared to the data recently provided by the MiniBooNE collaboration.
One pion production in neutrino reactions: Including nonresonant background
Lalakulich, O.; Leitner, T.; Buss, O.; Mosel, U.
2010-11-01
We investigate neutrino-induced one pion production on nucleons. The elementary neutrino-nucleon cross section is calculated as the sum of the leading Delta pole diagram and several background diagrams obtained within the nonlinear sigma model. This approach does not introduce any new adjustable parameters, which allows unambiguous predictions for the observables. Considering electroproduction experiments as benchmark, the model is shown to be applicable up to pion-nucleon invariant mass W<1.4 GeV and provides a good accuracy. With respect to the total one pion cross section, the model predicts the background at the level of 10% for the p{pi}{sup +}, 30% for p{pi}{sup 0}, and 50% for n{pi}{sup +} final states. The results are compared with experimental data for various differential cross sections. Distributions with respect to muon-nucleon and muon-pion invariant masses are presented for the first time. The model describes the data quite well, with the discrepancies being of the same order as those between different data sets.
Pion production in the MiniBooNE experiment
NASA Astrophysics Data System (ADS)
Lalakulich, O.; Mosel, U.
2013-01-01
Background: Charged current pion production gives information on the axial form factors of nucleon resonances. It also introduces a noticeable background to quasielastic measurements on nuclear targets.Purpose: Understand pion production in neutrino interactions with nucleons and the reaction mechanism in nuclei.Method: The Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) model is used for an investigation of neutrino-nucleus reactions.Results: Theoretical results for integrated and differential cross sections for the MiniBooNE neutrino flux are compared to the data. Two sets of pion production data on elementary targets are used to obtain limits for the neutrino-nucleus reactions.Conclusions: The MiniBooNE pion production data are approximately consistent with the Brookhaven National Laboratory elementary data if a small flux renormalization is performed while the Argonne National Laboratory input data lead to significantly too low cross sections. A final determination of in-medium effects requires new data on elementary (p,D) targets.
Pion absorption on {sup 3}He and {sup 4}He with emission of three energetic protons
LADS Collaboration
1997-06-01
Results from a 4{pi} solid angle measurement of the reactions {sup 3}He({pi}{sup +},ppp) and {sup 4}He({pi}{sup +},ppp)n at incident pion energies of T{sub {pi}{sup +}}=70, 118, 162, 239, and 330 MeV are presented. For {sup 3}He the total absorption cross sections and their decomposition into two-proton and three-proton components are evaluated; for {sup 4}He the three-proton absorption cross sections are given. The differential distributions of the three-proton multinucleon absorption mode of both nuclei are analyzed and compared to each other by making use of a complete set of variables. The data are investigated for signatures of initial and final state interactions: it is found that more than half of the three-proton yield cannot be accounted for by cascade mechanisms. The remaining strength shows dependence on the incident pion angular momentum, but also structures that are not explained by simple semiclassical models. {copyright} {ital 1997} {ital The American Physical Society}
Relativistic O ( q4 ) two-pion exchange nucleon-nucleon potential: Configuration space
NASA Astrophysics Data System (ADS)
Higa, R.; Robilotta, M. R.; da Rocha, C. A.
2004-03-01
We have recently performed a relativistic O ( q4 ) chiral expansion of the two-pion exchange NN potential, and here we explore its configuration space content. Interactions are determined by three families of diagrams, two of which involve just gA and fπ , whereas the third one depends on empirical coefficients fixed by subthreshold πN data. In this sense, the calculation has no adjusted parameters and gives rise to predictions, which are tested against phenomenological potentials. The dynamical structure of the eight leading nonrelativistic components of the interaction is investigated and, in most cases, found to be clearly dominated by a well defined class of diagrams. In particular, the central isovector and spin-orbit, spin-spin, and tensor isoscalar terms are almost completely fixed by just gA and fπ . The convergence of the chiral series in powers of the ratio (pion mass/nucleon mass) is studied as a function of the internucleon distance and, for r>1 fm , found to be adequate for most components of the potential. An important exception is the dominant central isoscalar term, where the convergence is evident only for r>2.5 fm . Finally, we compare the spatial behavior of the functions that enter the relativistic and heavy baryon formulations of the interaction and find that, in the region of physical interest, they differ by about 5% .
Radiative Negative Pion Proton Capture and the Low Energy Theorem.
NASA Astrophysics Data System (ADS)
Liu, Kailin
Four-point angular distributions of the differential cross section for the radiative capture reaction pi^-ptogamma n have been measured at pion laboratory energies of 9.8, 14.6 and 19.8 MeV. An undegraded pion beam was used, along with a bubble-free liquid hydrogen target of 1 cm thickness. The use of a high resolution NaI(Tl) spectrometer allowed us to resolve the in-flight capture gamma rays from those due to stopped pion capture at all pion beam energies and gamma-ray angles investigated. The lineshape response of the gamma-ray detector to ~130 MeV gamma rays was continuously measured over a broad energy range during the data collection with a second independent trigger. This allowed an accurate extraction of the in-flight capture yields and provided a precise measurement of the detector efficiency. From the measured angular distributions of cross section the electric dipole amplitude for capture of s-wave pions, E_{0+}, has been determined at each energy in a model-independent analysis. These data have been extrapolated to threshold by assuming an energy dependence given by the Born diagrams calculated with pseudovector coupling. The extrapolated E _{0+} value at threshold has been determined to be -34.7+/- 1.1 (10^ {-3}/m_pi) which is 9.4 +/- 3.2 percent larger in magnitude than the low energy theorem, which determines the threshold E_{0+} amplitude based upon the requirements of PCAC and electromagnetic gauge invariance.
Pion-photon reactions and chiral dynamics in Primakoff processes at COMPASS
NASA Astrophysics Data System (ADS)
Friedrich, Jan Michael
2016-01-01
With the COMPASS experiment at CERN, pion-photon reactions are investigated via the Primakoff effect, implying that high-energetic pions react with the quasi-real photon field surrounding the target nuclei. The production of a single hard photon in such a pion scattering at lowest momentum transfer to the nucleus is related to pion Compton scattering. From the measured cross-section shape, the pion polarisability is determined. The COMPASS measurement is in contradiction to the earlier dedicated measurements, and rather in agreement with the theoretical expectation from chiral perturbation theory. In the same data taking, reactions with neutral and charged pions in the final state are measured and analyzed. At low energy in the pion-photon centre-of-momentum system, these reactions are governed by chiral dynamics and contain information relevant for chiral perturbation theory. At higher energies, resonances are produced and their radiative coupling is investigated.
Large-angle production of charged pions with incident pion beams on nuclear targets
Apollonio, M.; Chimenti, P.; Giannini, G.; Artamonov, A.; Giani, S.; Gilardoni, S.; Gorbunov, P.; Grant, A.; Grossheim, A.; Ivanchenko, A.; Ivanchenko, V.; Kayis-Topaksu, A.; Panman, J.; Papadopoulos, I.; Tcherniaev, E.; Tsukerman, I.; Wiebusch, C.; Zucchelli, P.; Bagulya, A.; Grichine, V.
2009-12-15
Measurements of the double-differential {pi}{sup {+-}} production cross section in the range of momentum 100{<=}p{<=}800 MeV/c and angle 0.35{<=}{theta}{<=}2.15 rad using {pi}{sup {+-}} beams incident on beryllium, aluminum, carbon, copper, tin, tantalum, and lead targets are presented. The data were taken with the large-acceptance hadron production (HARP) detector in the T9 beam line of the CERN Proton Synchrotron. The secondary pions were produced by beams in a momentum range from 3 to 12.9GeV/c hitting a solid target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using a small-radius cylindrical time projection chamber placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross sections d{sup 2}{sigma}/dp d{theta} at six incident-beam momenta. Data at 3,5,8, and 12GeV/c are available for all targets, while additional data at 8.9 and 12.9GeV/c were taken in positive particle beams on Be and Al targets, respectively. The measurements are compared with several generators of GEANT4 and the MARS Monte Carlo simulation.
Large-angle production of charged pions with incident pion beams on nuclear targets
NASA Astrophysics Data System (ADS)
Apollonio, M.; Artamonov, A.; Bagulya, A.; Barr, G.; Blondel, A.; Bobisut, F.; Bogomilov, M.; Bonesini, M.; Booth, C.; Borghi, S.; Bunyatov, S.; Burguet-Castell, J.; Catanesi, M. G.; Cervera-Villanueva, A.; Chimenti, P.; Coney, L.; Capua, E. Di; Dore, U.; Dumarchez, J.; Edgecock, R.; Ellis, M.; Ferri, F.; Gastaldi, U.; Giani, S.; Giannini, G.; Gibin, D.; Gilardoni, S.; Gorbunov, P.; Gößling, C.; Gómez-Cadenas, J. J.; Grant, A.; Graulich, J. S.; Grégoire, G.; Grichine, V.; Grossheim, A.; Guglielmi, A.; Howlett, L.; Ivanchenko, A.; Ivanchenko, V.; Kayis-Topaksu, A.; Kirsanov, M.; Kolev, D.; Krasnoperov, A.; Martín-Albo, J.; Meurer, C.; Mezzetto, M.; Mills, G. B.; Morone, M. C.; Novella, P.; Orestano, D.; Palladino, V.; Panman, J.; Papadopoulos, I.; Pastore, F.; Piperov, S.; Polukhina, N.; Popov, B.; Prior, G.; Radicioni, E.; Schmitz, D.; Schroeter, R.; Skoro, G.; Sorel, M.; Tcherniaev, E.; Temnikov, P.; Tereschenko, V.; Tonazzo, A.; Tortora, L.; Tsenov, R.; Tsukerman, I.; Vidal-Sitjes, G.; Wiebusch, C.; Zucchelli, P.
2009-12-01
Measurements of the double-differential π± production cross section in the range of momentum 100⩽p⩽800 MeV/c and angle 0.35⩽θ⩽2.15 rad using π± beams incident on beryllium, aluminum, carbon, copper, tin, tantalum, and lead targets are presented. The data were taken with the large-acceptance hadron production (HARP) detector in the T9 beam line of the CERN Proton Synchrotron. The secondary pions were produced by beams in a momentum range from 3 to 12.9GeV/c hitting a solid target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using a small-radius cylindrical time projection chamber placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross sections d2σ/dpdθ at six incident-beam momenta. Data at 3,5,8, and 12GeV/c are available for all targets, while additional data at 8.9 and 12.9GeV/c were taken in positive particle beams on Be and Al targets, respectively. The measurements are compared with several generators of GEANT4 and the MARS Monte Carlo simulation.
Fritz-Niggli, H
1979-08-10
The radiobiological experiences over 4 years research with the biomedical pion channel of the 590 MeV proton-accelerator of the Swiss Institute for Nuclear Research (SIN) have been summarized. Mainly sensitive biological systems have been chosen (limiting factor: dose-rate not more than 10 rad/min, exceptionally till 30 rad/min). The RBE values in the peak region vary between 0.7-3.3 and in the plateau region between 0.4-1. The gain factors for pion radiotherapy of cancer are, beside the excellent physical dose distribution, irradiation in the same treatment with two types of radiation: sparsely ionizing (low LET) radiation in plateau (healthy tissue) region and densely ionizing (high LET) radiation in peak (tumor) region. The biological effectiveness ratio in peak and plateau as the clinically most important relation vary between 1.4-4.2. This is valid also for clinically limiting factors such as reaction of skin, of small intestine, vascular damage, dominant lethals in hypoxic cells, tumor induction. For peak pions the RBE in hypoxic cells (tumor cells) can be much higher than in euoxic cells (healthy tissue). This preclinical work supports the hope in a highly effective cancer therapy with negative pions. PMID:116302
1996-10-01
This report summarizes the work on experimental research in intermediate energy nuclear physics carried out by New Mexico State University from April 1, 1994, through March 31, 1996 under a grant from the US Department of Energy. During this period we began phasing out our programs of study of pion-nucleus and pion-nucleon interaction and of nucleon-nucleus charge-exchange reactions, which have been our major focus of the past two or three years. At the same time we continued moving in a new direction of research on studies of the internal structure of nucleons and nuclei in terms of quarks and gluons. The pion and nucleon work has been aimed at improving our understanding of the nature of pion and proton interactions in the nuclear medium and of various aspects of nuclear structure. The studies of the quark-gluon structure of nucleons are aimed at clarifying such problems as the nature of the quark sea and the relation of the nucleon spin to the spins of the quarks within the nucleon, questions which are of a very fundamental nature.
Extraction of electromagnetic properties of the {Delta}(1232) excitation from pion photoproduction
Wilbois, T.; Wilhelm, P.; Arenhoevel, H.
1998-01-01
Several methods for the treatment of pion photoproduction in the region of the {Delta}(1232) resonance are discussed, in particular the effective Lagrangian approach and the speed plot analysis are compared to a dynamical treatment. As a main topic, we discuss the extraction of the genuine resonance parts of the magnetic dipole and electric quadrupole multipoles of the electromagnetic excitation of the resonance. To this end, we try to relate the various values for the ratio R{sub EM} of the E2 to M1 multipole excitation strengths for the {Delta}(1232) resonance as extracted by the different methods to corresponding ratios of a dynamical model. Moreover, it is confirmed that all methods for extracting resonance properties suffer from an unitary ambiguity which is due to some phenomenological contributions entering the models. {copyright} {ital 1998} {ital The American Physical Society}
Compton scattering from a pion: Off-shell effects and the equivalence theorem
Scherer, S.; Fearing, H.W.
1995-05-10
We consider Compton scattering from a pion in the framework of chiral perturbation theory ({chi}{ital PT}). We investigate off-shell effects in the s- and u-channel pole diagrams. For that purpose we perform a field transformation which, in comparison with the standard Gasser and Leutwyler lagrangian, generates additional terms at order {ital p}{sup 4} proportional to the lowest-order equation of motion. We demonstrate that the two lagrangians which generate different off-shell form factors predict the same Compton scattering S-matrix. This result is interpreted as an application of a generalized equivalence theorem. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Disoriented chiral condensate formation from a state with collective pion fields
Biro, T.S.; Molnar, D.; Feng, Z.; Csernai, L.P.
1997-06-01
At high temperatures it is believed that one can create a highly excited state, the starting point of disoriented chiral condensate (DCC) formation, which is sitting at the top of a potential barrier. We study here instead the evolution of a state where energy is stored initially in the collective motion too, in particular, in chiral rotations representing collective pion fields. We simulate the creation of such an initial state by letting the hot system evolve in time without cooling. It covers the microcanonically allowed phase space if the classical dynamics of the system is chaotic. We find the collective field dynamics chaotic in the linear {sigma} model coupled to quarks with explicit symmetry breaking. A rapid linear expansion from such initial states leads eventually to DCC formation. {copyright} {ital 1997} {ital The American Physical Society}
Pion structure function F2π in the valon model
NASA Astrophysics Data System (ADS)
Arash, Firooz
2003-03-01
Partonic structure of constituent quark (or valon) in the next-to-leading order is used to calculate pion structure function. This is a further demonstration of the finding that the constituent quark structure is universal, and once it is calculated, the structure of any hadron can be predicted thereafter, using a convolution method, without introducing any new free parameter. The results are compared with the pion structure function from ZEUS Collaboration leading neutron production in e+p collisions at HERA. We found good agreement with the experiment. A resolution for the issue of normalization of the experimental data is suggested. In addition, the proportionality of F2π and F2p, which have caused confusion in the normalization of ZEUS data is discussed and resolved.
Unitary constraints on charged pion photoproduction at large p⊥
Laget, Jean-Marc
2010-01-25
Around $\\theta_{\\pi}=$90$^\\circ$, the coupling to the $\\rho^\\circ N$ channel leads to a good accounting of the charged pion exclusive photoproduction cross section in the energy range 3 < E_{γ} < 10 GeV, where experimental data exist. Starting from a Regge Pole approach that successfully describes vector meson production, the singular part of the corresponding box diagrams (where the intermediate vector meson-baryon pair propagates on-shell) is evaluated without any further assumptions (unitarity). Such a treatment provides an explanation of the $s^{-7}$ scaling of the cross section. Furthermore, elastic rescattering of the charged pion improves the basic Regge pole model at forward and backward angles.
Investigation of recent weak single-pion production data
NASA Astrophysics Data System (ADS)
Sobczyk, Jan T.; Żmuda, Jakub
2015-04-01
MiniBooNE [A. A. Aguilar-Arevalo et al. (MiniBooNE Collaboration), Phys. Rev. D 83, 052007 (2011), 10.1103/PhysRevD.83.052007] and MINERvA (B. Eberly et al., arXiv:1406.6415v2 [hep-ex]) charge current π+ production data in the Δ region are discussed. It is argued that despite the differences in neutrino flux, they measure the same dynamical mechanism of pion production and should be strongly correlated. The correlation is clearly seen in the Monte Carlo simulations done with the NuWro generator but is missing in the data. Both the normalization and the shape of the ratio of measured differential cross sections in pion kinetic energy are different from the Monte Carlo results; in the case of normalization the discrepancy is by a factor of 1.49 .
A CUPRONICKEL ROTATING BAND PION PRODUCTION TARGET FOR MUON COLLIDERS.
KING,B.J.; WEGGEL,R.J.; MOKHOV,N.V.; MOSER,S.S.
1999-03-29
A conceptual design is presented for a high power cupronickel pion production target. It forms a circular band in a horizontal plane with approximate dimensions of: 2.5 meters radius, 6 cm high and 0.6 cm thick. The target is continuously rotated at 3 m/s to carry heat away from the production region to a water cooling channel. Bunches of 16 GeV protons with total energies of 270 kl and repetition rates of 15 Hz are incident tangentially to arc of the target along the symmetry axis of a 20 Tesla solenoidal magnetic capture channel. The mechanical layout and cooling setup are described. Results are presented from realistic MARS Monte Carlo computer simulations of the pion yield and energy deposition in the target. ANSYS finite element calculations are beginning to give predictions for the resultant shock heating stresses.
Spontaneous pion emission as a new natural radioactivity
Ion, D.B.; Ivascu, M.; Ion-Mihai, R.
1986-10-15
In this paper the pionic nuclear radioactivity or spontaneous pion emission by a nucleus from its ground state is investigated. The Q/sub ..pi../-values as well as the statistical factors are calculated using the experimental masses tabulated by Wapstra and Audi. Then it was shown that the pionic radioactivity of the nuclear ground state is energetically possible via three-body channels for all nuclides with Z>80. This new type of natural radioactivity is statistically favored especially for Z = 92-106 for which F/sub ..pi..//F/sub S//sub F/ = 40-200 (MeV)/sup 2/. Experimental detection of the neutral pion and also some possible emission mechanisms are discussed.
Inelastic interaction mean free path of negative pions in tungsten
NASA Technical Reports Server (NTRS)
Cheshire, D. L.; Huggett, R. W.; Jones, W. V.; Rountree, S. P.; Schmidt, W. K. H.; Kurz, R. J.; Bowen, T.; Delise, D. A.; Krider, E. P.; Orth, C. D.
1975-01-01
The inelastic interaction mean free paths lambda of 5, 10, and 15 GeV/c pions were measured by determining the distribution of first interaction locations in a modular tungsten-scintillator ionization spectrometer. In addition to commonly used interaction signatures of a few (2-5) particles in two or three consecutive modules, a chi2 distribution is used to calculate the probability that the first interaction occurred at a specific depth in the spectrometer. This latter technique seems to be more reliable than use of the simpler criteria. No significant dependence of lambda on energy was observed. In tungsten, lambda for pions is 206 plus or minus 6 g/sq cm.
Pion Electroproduction form Helium 3, Deuterium, and Hydrogen
S. Avery
2002-05-01
A series of measurements for pion electroproduction from helium-3, deuterium, and hydrogen were completed at the Thomas Jefferson National Accelerator Facility by the NucPi Collaboration. E91003 began taking data in February 1998 and was completed in April 1998. The longitudinal and transverse parts of the differential cross section were extracted, by means of a Rosenbluth type separation, in the direction parallel to the virtual photon, at Q 2 = 0.4 GeV 2 , for W = 1.15 and W = 1.6 GeV. The mass dependence of the longitudinal cross section should provide insight into the surprising apparent absence of any significant cross section enhancement due to excess pions in the nuclear medium.
Pion Asymmetries due to Hyperon Decays in the Qweak Experiment
NASA Astrophysics Data System (ADS)
Elledge, Jacob
2015-10-01
The Qweak experiment took place at the Thomas Jefferson National Accelerator Facility between 2010 and 2012. In the experiment an electron beam was directed onto a liquid hydrogen target. The purpose of the Qweak experiment is to investigate the weak interaction between the proton and the electron. The experiment determined the proton's weak charge by measuring the asymmetry in elastic scattering when changing the helicity of the incoming electron beam 960 times per second. Under different kinematic conditions the experiment investigated inelastic scattering with pions in the final state, a background for the elastic scattering measurement. In this inelastic measurement, a false asymmetry due to parity-violating hyperon decays must be determined. Using the results of a simulation written in Geant4, I have been able to isolate the cross sections for samples of opposite helicities. By combining this cross section with the signal of detected pions from hyperon decay, I was able to isolate the expected false asymmetry.
Unitary constraints on charged pion photoproduction at large p⊥
Laget, Jean-Marc
2010-01-25
Aroundmore » $$\\theta_{\\pi}=$$90$$^\\circ$$, the coupling to the $$\\rho^\\circ N$$ channel leads to a good accounting of the charged pion exclusive photoproduction cross section in the energy range 3 < Eγ < 10 GeV, where experimental data exist. Starting from a Regge Pole approach that successfully describes vector meson production, the singular part of the corresponding box diagrams (where the intermediate vector meson-baryon pair propagates on-shell) is evaluated without any further assumptions (unitarity). Such a treatment provides an explanation of the $$s^{-7}$$ scaling of the cross section. Furthermore, elastic rescattering of the charged pion improves the basic Regge pole model at forward and backward angles.« less
Goldstone pion and other mesons using a scalar confining interaction
Gross, F. |; Milana, J.
1994-04-01
A covariant wave equation for q{bar q} interactions with an interaction kernel composed of the sum of constant vector and linear scalar confining interactions is solved for states with two quarks with identical mass. The model includes an NJL-like mechanism which links the dynamical breaking of chiral symmetry to the spontaneous generation of quark mass and the appearance of a low mass Goldstone pion. A novel feature of this approach is that it automatically explains the small mass of the pion even though the linear potential is a scalar interaction in Dirac space, and hence breaks chiral symmetry. Solutions for mesons composed of light quarks ({pi},{rho}, and low lying excited states) and heavy quarks ({rho}{sub c}, J/{Psi}, and low lying excited states) are presented and discussed.
Quark mass functions and pion structure in Minkowski space
Biernat, Elmer P.; Gross, Franz L.; Pena, Maria Teresa; Stadler, Alfred
2014-03-01
We present a study of the dressed quark mass function and the pion structure in Minkowski space using the Covariant Spectator Theory (CST). The quark propagators are dressed with the same kernel that describes the interaction between different quarks. We use an interaction kernel in momentum space that is a relativistic generalization of the linear confining q-qbar potential and a constant potential shift that defines the energy scale. The confining interaction has a Lorentz scalar part that is not chirally invariant by itself but decouples from the equations in the chiral limit and therefore allows the Nambu--Jona-Lasinio (NJL) mechanism to work. We adjust the parameters of our quark mass function calculated in Minkowski-space to agree with LQCD data obtained in Euclidean space. Results of a calculation of the pion electromagnetic form factor in the relativistic impulse approximation using the same mass function are presented and compared with experimental data.
Electroproduction of pions on the three-nucleon systems
Lee, T.S.H.; Chmielewski, C.; Sauer, P.U.
1995-08-01
The electroproduction of pions on {sup 3}He is being studied with the assumption that the basic pion production mechanisms can be described by the N(e,e{prime}{pi}) model developed by Nozawa and Lee. In the impulse approximation, the {sup 3}He(e,e{prime}{pi}) cross section is then determined from the N and {Delta} spectral functions generated from Hannover`s three-body calculation including the {Delta}. The objective is to investigate the effects due to the {Delta} components in {sup 3}He, as suggested by Lipkin and Lee. This is being investigated by calculating the ratio between {sup 3}He(e,e{prime}{pi}{sup +}p) and {sup 3}He(e,e{prime}{pi}{sup -}). In a calculation for {sup 3}He(e,e{prime}{pi}{sup +}p) at very high momentum transfer, questions concerning color transparency of {Delta}{sup ++} propagation can be addressed.
Threshold pion production from proton-proton collisions
Lee, T.S.H.
1995-08-01
We showed that the threshold production of {pi}{sup 0}pp, {pi}{sup +}np, and {pi}{sup +}d from proton-proton collisions can be consistently described by a model consisting of pion s-wave rescattering and N{bar N} pair-terms of heavy-meson exchanges. The large difference between {sigma}{sup tot}(pp {yields} {pi}{sup +}d) and {sigma}{sup tot}(pp {yields} {pi}{sup +}np) is understood from the orthogonality of the deuteron and the np scattering wave functions. In a calculation using the Paris potential, we find that the data can be reproduced best by using a soft {pi}NN form factor with {Delta} = 650 MeV for a monopole form. This is consistent with our earlier studies of pion production in the A-excitation region. A paper describing this result was submitted for publication.
Coherent pion production by neutrino scattering off nuclei
Kartavtsev, A.; Paschos, E. A.; Gounaris, G. J.
2006-09-01
The main part of coherent pion production by neutrinos on nuclei is essentially determined by partial conservation of the axial current (PCAC), provided that the leptonic momentum transferred square Q{sup 2} remains sufficiently small. We give the formulas for the charged and neutral current cross sections, including also the small non-PCAC transverse current contributions and taking into account the effect of the {mu}{sup -}-mass. Our results are compared with the experimental ones and other theoretical treatments.
Pion Photo- and Electroproduction and the Chiral MAID Interface
NASA Astrophysics Data System (ADS)
Hilt, Marius; Lehnhart, Björn C.; Scherer, Stefan; Tiator, Lothar
We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant baryon chiral perturbation theory. We present a calculation of pion photo- and electroproduction up to and including order q4. The low-energy constants have been fixed by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/).
First Measurements of Pion Correlations by the PHENIX Experiment
Johnson, S C
2001-04-11
First identical-pion correlations measured at RHIC energies by PHENIX are presented. Two analyses with separate detectors, systematics, and statistics provide consistent results. The resulting HBT radii are moderately larger than those measured at lower energies. The k{sub t} dependence of the Bertsch-Pratt HBT radii is also similar to previous measures and is consistent with the conjecture of an expanding source.
Isospin breaking in low-energy pion-nucleon scattering
Gibbs, W.R.; Ai, L.; Kaufmann, W.B.
1995-05-08
We have analyzed low-energy pion-nucleon data for isospin invariance by comparing charge-exchange amplitudes derived from charge-exchange data with those predicted from recent {pi}{sup {plus_minus}}{ital p} elastic data through the application of isospin invariance. A discrepancy of the order of 7% is observed beyond the contributions of the {pi}{sup {plus_minus}}{ital p} Coulomb interaction and the hadronic mass differences.
Observation of Color-Transparency in Diffractive Dissociation of Pions
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.; Devmal, 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 have studied the diffractive dissociation into dijets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where tmin-->0), we find that when the per-nucleus cross section for this process is parametrized as σ = σ0Aα, α has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calculations of color-transparency.
Conformal symmetry and pion form factor: Space- and timelike region
Choi, Ho-Meoyng; Ji, Chueng-Ryong
2008-06-01
We extend a recent analysis of the pion electromagnetic form factor constrained by the conformal symmetry to explore the timelike region. We show explicitly that the timelike form factor obtained by the analytic continuation of the spacelike form factor correctly satisfies the dispersion relation. Our results indicate that the quark spin and dynamical mass effects are crucial to yield the realistic features of the vector meson dominance phenomena.
Lattice QCD study of mixed systems of pions and kaons
William Detmold, Brian Smigielski
2011-07-01
The O(100) different ground state energies of N-pion and M-kaon systems for N+M <= 12 are studied in lattice QCD. These energies are then used to extract the various two- and three- body interactions that occur in these systems. These calculations are performed using one ensemble of 2+1 flavor anisotropic lattices with a spatial lattice spacing $a_s$ ~ 0.125 fm, an anisotropy factor $\\xi=a_s/a_t=3.5$, and a spatial volume $L^3\\sim (2.5\\ {\\rm fm})^3$. Particular attention is paid to additional thermal states present in the spectrum because of the finite temporal extent. The quark masses used correspond to pion and kaon masses of $m_\\pi$ ~ 383 MeV and $m_K$ ~ 537 MeV, respectively. The isospin and strangeness chemical potentials of these systems are found to be in the region where chiral perturbation theory and hadronic models predict a phase transition between a pion condensed phase and a kaon condensed phase.
Inelastic pion scattering by /sup 13/C at low energies
Mitchell, J.H.
1987-03-01
Angular distributions for inelastically scattered pions were obtained for several states in /sup 13/C at an incident energy of 65 MeV. The data include results from both ..pi../sup +/ and ..pi../sup -/ measurements. In addition, ..pi../sup -/ measurements were made at T/sub ..pi../ = 50 MeV at one angle to give a two point fixed-q excitation function. The data are compared to theory and the data of others. As might be expected, medium corrections are shown to be considerably more important at low energies than at resonance. This is true for inelastic transitions of multipolarity 0,2 and 3. Parameters derived from an analysis of elastic pion scattering and SCX data also provide an adequate description of the inelastic transitions. The charge asymmetry in the cross sections for the 9/2/sup +/ state that was seen at resonance persists at these energies. This result is consistent with an impulse approximation treatment of the spin-flip amplitude. This is true even though the incoming energy of the pions is far below the range where the validity of an impulse treatment is expected. 65 refs., 45 figs.
Magnetic and Electric Flux Quanta: the Pion Mass
P Cameron
2011-12-31
The angular momentum of the magnetic flux quantum is balanced by that of the associated supercurrent, such that in condensed matter the resultant angular momentum is zero. The notion of a flux quantum in free space is not so simple, needing both magnetic and electric flux quanta to propagate the stable dynamic structure of the photon. Considering these flux quanta at the scale where quantum field theory becomes essential, at the scale defined by the reduced Compton wavelength of the electron, exposes variants of a paradox that apparently has not been addressed in the literature. Leaving the paradox unresolved in this note, reasonable electromagnetic rationales are presented that permit to calculate the masses of the electron, muon, pion, and nucleon with remarkable accuracy. The calculated mass of the electron is correct at the nine significant digit limit of experimental accuracy, the muon at a part in one thousand, the pion at two parts in ten thousand, and the nucleon at seven parts in one hundred thousand. The accuracy of the pion and nucleon mass calculations reinforces the unconventional common notion that the strong force is electromagnetic in origin.
Confinement singularities in two-pion decays of mesons
Anisovich, A. V.; Anisovich, V. V. Matveev, M. A.; Nikonov, V. A.; Nyiri, J.; Sarantsev, A. V.
2010-07-15
We consider as an example the two-pion decay of the {rho} meson, the {sup 3}S{sub 1}qq-bar state of the constituent quarks-the decay being determined by the transition qq-bar {sup {yields} {pi}{pi}} contains information about confinement interactions. One can specify in this decay two types of transitions: (i) the bremsstrahlung radiation of a pion q {sup {yields}}q + {pi} (or q-bar {sup {yields}}q-bar + {pi}) with a subsequent fusion qq-bar {sup {yields} {pi}}, and (ii) the direct transition qq-bar {sup {yields} {pi}{pi}}. We demonstrate how in the amplitudes of the corresponding transitions the quark singularities have to disappear, i.e., what is the way the quark confinement at relatively short distances can be realized. We calculate and estimate the contributions of processes with bremsstrahlung radiation of the pion and of the direct transition qq-bar {sup {yields} {pi}{pi}}. The estimates demonstrate that the processes involving the direct transition qq-bar {sup {yields} {pi}{pi}} are necessary, but they cannot be determined unambiguously by the decay {rho}(775) {sup {yields} {pi}{pi}}. We conclude that for the determination of the qq-bar {sup {yields} {pi}{pi}} transition more complete data on the resonance decays into the {pi}{pi} channels are needed than those available at the moment.
Roy-Steiner-equation analysis of pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.
2016-04-01
We review the structure of Roy-Steiner equations for pion-nucleon scattering, the solution for the partial waves of the t-channel process ππ → N ¯ N, as well as the high-accuracy extraction of the pion-nucleon S-wave scattering lengths from data on pionic hydrogen and deuterium. We then proceed to construct solutions for the lowest partial waves of the s-channel process πN → πN and demonstrate that accurate solutions can be found if the scattering lengths are imposed as constraints. Detailed error estimates of all input quantities in the solution procedure are performed and explicit parameterizations for the resulting low-energy phase shifts as well as results for subthreshold parameters and higher threshold parameters are presented. Furthermore, we discuss the extraction of the pion-nucleon σ-term via the Cheng-Dashen low-energy theorem, including the role of isospin-breaking corrections, to obtain a precision determination consistent with all constraints from analyticity, unitarity, crossing symmetry, and pionic-atom data. We perform the matching to chiral perturbation theory in the subthreshold region and detail the consequences for the chiral convergence of the threshold parameters and the nucleon mass.
Two-pion exchange currents in photodisintegration of the deuteron
Rozp edzik, D.; Golak, J.; Koelling, S.; Epelbaum, E.
2011-10-24
Chiral effective field theory (ChEFT) is a modern framework to analyze the properties of few-nucleon systems at low energies. It is based on the most general effective Lagrangian for pions and nucleons consistent with the chiral symmetry of QCD. For energies below the pion-production threshold it is possible to eliminate the pionic degrees of freedom and derive nuclear potentials and nuclear current operators solely in terms of the nucleonic degrees of freedom. This is very important because, despite a lot of experience gained in the past, the consistency between two-nucleon forces, many-nucleon forces and the corresponding current operators has not been achieved yet. In this presentation we consider the recently derived long-range two-pion exchange (TPE) contributions to the nuclear current operator which appear at next-to leading order of the chiral expansion. These operators do not contain any free parameters. We study their role in the deuteron photodisintegration reaction and compare our predictions with experimental data from Refs [3]. The bound and scattering states are calculated using five different chiral N2LO nucleon-nucleon (NN) potentials which allows to estimate the theoretical uncertainty at a given order in the chiral expansion. For some observables the results are very close to the reference predictions based on the AV18 NN potential and the current operator (partly) consistent with this force.
Quark and pion effective couplings from polarization effects
NASA Astrophysics Data System (ADS)
Braghin, Fábio L.
2016-05-01
A flavor SU(2) effective model for pions and quarks is derived by considering polarization effects departing from the usual quark-quark effective interaction induced by dressed gluon exchange, i.e. a global color model for QCD. For that, the quark field is decomposed into a component that yields light mesons and the quark-antiquark condensate, being integrated out by means of the auxiliary field method, and another component which yields constituent quarks, which is basically a background quark field. Within a long-wavelength and weak quark field expansion (or large quark effective mass expansion) of a quark determinant, the leading terms are found up to the second order in a zero-order derivative expansion, by neglecting vector mesons that are considerably heavier than the pion. Pions are considered in the structureless limit and, besides the chiral invariant terms that reproduce previously derived expressions, symmetry breaking terms are also presented. The leading chiral quark-quark effective couplings are also found corresponding to a NJL and a vector-NJL couplings. All the resulting effective coupling constants and parameters are expressed in terms of the current and constituent quark masses and of the coupling g.
Two-pion correlations in heavy ion collisions
Zajc, W.A.
1982-08-01
An application of intensity interferometry to relativistic heavy ion collisions is reported. Specifically, the correlation between two like-charged pions is used to study the reactions Ar+KCl..-->..2..pi../sup +-/+X and Ne+NaF..-->..2..pi../sup -/+X. Source sizes are obtained that are consistent with a simple geometric interpretation. Lifetimes are less well determined but are indicative of a faster pion production process than predicted by Monte Carlo cascade calculations. There appears to be a substantial coherent component of the pion source, although measurement is complicated by the presence of final state interactions. Additionally, the generation of spectra of uncorrelated events is discussed. In particular, the influence of the correlation function on the background spectrum is analyzed, and a prescription for removal of this influence is given. A formulation to describe the statistical errors in the background is also presented. Finally, drawing from the available literature, a self-contained introduction to Bose-Einstein correlations and the Hanbury-Brown - Twiss effect is provided, with an emphasis on points of contact between classical and quantum mechanical descriptions.
Proton and pion production relative to the reaction plane in Au + Au collisions at 11A GeV/c
David, G.; Herrmann, N. |; Drigert, M.; Dai, Y.; Filimonov, K.; Clemen, M.; Chang, W.C.; Dee, J.; Hemmick, T.K.; Johnson, S.C. Dietzsch, O.; Cormier, T.M.; Hall, J.R.
1997-12-01
Results are presented of an analysis of proton and charged pion azimuthal distributions measured with respect to the reaction plane in Au + Au collisions at a beam momentum of about 11A GeV/c. The azimuthal anisotropy is studied as a function of particle rapidity and transverse momentum for different centralities of the collisions. The triple differential (in rapidity, transverse momentum, and azimuthal angle) distributions are reconstructed. A comparison of the results with a previous analysis of charged-particle and transverse energy flow as well as with model predictions are presented. {copyright} {ital 1997} {ital The American Physical Society}
Chaoticity parameter λ in two-pion interferometry in an expanding boson gas model
Liu, Jie; Ru, Peng; Zhang, Wei-Ning; Wong, Cheuk-Yin
2014-10-15
We investigate the chaoticity parameter λ in two-pion interferometry in an expanding boson gas model. The degree of Bose-Einstein condensation of identical pions, density distributions, and Hanbury-Brown-Twiss (HBT) correlation functions are calculated for the expanding gas within the mean-field description with a harmonic oscillator potential. The results indicate that a sources with thousands of identical pions may exhibit a degree of Bose-Einstein condensation at the temperatures during the hadronic phase in relativistic heavy-ion collisions. This finite condensation may decrease the chaoticity parameter λ in the two-pion interferometry measurements at low pion pair momenta, but influence only slightly the λ valuemore » at high pion pair momentum.« less
Recent Physics Results with the COMPASS Experiment
Paul, Stephan
2006-02-11
The COMPASS experiment has obtained first physics results in the field of polarized distribution functions for quarks and gluons using muon scattering off polarized deuterons. The analysis using open charm production and pairs of high pT hadrons is presented. We also have used a transversely polarized target to address transverse information for quarks inside the nucleon. In addition, a pilot run with incoming pions taken late 2004 will give first information on the pion polarizabilities and hadron resonances. The physics prospects from this run as well as from future data taking in this field are also outlined.
Pion Decay Constant, Z{sub A} and Chiral Log from Overlap Fermions
Shao-Jing Dong; Terrence Draper; Ivan Horvath; Frank X. Lee; Jianbo Zhang
2002-03-01
We report our calculation of the pion decay constant f{sub {pi}}, the axial renormalization constant Z{sub A}, and the quenched chiral logarithms from the overlap fermions. The calculation is done on a quenched 20{sup 4} lattice at a=0.148 fm using tree level tadpole improved gauge action. The smallest pion mass we reach is about 280 MeV. The lattice size is about 4 times the Compton wavelength of the lowest mass pion.
Effect of three-pion unitarity on resonance poles from heavy meson decays
Satoshi X. Nakamura
2011-10-01
We study the final state interaction in 3-pion decay of meson resonances at the Excited Baryon Analysis Center (EBAC) of JLab. We apply the dynamical coupled-channels formulation which has been extensively used by EBAC to extract N* information. The formulation satisfies the 3-pion unitarity condition which has been missed in the existing works with the isobar models. We report the effect of the 3-pion unitarity on the meson resonance pole positions and Dalitz plot.
Harada, Koji; Kubo, Hirofumi; Yamamoto, Yuki
2011-03-15
Nuclear effective field theory (NEFT) including pions in the two-nucleon sector is examined from the Wilsonian renormalization group point of view. The pion exchange is cut off at the floating cutoff scale, {Lambda}, with the short-distance part being represented as contact interactions in accordance with the general principle of renormalization. We derive the nonperturbative renormalization group equations in the leading order of the nonrelativistic approximation in the operator space up to including O(p{sup 2}), and find the nontrivial fixed points in the {sup 1}S{sub 0} and {sup 3}S{sub 1}-{sup 3}D{sub 1} channels which are identified with those in the pionless NEFT. The scaling dimensions, which determine the power counting, of the contact interactions at the nontrivial fixed points are also identified with those in the pionless NEFT. We emphasize the importance of the separation of the pion exchange into the short-distance and the long-distance parts, since a part of the former is nonperturbative while the latter is perturbative.
Pion-photon reactions and chiral dynamics in Primakoff processes at COMPASS
NASA Astrophysics Data System (ADS)
Krämer, Markus
2016-05-01
At the COMPASS experiment at CERN, pion-photon reactions are investigated using the Primakoff effect, where high-energetic pions react with the quasi-real photons surrounding the target nuclei. The production of a single hard photon in such a pion scattering, at lowest momentum transfer to the nucleus, is related to pion Compton scattering. Studying the energy distribution of the outgoing photons, the pion polarizability can be extracted. In addition to the measurement with a pion beam, control measurements with a muon beam allow us to estimate the systematics. The COMPASS result is in tension with earlier dedicated measurements and rather in agreement with the theoretical expectation from chiral perturbation theory. Based on the same data set, reactions with neutral and charged pions in the final state are studied. At low invariant mass of the pion-photon system, these reactions are governed by chiral dynamics. Using partial-wave analysis techniques, the absolute cross sections for the production of π-π+π- and π-π0π0 states from π-γ interactions are measured and compared to predictions from chiral perturbation theory. At higher pion-photon masses, the production of 3π resonances is studied with the focus on their radiative couplings.
Decay constants of the pion and its excitations on the lattice.
Mastropas, Ekaterina V.; Richards, David G.
2014-07-01
We present a calculation using lattice QCD of the ratios of decay constants of the excited states of the pion, to that of the pion ground state, at three values of the pion mass between 400 and 700 MeV, using an anisotropic clover fermion action with three flavors of quarks. We find that the decay constant of the first excitation, and more notably of the second, is suppressed with respect to that of the ground-state pion, but that the suppression shows little dependence on the quark mass. The strong suppression of the decay constant of the second excited state is consistent with its interpretation as a predominantly hybrid state.
Charged Pion Multiplicity Below 1.0 GeV/c from the MIPP Experiment
NASA Astrophysics Data System (ADS)
Hart, Andrew; MIPP Collaboration
2011-04-01
The MIPP experiment is designed to study particle production from several targets, using various beam species and momenta. Using beams of +/- 58 GeV / c pions, kaons, and protons, we present multiplicities of 0 . 1 - 1 . 0 GeV / c charged pions versus target atomic weight (A) for the following targets: liquid hydrogen, beryllium, carbon, aluminum, copper, bismuth, and uranium. We fit Aα to these results and present α for each case. In addition, for liquid hydrogen, we present charged pion multiplicities for +/- 20 and +/- 85 GeV / c pion, kaon, and proton beam particles, illustrating the dependence on beam momentum.
Measurement of pion double charge exchange on carbon-13, carbon-14, magnesium-26, and iron-56
Seidl, P.A.
1985-02-01
Cross sections for the /sup 13,14/C,/sup 26/Mg,/sup 56/Fe(..pi../sup +/,..pi../sup -/)/sup 13,14/O,/sup 26/Si,/sup 56/Ni reactions were measured with the Energetic Pion Channel and Spectrometer at the Clinton P. Anderson Meson Physics Facility for 120 less than or equal to T/sub ..pi../ less than or equal to 292 MeV and 0 less than or equal to theta less than or equal to 50. The double isobaric analog states (DIAS) are of primary interest. In addition, cross sections for transitions to /sup 14/O(0/sup +/, 5.92 MeV), /sup 14/O(2/sup +/, 7.77 MeV), /sup 56/Ni(gs), /sup 13/O(gs), and /sup 13/O(4.21 MeV) are presented. The /sup 13/O(4.21 MeV) state is postulated to have J/sup ..pi../ = 1/2/sup -/. The data are compared to previously measured double-charge-exchange cross sections on other nuclei, and the systematics of double charge exchange on T greater than or equal to 1 target nuclei leading to the DIAS are studied. Near the ..delta../sub 33/ resonance, cross sections for the DIAS transitions are in disagreement with calculations in which the reaction is treated as sequential charge exchange through the free pion-nucleon amplitude, while for T/sub ..pi../ > 200 MeV the anomalous features of the 164 MeV data are not apparent. This is evidence for significant higher order contributions to the double-charge-exchange amplitude near the reasonable energy. Two theoretical approaches that include two nucleon processes are applied to the DIAS data. 64 references.
Research in experimental nuclear physics
Moore, C.F.
1990-09-01
This paper discusses the following topics; Pion scattering from a polarized target; pion elastic, inelastic scattering, and pion absorption; pion DCX studies; coincidence measurements; isospin splitting of the giant dipole built on the isobaric analog state; pion DCX above the {triangle}{sub 3/2,3/2}(1232) resonance; pion scattering from polarized {sup 13}C target; 6{sup {minus}} stretched configuration on {sup 32}S; and, energy dependence of the pion absorption cross section on {sup 12}C.
Peterson, R.J.
1993-10-01
This report summarizes work carried out between October 1, 1992 and September 30, 1993 at the Nuclear Physics Laboratory of the University of Colorado, Boulder. The experimental program in intermediate-energy nuclear physics is very broadly based; it includes pion-nucleon and pion-nucleus studies at LAMPF and TRIUMF, kaon-nucleus scattering at the AGS, and equipment development for experiments at the next generation of accelerator facilities.
Realistic models of pion-exchange three-nucleon interactions
Pieper, Steven C.; Pandharipande, V. R.; Wiringa, R. B.; Carlson, J.
2001-07-01
We present realistic models of pion-exchange three-nucleon interactions obtained by fitting the energies of all the 17 bound or narrow states of 3{<=}A{<=}8 nucleons, calculated with less than 2% error using the Green's function Monte Carlo method. The models contain two-pion-exchange terms due to {pi}N scattering in S and P waves, three-pion-exchange terms due to ring diagrams with one {Delta} in the intermediate states, and a phenomenological repulsive term to take into account relativistic effects, the suppression of the two-pion-exchange two-nucleon interaction by the third nucleon, and other effects. The models have five parameters, consisting of the strength of the four interactions and the short-range cutoff. The 17 fitted energies are insufficient to determine all of them uniquely. We consider five models, each having three adjustable parameters and assumed values for the other two. They reproduce the observed energies with an rms error <1% when used together with the Argonne v{sub 18} two-nucleon interaction. In one of the models the {pi}N S-wave scattering interaction is set to zero; in all others it is assumed to have the strength suggested by chiral effective-field theory. One of the models also assumes that the {pi}N P-wave scattering interaction has the strength suggested by effective-field theories, and the cutoff is adjusted to fit the data. In all other models the cutoff is taken to be the same as in the v{sub 18} interaction. The effect of relativistic boost correction to the two-nucleon interaction on the strength of the repulsive three-nucleon interaction is estimated. Many calculated properties of A{<=}8 nuclei, including radii, magnetic dipole, and electric quadrupole moments, isobaric analog energy differences, etc., are tabulated. Results obtained with only Argonne v{sub 8}' and v{sub 18} interactions are also reported. In addition, we present results for seven- and eight-body neutron drops in external potential wells.
Pion absorption processes. [32 to 74 MeV
Doss, K G.R.
1980-04-01
Proton and deuteron production from low-energy pion absorption in light nuclei leading to discrete and continuum states were measured. The LEP beam line at LAMPF was used with a stack of 8 intrinsic germanium crystals. The proton energy spectra are in general characterized by a broad bump at an energy approximately corresponding to ..pi../sup +/d ..-->.. pp reaction kinematics, suggestive of pion absorption on 2 nucleons. The energy-integrated cross-section for production of deuterons has an angular distribution similar to that for production of protons. The dependence of the total pion absorption cross-section on A is explained using a semi-classical model for pion transport in nuclei. The (..pi../sup +/,p) as well as (..pi../sup +/,d) reactions generally favor transitions involving larger angular momentum transfer to the residual nucleus when states of similar nuclear structure are considered. The low-energy excitation spectra from the (..pi../sup +/,p) reaction are similar to the spectra from (p,d) reaction on /sup 12/C and /sup 13/C. However, a calculation of the (..pi.. = ,p) cross-section using the measured (p,d) reaction with the formulation of Wilkin to relate the two reactions is in moderate disagreement with the measured (..pi../sup +/,p) cross-sections. The excitation spectra from the (..pi../sup +/,p) reaction indicte the importance of two-step processes for the reaction. The (..pi../sup +/,d) reaction leading to the ground state of -- residual nucleus has been seen for /sup 7/Li, /sup 12/C, and /sup 13/C targets. The measured cross section for the /sup 12/C(..pi../sup +/,d)/sup 10/C reaction to the 2/sup +/ state is much higher than that for the ground state. For the case of /sup 18/O, no counts were seen for excitation energy of < 10 MeV, at a sensitivity of approx. 100 nb/sr count. These features indicate a possible failure of the model of Betz and Kerman for the (..pi../sup +/,d) reaction.
Single pion contribution to the hyperfine splitting in muonic hydrogen
NASA Astrophysics Data System (ADS)
Huong, Nguyen Thu; Kou, Emi; Moussallam, Bachir
2016-06-01
A detailed discussion of the long-range one-pion exchange (Yukawa potential) contribution to the 2 S hyperfine splitting in muonic hydrogen, which had, until recently, been disregarded, is presented. We evaluate the relevant vertex amplitudes, in particular π0μ+μ-, combining low energy chiral expansions together with experimental data on π0 and η decays into two leptons. A value of Δ EHFSπ=-(0.09 ±0.06 ) μ eV is obtained for this contribution.
Spontaneous pion emission as a new natural radioactivity
NASA Astrophysics Data System (ADS)
Ion, D. B.; Ivascu, M.; Ion-Mihai, R.
1986-10-01
In this paper the pionic nuclear radioactivity or spontaneous poin emission by a nucleus from its ground state is investigated. The Qπ-values as well as the statistical factors are calculated using the experimental masses tabulated by Wapstra and Audi. Then it was shown that the pionic radioactivity of the nuclear ground state is energetically possible via three-body channels for all nuclides with Z > 80. This new type of natural radioactivity is statistically favored especially for Z = 92 - 106 for which F π/F SF = 40 - 200 [ MeV] 2. Experimental detection of the neutral pion and also some possible emission mechanisms are discussed.
Electromagnetic triangle anomaly and neutral pion condensation in QCD vacuum
NASA Astrophysics Data System (ADS)
Cao, Gaoqing; Huang, Xu-Guang
2016-06-01
We study the QCD vacuum structure under the influence of an electromagnetic field with a nonzero second Lorentz invariant I2 = E ṡ B. We show that the presence of I2 can induce neutral pion (π0) condensation in the QCD vacuum through the electromagnetic triangle anomaly. Within the frameworks of chiral perturbation theory at leading small-momenta expansion as well as the Nambu-Jona-Lasinio model at leading 1 /Nc expansion, we quantify the dependence of the π0 condensate on I2. The stability of the π0-condensed vacuum against the Schwinger charged pair production due to electric field is also discussed.
Two-pion exchange and chiral symmetry restoration
Birse, M.C. )
1994-04-01
The scalar, isoscalar piece of the two-pion exchange force between two nucleons is calculated in the linear [sigma] model. A large contribution to this force is found to come from terms involving direct coupling of the [sigma] field to the nucleons. This part of the interaction can be related to the partial restoration of chiral symmetry experienced by a nucleon in nuclear matter, and it has a strength determined by the [sigma] commutator. Even if the elementary'' [sigma] is taken to be heavy ([ital m][sub [sigma
Transverse momentum dependence of semi-inclusive pion production
Hamlet Mkrtchyan; Peter Bosted
2007-09-19
Cross sections for semi-inclusive electroproduction of charged pions ($\\pi^{\\pm}$) from both proton and deuteron targets were measured for $0.2<0.5$, $2<4$ GeV$^2$, $0.3<1$, and $P_t^2<0.2$ GeV$^2$. We find the azimuthal dependence to be small and consistent with zero, for $P_t<0.1$ GeV. In the context of a simple fit, the initial transverse momenta of $d$ quarks tends to be larger than for $u$ quarks, while the transverse momentum width of the favored fragmentation function is slightly larger than that of the unfavored function.
Compton scattering by a pion and off-shell effects
Scherer, S.; Fearing, H.W. )
1995-01-01
We consider Compton scattering by a pion in the framework of chiral perturbation theory. We investigate off-shell effects in the [ital s]- and [ital u]-channel pole diagrams. For that purpose we perform a field transformation which, in comparison with the standard Gasser and Leutwyler Lagrangian, generates additional terms at order [ital p][sup 4] proportional to the lowest-order equation of motion. As a result of the equivalence theorem the two Lagrangians predict the same Compton scattering [ital S]-matrix even though they generate different off-shell form factors. We conclude that off-shell effects are not only model dependent but also representation dependent.
eA Pion Production at CLAS Aimed at Neutrinos
NASA Astrophysics Data System (ADS)
Manly, S.
2011-11-01
Preliminary results on semi-inclusive charged pion production in eA collisions at Ebeam = 5 GeV/c2 are presented. The data were collected using the CLAS detector, which is a multipurpose, large acceptance, magnetic spectrometer located in Hall B at the Thomas Jefferson National Accelerator Facility. Distributions in W, Q2, pπ, and θπ are shown for data produced using deuterium and carbon targets. Preliminary comparisons with data simulated using the GENIE generator are made. The motivation for this work is to provide distributions useful for tuning the hadronic production models used in extracting results from current and next-generation neutrino oscillation experiments.
Beyond the rainbow: Effects from pion back-coupling
Fischer, Christian S.; Williams, Richard
2008-10-01
We investigate hadronic unquenching effects in light quarks and mesons. To this end, we take into account the back-coupling of the pion onto the quark propagator within the nonperturbative continuum framework of Schwinger-Dyson equations (SDE) and Bethe-Salpeter equations (BSE). We improve on a previous approach by explicitly solving both the coupled system of SDEs and BSEs in the complex plane and the normalization problem for Bethe-Salpeter kernels depending on the total momentum of the meson. As a result of our study, we find considerable unquenching effects in the spectrum of light pseudoscalar, vector and axial-vector mesons.
Gluon condensate in a pion superfluid beyond the mean-field approximation
Jiang Yin; Zhuang Pengfei
2011-03-15
We study gluon condensate in a pion superfluid by calculating the equation of state of the system in the Nambu-Jona-Lasinio model. While in mean-field approximation the growing pion condensate leads to an increasing gluon condensate, meson fluctuations reduce the gluon condensate, and the broken scalar symmetry can be smoothly restored at finite isospin density.
Peturbative gluon exchange in a covariant quark model of the pion
Ito, Hiroshi; Buck, W.W. . Dept. of Physics); Gross, F. . Dept. of Physics Continuous Electron Beam Accelerator Facility, Newport News, VA )
1990-01-01
A covariant pion wave function, which reproduces the low energy data, is used to calculate the perturbative gluon exchange contributions to the pion charge form factor. It is found that the perturbative process dominates at q > 3.5 GeV/c. The dependence on the quark mass and the asymptotic behavior of the form factor are explicitly displayed.
Maramattom, Boby Varkey; Sundar, Shyam; Thomas, Dalvin; Panikar, Dilip
2016-01-01
Postoperative visual loss (POVL) is an unpredictable complication of nonocular surgeries. Posterior ischemic optic neuropathy (PION) is particularly feared in spinal surgeries in the prone position. We report a rare case of PION occurring after surgery for a pterional meningioma and discuss the various factors implicated in POVL.
Maramattom, Boby Varkey; Sundar, Shyam; Thomas, Dalvin; Panikar, Dilip
2016-01-01
Postoperative visual loss (POVL) is an unpredictable complication of nonocular surgeries. Posterior ischemic optic neuropathy (PION) is particularly feared in spinal surgeries in the prone position. We report a rare case of PION occurring after surgery for a pterional meningioma and discuss the various factors implicated in POVL. PMID:27570391
Nakamura, Hiroki; Seki, Ryoichi
2000-11-01
Two- and three-pion correlations are investigated in cases when a disoriented chiral condensate (DCC) occurs. A chaoticity and weight factor are used as measures of two- and three-pion correlations, and the various models for the DCC are investigated. Some models are found to yield the chaoticity and weight factor in a reasonable agreement with recent experimental data.
NASA Astrophysics Data System (ADS)
Prorok, Dariusz
2016-06-01
Many data in the high energy physics are, in fact, sample means. It is shown that when this exact meaning of the data is taken into account and the most weakly bound states are removed from the hadron resonance gas, the acceptable fit to the whole spectra of pions, kaons and protons measured at midrapidity in central Pb-Pb collisions at \\sqrt{{s}{NN}}=2.76 TeV (2012 Phys. Rev. Lett. 109 252301) is obtained. The invariant distributions are predicted with the help of the single-freeze-out model in the chemical equilibrium framework. Low p T pions and protons are reproduced simultaneously as well as the p/π ratio. Additionally, correct predictions extend over lower parts of large p T data. Some more general, possible implications of this approach are pointed out.
Hoffman, Alan
2009-08-04
A primary goal of the STAR spin physics program is measuring the polarized gluon distribution function, {delta}g(x), accessible through the double longitudinal spin asymmetry, A{sub LL}. The STAR detector is uniquely suited for measuring A{sub LL} in a number of different final-state channels, such as inclusive jet and pion production, in polarized pp collisions. We present preliminary A{sub LL} results from RHIC run 6 for neutral pion production at mid-rapidity. These A{sub LL} measurements allow for discrimination among a number of different next-to-leading order (NLO) perturbative Quantum Chromodynamics (pQCD) predictions and provide meaningful constraints on {delta}g(x)
Cross section calculations for subthreshold pion production in peripheral heavy-ion collisions
NASA Technical Reports Server (NTRS)
Norbury, J. W.; Cucinotta, F. A.; Deutchman, P. A.; Townsend, L. W.
1986-01-01
Total cross sections angular distributions, and spectral distributions for the exclusive production of charged and neutral subthreshold pions produced in peripheral nucleus-nucleus collisions are calculated by using a particle-hole formalism. The pions result from the formation and decay of an isobar giant resonance state formed in a C-12 nucleus. From considerations of angular momentum conservation and for the sake of providing a unique experimental signature, the other nucleus, chosen for this work to be C-12 also, is assumed to be excited to one of its isovector (1+) giant resonance states. The effects of nucleon recoil by the pion emission are included, and Pauli blocking and pion absorption effects are studied by varying the isobar width. Detailed comparisons with experimental subthreshold pion data for incident energies between 35 and 86 MeV/nucleon are made.
Measurement of stopping power ratios for 60 MeV positive or negative pions.
Nordin, J A; Henkelman, R M
1979-07-01
Pion stopping power ratios are essential parameters for pion radiotherapy treatment planning. The validity of scaling proton stopping powers to pions is called into question since the pion mass is intermediate between the electron and proton masses. Direct measurements of stopping power ratios with respect to water were made for 60 MeV pions of both charges in Teflon, Plexiglas, nylon, paraffin, gelatine, tissue-equivalent plastic (Shonka A150), graphite, aluminium, steel and copper. Corrections for multiple scattering and energy dependence of the stopping power are applied. Measured stopping power ratios at an accuracy of 0.6% are in agreement to within the limits of experimental error with stopping power ratios calculated from the Bethe-Bloch equation using elemental I-values and Bragg additivity. PMID:112597
Decay constants of the pion and its excitations on the lattice
Mastropas, Ekaterina V.; Richards, David G.
2014-06-23
We present a lattice QCD calculation of the ratios of decay constants of the excited states of the pion, to that of the pion ground state. We use an anisotropic clover fermion action with three flavors of quarks, and study the pion decay constants at three values of the light-quark masses, corresponding to pion masses of 391, 524 and 702 MeV. We find that the decay constant of the first excitation, and more notably of the second, is suppressed with respect to that of the ground-state pion, but that the suppression shows little dependence on the quark mass. The strong suppression of the decay constant of the second excited state is consistent with its interpretation as a predominantly hybrid state.
Investigation of the W and Q 2 dependence of charged pion distributions in μ p scattering
NASA Astrophysics Data System (ADS)
Arneodo, M.; Arvidson, A.; Aubert, J. J.; Badelek, B.; Beaufays, J.; Bee, C. P.; Benchouk, C.; Berghoff, G.; Bird, I.; Blum, D.; Böhm, E.; de Bouard, X.; Brasse, F. W.; Braun, H.; Broll, C.; Brown, S.; Brück, H.; Calen, H.; Chima, J. S.; Ciborowski, J.; Clifft, R.; Coignet, G.; Combley, F.; Coughlan, J.; D'Agostini, G.; Dahlgren, S.; Dengler, F.; Derado, I.; Dreyer, T.; Drees, J.; Düren, M.; Eckardt, V.; Edwards, A.; Ernst, T.; Eszes, G.; Favier, J.; Ferrero, M. I.; Figiel, J.; Flauger, W.; Foster, J.; Gabathuler, E.; Gajewski, J.; Gamet, R.; Gayler, J.; Geddes, N.; Giubellino, P.; Grafström, P.; Grard, F.; Haas, J.; Hagberg, E.; Hasert, F. J.; Hayman, P.; Heusse, P.; Hoppe, C.; Jaffré, M.; Jacholkowska, A.; Janata, F.; Jancso, G.; Johnson, A. S.; Kabuss, E. M.; Kellner, G.; Korbel, V.; Krüger, J.; Kullander, S.; Landgraf, U.; Lanske, D.; Loken, J.; Long, K.; Maire, M.; Malecki, P.; Manz, A.; Maselli, S.; Mohr, W.; Montanet, F.; Montgomery, H. E.; Nagy, E.; Nassalski, J.; Norton, P. R.; Oakham, F. G.; Osborne, A. M.; Pascaud, C.; Pawlik, B.; Payre, P.; Peroni, C.; Pessard, H.; Pettingale, J.; Pietrzyk, B.; Pönsgen, B.; Pötsch, M.; Renton, P.; Ribarics, P.; Rith, K.; Rondio, E.; Scheer, M.; Schlagböhmer, A.; Schiemann, H.; Schmitz, N.; Schneegans, M.; Scholz, M.; Schröder, T.; Schouten, M.; Schultze, K.; Sloan, T.; Stier, H. E.; Studt, M.; Taylor, G. N.; Thénard, J. M.; Thompson, J. C.; de La Torre, A.; Toth, J.; Urban, L.; Wallucks, W.; Whalley, M.; Wheeler, S.; Williams, W. S. C.; Wimpenny, S. J.; Windmolders, R.; Wolf, G.
1986-03-01
The W and Q 2 dependence of the fragmentation functions and of the average multiplicity of charged pions is investigated, using data from the NA9 experiment at the CERN SPS on muon-proton scattering at 280 GeV. A significant increase of pion production with increasing W is observed at fixed Q 2, leading to a rise of the average charged pion multiplicity, linear in ln W 2, and of the pion fragmentation function in the central region, i.e. at small | x F |. This increase can be understood from the kinematic widening of the cms rapidity range proportional to ln W 2 and the observed W independent height of the rapidity distribution. At fixed W, a rise of the average charged pion multiplicity with Q 2 is observed. This rise appears to be weaker than that observed for all charged hadrons implying a stronger rise with Q 2 for kaons and protons.
NASA Astrophysics Data System (ADS)
Xiao, Zhi-Gang; Yong, Gao-Chan; Chen, Lie-Wen; Li, Bao-An; Zhang, Ming; Xiao, Guo-Qing; Xu, Nu
2014-02-01
The high-density behavior of nuclear symmetry energy is among the most uncertain properties of dense neutron-rich matter. Its accurate determination has significant ramifications in understanding not only the reaction dynamics of heavy-ion reactions, especially those induced by radioactive beams, but also many interesting phenomena in astrophysics, such as the explosion mechanism of supernova and the properties of neutron stars. The heavy-ion physics community has devoted much effort during the last few years to constrain the high-density symmetry using various probes. In particular, the / ratio has been most extensively studied both theoretically and experimentally. All models have consistently predicted qualitatively that the / ratio is a sensitive probe of the high-density symmetry energy especially with beam energies near the pion production threshold. However, the predicted values of the / ratio are still quite model dependent mostly because of the complexity of modeling pion production and reabsorption dynamics in heavy-ion collisions, leading to currently still controversial conclusions regarding the high-density behavior of nuclear symmetry energy from comparing various model calculations with available experimental data. As more / data become available and a deeper understanding about the pion dynamics in heavy-ion reactions is obtained, more penetrating probes, such as the K +/ K 0 ratio, meson and high-energy photons are also being investigated or planned at several facilities. Here, we review some of our recent contributions to the community effort of constraining the high-density behavior of nuclear symmetry energy in heavy-ion collisions. In addition, the status of some worldwide experiments for studying the high-density symmetry energy, including the HIRFL-CSR external target experiment (CEE) are briefly introduced.
NASA Astrophysics Data System (ADS)
Zhong, Tao; Wu, Xing-Gang; Huang, Tao
2016-07-01
The low-energy and high-energy behavior of the pion-photon transition form factor F_{π γ }(Q^2) are sensitive to the transverse and longitudinal distributions of the pion wave function, respectively. A careful study of F_{π γ }(Q^2) shall thus provide helpful constraints on the properties of the pion wave function. In this paper, we present a combined analysis of the data on F_{π γ }(Q^2) reported by the CELLO, the CLEO, the BABAR, and the BELLE Collaborations. It is performed by using the method of least squares. By using the combined measurements of the BELLE and CLEO Collaborations, the pion wave function longitudinal and transverse behavior can be fixed to a certain degree, i.e. we obtain β in [0.691,0.757] GeV and B in [0.00,0.235] for P_{χ ^2} ≥ 90 %, where β and B are two parameters of a convenient pion wave function model. It is noted that the distribution amplitude of such a pion wave function can mimic various longitudinal behaviors, as suggested in the literature under a proper choice of parameters. We observe that the CELLO, CLEO, and BELLE data are consistent with each other, all of which prefer the asymptotic-like distribution amplitude; while the BABAR data prefers a more broad distribution amplitude, such as the CZ-like one.
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.
Impact of pion dynamics on nuclear shell structure
Litvinova, Elena
2015-10-15
Spin-isospin response in exotic nuclear systems is investigated. It is found that in some nuclei excitations with pionic quantum numbers (0{sup −}, 1{sup +}, 2{sup −}, …) appear at very low energies with large transition probabilities, which is an indication of the vicinity of the onset of pion condensation. As an example, 2{sup −} components of the spin-dipole resonance in {sup 78}Ni and {sup 132}Sn are considered. The existence of such modes points out to the necessity of taking into account their coupling to other elementary modes of excitation, e.g. single-quasiparticle ones. This coupling is introduced in the theory for the first time. Thereby, both rho-meson and pion-exchange contributions to the nucleon-nucleon interaction are included in the relativistic framework beyond the Hartree-Fock approximation. Namely, classes of Feynman diagrams are selected according to their significance for nuclear spectroscopic characteristics, such as single-particle energies and strength functions, and included into the nucleonic self-energy in all orders of meson-exchange. As an illustration, the impact of these new contributions on the single-particle energies of {sup 100}Sn is discussed.
Direct pion emission in D*+ → D+π decays
NASA Astrophysics Data System (ADS)
Guo, Xing-Dao; Liu, Xue-Wen; Ke, Hong-Wei; Li, Xue-Qian
2016-07-01
The QCD multipole expansion (QCDME) is based on quantum field theory and has been extensively applied to study transitions among ϒ and ψ family members. As it refers to non-perturbative QCD, however, it has only a certain application range. Even though it successfully explains the transition data among members of the ϒ (ψ) family, as Eichten indicates, beyond the production threshold of mediate states it fails to match data by several orders of magnitude. In this work, by studying a simple decay mode D*→ D + π0, where a pion may be emitted before D* transitions into D, we analyze the contribution of QCD multipole expansion. As the Dπ portal is open, the dominant contribution is an OZI-allowed process where a light quark-pair is excited out from vacuum, and its contribution can be evaluated by the 3 P 0 model. Since direct pion emission is OZI-suppressed and violates isospin conservation, its contribution must be much smaller than the dominant one. By a careful calculation, we estimate that the QCDME contribution should be 3–4 orders smaller than the dominant contribution and this result can offer a quantitative interpretation for Eichten's statement. Supported by National Natural Science Foundation of China (11375128)
Influence of pions on the hadron-quark phase transition
Lourenco, O.; Dutra, M.; Frederico, T.; Malheiro, M.; Delfino, A.
2013-05-06
In this work we present the features of the hadron-quark phase transition diagrams in which the pions are included in the system. To construct such diagrams we use two different models in the description of the hadronic and quark sectors. At the quark level, we consider two distinct parametrizations of the Polyakov-Nambu-Jona-Lasinio (PNJL) models. In the hadronic side, we use a well known relativistic mean-field (RMF) nonlinear Walecka model. We show that the effect of the pions on the hadron-quark phase diagrams is to move the critical end point (CEP) of the transitions lines. Such an effect also depends on the value of the critical temperature (T{sub 0}) in the pure gauge sector used to parametrize the PNJL models. Here we treat the phase transitions using two values for T{sub 0}, namely, T{sub 0}= 270 MeV and T{sub 0}= 190 MeV. The last value is used to reproduce lattice QCD data for the transition temperature at zero chemical potential.
Strong Coulomb effects on pions produced in heavy ion collisons
NASA Astrophysics Data System (ADS)
Sullivan, J. P.; Bistirlich, J. A.; Bowman, H. R.; Bossingham, R.; Buttke, T.; Crowe, K. M.; Frankel, K. A.; Martoff, C. J.; Miller, J.; Murphy, D. L.; Rasmussen, J. O.; Zajc, W. A.; Hashimoto, O.; Koike, M.; Péter, J.; Benenson, W.; Crawley, G. M.; Kashy, E.; Nolen, J. A.
1982-03-01
Doubly differential cross sections for the production of π+ and π- near the velocity of the incident beam for pion laboratory angles from 0 to 20 degrees are presented. Beams of 20Ne with EA=280, 380, and 480 MeV and 40Ar with EA=535 MeV incident on C, NaF, KCl, Cu, and U targets were used. A sharp peak in the π- spectrum and a depression in the π+ spectrum is observed at 0° near the incident projectile velocity. The effect is explained in terms of Coulomb interactions between pions and fragments of the incident beam. Least squares fits to the data using the Coulomb correction formulas of Gyulassy and Kauffmann and an effective projectile fragment charge are made. The relationship between these data and previously measured projectile fragmentation data is discussed and a simple parametrization of projectile mass, target mass, and beam energy dependence of the differential cross sections is given. NUCLEAR REACTIONS C, NaF, Cu, U (20Ne,π+/-)X, EA=280-480 MeV; C, KCl (40Ar,π+/-)X, EA=535 MeV; measured σ(Eπ,θπ), θπ=0°-20°, π velocity near beam velocity; deduced projectile fragment charges, Coulomb effects.
Experiments on the nuclear interactions of pions and electrons
Minehart, R. C.; Ziock, K. O.H.
1990-06-01
This paper discusses: {pi}{sup +} + d {yields} 2p; Pion Absorption in {sup 3}He; Pion Absorption in {sup 4}He; Evidence for narrow structure in the analyzing power of the {sup 3}He ({rvec p}, d)X reaction; Coherent {eta}-Meson Production in the Reaction {pi}{minus} + {sup 3}He {yields} {eta} + t; Search for heavy neutrinos; The search for fractionally charged particles; Search for the rare decay, {mu} {sup +} {yields} e{sup +} + {gamma}; A Precise Measurement of the {pi}{sup +} {yields} {pi}{sup 0} e{sup +}{nu} Decay Rate; Transverse and Longitudinal Response Functions for Several Nuclei near Q{sup 2} = 1 (GeV/c){sup 2}; The Q{sup 2}-dependence of the {sup 4}He (e, e'p) coincidence cross section at the quasielastic peak; The Response Function R{sub LT} in the reaction {sup 16}O(e, e' p); and Absorption of anti-protons in heavy nuclei.
Search for dinucleon decay into pions at Super-Kamiokande
NASA Astrophysics Data System (ADS)
Gustafson, J.; Abe, K.; Haga, Y.; Hayato, Y.; Ikeda, M.; Iyogi, K.; Kameda, J.; Kishimoto, Y.; Miura, M.; Moriyama, S.; Nakahata, M.; Nakajima, T.; Nakano, Y.; Nakayama, S.; Orii, A.; Sekiya, H.; Shiozawa, M.; Takeda, A.; Tanaka, H.; Tomura, T.; Wendell, R. A.; Irvine, T.; Kajita, T.; Kametani, I.; Kaneyuki, K.; Nishimura, Y.; Richard, E.; Okumura, K.; Labarga, L.; Fernandez, P.; Berkman, S.; Tanaka, H. A.; Tobayama, S.; Kearns, E.; Raaf, J. L.; Stone, J. L.; Sulak, L. R.; Goldhaber, M.; Carminati, G.; Kropp, W. R.; Mine, S.; Weatherly, P.; Renshaw, A.; Smy, M. B.; Sobel, H. W.; Takhistov, V.; Ganezer, K. S.; Hartfiel, B. L.; Hill, J.; Hong, N.; Kim, J. Y.; Lim, I. T.; Akiri, T.; Himmel, A.; Scholberg, K.; Walter, C. W.; Wongjirad, T.; Ishizuka, T.; Tasaka, S.; Jang, J. S.; Learned, J. G.; Matsuno, S.; Smith, S. N.; Hasegawa, T.; Ishida, T.; Ishii, T.; Kobayashi, T.; Nakadaira, T.; Nakamura, K.; Oyama, Y.; Sakashita, K.; Sekiguchi, T.; Tsukamoto, T.; Suzuki, A. T.; Takeuchi, Y.; Yano, T.; Hirota, S.; Huang, K.; Ieki, K.; Kikawa, T.; Minamino, A.; Nakaya, T.; Suzuki, K.; Takahashi, S.; Fukuda, Y.; Choi, K.; Itow, Y.; Mitsuka, G.; Suzuki, T.; Mijakowski, P.; Hignight, J.; Imber, J.; Jung, C. K.; Palomino, J. L.; Yanagisawa, C.; Ishino, H.; Kayano, T.; Kibayashi, A.; Koshio, Y.; Mori, T.; Sakuda, M.; Kuno, Y.; Tacik, R.; Kim, S. B.; Okazawa, H.; Choi, Y.; Nishijima, K.; Koshiba, M.; Suda, Y.; Totsuka, Y.; Yokoyama, M.; Bronner, C.; Martens, K.; Marti, Ll.; Suzuki, Y.; Vagins, M. R.; Martin, J. F.; de Perio, P.; Konaka, A.; Wilking, M. J.; Chen, S.; Zhang, Y.; Wilkes, R. J.; Super-Kamiokande Collaboration
2015-04-01
A search for dinucleon decay into pions with the Super-Kamiokande detector has been performed with an exposure of 282.1 kiloton-years. Dinucleon decay is a process that violates baryon number by two units. We present the first search for dinucleon decay to pions in a large water-Cherenkov detector. The modes 16O (p p )→ 14C π+π+ , 16O (p n )→14N π+π0 , and 16O (n n )→14O π0π0 are investigated. No significant excess in the Super-Kamiokande data has been found, so a lower limit on the lifetime of the process per oxygen nucleus is determined. These limits are τp p →π+π+>7.22 ×1 031 years , τp n →π+π0>1.70 ×1 032 years , and τn n →π0π0>4.04 ×1 032 years . The lower limits on each mode are about 2 orders of magnitude better than previous limits from searches for dinucleon decay in iron.
A simple charged particle spectrometer for a pion production experiment
NASA Astrophysics Data System (ADS)
Borozdin, Konstantin; Brockwell, Michael; Chung, Kiwhan; Green, Andrew; Hogan, Gary; Jason, Andy; Mariam, Fesseha; Miyadera, Haruo; Morris, Christopher; Spaulding, Randy; Wang, Zhehui
2010-02-01
Measurement of a charged particle energy is not a new task, but inexpensive ways of such measurement are of interest, in particular as they open new opportunities for advanced charged particle radiography. We describe a magnetic spectrometer we have recently built for pion production measurement experiments at LANSCE (Los Alamos). The spectrometer consists of four modules of drift tubes and a bending magnet. A maximum magnetic field in the bending magnet was about 7500 Gauss. Drift tubes of 2 inches in diameter were made of thin carbon fiber to minimize multiple scattering in their walls. The spectrometer was used in the scattering experiment with primary beam of 800 MeV protons and C or Al target. We present measurements of secondary protons, pions and muons scattered in the reverse direction. Energy deposited in 1 cm thick plastic scintillator and 4" CsI was compared to the energy measured from the particle bending in the magnetic field. Experimental data are compared to GEANT4 modeling. We discuss, how this technology may be applied to the particle identification and to the energy loss measurements. )
Kaon and pion production in relativistic heavy-ion collisions
Wagner, M.; Larionov, A.B.; Mosel, U.
2005-03-01
The Boltzmann-Uehling-Uhlenbeck (BUU) transport model is applied to study strangeness and pion production in nucleus-nucleus collisions. Starting from proton induced reactions, we further investigate Si+Au, Au+Au, and Pb+Pb collisions in the energy range between 2 and 40A GeV and compare the results with data and other transport calculations. The qq-annihilation, or resonance, channel simulated by the string model in meson-nucleon collisions at {radical}(s)>2 GeV is introduced. The importance of this channel for a good description of the proton-nucleus data on K{sup +} production is demonstrated. We further show that meson-meson collisions contribute significantly to the KK{sup lowbar} production in heavy-ion collisions above 5A GeV and improve the agreement with data on the K{sup +}/{pi}{sup +} ratio. Finally, we study the influence of in-medium modifications of the FRITIOF model on pion and kaon production.
Research activities in high energy physics
NASA Astrophysics Data System (ADS)
Electron scattering experiments are described. Construction and testing of the MEA Accelerator and of the instrumentation in the experimental halls was surveyed. Work on the building of a pion channel and a 180 deg electron scattering set-up was also reviewed. Progress in muon and hadron physics, radio and nuclear chemistry and in theoretical and technical departments is outlined.
Dynamical coupled channel calculation of pion and omega meson production
Paris, Mark
2009-01-01
A dynamical coupled channel approach is used to study $\\pi$ and $\\omega$--meson production induced by pions and photons scattering from the proton. Six-channels are used to fit unpolarized and polarized scattering data including $\\pi N$, $\\eta N$, $\\pi\\Delta$, $\\sigma N$, $\\rho N$, $\\omega N$. Bare parameters in an effective hadronic Lagrangian are fixed in $\\chi^2$-fits to data from $\\pi N \\to \\pi N$, $\\gamma N \\to \\pi N$, $\\pi^- p \\to \\omega n$, and $\\gamma p \\to \\omega p$ reactions at center-of-mass energies from threshold to $E < 2.0$ GeV. The $T$ matrix determined in these fits is used to calculate the photon beam asymmetry for $\\omega$-meson production and the $\\omega N \\to \\omega N$ total cross section and scattering lengths.
Incoherent Neutral Pion Photoproduction on {sup 12}C
Tarbert, C. M.; Watts, D. P.; Branford, D.; Foehl, K.; Glazier, D. I.; Aguar, P.; Ahrens, J.; Arends, H. J.; Heid, E.; Jahn, O.; Krambrich, D.; Martinez, M.; Rost, M.; Thomas, A.; Walcher, Th.; Annand, J. R. M.; Codling, R.; Downie, E. J.; Livingston, K.; MacGregor, I. J. D.
2008-04-04
We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The {sup 12}C({gamma},{pi}{sup 0}){sup 12}C{sub 4.4} {sub MeV}* reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a {pi}{sup 0} spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the {delta} in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a {delta}-hole model.
Influence of pions and hyperons on stellar black hole formation
NASA Astrophysics Data System (ADS)
Peres, Bruno; Oertel, Micaela; Novak, Jérôme
2013-02-01
We present numerical simulations of stellar core collapse with spherically symmetric, general relativistic hydrodynamics up to black hole formation. Using the CoCoNuT code, with a newly developed grey leakage scheme for the neutrino treatment, we investigate the effects of including pions and Λ hyperons into the equation of state at high densities and temperatures on the black hole formation process. Results show non-negligible differences between the models with reference equation of state without any additional particles and models with the extended ones. For the latter, the maximum masses supported by the proto-neutron star are smaller and the collapse to a black hole occurs earlier. A phase transition to hyperonic matter is observed when the progenitor allows for a high enough accretion rate onto the proto-neutron star. Rough estimates of neutrino luminosity from these collapses are given, too.
Measurement of Charged Pions from Neutrino-produced Nuclear Resonance
Simon, Clifford N.
2014-01-01
A method for identifying stopped pions in a high-resolution scintillator bar detector is presented. I apply my technique to measure the axial mass M^{Δ}_{A}for production of the Δ(1232) resonance by neutrino, with the result M^{Δ}_{A} = 1.16±0.20 GeV (68% CL) (limited by statistics). The result is produced from the measured spectrum of reconstructed momentum-transfer Q^{2}. I proceed by varying the value of M^{Δ}_{A} in a Rein-Sehgal-based Monte Carlo to produce the best agreement, using shape only (not normalization). The consistency of this result with recent reanalyses of previous bubble-chamber experiments is discussed.
Recoil Polarization for {delta} Excitation in Pion Electroproduction
Kelly, J.J.; Beise, E.J.; Breuer, H.; Chang, C.C.; Chant, N.S.; Roos, P.G.; Roche, R.E.; McAleer, S.; Meekins, D.; Chai, Z.; Gayou, O.; Bertozzi, W.; Gilad, S.; Higinbotham, D.W.; Rvachev, M.; Sirca, S.; Suleiman, R.; Zheng, X.; Zhu, L.; Jones, M.K.
2005-09-02
We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W=1.23 GeV at Q{sup 2}=1.0 (GeV/c){sup 2}, obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S{sub 1+}/M{sub 1+})=-(6.84{+-}0.15)% and Re (E{sub 1+}/M{sub 1+})=-(2.91{+-}0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M{sub 1+} dominance and l{sub {pi}}{<=}1 truncation.
Recoil polarization for delta excitation in pion electroproduction.
Kelly, J J; Roché, R E; Chai, Z; Jones, M K; Gayou, O; Sarty, A J; Frullani, S; Aniol, K; Beise, E J; Benmokhtar, F; Bertozzi, W; Boeglin, W U; Botto, T; Brash, E J; Breuer, H; Brown, E; Burtin, E; Calarco, J R; Cavata, C; Chang, C C; Chant, N S; Chen, J-P; Coman, M; Crovelli, D; De Leo, R; Dieterich, S; Escoffier, S; Fissum, K G; Garde, V; Garibaldi, F; Georgakopoulus, S; Gilad, S; Gilman, R; Glashausser, C; Hansen, J-O; Higinbotham, D W; Hotta, A; Huber, G M; Ibrahim, H; Iodice, M; de Jager, C W; Jiang, X; Klimenko, A; Kozlov, A; Kumbartzki, G; Kuss, M; Lagamba, L; Laveissière, G; Lerose, J J; Lindgren, R A; Liyanage, N; Lolos, G J; Lourie, R W; Margaziotis, D J; Marie, F; Markowitz, P; McAleer, S; Meekins, D; Michaels, R; Milbrath, B D; Mitchell, J; Nappa, J; Neyret, D; Perdrisat, C F; Potokar, M; Punjabi, V A; Pussieux, T; Ransome, R D; Roos, P G; Rvachev, M; Saha, A; Sirca, S; Suleiman, R; Strauch, S; Templon, J A; Todor, L; Ulmer, P E; Urciuoli, G M; Weinstein, L B; Wijesooriya, K; Wojtsekhowski, B; Zheng, X; Zhu, L
2005-09-01
We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation. PMID:16196919
Pion double charge exchange scattering above the delta resonance
Burleson, G.R.
1989-01-01
Data are presented on pion-nucleus double-charge-exchange scattering at energies between 300 and 500 MeV, the highest energies measured so far, together with a review of results at lower energies. The small-angle excitation functions disagree with predictions based on a sex-quark cluster model and on an optical model consistent with single-charge-exchange scattering at these energies, but they are consistent with a distorted-wave calculation. Data on f{sub 7/2}-shell nuclei are in partial agreement with a two-amplitude model which is successful at lower energies. In order to achieve good understanding of this process at these energies, more work; both experimental and theoretical, is needed. 16 refs., 6 figs.
Ratio of Pion Kaon Production in Proton Carbon Interactions
Lebedev, Andrey V.; /Harvard U.
2007-05-01
The ratio of pion-kaon production by 120 GeV/c protons incident on carbon target is presented. The data was recorded with the Main Injector Particle Production experiment at Fermi National Accelerator Laboratory. Production ratios of K{sup +}/{pi}{sup +}, K{sup -}/{pi}{sup -}, K{sup -}/K{sup +}, and {pi}{sup -}/{pi}{sup +} are measured in 24 bins in longitudinal momentum from 20 to 90 GeV/c and transverse momentum up to 2 GeV/c. The measurement is compared to existing data sets, particle production Monte Carlo results from FLUKA-06, parametrization of proton-beryllium data at 400/450 GeV/c, and ratios measured by the MINOS experiment on the NuMI target.
Recoil Polarization for Delta Excitation in Pion Electroproduction
J. J. Kelly; R. E. Roche; Z. Chai; M. K. Jones; O. Gayou; A. J. Sarty; S. Frullani; K. Aniol; E. J. Beise; F. Benmokhtar; W. Bertozzi; W. U. Boeglin; T. Botto; E. J. Brash; H. Breuer; E. Brown; E. Burtin; J. R. Calarco; C. Cavata; C. C. Chang; N. S. Chant; J.-P. Chen; M. Coman; D. Crovelli; R. De Leo; S. Dieterich; S. Escoffier; K. G. Fissum; V. Garde; F. Garibaldi; S. Georgakopoulus; S. Gilad; R. Gilman; C. Glashausser; J.-O. Hansen; D. W. Higinbotham; A. Hotta; G. M. Huber; H. Ibrahim; M. Iodice; C. W. de Jager; X. Jiang; A. Klimenko; A. Kozlov; G. Kumbartzki; M. Kuss; L. Lagamba; G. Laveissiere; J. J. LeRose; R. A. Lindgren; N. Liyanage; G. J. Lolos; R. W. Lourie; D. J. Margaziotis; F. Marie; P. Markowitz; S. McAleer; D. Meekins; R. Michaels; B. D. Milbrath; J. Mitchell; J. Nappa; D. Neyret; C. F. Perdrisat; M. Potokar; V. A. Punjabi; T. Pussieux; R. D. Ransome; P. G. Roos; M. Rvachev; A. Saha; S. Sirca; R. Suleiman; S. Strauch; J. A. Templon; L. Todor; P. E. Ulmer; G. M. Urciuoli; L. B. Weinstein; K. Wijesooriya; B. Wojtsekhowski; X. Zheng; and L. Zhu
2005-08-01
We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W=1.23 GeV at Q{sup 2}=1.0 (GeV/c){sup 2}, obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re(S1+/M1+)=-(6.84+/-0.15)% and Re(E1+/M1+)=-(2.91+/-0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and sp truncation.
Lattice study of the Boer-Mulders transverse momentum distribution in the pion
Engelhardt, Michael; Musch, Bernhard; Haegler, Philipp; Negele, John; Schaefer, Andreas
2014-11-01
The Boer-Mulders transverse momentum-dependent parton distribution (TMD) characterizes polarized quark transverse momentum in an unpolarized hadron. Techniques previously developed for lattice calculations of nucleon TMDs are applied to the pion. These techniques are based on the evaluation of matrix elements of quark bilocal operators containing a staple-shaped Wilson connection. Results for the Boer-Mulders transverse momentum shift in the pion, obtained at a pion mass of mπ=518MeV, are presented and compared to corresponding results in the nucleon.
Adolph, C.; Akhunzyanov, R.; Alexeev, M. G.; Alexeev, G. D.; Amoroso, A.; Andrieux, V.; Anosov, V.; Austregesilo, A.; Badełek, B.; Balestra, F.; Barth, J.; Baum, G.; Beck, R.; Bedfer, Y.; Berlin, A.; Bernhard, J.; Bicker, K.; Bielert, E. R.; Bieling, J.; Birsa, R.; Bisplinghoff, J.; Bodlak, M.; Boer, M.; Bordalo, P.; Bradamante, F.; Braun, C.; Bressan, A.; Büchele, M.; Burtin, E.; Capozza, L.; Chiosso, M.; Chung, S. U.; Cicuttin, A.; Crespo, M. L.; Curiel, Q.; Dalla Torre, S.; Dasgupta, S. S.; Dasgupta, S.; Denisov, O. Yu.; Donskov, S. V.; Doshita, N.; Duic, V.; Dünnweber, W.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P. D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Finger, M.; Finger, M.; Fischer, H.; Franco, C.; N. du Fresne von Hohenesche; Friedrich, J. M.; Frolov, V.; Gautheron, F.; Gavrichtchouk, O. P.; Gerassimov, S.; Geyer, R.; Gnesi, I.; Gobbo, B.; Goertz, S.; Gorzellik, M.; Grabmüller, S.; Grasso, A.; Grube, B.; Grussenmeyer, T.; Guskov, A.; Haas, F.; von Harrach, D.; Hahne, D.; Hashimoto, R.; Heinsius, F. H.; Herrmann, F.; Hinterberger, F.; Höppner, Ch.; Horikawa, N.; d'Hose, N.; Huber, S.; Ishimoto, S.; Ivanov, A.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jasinski, P.; Jörg, P.; Joosten, R.; Kabuß, E.; Ketzer, B.; Khaustov, G. V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koivuniemi, J. H.; Kolosov, V. N.; Kondo, K.; Königsmann, K.; Konorov, I.; Konstantinov, V. F.; Kotzinian, A. M.; Kouznetsov, O.; Krämer, M.; Kroumchtein, Z. V.; Kuchinski, N.; Kunne, F.; Kurek, K.; Kurjata, R. P.; Lednev, A. A.; Lehmann, A.; Levillain, M.; Levorato, S.; Lichtenstadt, J.; Maggiora, A.; Magnon, A.; Makke, N.; Mallot, G. K.; Marchand, C.; Martin, A.; Marzec, J.; Matousek, J.; Matsuda, H.; Matsuda, T.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu. V.; Miyachi, Y.; Nagaytsev, A.; Nagel, T.; Nerling, F.; Neubert, S.; Neyret, D.; Novy, J.; Nowak, W. -D.; Nunes, A. S.; Olshevsky, A. G.; Orlov, I.; Ostrick, M.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Pesaro, G.; Peshekhonov, D. V.; Platchkov, S.; Pochodzalla, J.; Polyakov, V. A.; Pretz, J.; Quaresma, M.; Quintans, C.; Ramos, S.; Regali, C.; Reicherz, G.; Rocco, E.; Rossiyskaya, N. S.; Ryabchikov, D. I.; Rychter, A.; Samoylenko, V. D.; Sandacz, A.; Sarkar, S.; Savin, I. A.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schlüter, T.; Schmidt, K.; Schmieden, H.; Schönning, K.; Schopferer, S.; Schott, M.; Shevchenko, O. Yu.; Silva, L.; Sinha, L.; Sirtl, S.; Slunecka, M.; Sosio, S.; Sozzi, F.; Srnka, A.; Steiger, L.; Stolarski, M.; Sulc, M.; Sulej, R.; Suzuki, H.; Szabelski, A.; Szameitat, T.; Sznajder, P.; Takekawa, S.; ter Wolbeek, J.; Tessaro, S.; Tessarotto, F.; Thibaud, F.; Uhl, S.; Uman, I.; Virius, M.; Wang, L.; Weisrock, T.; Wilfert, M.; Windmolders, R.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zink, A.
2015-05-01
Measurements of the Collins and Sivers asymmetries for charged pions and charged and neutral kaons produced in semi-inclusive deep-inelastic scattering of high energy muons off transversely polarised protons are presented. The results were obtained using all the available COMPASS proton data, which were taken in the years 2007 and 2010. The Collins asymmetries exhibit in the valence region a non-zero signal for pions and there are hints of non-zero signal also for kaons. The Sivers asymmetries are found to be positive for positive pions and kaons and compatible with zero otherwise.
Invited Parallel Talk: Forward pion-nucleon charge exchange reaction and Regge constraints
NASA Astrophysics Data System (ADS)
Huang, Fei; Sibirtsev, A.; Krewald, S.; Hanhart, C.; Haidenbauer, J.; Meißner, U.-G.
2009-12-01
We present our recent study of pion-nucleon charge exchange amplitudes above 2 GeV. We analyze the forward pion-nucleon charge exchange reaction data in a Regge model and compare the resulting amplitudes with those from the Karlsruhe-Helsinki and George-Washington-University partial-wave analyses. We explore possible high-energy constraints for theoretical baryon resonance analyses in the energy region above 2 GeV. Our results show that for the pion-nucleon charge exchange reaction, the appropriate energy region for matching meson-nucleon dynamics to diffractive scattering should be around 3 GeV for the helicity flip amplitude.
Lattice study of the leptonic decay constant of the pion and its excitations
Mastropas, Ekaterina; Richard, David
2014-11-01
We present a calculation of the decay constant of the pion, and its lowest-lying three excitations, at three values of the pion mass between around 400 and 700 MeV, using anisotropic clover lattices. We use the variational method to determine an optimal interpolating operator for each of the states. We find that the decay constant of the first excitation, and more notably of the second, is suppressed with respect to that of the ground-state pion, but that the suppression shows little dependence on the quark mass.
Pion-photon transition distribution amplitudes in the Nambu Jona-Lasinio model
NASA Astrophysics Data System (ADS)
Courtoy, A.; Noguera, S.
2007-11-01
We define the pion-photon transition distribution amplitudes (TDA) in a field theoretic formalism from a covariant Bethe-Salpeter approach for the determination of the bound state. We apply our formalism to the Nambu Jona-Lasinio model, as a realistic theory of the pion. The obtained vector and axial TDAs satisfy all features required by general considerations. In particular, sum rules and the polynomiality condition are explicitly verified. We have numerically proved that the odd coefficients in the polynomiality expansion of the vector TDA vanish in the chiral limit. The role of PCAC and the presence of a pion pole are explicitly shown.
Investigations in the problem of pion condensation using generator co-ordinate methods
NASA Astrophysics Data System (ADS)
Chattopadhyay, P.; Da Providencia, J.
1981-11-01
Pion condensation in neutron matter has been investigated using the generator coordinate method and a simple p-wave interaction. The assumption of a condensed mode corresponding to one pion momentum (determined variationally) helps evaluate all the necessary matrix elements exactly. The technique of charge projection from a coherent state of negative pions is discussed, and calculations have been carried out for the cases of average charge conservation, charge projection before variation and for a charge conserving trial function. The ground-state energies and the lowest excitations of the system are obtained from numerical solutions of the Hill-Wheeler equation.
Charged pions from the isotopes sup 58,64 Ni by 201 MeV protons
Palmeri, A.; Aiello, S.; Badala, A.; Barbera, R.; Pappalardo, G.S. ); Bimbot, L. ); Reide, F. ); Willis, N.; Oeschler, H.
1989-08-01
Charged pion production induced by 201 MeV protons on {sup 58}Ni and {sup 64}Ni has been studied. The double differential cross sections have been measured over a wide angular range. Different behavior of the angular distribution is observed for low and high energy pions. The yield of positive pions shows a pronounced forward peaked component. The deduced total production yields are about the same for ({ital p},{pi}{sup +}) on both isotopes whereas that for {sup 64}Ni({ital p},{pi}{sup {minus}}) is twice as large as for {sup 58}Ni({ital p},{pi}{sup {minus}}).
Pion-photon transition distribution amplitudes in the Nambu-Jona-Lasinio model
Courtoy, A.; Noguera, S.
2007-11-01
We define the pion-photon transition distribution amplitudes (TDA) in a field theoretic formalism from a covariant Bethe-Salpeter approach for the determination of the bound state. We apply our formalism to the Nambu-Jona-Lasinio model, as a realistic theory of the pion. The obtained vector and axial TDAs satisfy all features required by general considerations. In particular, sum rules and the polynomiality condition are explicitly verified. We have numerically proved that the odd coefficients in the polynomiality expansion of the vector TDA vanish in the chiral limit. The role of PCAC and the presence of a pion pole are explicitly shown.
Comparison of the energy response of an ionization spectrometer for pions and protons
NASA Technical Reports Server (NTRS)
Jones, W. V.; Verma, S. D.
1971-01-01
An ionization spectrometer consisting of a sandwich of iron absorbers and plastic scintillation counters was used to measure the energy of pions and protons in the interval 10 to 1000 GeV. For the limited energy interval of 10 to 40 GeV, pions and protons were identified by an air cerenkov counter. Interactions in carbon were studied in a multiplate cloud chamber placed between the cerenkov counter and the spectrometer. Knowledge of these interactions were used in conjunction with a Monte Carlo simulation of the cascade process to study differences in the response of the spectrometer to pions and protons.
Exclusive single pion electroproduction off the proton: Results from CLAS
Park, Kijun
2016-08-13
Exclusive meson electroproduction off protons is a powerful tool to probe the effective degrees of freedom in excited nucleon states at the varying distance scale where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance. During the past decade, the CLAS collaboration has executed a broad experimental program to study the excited states of the proton using polarized electron beam and both polarized and unpolarized proton targets. The measurements covered a broad kinematic range in the invariant massmore » $W$ and photon virtuality $Q^2$ with nearly full coverage in polar and azimuthal angles in the hadronic CM system. As results, several low-lying nucleon resonance states in particular from pion threshold to $W < 1.6$ GeV have been explored. These include $$\\Delta$$(1232)$$\\frac{3}{2}^+$$, $$N(1440)\\frac{1}{2}^+$$, $$N(1520)\\frac{3}{2}^-$$, and $$N(1535)\\frac{1}{2}^-$$ states. In addition, we recently published the differential cross sections and helicity amplitudes of the reaction $$\\gamma^*p\\to n\\pi^+$$ at higher $W$ (1.6 to 2.0 GeV) which are the $$N(1675)\\frac{5}{2}^-$$, $$N(1680)\\frac{5}{2}^+$$, and $$N(1710)\\frac{1}{2}^+$$ states. These excited states with isospin $1/2$ and with masses near 1.7 GeV can be accessed in single $$n\\pi^+$$ production as there are no isospin $3/2$ states present in this mass range with the same spin-parity assignments. As a result, I will briefly discuss these states from CLAS results of the single charged pion electroproduction data.« less
Pion form factor using domain wall valence quarks and asqtad sea quarks
George Fleming; Frederic Bonnet; Robert Edwards; Randal Lewis; David Richards
2004-09-01
We compute the pion electromagnetic form factor in a hybrid calculation with domain wall valence quarks and improved staggered (asqtad) sea quarks. This method can easily be extended to rho-to-gamma-pi transition form factors.
Mechanism of pion production in {alpha}p scattering at 1 GeV/nucleon
Alkhazov, G. D.; Prokofiev, A. N. Smirnov, I. B.; Strokovsky, E. A.
2012-09-15
An analysis of the experimental data on one-pion and two-pion production in the p({alpha}, {alpha} Prime )X reaction studied in a semi-exclusive experiment at an energy of E{sub {alpha}} = 4.2 GeV has been performed. The obtained results demonstrate that the inelastic {alpha}-particle scattering on the proton at the energy of the experiment proceeds either through excitation and decay of the {Delta} resonance in the projectile {alpha} particle, or through excitation in the target proton of the Roper resonance, which decays into a nucleon and a pion, or a nucleon and a {sigma} meson-a system of two pions in the isospin I = 0, S-wave state.
Response of pure CsI to charged pions in the intermediate energy region
NASA Astrophysics Data System (ADS)
Yamazaki, H.; Yorita, T.; Yuki, H.; Kasagi, J.; Kato, S.; Shimizu, H.; Yoshida, H. Y.; Maruyama, K.; Okuno, H.; Sawamoto, T.
1997-02-01
The response of a scintillation detector array consisting of 7 pure CsI crystals with a thickness of 13.5 radiation lenghths has been measured to electrons, positrons and charged pions with momenta ranging from 250 to 1000 MeV/ c. For electrons and positrons the detector provides a very linear response to the incident energy. High energy charged pions make a peak at around 150 MeV corresponding to the ionization energy loss. In addition to the peak, comparable yields which are caused by nuclear reactions are distributed up to the maximum available enegy and form a broad bump. The shape of the broad bump for positive pions is different from that for negative pions with the same momentum. A simulation with a GEANT program cannot reproduce the shape of the broad bump.
Using a New Smearing Technique to Find Moments of the Quark Distribution Amplitude of the Pion
NASA Astrophysics Data System (ADS)
Roberts, H. L. L.; Richards, David; Thomas, Christopher
2011-09-01
We study the distribution of momentum between valence quarks of the ground state and the first excited state of the pion using Lattice QCD on the anisotropic lattice. Our final goal is to extract the second moment of distribution amplitudes of the ground state and first excited state of the pion for exclusive processes at high momentum transfer. At this stage of the project, we can compute the ground state pion decay constant in a lattice renormalization scheme up to an overall normalization constant. We employ a variational technique that will allow us to determine the decay constant and second moment of the distribution amplitude of the first excited state of the pion also. We use a new smearing technique in order to minimize pollution of the data from higher-lying excited states. The anisotropy of the lattice is a novel feature of our approach, and strongly increases sensitivity to excited states through a better temporal resolution.
Experimental studies of pion-nucleus interactions at intermediate energies. Annual progress report
Not Available
1992-12-31
This report summarizes investigations of various pion-nucleus interactions and nucleon-nucleus charge-exchange reactions. The work was carried out with the LAMPF accelerator at the Los Alamos National Laboratory and the cyclotrons at the Paul Scherrer Institute (PSI) near Zurich, Switzerland, and at Indiana University (IUCF), as a collaborative effort among several laboratories and universities. The experimental activity at LAMPF involved measurements of new data on pion double-charge-exchange scattering, some initial work on a new Neutral Meson Spectrometer system, a search for deeply-bound pionic atoms, measurements of elastic scattering, and studies of the (n,p) reaction on various nuclei. At PSI measurements of pion quasielastic scattering were carried out, with detection of the recoil proton. Work on the analysis of data from a previous experiment at PSI on pion absorption in nuclei was continued. This experiment involved using a detector system that covered nearly the full solid angle.
Pion in the Holographic Model with 5D Yang-Mills Fields
Grigoryan, Hovhannes; Radyushkin, Anatoly
2008-12-01
We study pion in the holographic model of Hirn and Sanz which contains two Yang-Mills fields defined in the background of the sliced AdS space. The infrared boundary conditions imposed on these fields generate the spontaneous breaking of the chiral symmetry down to its vector subgroup. Within the framework of this model, we get an analytic expression for the pion form factor and a compact result for its radius. We also extend the holographic model to include Chern-Simons term which is required to reproduce the appropriate axial anomaly of QCD. As a result, we calculate the anomalous form factor of the pion and predict its Q^2-slope for the kinematics when one of the photons is almost on-shell. We also observe that the anomalous form factor with one real and one virtual photon is given by the same analytic expression as the electromagnetic form factor of a charged pion.
DSE inspired model for the pion's valence dressed-quark GPD
NASA Astrophysics Data System (ADS)
Chang, L.; Mezrag, C.; Moutarde, H.; Roberts, C. D.; Rodríguez-Quintero, J.; Sabatié, F.
2015-07-01
We sketch here an approach to the computation of genaralised parton distributions (GPDs), based upon a rainbow-ladder (RL) truncation of QCD's Dyson-Schwinger equations and exemplified via the pion's valence dressed-quark GPD, Hvπ(x,ξ,t). Our analysis focuses on the case of zero skewness, ξ = 0, and underlines that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for Hvπ(x,0,t), expressed as the Radon transform of a single amplitude. Therewith we obtain results for Hvπ(x,0,t) and the associated impact-parameter dependent distribution, , which provide a qualitatively sound picture of the pion's dressed-quark structure at an hadronic scale.
Possibility of an s-wave pion condensate in neutron stars reexamined
Ohnishi, A.; Jido, D.; Sekihara, T.; Tsubakihara, K.
2009-09-15
We examine possibilities of pion condensation with zero momentum (s-wave condensation) in neutron stars by using the pion-nucleus optical potential U and the relativistic mean field (RMF) models. We use low-density phenomenological optical potentials parametrized to fit deeply bound pionic atoms or pion-nucleus elastic scatterings. The proton fraction (Y{sub p}) and electron chemical potential ({mu}{sub e}) in neutron star matter are evaluated in RMF models. We find that the s-wave pion condensation hardly takes place in neutron stars and especially has no chance if hyperons appear in neutron star matter and/or the b{sub 1} parameter in U has density dependence.
750 GeV dark pion: Cousin of a dark G -parity odd WIMP
NASA Astrophysics Data System (ADS)
Bai, Yang; Berger, Joshua; Lu, Ran
2016-04-01
We point out a potential common origin of the recently observed 750 GeV diphoton resonance and a weakly interacting massive particle (WIMP) candidate. In a dark QCD sector with an unbroken dark G parity, the diphoton resonance could be a dark G -even pion, while the WIMP could be the lightest dark G -odd pion. Both particles are Standard Model gauge singlets and have the same decay constant. For the dark pion decay constant of around 500 GeV, both the diphoton excess at the LHC and the dark matter thermal abundance can be accommodated in our model. Our model predicts additional dark G -even and dark G -odd color-octet pions within reach of the 13 TeV LHC runs. For the 5 +5 ¯ model, compatible with the grand unified theories, the WIMP mass is predicted to be within (613,750) GeV.
Endpoint behavior of the pion distribution amplitude in QCD sum rules with nonlocal condensates
Mikhailov, S. V.; Pimikov, A. V.; Stefanis, N. G.
2010-09-01
Starting from the QCD sum rules with nonlocal condensates for the pion distribution amplitude, we derive another sum rule for its derivative and its ''integral derivatives''--defined in this work. We use this new sum rule to analyze the fine details of the pion distribution amplitude in the endpoint region x{approx}0. The results for endpoint-suppressed and flattop (or flatlike) pion distribution amplitudes are compared with those we obtained with differential sum rules by employing two different models for the distribution of vacuum-quark virtualities. We determine the range of values of the derivatives of the pion distribution amplitude and show that endpoint-suppressed distribution amplitudes lie within this range, while those with endpoint enhancement--flat-type or Chernyak-Zhitnitsky like--yield values outside this range.
Thermal dileptons from {pi}-{rho} interactions in a hot pion gas
Baier, R.; Dirks, M.; Redlich, K. |
1997-04-01
The production of low mass dileptons from {pi}-{rho} interactions in a hot medium is studied. Applying finite temperature perturbation theory the dilepton rate is computed up to order g{sub {rho}}{sup 2}. For dilepton masses below the {rho} the two-body reactions {pi}{pi}{r_arrow}{rho}{gamma}{sup {asterisk}}, {pi}{rho}{r_arrow}{pi}{gamma}{sup {asterisk}}, and the decay process {rho}{r_arrow}{pi}{pi}{gamma}{sup {asterisk}} give significant contributions. Nonequilibrium contributions to the thermal rate are estimated, including the modification of the particle distribution function with a nonzero pion chemical potential. A comparison of the dilepton rate with the recent data measured in nucleus-nucleus collisions at CERN SPS energy by the CERES Collaboration is also performed. It is shown that the additional thermal dileptons from {pi}-{rho} interactions can partially account for the excess of the soft dilepton yield seen experimentally. {copyright} {ital 1997} {ital The American Physical Society}
Pion-Nucleon Scattering and Analysis from threshold to the N*(1440) Resonance Region
NASA Astrophysics Data System (ADS)
Sadler, Michael; Watson, Shon; Stahov, Jugoslav
2008-10-01
Many measurements for pion-nucleon scattering from threshold to the N*(1440) resonance region have been made since 1980, when the landmark Karlsruhe-Helsinki (KH) and Carnegie Mellon-Berkeley (CMB) partial wave analyses (PWA) were completed. These measurements consist of differential cross sections and analyzing powers for elastic scattering and charge exchange. Spin rotation parameters for elastic scattering in the momentum interval 0.4 -- 0.7 GeV/c have also been obtained. The program culminated with measurements of π-p -> Neutrals (charge exchange, multiple pi-zero final states, eta production, and inverse photoproduction) using the Crystal Ball at BNL. Resonance parameters for the N*(1440) in the Review of Particle Physics by the Particle Data Group have been obtained from the KH and CMB analyses. The 2006 edition also includes the analysis by George Washington University (GWU) ``for averages, fits, limits, etc.'', but the parameters were unchanged. An overview of the data will be presented along with comparisons to PWA.
Monte Carlo Analysis of Pion Contribution to Absorbed Dose from Galactic Cosmic Rays
NASA Technical Reports Server (NTRS)
Aghara, S.K.; Battnig, S.R.; Norbury, J.W.; Singleterry, R.C.
2009-01-01
Accurate knowledge of the physics of interaction, particle production and transport is necessary to estimate the radiation damage to equipment used on spacecraft and the biological effects of space radiation. For long duration astronaut missions, both on the International Space Station and the planned manned missions to Moon and Mars, the shielding strategy must include a comprehensive knowledge of the secondary radiation environment. The distribution of absorbed dose and dose equivalent is a function of the type, energy and population of these secondary products. Galactic cosmic rays (GCR) comprised of protons and heavier nuclei have energies from a few MeV per nucleon to the ZeV region, with the spectra reaching flux maxima in the hundreds of MeV range. Therefore, the MeV - GeV region is most important for space radiation. Coincidentally, the pion production energy threshold is about 280 MeV. The question naturally arises as to how important these particles are with respect to space radiation problems. The space radiation transport code, HZETRN (High charge (Z) and Energy TRaNsport), currently used by NASA, performs neutron, proton and heavy ion transport explicitly, but it does not take into account the production and transport of mesons, photons and leptons. In this paper, we present results from the Monte Carlo code MCNPX (Monte Carlo N-Particle eXtended), showing the effect of leptons and mesons when they are produced and transported in a GCR environment.
Measuring Active-Sterile Neutrino Oscillations with a Stopped Pion Neutrino Source
NASA Astrophysics Data System (ADS)
van de Water, Richard; Louis, Bill; Mills, Geoff
2007-04-01
The question of the existence of light sterile neutrinos is of great interest in many areas of particle physics, astrophysics, and cosmology. Furthermore, should the MiniBooNE experiment at Fermilab confirm the LSND oscillation signal, then new measurements are required to identify the mechanism responsible for these oscillations. Possibilities include sterile neutrinos, CP or CPT violation, variable mass neutrinos, and Lorentz violation. Here we consider an experiment at a stopped pion neutrino source (the Spallation Neutron Source at ORNL) to determine if active-sterile neutrino oscillations with δm ^2 greater than 0.1 eV^2 can account for the signal. By exploiting stopped +circ decay to produce a monoenergetic νμ source, and measuring the rate of the neutral current reaction νx0.05in ^12C ->νx0.05in ^12C^*(15.11) as a function of distance from the source, we show that a convincing test for active-sterile neutrino oscillations can be performed.
First measurements of muon production rate using a novel pion capture system at MuSIC
NASA Astrophysics Data System (ADS)
Cook, S.; D'Arcy, R.; Fukuda, M.; Hatanaka, K.; Hino, Y.; Kuno, Y.; Lancaster, M.; Mori, Y.; Nam, T. H.; Ogitsu, T.; Sakamoto, H.; Sato, A.; Truong, N. M.; Yamamoto, A.; Yoshida, M.; Wing, M.
2013-02-01
The MuSIC (Muon Science Innovative Channel) beam line at RCNP (Research Centre for Nuclear Physics), Osaka will be the most intense source of muons in the world. A proton beam is incident on a target and, by using a novel capture solenoid, guides the produced pions into the beam line where they subsequently decay to muons. This increased muon flux will allow more precise measurements of cLFV (charged Lepton Flavour Violation) as well as making muon beams more economically feasible. Currently the first 36° of solenoid beam pipe have been completed and installed for testing with low proton current of 1 nA. Measurements of the total particle flux and the muon life time were made. The measurements were taken using thin plastic scintillators coupled to MPPCs (Multi-Pixel Photon Counter) that surrounded a magnesium or copper stopping target. The scintillators were used to record which particles stopped and their subsequent decay times giving a muon yield of 8.5 × 105 muons W-1proton beam or 3 × 108 muons s-1 when using the RCNP's full power (400 W).
Structure of /sup 13/C studied by pion scattering near the (3,3) resonance
Seestrom-Morris, S.J.
1981-09-01
Good resolution (..pi../sup +/,..pi../sup +/') and (..pi../sup -/,..pi../sup -/') data were obtained for many states in /sup 13/C using the Energetic Pion Channel and Spectrometer at the Los Alamos Meson Physics Facility. Differential cross sections were measured for angles between 20/sup 0/ and 105/sup 0/ at an incident pion energy of 162 MeV for the elastic scattering as well as for states at excitation energies of 3.09, 3.68, 3.85, 7.55, 8.86, 9.5, 11.82, 16.05, 17.92, 21.37, and 21.6 MeV. Excitation functions were measured at momentum transfers of q = 1.1 h fm /sup -1/ and q = 1.4 h fm/sup -1/, for energies between 100 and 300 MeV. A sigma(..pi../sup -/)/sigma(..pi../sup +/) ratio of 9:1 was observed for the first time, indicating a pure neutron particle-hole excitation of a high spin state (J/sup ..pi../ = 9/2/sup +/). Strikingly different energy dependences were found for ..delta..S = 0 and ..delta..S = 1 transitions. Data for all states were compared with the microscopic model calculations of Lee and Kurath. Very good agreement was found between experiment and theory for the strongly excited states and the 9/2/sup +/ state at 9.5 MeV, in sharp contrast to the disagreement for weak transitions. The excitation function data and comparisons with the microscopic model calculations were used to identify the states at 16.05, 17.92, 21.37, and 21.6 MeV as either 7/2/sup +/ or 9/2/sup +/ states. The elastic scattering data were analyzed with an optical modeland the results were found to be consistent with neutron and proton distributions having equal rms radii. The optical potentials generated were used in a collective model analysis of the 3/2/sup -/ (3.68 MeV) and 5/2/sup -/ (7.55 MeV) states. The reduced transition probabilities (B(E2)) derived from the proton parts of the transition strength are in agreement with those determined from electromagnetic measurements.
Measurement of muon neutrino and antineutrino induced single neutral pion production cross sections
Anderson, Colin E.
2011-05-01
Elucidating the nature of neutrino oscillation continues to be a goal in the vanguard of the efforts of physics experiment. As neutrino oscillation searches seek an increasingly elusive signal, a thorough understanding of the possible backgrounds becomes ever more important. Measurements of neutrino-nucleus interaction cross sections are key to this understanding. Searches for ν_{μ} → ν_{e} oscillation - a channel that may yield insight into the vanishingly small mixing parameter θ_{1}3, CP violation, and the neutrino mass hierarchy - are particularly susceptible to contamination from neutral current single π^{0} (NC 1π^{0}) production. Unfortunately, the available data concerning NC 1π^{0} production are limited in scope and statistics. Without satisfactory constraints, theoretical models of NC 1π^{0} production yield substantially differing predictions in the critical E_{ν} ~ 1 GeV regime. Additional investigation of this interaction can ameliorate the current deficiencies. The Mini Booster Neutrino Experiment (MiniBooNE) is a short-baseline neutrino oscillation search operating at the Fermi National Accelerator Laboratory (Fermilab). While the oscillation search is the principal charge of the MiniBooNE collaboration, the extensive data (~ 10^{6} neutrino events) offer a rich resource with which to conduct neutrino cross section measurements. This work concerns the measurement of both neutrino and antineutrino NC 1π^{0} production cross sections at MiniBooNE. The size of the event samples used in the analysis exceeds that of all other similar experiments combined by an order of magnitude. We present the first measurements of the absolute NC 1π^{0} cross section as well as the first differential cross sections in both neutrino and antineutrino mode. Specifically, we measure single differential cross sections with respect to pion momentum and pion angle. We find the
NASA Astrophysics Data System (ADS)
Sawada, Takahiro; Chang, Wen-Chen; Kumano, Shunzo; Peng, Jen-Chieh; Sawada, Shinya; Tanaka, Kazuhiro
2016-06-01
Generalized parton distributions (GPDs) encoding multidimensional information of hadron partonic structure appear as the building blocks in a factorized description of hard exclusive reactions. The nucleon GPDs have been accessed by deeply virtual Compton scattering and deeply virtual meson production with lepton beam. A complementary probe with hadron beam is the exclusive pion-induced Drell-Yan process. In this paper, we discuss recent theoretical advances on describing this process in terms of nucleon GPDs and pion distribution amplitudes. Furthermore, we address the feasibility of measuring the exclusive pion-induced Drell-Yan process π-p →μ+μ-n via a spectrometer at the High Momentum Beamline being constructed at J-PARC in Japan. Realization of such measurement at J-PARC will provide a new test of perturbative QCD descriptions of a novel class of hard exclusive reactions. It will also offer the possibility of experimentally accessing nucleon GPDs at large timelike virtuality.
PiP - a large solid angle scintillation telescope for detecting protons and pions
NASA Astrophysics Data System (ADS)
MacGregor, I. J. D.; Annand, J. R. M.; Brandford, D.; Cross, G. E.; Grabmayr, P.; Harty, P. D.; Hehl, T.; Lamparter, T.; MacKenzie, J. A.; McAllister, S.; McGeorge, J. C.; Owens, R. O.; Schneider, R.; Terzoudi, P.; Watts, D. P.; Yau, T. T.-H.
1996-02-01
A ~ 1 sr solid angle scintillation detector hodoscope for protons of up to ~ 280 MeV and positive pions of up to ~ 180 MeV energy has been developed for use in (γ,pN), (γ,pπ+/-) and (γ,π+N) experiments with tagged photons. This paper reports the detailed design of the hodoscope and its performance for detecting protons and positive pions.
Inclusive pion double charge exchange in light p-shell nuclei
Fong, W.; Matthews, J. L.; Dowell, M. L.; Kinney, E. R.; Soos, T.; Wang, M. Y.; Wood, S. A.; Gram, P. A. M.; Rebka, G. A. Jr.; Roberts, D. A.
2007-06-15
We report the results of a series of measurements of the differential cross sections for inclusive pion double charge exchange in {sup 6,7}Li, {sup 9}Be, and {sup 12}C for positive and negative incident pions of energies 120, 180, and 240 MeV. The data are compared with the predictions of an intranuclear cascade model and a model based on two sequential single charge exchange processes.
Using baryon octet magnetic moments and masses to fix the pion cloud contribution
Franz Gross, Gilberto Ramalho, Kazuo Tsushima
2010-06-01
Using SU(3) symmetry to constrain the $\\pi BB'$ couplings, assuming SU(3) breaking comes only from one-loop pion cloud contributions, and using the the covariant spectator theory to describe the photon coupling to the quark core, we show how the experimental masses and magnetic moments of the baryon octet can be used to set a model independent constraint on the strength of the pion cloud contributions to the octet, and hence the nucleon, form factors at $Q^2=0$.
A relativistic description of the quasifree radiative pion-capture reaction on nuclei
NASA Astrophysics Data System (ADS)
Johansson, J. I.; Sherif, H. S.
1995-02-01
We present a relativistic model for the reaction A( π+, γp) A - 1. This is an extension of our recent model for negative-pion photoproduction. The interaction of the pion with the target nucleon is comprised of the set of Born terms arising from the pseudovector form of the pion-nucleon interaction lagrangian, as well as s- and u-channel diagrams involving the propagation of the Δ(1232). The bound and continuum nucleons are described by solutions of the Dirac equation with appropriate scalar and vector potentials, while the pion wave function is a solution of the Klein-Gordon equation containing a pion-nucleus optical potential. Calculations of the triple differential cross section {d3σ }/{dω p dω γdEγ } as well as the polarization of the final proton are presented for the kinematics of TRIUMF experiment 550. Under appropriate kinematic conditions the contribution of the Δ(1232) is found to be dominant in this reaction. The results are sensitive to the choice of pion-nucleus optical potential but are not very sensitive to the nucleon interactions with the nucleus. We obtain qualitative agreement with data from TRIUMF experiment 550.
Collective and fractal properties of pion jets in the space of 4-velocities at intermediate energies
Okorokov, V. A. Ponosov, A. K.; Sergeev, F. M.
2010-11-15
Experimental results obtained by studying collective and fractal properties of soft pion jets in the space of relative 4-velocities at intermediate energies are presented. The mean square of the distance between secondary particles and the jet axis is found to be significantly smaller in the case of pion-proton interactions at initial energies of about 3 GeV than in the case of hadron-hadron collisions at similar energies. This reduction leads to a power-law dependence of this quantity on the interaction energy in the energy range between about 2 and 4 GeV, and this makes it possible to estimate the lower boundary of the region where color degrees of freedom manifest themselves in pion-jet production. The cluster dimensions of pion jets in various reactions were obtained for the first time. Fractional values of this dimension may be a manifestation of fractal properties of pion jets. The change in the mean kinetic energy of particles in the jet and the change in the fractal dimension in response to the change in the collision energy is compatible with the assumption that color degrees of freedom come into play in pion-jet production at intermediate energies.
A Precision Measurement of the Neutral Pion Lifetime via the Primakoff Effect
Clinton, Eric
2007-09-01
The neutral pion radiative width has been measured to 8.411 eV ± 1.8% + 1.13% - 1.70% (lifetime = 7.826 ± 0.14 + 0.088 - 0.133 x 10^{-17} s) utilizing the Primakoff effect and roughly 4.9 to 5.5 GeV photons at the Thomas Jefferson National Accelerator Facility in Newport News, VA. The Hall B Photon Tagger, the Hall B Pair Spectrometer, a state of the art Hybrid Calorimter enabled precision incident photon energy measurement, photon flux measurement, and neutral pion identification, respectively. With these and other hardware and software tools, elastic neutral pion yields were extracted from the data. A well developed and understood simulation calculated geometric and software cut efficiency curves. The simulation also provided photo-pion production response functions to fit the experimental cross sections and extract the Primakoff cross section and thus the neutral pion radiative width and lifetime. Future work includes improving understanding of the nuclear incoherent process and any other background sources of elastic neutral pions in this data.
Comparison of GiBUU calculations with MiniBooNE pion production data
Lalakulich, O.; Mosel, U.
2015-05-15
Background: Neutrino-induced pion production can give important informationon the axial coupling to nucleon resonances. Furthermore, pion production represents a major background to quasielastic-like events. one pion production data from the MiniBooNE in charged current neutrino scattering in mineral oil appeared higher than expected within conventional theoretical approaches. Purpose: We aim to investigate which model parameters affect the calculated cross section and how they do this. Method: The Giessen Boltzmann–Uehling–Uhlenbeck (GiBUU) model is used for an investigation of neutrino-nucleus reactions. Results: Presented are integrated and differential cross sections for 1π{sup +} and 1π{sup 0} production before and after final state interactions in comparison with the MiniBooNE data. Conclusions: For the MiniBooNE flux all processes (QE, 1π-background, Δ, higher resonance production, DIS) contribute to the observed final state with one pion of a given charge. The uncertainty in elementary pion production cross sections leads to a corresponding uncertainty in the nuclear cross sections. Final state interactions change the shape of the muon-related observables only slightly, but they significantly change the shape of pion distributions.
Pion structure function from leading neutron electroproduction and SU(2) flavor asymmetry
McKenney, Joshua R.; Sato, Nobuo; Melnitchouk, Wally; Ji, Chueng-Ryong
2016-03-07
In this paper, we examine the efficacy of pion exchange models to simultaneously describe leading neutron electroproduction at HERA and themore » $$\\bar{d}-\\bar{u}$$ flavor asymmetry in the proton. A detailed $$\\chi^2$$ analysis of the ZEUS and H1 cross sections, when combined with constraints on the pion flux from Drell-Yan data, allows regions of applicability of one-pion exchange to be delineated. The analysis disfavors several models of the pion flux used in the literature, and yields an improved extraction of the pion structure function and its uncertainties at parton momentum fractions in the pion of $$4 \\times 10^{-4} \\lesssim x_\\pi \\lesssim 0.05$$ at a scale of $Q^2$=10 GeV$^2$. Also, we provide estimates for leading proton structure functions in upcoming tagged deep-inelastic scattering experiments on the deuteron with forward protons, based on the fit results, at Jefferson Lab.« less
NASA Astrophysics Data System (ADS)
Nebreda, J.; Peláez, J. R.; Ríos, G.
2013-09-01
We determine the values of the one- and two-loop low energy constants appearing in the SU(2) Chiral Perturbation Theory calculation of pion-pion scattering. For this we use a recent and precise sum rule determination of some scattering lengths and slopes that appear in the effective range expansion. In addition we provide sum rules for these coefficients up to third order in the expansion. Our results when using only the scattering lengths and slopes of the S, P, D, and F waves are consistent with previous determinations but seem to require higher order contributions if they are to accommodate the third order coefficients of the effective range expansion.
NASA Astrophysics Data System (ADS)
Lightman, Matthew
We calculate matrix elements for kaon to two pion decays in the Delta I = 3/2 channel using lattice gauge theory simulations. From these we can extract the decay amplitude A2, for which the real part is related to the decay rate and can be compared to the experimental result Re(A2) = 1.484x10-8 GeV, and for which the imaginary part is related to direct charge-parity violation in the neutral kaon system. We report the results of one simulation with nearly physical particle masses and kinematics, specifically mK = 509.0(9.1) MeV, mpi = 142.8(2.5) MeV, and Epipi = 485.7(8.0) MeV. This simulation was performed on RBC/UKQCD 323 x 64, Ls = 32 lattices, using 2+1 dynamical flavors of domain wall fermions and a Dislocation Suppressing Determinant Ratio plus Iwasaki gauge action, and with an inverse lattice spacing a-1 = 1.373(24) GeV so that the spatial extent of the lattice is 4.60 fm and mpi L = 3.3. We find that Re(A2) = 1.461(87)stat(200)sys x 10 -8 GeV, in good agreement with the experimental value. We also find Im(A2) = .8.67(45)stat(1.95)sys x10-13 GeV, and Im(A2)/Re( A2) = .5.93(27)stat(1.42)sys x10 -5, however the value of Im(A2) depends on a rough hypothesis for some of the renormalization constants which have not yet been calculated, and thus we quote a large systematic error. We also report the results of a simulation involving a variety of kaon and pion masses and momenta, which was conducted in order to study the dependence of the decay amplitude on particle masses and kinematics, and to study the effect of not having exactly physical masses and kinematics in the first simulation. The use of the quenched approximation and smaller spatial volume in this second simulation allowed for multiple masses to be simulated in a reasonable amount of time, but introduced an uncontrolled approximation and forced us to use pion masses a bit larger than the physical mass. The study was conducted on 243 x 64, Ls = 16 lattices, with the quenched Doubly Blocked Wilson 2 gauge
Badala, A.; Barbera, R.; Palmeri, A.; Pappalardo, G.S.; Riggi, F.; Russo, A.C.; Russo, G.; Turrisi, R. ||
1996-04-01
Inclusive and exclusive measurements of neutral pions in heavy-ion collisions around 100 MeV/nucleon, carried out in a near 4{pi} geometry, have been analyzed to obtain information on the nuclear stopping of the projectile. Stopping of the projectile has been investigated by the analysis of the source velocity, of the distribution of the energetic products of the collisions, and of the associated rapidity distribution of the baryon matter. Collisions were classified according to their centrality by the charged particle multiplicity. Clear evidence for this phenomenon has been obtained by the study of different observables. Both stopping and reabsorption effects play an essential role in the interpretation of the results. {copyright} {ital 1996 The American Physical Society.}
NASA Astrophysics Data System (ADS)
Ishii, Masahiro; Yonemura, Koji; Takahashi, Junichi; Kouno, Hiroaki; Yahiro, Masanobu
2016-01-01
We incorporate the effective restoration of U (1 )A symmetry in the 2 +1 -flavor entanglement Polyakov-loop extended Nambu-Jona-Lasinio (EPNJL) model by introducing a temperature-dependent strength K (T ) to the Kobayashi-Maskawa-'t Hooft determinant interaction. T dependence of K (T ) is well determined from pion and a0-meson screening masses obtained by lattice QCD (LQCD) simulations with improved p4 staggered fermions. The strength is strongly suppressed in the vicinity of the pseudocritical temperature of chiral transition. The EPNJL model with the K (T ) well reproduces meson susceptibilities calculated by LQCD with domain-wall fermions. The model shows that the chiral transition is second order at the "light-quark chiral-limit" point where the light quark mass is zero and the strange quark mass is fixed at the physical value. This indicates that there exists a tricritical point. Hence, the location is estimated.
NASA Technical Reports Server (NTRS)
Norbury, J. W.; Cucinotta, F. A.; Deutchman, P. A.; Townsend, L. W.
1985-01-01
A coherent isobar formalism is employed to model subthreshold production of neutral pions in carbon-carbon collisions at energies below 100 MeV/nucleon. No arbitrary scale factors or adjustable free parameters are used in calculation of the Lorentz-invariant cross sections for pion production in the projectile, which produces an excited state that goes to M1 resonance in the target by conservation of spin and isospin. Pion production is also modeled for the projectile, which also reaches M1 resonance. The overall pion spectral distribution in the center of mass system is then integrated over the energy range 35-84 MeV/nucleon. The results expose an energy loss in the incident ions, as observed experimentally, and indicate that an isobar mechanism is responsible for higher energy pion production. Lower energy pions are a result of thermal processes.
Chaoticity parameter λ in two-pion interferometry in an expanding boson gas model
Liu, Jie; Ru, Peng; Zhang, Wei-Ning; Wong, Cheuk-Yin
2014-10-15
We investigate the chaoticity parameter λ in two-pion interferometry in an expanding boson gas model. The degree of Bose-Einstein condensation of identical pions, density distributions, and Hanbury-Brown-Twiss (HBT) correlation functions are calculated for the expanding gas within the mean-field description with a harmonic oscillator potential. The results indicate that a sources with thousands of identical pions may exhibit a degree of Bose-Einstein condensation at the temperatures during the hadronic phase in relativistic heavy-ion collisions. This finite condensation may decrease the chaoticity parameter λ in the two-pion interferometry measurements at low pion pair momenta, but influence only slightly the λ value at high pion pair momentum.
Virtuality and transverse momentum dependence of the pion distribution amplitude
NASA Astrophysics Data System (ADS)
Radyushkin, A. V.
2016-03-01
We describe basics of a new approach to transverse momentum dependence in hard exclusive processes. We develop it in application to the transition process γ*γ →π0 at the handbag level. Our starting point is coordinate representation for matrix elements of operators [in the simplest case, bilocal O (0 ,z ) ] describing a hadron with momentum p . Treated as functions of (p z ) and z2, they are parametrized through virtuality distribution amplitudes (VDA) Φ (x ,σ ) , with x being Fourier conjugate to (p z ) and σ Laplace conjugate to z2. For intervals with z+=0 , we introduce the transverse momentum distribution amplitude (TMDA) Ψ (x ,k⊥), and write it in terms of VDA Φ (x ,σ ). The results of covariant calculations, written in terms of Φ (x ,σ ), are converted into expressions involving Ψ (x ,k⊥). Starting with scalar toy models, we extend the analysis onto the case of spin-1 /2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BABAR and BELLE) data on the pion transition form factor. We also discuss how one can generate high-k⊥ tails from primordial soft distributions.
SPIN EFFECTS IN LARGE RAPIDITY NEUTRAL PION PRODUCTION AT STAR.
MOROZOV, D.A.
2005-09-27
Measurements by the STAR collaboration of neutral pion production at large Feynman x (x{sub F}) in the first polarized proton collisions at {radical}s = 200 GeV were reported previously. During the following two runs additional statistics were acquired with an improved forward calorimeter for the {pi}{sup 0} cross-section and analyzing power measurements. First data from pp collisions at {radical}s = 410 GeV were taken during the RHIC run that ended in June, 2005. The cross section was measured at {eta} = 3.3, 3.8 and 4.0 and was found to be consistent with next-to-leading order perturbative QCD calculations. The analyzing power was found to be zero at negative 23 and at positive x{sub F} up to 0.3, then increased with increasing x{sub F}. This behavior can be described by phenomenological models including the Sivers effect, the Collins effect or higher twist contributions in initial and final states. Results for the analyzing power at {eta} = 3.7 and 4.0 from all data acquired at {radical}s = 200 GeV and the status of the analysis of the {radical}s = 410 GeV data will be presented. Future upgrade plans and status will also be discussed.
Nuclear interactions of 340-GeV pions in emulsion
Tufail, A.; Ahmad, S.; Khan, A.R.; Zafar, M.; Shafi, M. )
1990-10-01
Some results on heavy- and shower-particle multiplicities produced in interactions of 340-GeV pions in nuclear emulsion are presented and compared with similar results in proton-nucleus interactions at different energies. Values of {l angle}{ital N}{sub {ital g}}{r angle} in {pi}{sup {minus}}{ital A} interactions are found to be less than its value in {ital pA} interactions at similar energies. This is understood in terms of additive quark model. The result on mean normalized multiplicity reveals that the values of {ital R}{sub {ital A}1} are almost constant in the forward direction for all values of {l angle}{nu}({ital N}{sub {ital g}}){r angle} and {ital R}{sub {ital A}1} increases with {l angle}{nu}({ital N}{sub {ital g}}){r angle} in the intervals 1.2{lt}{eta}{le}2.0 and {eta}{le}1.2.
Flare gamma ray continuum emission from neutral pion decay
NASA Technical Reports Server (NTRS)
Alexander, David; Mackinnon, Alec L.
1992-01-01
We investigate, in detail, the production of solar flare gamma ray emission above 100 MeV via the interaction of high energy protons with the ambient solar atmosphere. We restrict our considerations to the broadband gamma ray spectrum resulting from the decay of neutral pions produced in p-H reactions. Thick-target calculations are performed to determine the photon fluences. However, proton transport is not considered. Inferences about the form of the proton spectrum at 10-100 MeV have already been drawn from de-excitation gamma ray lines. Our aim is to constrain the proton spectrum at higher energies. Thus, the injected proton spectrum is assumed to have the form of a Bessel Function, characteristics of stochastic energy at higher energies. The detailed shape of the gamma ray spectra around 100 MeV is found to have a strong dependence on the spectral index of the power law and on the turnover energy (from Bessel function to power law). As would be expected, the harder the photon spectrum the wider the 100 MeV feature. The photon spectra are to be compared with observations and used to place limits upon the number of particles accelerated and to constrain acceleration models.
Virtuality and transverse momentum dependence of the pion distribution amplitude
Radyushkin, Anatoly V.
2016-03-08
We describe basics of a new approach to transverse momentum dependence in hard exclusive processes. We develop it in application to the transition process γ*γ → π0 at the handbag level. Our starting point is coordinate representation for matrix elements of operators (in the simplest case, bilocal O (0,z)) describing a hadron with momentum p. Treated as functions of (pz) and z2, they are parametrized through virtuality distribution amplitudes (VDA) Φ(x,σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z+ = 0, we introduce the transverse momentum distribution amplitude (TMDA) ψ(x, k), and writemore » it in terms of VDA Φ(x,σ). The results of covariant calculations, written in terms of Φ(x, σ) are converted into expressions involving ψ(x, k). Starting with scalar toy models, we extend the analysis onto the case of spin-1/2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data on the pion transition form factor. Furthermore, we discuss how one can generate high-k tails from primordial soft distributions.« less
Beam-spin Asymmetries from Semi-inclusive Pion Electroproduction
Gohn, Wesley P.; Avakian, Harut A.; Joo, Kyungseon; Ungaro, Maurizio
2014-04-01
We have measured the moment A{sup sin{phi}}{sub LU} corresponding to the polarized electron beam-spin asymmetry in SIDIS. A{sup sin{phi}}{sub LU} is a twist-3 quantity providing information about quark-gluon correlations. Data were taken with the CLAS Spectrometer at Jefferson Lab using a 5.498 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. All three pion channels (pi{sup +}, pi{sup 0} and pi{sup -}) were measured simultaneously over a large range of kinematics within the virtuality range Q{sup 2} ~ 1.0-4.5 GeV{sup 2}. The observable was measured with good statistical precision over a large range of z, P{sub T}, x{sub B}, and Q{sup 2}, which permits comparison with several reaction models. The discussed measurements provide an upgrade in statistics over previous measurements, and serve as the first evidence for the negative sign of the {pi}{sup -} sin{phi} Moment.
Dynamical coupled channels calculation of pion and omega meson production
Paris, Mark W.
2009-02-15
The dynamical coupled-channels approach developed at the Excited Baryon Analysis Center is extended to include the {omega}N channel to study {pi}- and {omega}-meson production induced by scattering pions and photons from the proton. Six intermediate channels, including {pi}N, {eta}N, {pi}{delta}, {sigma}N, {rho}N, and {omega}N, are employed to describe unpolarized and polarized data. Bare parameters in an effective hadronic Lagrangian are determined in a fit to the data for {pi}N{yields}{pi}N, {gamma}N{yields}{pi}N, {pi}{sup -}p{yields}{omega}n, and {gamma}p{yields}{omega}p reactions at center-of-mass energies from threshold to W<2.0 GeV. The T matrix determined in these fits is used to calculate the photon beam asymmetry for {omega}-meson production and the {omega}N{yields}{omega}N total cross section and {omega}N-scattering lengths. The calculated beam asymmetry is in good agreement with the observed in the range of energies near threshold to W < or approx. 2.0 GeV.
Axions, SN 1987A, and one pion exchange
NASA Technical Reports Server (NTRS)
Turner, Michael S.; Kang, Ho-Shik; Steigman, Gary
1988-01-01
Nucleon-nucleon, axion bremsstrahlung is the primary mechanism for axion emission from the nascent neutron star associated with SN 1987A, and the rate for this process has been calculated in the one pion exchange approximation (OPE). The axion mass limit which follows from SN 1987A, m sub a less than or approx equal to 10 to the -3 eV, is the most stringent astrophysical bound, and has received much scrutiny. It has been suggested that by using OPE to calculate the cross section for the analog process, pp yields pp + pi sup o, and comparing the result of the experimental data one can test the validity of this approximation, and further, that such a comparison indicates that OPE leads to a value for this cross section which is a factor of 30 to 40 too large. If true, this would suggest that the axion mass limit should be revised upward by a factor of approximately 6. The cross section for pp yields pp + pi sup o using OPE is carefully evaluated, and excellent agreement found (to better than a factor of 2) with the experimental data.
Neutron Skin of Pb208 from Coherent Pion Photoproduction
NASA Astrophysics Data System (ADS)
Tarbert, C. M.; Watts, D. P.; Glazier, D. I.; Aguar, P.; Ahrens, J.; Annand, J. R. M.; Arends, H. J.; Beck, R.; Bekrenev, V.; Boillat, B.; Braghieri, A.; Branford, D.; Briscoe, W. J.; Brudvik, J.; Cherepnya, S.; Codling, R.; Downie, E. J.; Foehl, K.; Grabmayr, P.; Gregor, R.; Heid, E.; Hornidge, D.; Jahn, O.; Kashevarov, V. L.; Knezevic, A.; Kondratiev, R.; Korolija, M.; Kotulla, M.; Krambrich, D.; Krusche, B.; Lang, M.; Lisin, V.; Livingston, K.; Lugert, S.; MacGregor, I. J. D.; Manley, D. M.; Martinez, M.; McGeorge, J. C.; Mekterovic, D.; Metag, V.; Nefkens, B. M. K.; Nikolaev, A.; Novotny, R.; Owens, R. O.; Pedroni, P.; Polonski, A.; Prakhov, S. N.; Price, J. W.; Rosner, G.; Rost, M.; Rostomyan, T.; Schadmand, S.; Schumann, S.; Sober, D.; Starostin, A.; Supek, I.; Thomas, A.; Unverzagt, M.; Walcher, Th.; Zana, L.; Zehr, F.; Crystal Ball at MAMI; A2 Collaboration
2014-06-01
Information on the size and shape of the neutron skin on Pb208 is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be cn=6.70±0.03(stat.) fm and an=0.55±0.01(stat.)-0.03+0.02(sys.) fm, respectively, corresponding to a neutron skin thickness Δrnp=0.15±0.03(stat.)-0.03+0.01(sys.) fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of Pb208 has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.
Huber, Garth; Blok, Henk; Horn, Tanja; Beise, Elizabeth; Gaskell, David; Mack, David; Tadevosyan, Vardan; Volmer, Jochen; Abbott, David; Aniol, Konrad; Anklin, Heinz; Armstrong, Christopher; Arrington, John; Assamagan, Ketevi; Avery, Steven; Baker, O.; Barrett, Robert; Bochna, Christopher; Boeglin, Werner; Brash, Edward; Breuer, Herbert; Chang, C.; Chang, C.C.; Chant, Nicholas; Christy, Michael; Dunne, James; Eden, Thomas; Ent, Rolf; Fenker, Benjamin; Gibson, Edward; Gilman, Ronald; Gustafsson, Kenneth; Hinton, Wendy; Holt, Roy; Jackson, Harold; uk Jin, Seong; Jones, Mark; Keppel, Cynthia; Kim, pyunghun; Kim, Wooyoung; King, Paul; Klein, Andreas; Koltenuk, Douglas; Kovaltchouk, Vitali; Liang, Meihua; Liu, Jinghua; Lolos, George; Lung, Allison; Margaziotis, Demetrius; Markowitz, Pete; Matsumura, Akihiko; McKee, David; Meekins, David; Mitchell, Joseph; Miyoshi, Toshinobu; Mkrtchyan, Hamlet; Mueller, Robert; Niculescu, Gabriel; Niculescu, Maria-Ioana; Okayasu, Yuichi; Pentchev, Lubomir; Perdrisat, Charles; Pitz, David; Potterveld, David; Punjabi, Vina; Qin, Liming; Reimer, Paul; Reinhold, Joerg; Roche, Julie; Roos, Philip; Sarty, Adam; Shin, Ilkyoung; Smith, Gregory; Stepanyan, Stepan; Tang, Liguang; Tvaskis, Vladas; van der Meer, Rob; Vansyoc, Kelley; Van Westrum, Derek; Vidakovic, Sandra; Vulcan, William; Warren, Glen; Wood, Stephen; Xu, Chen; Yan, Chen; Zhao, Wenxia; Zheng, Xiaochao; Zihlmann, Benedikt
2008-10-01
DOI: http://dx.doi.org/10.1103/PhysRevC.78.045203
The charged pion form factor, Fpi(Q2), is an important quantity that can be used to advance our knowledge of hadronic structure. However, the extraction of Fpi from data requires a model of the 1H(e,e'pi+)n reaction and thus is inherently model dependent. Therefore, a detailed description of the extraction of the charged pion form factor from electroproduction data obtained recently at Jefferson Lab is presented, with particular focus given to the dominant uncertainties in this procedure. Results for Fpi are presented for Q2=0.60-2.45 GeV2. Above Q2=1.5 GeV2, the Fpi values are systematically below the monopole parametrization that describes the low Q2 data used to determine the pion charge radius. The pion form factor can be calculated in a wide variety of theoretical approaches, and the experimental results are compared to a number of calculations. This comparison is helpful in understanding the role of soft versus hard c
Ion recombination correction factors (P(ion)) for Varian TrueBeam high-dose-rate therapy beams.
Kry, Stephen F; Popple, Richard; Molineu, Andrea; Followill, David S
2012-01-01
Ion recombination is approximately corrected for in the Task Group 51 protocol by Pion, which is calculated by a two-voltage measurement. This measurement approach may be a poor estimate of the true recombination, particularly if Pion is large (greater than 1.05). Concern exists that Pion in high-dose-per-pulse beams, such as flattening filter free (FFF) beams, may be unacceptably high, rendering the two-voltage measurement technique inappropriate. Therefore, Pion was measured for flattened beams of 6, 10, 15, and 18 MV and for FFF beams of 6 and 10 MV. The values for the FFF beams were verified with 1/V versus 1/Q curves (Jaffé plots). Pion was also measured for electron beams of 6, 12, 16, 18, and 20 MeV on a traditional accelerator, as well as on the high-dose-rate Varian TrueBeam accelerator. The measurements were made at a range of depths and with PTW, NEL, and Exradin Farmer-type chambers. Consistent with the increased dose per pulse, Pion was higher for FFF beams than for flattening filter beams. However, for all beams, measurement locations, and chambers examined, Pion never exceeded 1.018. Additionally, Pion was always within 0.3% of the recombination calculated from the Jaffé plots. We conclude that ion recombination can be adequately accounted for in high-dose-rate FFF beams using Pion determined with the standard two-voltage technique. PMID:23149774
Chiral Restoration in a Nuclear Medium ---Probed by S-Wave Pion Dynamics---
NASA Astrophysics Data System (ADS)
Kienle, P.
Using 500 MeV (d,^3He π^-) pion transfer reactions in recoil free kinematics, pionic 1s-states were populated in the ^{115,119,123}Sn isotopes and their binding energies and widths determined by precision missing mass spectroscopy. Using these data and corresponding ones from iso-scalar light nuclei nuclei, ^{16}O, ^{20}Ne and ^{28}Si, we determined the pion nucleus s-wave strength parameters, b_0, b_1, Re B_0, and Im B_0. By comparison of the iso-vector pion nucleon strength, determined from pionic hydrogen X-ray spectroscopy b_1^{free}, with the b_1 in a nuclear medium scaled to the density ρ(0), we deduced a scaling factor, the square of the pion decay constant in the vacuum and in nuclear medium, as R = b_1^{free} / b_1 = f^2_{π}(ρ_0)/f^2_{π} = 0.64. Thus from the observed increase of the pion s-wave iso-vector strength in a nuclear medium a reduction of f^2_{π}, the order parameter of chiral symme try breaking, is indicated in accordance with theoretical expectations. This finding is supported by recent π^+ and π^- scattering experiments. A short outlook is given on a future program at RIBF in RIKEN for precision studies of deeply bound 1s-states in heavy nuclei.
ν¯l induced pion production from nuclei at ˜1GeV
NASA Astrophysics Data System (ADS)
Alam, M. Rafi; Chauhan, S.; Athar, M. Sajjad; Singh, S. K.
2013-10-01
We have studied charged current ν¯l induced one pion production from C12 and O16 nuclear targets at MiniBooNE and atmospheric antineutrino energies. The calculations have been done for the incoherent pion production process as well as for the pions coming from the hyperons in the quasielastic production of Λ and Σ. The calculations are done in the local density approximation. For the inelastic processes the calculations have been done in the Δ dominance model, and we take into account the effect of Pauli blocking, Fermi motion of the nucleon, and renormalization of Δ properties in the nuclear medium. The effect of final state interaction (FSI) of pions is also taken into account. For the hyperon production, the nuclear medium effects due to Fermi motion and FSI effects due to hyperon-nucleon scattering have been taken into account. These results may be quite useful in the analysis of SciBooNE, MicroBooNE, MINERνA, and ArgoNeuT experiments when the pion analysis is done by using antineutrino beams.
Pion-Induced Fission of 209Bi and 119Sn:. Measurements, Calculations, Analyses and Comparison
NASA Astrophysics Data System (ADS)
Rana, Mukhtar Ahmed; Sher, Gul; Manzoor, Shahid; Shehzad, M. I.
Cross-sections for the π--induced fission of 209Bi and 119Sn have been measured using the most sensitive CR-39 solid-state nuclear track detector. In experiments, target-detector stacks were exposed to negative pions of energy 500, 672, 1068, and 1665 MeV at the Brookhaven National Laboratory, USA. An important aspect of the present paper is the comparison of pion-induced fission fragment spectra of above mentioned nuclei with the spontaneous fission fragment spectra of 252Cf. This comparison is made in terms of fission fragment track lengths in the CR-39 detectors. Measurement results are compared with calculations of Monte Carlo and statistical weight functions methods using the computer code CEM95. Agreement between measurements and calculations is fairly good for 209Bi target nuclei whereas it is indigent for the case of 119Sn. The possibilities of the trustworthy calculations, using the computer code CEM95, comparable with measurements of pion-induced fission in intermediate and heavy nuclei are explored by employing various systematics available in the code. Energy dependence of pion-induced fission in 119Sn and 209Bi is analyzed employing a newly defined parameter geometric-size-normalized fission cross-section (χfg). It is found that the collective nuclear excitations, which may lead to fission, become more probable for both 209Bi and 119Sn nuclei with increasing energy of negative pions from 500 to 1665 MeV.
Study of the single neutral top pion production process at {gamma}{gamma} collider
Wang Xuelei; Wang Xiaoxue
2005-11-01
{gamma}{gamma}{yields}{pi}{sub t}{sup 0} is the major production mechanism of the neutral top pion at the linear colliders. In this paper, we calculate the cross section of the process {gamma}{gamma}{yields}{pi}{sub t}{sup 0} and discuss the potential to observe the neutral top pion via its various decay modes at the planned International Linear Collider. The study shows that, among the various neutral top-pion production processes at the linear colliders, the cross section of {gamma}{gamma}{yields}{pi}{sub t}{sup 0} is the largest one which can reach the level of 10{sup 1}-10{sup 2} fb. Because of the existence of the tree-level flavor-changing coupling {pi}{sub t}{sup 0}tc, {gamma}{gamma}{yields}{pi}{sub t}{sup 0}{yields}tc can provide enough number of typical signals to identify the neutral top pion with the clean SM background. Therefore, the process {gamma}{gamma}{yields}{pi}{sub t}{sup 0} plays an important role in searching for the neutral top pion and tests the TC2 model.
Kaon to Two Pions decays from Lattice QCD: Delta I = 1/2 rule and CP violation
NASA Astrophysics Data System (ADS)
Liu, Qi
We report a direct lattice calculation of the K to pipi decay matrix elements for both the DeltaI=1/2 and 3/2 amplitudes A0 and A2 on a 2+1 flavor, domain wall fermion, 163x32x16 lattice ensemble and a 243x64x16 lattice ensemble. This is a complete calculation in which all contractions for the required ten, four-quark operators are evaluated, including the disconnected graphs in which no quark line connects the initial kaon and final two-pion states. These lattice operators are non-perturbatively renormalized using the Rome-Southampton method and the quadratic divergences are studied and removed. This is an important but notoriously difficult calculation, requiring high statistics on a large volume. In this work we take a major step towards the computation of the physicalK→pipi amplitudes by performing a complete calculation at unphysical kinematics with pions of mass 422 MeV and 329 MeV at rest in the kaon rest frame. With this simplification we are able to resolve Re(A0) from zero for the first time, with a 25% statistical error on the 163 lattice and 15% on the 243 lattice. The complex amplitude A2 is calculated with small statistical errors. We obtain the DeltaI=1/2 rule with an enhancement factor of 9.1(21) and 12.0(17) on these two ensembles. From the detailed analysis of the results we gain a deeper understanding of the origin of the DeltaI=1/2 rule. We also calculate the complex amplitude A0, a calculation central to understanding and testing the standard model of CP violation in the kaon system. The final result for the measure of direct CP violation, epsilon', calculated at unphysical kinematics has an order of 100% statistical error, so this only serves as an order of magnitude check.
Soft-Pion theorems for large scale structure
Horn, Bart; Hui, Lam; Xiao, Xiao E-mail: lhui@astro.columbia.edu
2014-09-01
Consistency relations — which relate an N-point function to a squeezed (N+1)-point function — are useful in large scale structure (LSS) because of their non-perturbative nature: they hold even if the N-point function is deep in the nonlinear regime, and even if they involve astrophysically messy galaxy observables. The non-perturbative nature of the consistency relations is guaranteed by the fact that they are symmetry statements, in which the velocity plays the role of the soft pion. In this paper, we address two issues: (1) how to derive the relations systematically using the residual coordinate freedom in the Newtonian gauge, and relate them to known results in ζ-gauge (often used in studies of inflation); (2) under what conditions the consistency relations are violated. In the non-relativistic limit, our derivation reproduces the Newtonian consistency relation discovered by Kehagias and Riotto and Peloso and Pietroni. More generally, there is an infinite set of consistency relations, as is known in ζ-gauge. There is a one-to-one correspondence between symmetries in the two gauges; in particular, the Newtonian consistency relation follows from the dilation and special conformal symmetries in ζ-gauge. We probe the robustness of the consistency relations by studying models of galaxy dynamics and biasing. We give a systematic list of conditions under which the consistency relations are violated; violations occur if the galaxy bias is non-local in an infrared divergent way. We emphasize the relevance of the adiabatic mode condition, as distinct from symmetry considerations. As a by-product of our investigation, we discuss a simple fluid Lagrangian for LSS.
Soft-Pion theorems for large scale structure
NASA Astrophysics Data System (ADS)
Horn, Bart; Hui, Lam; Xiao, Xiao
2014-09-01
Consistency relations — which relate an N-point function to a squeezed (N+1)-point function — are useful in large scale structure (LSS) because of their non-perturbative nature: they hold even if the N-point function is deep in the nonlinear regime, and even if they involve astrophysically messy galaxy observables. The non-perturbative nature of the consistency relations is guaranteed by the fact that they are symmetry statements, in which the velocity plays the role of the soft pion. In this paper, we address two issues: (1) how to derive the relations systematically using the residual coordinate freedom in the Newtonian gauge, and relate them to known results in ζ-gauge (often used in studies of inflation); (2) under what conditions the consistency relations are violated. In the non-relativistic limit, our derivation reproduces the Newtonian consistency relation discovered by Kehagias & Riotto and Peloso & Pietroni. More generally, there is an infinite set of consistency relations, as is known in ζ-gauge. There is a one-to-one correspondence between symmetries in the two gauges; in particular, the Newtonian consistency relation follows from the dilation and special conformal symmetries in ζ-gauge. We probe the robustness of the consistency relations by studying models of galaxy dynamics and biasing. We give a systematic list of conditions under which the consistency relations are violated; violations occur if the galaxy bias is non-local in an infrared divergent way. We emphasize the relevance of the adiabatic mode condition, as distinct from symmetry considerations. As a by-product of our investigation, we discuss a simple fluid Lagrangian for LSS.
High-energy Physics with Hydrogen Bubble Chambers
DOE R&D Accomplishments Database
Alvarez, L. W.
1958-03-07
Recent experience with liquid hydrogen bubble chambers of 25 and 40 cm dia. in high-energy physics experiments is discussed. Experiments described are: interactions of K{sup -} mesons with protons, interactions of antiprotons with protons, catalysis of nuclear fusion reactions by muons, and production and decay of hyperons from negative pions. (W.D.M.)
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).
Hidden dibaryons in one- and two-pion production in NN collisions
NASA Astrophysics Data System (ADS)
Platonova, M. N.; Kukulin, V. I.
2016-02-01
Processes of one- and two-pion production in NN collisions are considered in connection with excitation of intermediate dibaryon resonances. In particular, relative contributions of the conventional meson-exchange and dibaryon excitation mechanisms in the reaction pp → dπ+ are investigated in detail. Inclusion of the intermediate isovector dibaryon resonances is shown to essentially improve the description of experimental data for this reaction, provided the soft meson-baryon form factors consistent with πN elastic scattering are used. Manifestation of the intermediate isoscalar and isovector dibaryons in the two-pion production processes is also studied. The role of the isovector dibaryon resonances in the reaction pp → ppππ is discussed for the first time. An explanation of the observed strong differences between two-pion production cross sections in pn and pp collisions based in part on the analysis of dibaryon structure is suggested.
{nu} induced threshold production of two pions and N*(1440) electroweak form factors
Hernandez, E.; Nieves, J.; Valverde, M.; Singh, S. K.; Vacas, M. J. Vicente
2008-03-01
We study the threshold production of two pions induced by neutrinos in nucleon targets. The contribution of nucleon, pion, and contact terms are calculated using a chiral Lagrangian. The contribution of the Roper resonance, neglected in earlier studies, has also been taken into account. The numerical results for the cross sections are presented and compared with the available experimental data. It has been found that in the two-pion channels with {pi}{sup +}{pi}{sup -} and {pi}{sup 0}{pi}{sup 0} in the final state, the contribution of the N*(1440) is quite important and could be used to determine the N*(1440) electroweak transition form factors if experimental data with better statistics become available in the future.
Low-energy theorems for nucleon-nucleon scattering at unphysical pion masses
NASA Astrophysics Data System (ADS)
Baru, V.; Epelbaum, E.; Filin, A. A.; Gegelia, J.
2015-07-01
The longest-range part of the nuclear force from the one-pion exchange governs the energy dependence of the scattering amplitude in the near-threshold region and imposes correlations between the coefficients in the effective range expansion. These correlations may be regarded as low-energy theorems and are known to hold to a high accuracy in the neutron-proton 3S1 partial wave. We generalize the low-energy theorems to the case of unphysical pion masses and provide results for the correlations between the coefficients in the effective range expansion in this partial wave for pion masses up to Mπ˜400 MeV . We discuss the implications of our findings for the available and upcoming lattice-quantum-chromodynamics simulations of two-nucleon observables.
A ROTATING METAL BAND TARGET FOR PION PRODUCTION AT NEUTRINO FACTORIES AND MUON COLLIDERS.
KING, B.J.; SIMOS, N.; WEGGEL, R.V.; MOKHOV, N.V.
2001-06-18
A conceptual design is presented for a high power pion production target for neutrino factories and muon colliders that is based on a rotating metal band of either inconel alloy 718, titanium alloy 6AL4V grade 5 or nickel. The band is 5 meters in diameter and is tangentially intercepted by a pulsed proton beam inside a 20 Tesla tapered solenoidal magnetic pion capture channel. The mechanical layout and cooling setup of the target are summarized and results are presented from realistic MARS and ANSYS computer simulations of pion yields, energy depositions and shock heating stresses. The target scenario is predicted to perform satisfactorily and with conservative safety margins for multi-megawatt pulsed proton beams.
Two-pion exchange potential and the {pi}N amplitude
M. T. Pena; Franz Gross; Yohanes Surya
1996-05-01
The authors discuss the two-pion exchange potential which emerges from a box diagram with one nucleon (the spectator) restricted to its mass shell, and the other nucleon line replaced by a subtracted, covariant {pi}N scattering amplitude which includes {Delta}, Roper, and D{sub 13} isobars, as well as contact terms and off-shell (non-pole) dressed nucleon terms. The {pi}N amplitude satisfies chiral symmetry constraints and fits {pi}N data below {approximately} 700 MeV pion energy. They find that this TPE potential can be well approximated by the exchange of an effective sigma and delta meson, with parameters close to the ones used in one-boson-exchange models that fit NN data below the pion production threshold.
Detection of the characteristic pion-decay signature in supernova remnants.
Ackermann, M; Ajello, M; Allafort, A; Baldini, L; Ballet, J; Barbiellini, G; Baring, M G; Bastieri, D; Bechtol, K; Bellazzini, R; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bottacini, E; Brandt, T J; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Busetto, G; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, O; Charles, E; Chaty, S; Chaves, R C G; Chekhtman, A; Cheung, C C; Chiang, J; Chiaro, G; Cillis, A N; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Corbel, S; Cutini, S; D'Ammando, F; de Angelis, A; de Palma, F; Dermer, C D; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Falletti, L; Favuzzi, C; Ferrara, E C; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Germani, S; Giglietto, N; Giommi, P; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashida, M; Hayashi, K; Hays, E; Hewitt, J W; Hill, A B; Hughes, R E; Jackson, M S; Jogler, T; Jóhannesson, G; Johnson, A S; Kamae, T; Kataoka, J; Katsuta, J; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Madejski, G M; Massaro, F; Mayer, M; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mignani, R P; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Nemmen, R; Nuss, E; Ohno, M; Ohsugi, T; Omodei, N; Orienti, M; Orlando, E; Ormes, J F; Paneque, D; Perkins, J S; Pesce-Rollins, M; Piron, F; Pivato, G; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Ritz, S; Romoli, C; Sánchez-Conde, M; Schulz, A; Sgrò, C; Simeon, P E; Siskind, E J; Smith, D A; Spandre, G; Spinelli, P; Stecker, F W; Strong, A W; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J G; Thayer, J B; Thompson, D J; Thorsett, S E; Tibaldo, L; Tibolla, O; Tinivella, M; Troja, E; Uchiyama, Y; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Werner, M; Winer, B L; Wood, K S; Wood, M; Yamazaki, R; Yang, Z; Zimmer, S
2013-02-15
Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs. PMID:23413352
Measurements of pion production in eA with the CLAS detector
Manly, Steven L.; Lee, Hyupwoo
2015-05-01
Preliminary results on semi-inclusive charged pion production in eA collisions at E_{beam}=5 GeV/c^{2} are presented. These data are thought to be useful for tuning the hadronic production models used in extracting results from current and next-generation neutrino oscillation experiments. The data were collected using the CLAS detector, which is a multipurpose, large acceptance, magnetic spectrometer located in Hall B at the Thomas Jefferson National Accelerator Facility. Distributions (integrated and differential) in W, Q^{2}, pion momentum, and pion angle are shown for data produced using deuterium, carbon, and iron targets, including radiative corrections. Preliminary comparisons with data simulated using the GENIE generator are made.
Double and single pion photoproduction within a dynamical coupled-channels model
Hiroyuki Kamano; Julia-Diaz, Bruno; Lee, T. -S. H.; Matsuyama, Akihiko; Sato, Toru
2009-12-16
Within a dynamical coupled-channels model which has already been fixed from analyzing the data of the πN → πN and γN → πN reactions, we present the predicted double pion photoproduction cross sections up to the second resonance region, W < 1.7 GeV. The roles played by the different mechanisms within our model in determining both the single and double pion photoproduction reactions are analyzed, focusing on the effects due to the direct γN → ππN mechanism, the interplay between the resonant and non-resonant amplitudes, and the coupled-channels effects. As a result, the model parameters which can be determined mostmore » effectively in the combined studies of both the single and double pion photoproduction data are identified for future studies.« less
Detection of pion-induced radioactivity by autoradiography and positron emission tomography (PET)
Shirato, H.; Harrison, R.; Kornelsen, R. O.; Lam, G. K. Y.; Gaffney, C. C.; Goodman, G. B.; Grochowski, E.; Pate, B.
1989-05-01
An autoradiographic technique incorporating a new imaging system was used to detect pion-induced radioactivity in Plexiglass and the results were compared with aluminium activation and PET imaging. The activity distribution in the region of the pion-stopping peak was similar in all three cases. Another large signal in the entrance region due to in-flight interactions (/sup 12/C(..pi../minus/,..pi../minus//ital n/)/sup 11/C) was detected by autoradiography and by PET but was not reflected in the aluminium activation measurements. This new technique is capable of defining the stopping region in phantoms with a better resolution than PET scanning and is useful as a complementary technique to other methods of pion dosimetry.
Pion dominance in R-parity violating supersymmetry induced neutrinoless double beta decay
Faessler, Amand; Gutsche, Thomas; Simkovic, Fedor; Kovalenko, Sergey
2008-06-01
At the quark level there are basically two types of contributions of R-parity violating supersymmetry (Re{sub p} SUSY) to neutrinoless double beta decay: the short-range contribution involving only heavy virtual superpartners and the long-range one with the virtual squark and neutrino. Hadronization of the effective operators, corresponding to these two types of contributions, may in general involve virtual pions in addition to close on-mass-shell nucleons. From the previous studies it is known that the short-range contribution is dominated by the pion exchange. In the present paper we show that this is also true for the long-range Re{sub p} SUSY contribution. Therefore, we conclude that the Re{sub p} SUSY contributes to the neutrinoless double beta decay dominantly via charged pion exchange between the decaying nucleons.
Pion-kaon femtoscopy in Au+Au collisions at STAR
NASA Astrophysics Data System (ADS)
Poniatowska, Katarzyna;
2015-05-01
In non-identical particle correlations, e.g. pion-kaon femtoscopy, one can obtain information about source size and asymmetry in emission processes of pions and kaons. Such asymmetry give us knowledge of which type of particles is emitted first/second and/or from which region of the source. The studies of non-identical particle femtoscopy for Beam Energy Scan energies give us the opportunity to study how the source size and asymmetry in particle emission depend on the initial conditions of the collision. It also allows one to examine these parameters in the vicinity of the theoretical critical point. In these proceedings, we present STAR results of pion-kaon femtoscopy at mid-rapidity in Au+Au collisions at \\sqrt{sNN} = 7.7, 19.6 and 39 GeV.
Pion-kaon femtoscopy in Au+Au collisions at STAR
NASA Astrophysics Data System (ADS)
Poniatowska, Katarzyna
2015-05-01
Femtoscopy analysis allows us to extract information about the properties of particle emission source created after collision. From HBT of two correlated pions one can calculate source sizes; in addition, from the non-identical particle correlations, e.g. pion-kaon femtoscopy, one can obtain information not only about source sizes but the asymmetry in the emission processes of particles of different types as well. Such asymmetry gives knowledge of which kind of particles are emitted first/second and/or from which region of the source. The studies of non-identical particle femtoscopy for different collision energies gives us the opportunity to study how the source size and asymmetry in particle emission depend on the initial conditions of the collision. In these proceedings, we will present STAR results of pion-kaon femtoscopy at mid-rapidity in Au + Au collisions from the Beam Energy Scan program.
Pion generalized parton distributions within a fully covariant constituent quark model
NASA Astrophysics Data System (ADS)
Fanelli, Cristiano; Pace, Emanuele; Romanelli, Giovanni; Salmè, Giovanni; Salmistraro, Marco
2016-05-01
We extend the investigation of the generalized parton distribution for a charged pion within a fully covariant constituent quark model, in two respects: (1) calculating the tensor distribution and (2) adding the treatment of the evolution, needed for achieving a meaningful comparison with both the experimental parton distribution and the lattice evaluation of the so-called generalized form factors. Distinct features of our phenomenological covariant quark model are: (1) a 4D Ansatz for the pion Bethe-Salpeter amplitude, to be used in the Mandelstam formula for matrix elements of the relevant current operators, and (2) only two parameters, namely a quark mass assumed to be m_q=~220 MeV and a free parameter fixed through the value of the pion decay constant. The possibility of increasing the dynamical content of our covariant constituent quark model is briefly discussed in the context of the Nakanishi integral representation of the Bethe-Salpeter amplitude.
Measuring the charged pion polarizability in the gamma gamma -> pi+pi- reaction
Lawrence, David W.; Miskimen, Rory A.; Mushkarenkov, Alexander Nikolaevich; Smith, Elton S.
2013-08-01
Development has begun of a new experiment to measure the charged pion polarizability $\\alpha_{\\pi}-\\beta_{\\pi}$. The charged pion polarizability ranks among the most important tests of low-energy QCD presently unresolved by experiment. Analogous to precision measurements of $\\pi^{\\circ}\\rightarrow\\gamma\\gamma$ that test the intrinsic odd-parity (anomalous) sector of QCD, the pion polarizability tests the intrinsic even-parity sector of QCD. The measurement will be performed using the $\\gamma\\gamma\\rightarrow\\pi^{+{}}\\pi^{-{}}$ cross section accessed via the Primakoff mechanism on nuclear targets using the GlueX detector in Hall D at Jefferson Lab. The linearly polarized photon source in Hall-D will be utilized to separate the Primakoff cross-section from coherent $\\rho^{\\circ}$ production.
Pion-induced double-charge exchange reactions in the {delta} resonance region
Buss, O.; Alvarez-Ruso, L.; Larionov, A. B.; Mosel, U.
2006-10-15
We have applied the Giessen BUU (GiBUU) transport model to the description of the double-charge exchange (DCX) reaction of pions with different nuclear targets at incident kinetic energies of 120-180 MeV. The DCX process is highly sensitive to details of the interactions of pions with the nuclear medium and, therefore, represents a major benchmark for any model of pion scattering off nuclei at low and intermediate energies. The impact of surface effects, such as the neutron skins of heavy nuclei, is investigated. The dependence of the total cross section on the nuclear mass number is also discussed. We achieve a good quantitative agreement with the extensive data set obtained at LAMPF. Furthermore, we compare the solutions of the transport equations obtained in the test-particle ansatz using two different schemes: the full and the parallel ensemble methods.
A study of gamma-families generated in nucleon-nucleus (NA) and pion-nucleus (pi A) interactions
NASA Technical Reports Server (NTRS)
Azimov, S. A.; Mulladjanov, E. J.; Nuritdinov, H.; Yuldashbaev, T. S.
1985-01-01
The separation of the gamma families generated in nucleon-nuclear and pion-nuclear (PI-A) interactions is realized from the analysis of simulated gamma families. Some characteristics of NA and PI families and the influence of the process of inelastic charge-exchange of charged pions neutral ones type of PI + or - A yields are studied.
NASA Astrophysics Data System (ADS)
Cernigoi, C.; Gabrielli, I.; Grion, N.; Pauli, G.; Saitta, B.; Ricci, R. A.; Boccaccio, P.; Viesti, G.
1981-02-01
Energy spectra have been measured of single neutrons, protons and deuterons emitted following the capture at rest of negative pions in 4He. The neutron energy spectrum has been measured with an energy resolution of 4% at 90 MeV. The absolute number of stopped pions has been measured.
Egorov, M. V.; Fix, A. I.
2013-05-15
The role of two-nucleon mechanisms in pion photoproduction on nuclei was studied in the region of high momentum transfers to the residual nucleus. The process in which the photoproduction of negative pions on a {sup 12}C nucleus is accompanied by proton emission was considered by way of example. The results of the calculations were compared with available experimental data.
Double neutral pion photoproduction off the proton with FOREST at ELPH
NASA Astrophysics Data System (ADS)
He, Q.; Fujimura, H.; Fukasawa, H.; Hashimoto, R.; Honda, Y.; Ishikawa, T.; Iwata, T.; Kaida, S.; Kasagi, J.; Kawano, A.; Kuwasaki, S.; Maeda, K.; Masumoto, S.; Miyabe, M.; Miyahara, F.; Mochizuki, K.; Muramatsu, N.; Nakamura, A.; Nawa, K.; Ogushi, S.; Okada, Y.; Onodera, Y.; Ozawa, K.; Sakamoto, Y.; Sato, M.; Shimizu, H.; Sugai, H.; Suzuki, K.; Tajima, Y.; Takahashi, S.; Taniguchi, Y.; Tsuchikawa, Y.; Yamazaki, H.; Yamazaki, R.; Yoshida, H. Y.
2016-02-01
Total cross section for the double neutral pion photoproduction off the proton is presented in the incident photon energy range of 0.58 to 1.15 GeV. The data were accumulated in the years 2009-2010, recorded by a 4π EM calorimeter at ELPH, named FOREST. The number of recorded events obtained during this period is 1.6×109 for a hydrogen target. Two neutral pions are reconstructed via detecting their decay products, four gammas (2π0 → 4γ). Compared to the previous results obtained by other groups, our data are in good agreement with theirs within error bars.
Unitary constraints on charged pion photoproduction at large p_perp
J.M. Laget
2010-03-01
Around $\\theta_{\\pi}=$~90$^\\circ$, the coupling to the $\\rho^\\circ N$ channel leads to a good accounting of the charged pion exclusive photoproduction cross section in the energy range 3~$<$~10~GeV, where experimental data exist. Starting from a Regge Pole approach that successfully describes vector meson production, the singular part of the corresponding box diagrams (where the intermediate vector meson-baryon pair propagates on-shell) is evaluated without any further assumptions (unitarity). Such a treatment provides an explanation of the $s^{-7}$ scaling of the cross section. Elastic rescattering of the charged pion improves the basic Regge pole model at forward and backward angles.
On the origin of the pion-decay radiation in the 1982 June 3 solar flare
NASA Technical Reports Server (NTRS)
Ramaty, R.; Murphy, R. J.; Dermer, C. D.
1987-01-01
The June 3, 1982 flare produced a wealth of observed gamma-ray, energetic particle, and neutron emissions. It is shown that the predictions of an interaction model developed for the June 3 flare by Murphy, Dermer, and Ramaty (1987) compare favorably with new data on the time-dependent flux on pion-decay emission from this flare. It is concluded that the particles which produced the bulk of the pions could have the same origin as the particle observed in interplanetary space from the June 3 flare.
Photoproduction of the Charged Top-Pions at the LHeC
NASA Astrophysics Data System (ADS)
Guo, Jing; Yue, Chong-Xing; Zhang, Jiao; Zeng, Qing-Guo
2012-11-01
The top triangle moose (TTM) model, which can be seen as the deconstructed version of the topcolor-assisted technicolor (TC2) model, predicts the existence of the charged top-pions πt± in low energy spectrum. In the context of this model, we consider photoproduction of πt± via the subprocesses γb → tπt- and at the large hadron-electron collider (LHeC), in which high energy photon beams are generated by using the Compton backscatting method. We find that, as long as the charged top-pions are not too heavy, they can be abundantly produced via 76 collision.
Constraining pion interactions at very high energies by cosmic ray data
NASA Astrophysics Data System (ADS)
Ostapchenko, Sergey; Bleicher, Marcus
2016-03-01
We demonstrate that a substantial part of the present uncertainties in model predictions for the average maximum depth of cosmic ray-induced extensive air showers is related to very high energy pion-air collisions. Our analysis shows that the position of the maximum of the muon production profile in air showers is strongly sensitive to the properties of such interactions. Therefore, the measurements of the maximal muon production depth by cosmic ray experiments provide a unique opportunity to constrain the treatment of pion-air interactions at very high energies and to reduce thereby model-related uncertainties for the shower maximum depth.
Using baryon octet magnetic moments and masses to fix the pion cloud contribution
Franz L. Gross; Ramalho, Gilberto T. F.; Tsushima, Kazuo
2010-05-12
In this study, using SU(3) symmetry to constrain the $\\pi BB'$ couplings, assuming SU(3) breaking comes only from one-loop pion cloud contributions, and using the the covariant spectator theory to describe the photon coupling to the quark core, we show how the experimental masses and magnetic moments of the baryon octet can be used to set a model independent constraint on the strength of the pion cloud contributions to the octet, and hence the nucleon, form factors at $Q^2=0$.
Using baryon octet magnetic moments and masses to fix the pion cloud contribution
Franz L. Gross; Ramalho, Gilberto T. F.; Tsushima, Kazuo
2010-05-12
In this study, using SU(3) symmetry to constrain themore » $$\\pi BB'$$ couplings, assuming SU(3) breaking comes only from one-loop pion cloud contributions, and using the the covariant spectator theory to describe the photon coupling to the quark core, we show how the experimental masses and magnetic moments of the baryon octet can be used to set a model independent constraint on the strength of the pion cloud contributions to the octet, and hence the nucleon, form factors at $Q^2=0$.« less
Medium effects on the relaxation of dissipative flows in a hot pion gas
NASA Astrophysics Data System (ADS)
Mitra, Sukanya; Gangopadhyaya, Utsab; Sarkar, Sourav
2015-05-01
The relaxation times over which dissipative fluxes restore their steady-state values are evaluated for a pion gas using the 14-moment method. The effect of the medium is implemented through a temperature-dependent π π cross section in the collision integral which is obtained by including one-loop self-energies in the propagators of the exchanged ρ and σ mesons. To account for chemical freeze-out in heavy-ion collisions, a temperature-dependent pion chemical potential is introduced in the distribution function. The temperature dependence of the relaxation times for shear and bulk viscous flows as well as the heat flow is significantly affected.
Pion, Kaon, Proton and Antiproton Production in Proton-Proton Collisions
NASA Technical Reports Server (NTRS)
Norbury, John W.; Blattnig, Steve R.
2008-01-01
Inclusive pion, kaon, proton, and antiproton production from proton-proton collisions is studied at a variety of proton energies. Various available parameterizations of Lorentz-invariant differential cross sections as a function of transverse momentum and rapidity are compared with experimental data. The Badhwar and Alper parameterizations are moderately satisfactory for charged pion production. The Badhwar parameterization provides the best fit for charged kaon production. For proton production, the Alper parameterization is best, and for antiproton production the Carey parameterization works best. However, no parameterization is able to fully account for all the data.
One-pion exchange current effects on magnetic form factor in the relativistic formalism
NASA Astrophysics Data System (ADS)
Zhang, Cun; Liu, Jian; Ren, Zhongzhou
2016-08-01
One-pion exchange current effects on the magnetic form factors of some odd nuclei are studied in the relativistic formalism. The Dirac wave functions of nucleons are calculated from the relativistic mean-field theory. After fitting to experimental data by quenching factors, it is found that taking the one-pion exchange currents into account gives a better description of the magnetic form factor. The root-mean-square radii of the valance nucleon orbits are also calculated in RMF model, which coincide with experimental radii extracted with meson exchange current corrections.
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
Tsukamoto, Takafumi; Yasunaga, Takuo
2014-11-01
need to provide common workspace for analysis because the client is physically separated from a server. We solved the file format problem by extension of rules of OptionControlFile of Eos. Furthermore, to solve workspace problems, we have developed two type of system. The first system is to use only local environments. The user runs a web server provided by Eos, access to a web client through a web browser, and manipulate the local files with GUI on the web browser. The second system is employing PIONE (Process-rule for Input/Output Negotiation Environment), which is our developing platform that works under heterogenic distributed environment. The users can put their resources, such as microscopic images, text files and so on, into the server-side environment supported by PIONE, and so experts can write PIONE rule definition, which defines a workflow of image processing. PIONE run each image processing on suitable computers, following the defined rule. PIONE has the ability of interactive manipulation, and user is able to try a command with various setting values. In this situation, we contribute to auto-generation of GUI for a PIONE workflow.As advanced functions, we have developed a module to log user actions. The logs include information such as setting values in image processing, procedure of commands and so on. If we use the logs effectively, we can get a lot of advantages. For example, when an expert may discover some know-how of image processing, other users can also share logs including his know-hows and so we may obtain recommendation workflow of image analysis, if we analyze logs. To implement social platform of image processing for electron microscopists, we have developed system infrastructure, as well. PMID:25359837
NASA Astrophysics Data System (ADS)
Kulkarni, Arun Venkatesh
Pi-nuclear scattering calculations that use multiple scattering usually require the knowledge not only of the pi-nucleon interaction in free space but also its modification inside a nuclear medium. A relativistic 3-Body model consisting of the pion, the i^ {rm th}-nucleon and the residual nucleus also called the core, is developed. In this model the nucleon core separation in co-ordinate space is approximated by the separation between the center of mass of the pi-i^{rm th} nucleon subsystem called the Composite, and the core. The instant form of dynamics was employed to introduce interactions between the pion and the nucleon and between the pi N Composite and the Core. The Composite-Core Hamiltonian is assumed to admit no bound states. The relativistic 3-Body total Hamiltonian is then diagonalized by nested-separable eigenfunctions. This diagonalization allows the construction of an expression for matrix elements of the medium modified pi N scattering operator tau_ {i} in the lab frame in terms of the CM pi N free space t-matrix elements. Terms that are quadratic in the pi N t -matrix elements in this expression are neglected. The Sequential Single Charge eXchange (SSCX) mechanism contribution to inclusive pi- ^4He Double Charge eXchange (DCX) is calculated using only the double scattering term of the Watson multiple scattering series. The tau-matrix elements obtained from the 3-Body model are used for the first scattering. It contains explicit dependance upon the matrix elements of the Composite-Core scattering operator t_{pi N-C}. This explicit dependance is ignored in the second scattering. The pole of the intermediate pion Green function is fixed from 3-Body model considerations and the requirement that pion be on the mass shell at the pole. The calculated inclusive cross sections {{d^2sigma}over{d Omega dT_pi}} are compared with the Kinney et al. experimental results and essential agreement with the spectrum for incident pion kinetic energy T_sp{pi}{rm In
Neutrinoproduction of photons and pions from nucleons in a chiral effective field theory for nuclei
NASA Astrophysics Data System (ADS)
Serot, Brian D.; Zhang, Xilin
2012-07-01
Neutrino-induced production (neutrinoproduction) of photons and pions from nucleons and nuclei is important for the interpretation of neutrino-oscillation experiments, as these photons and pions are potential backgrounds in the MiniBooNE experiment [A. A. Aquilar-Arevalo (MiniBooNE Collaboration), Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.100.032301 100, 032301 (2008)]. These processes are studied at intermediate energies, where the Δ(1232) resonance becomes important. The Lorentz-covariant effective field theory, which is the framework used in this series of studies, contains nucleons, pions, Δs, isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields. The Lagrangian exhibits a nonlinear realization of (approximate) SU(2)L⊗SU(2)R chiral symmetry and incorporates vector meson dominance. In this paper, we focus on setting up the framework. Power counting for vertices and Feynman diagrams is explained. Because of the built-in symmetries, the vector current is automatically conserved, and the axial-vector current is partially conserved. To calibrate the axial-vector transition current (N↔Δ), pion production from the nucleon is used as a benchmark and compared to bubble-chamber data from Argonne and Brookhaven National Laboratories. At low energies, the convergence of our power-counting scheme is investigated, and next-to-leading-order tree-level corrections are found to be small.
Weak Pion and Photon Production from Nuclei in a Chiral Effective Field Theory (Update)
NASA Astrophysics Data System (ADS)
Zhang, Xilin; Serot, Brian D.
2011-04-01
Neutrino-induced pion and photon production from nucleons and nuclei are important for the interpretation of neutrino-oscillation experiments. [A. A. Aquilar-Arevalo et al. (MiniBooNE Collaboration), Phys. Rev. Lett. 100, 032301 (2008)]. We have been working on these problems in a Lorentz-covariant effective field theory (known as QHD EFT), which contains nucleons, pions, Deltas (Δ), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields and has nonlinear chiral symmetry built in. Here we update our results on weak pion and photon production from nuclei, including both incoherent and coherent scattering. Connections between our results and the background analysis from MiniBooNE will be presented. In particular, coherent production of photons will be emphasized, and the possible relevance to the low-energy excess events at MiniBooNE will be explored. To justify our approximation scheme, we compare our results with data for inclusive electron scattering off nuclei up to the Δ peak and with coherent photoproduction of pions. Finally, we focus on the approximation scheme used and discuss the important Δ dynamics in the medium. An interesting mechanism to generate the Δ's spin-orbit coupling in the nucleus will be introduced, together with its possible consequences. Supported in part by the Department of Energy under Contract No. DE-FG02-87ER40365.
In vitro and in vivo studies of the TRIUMF pion therapy beam.
Skarsgard, L D; Douglas, B G; Denekamp, J; Chaplin, D J; Lam, G K; Harrison, R W; Kornelsen, R O; Palcic, B
1985-01-01
Patient treatments at TRIUMF (Tri-University Meson Facility, Vancouver, B. C.) use a moving spot raster scan technique where the pion range is modulated in depth for each position of the moving spot. The spot scans in a stepwise fashion and can produce any desired field shape. This approach provides very good dose uniformity across the treatment field and allows maximum flexibility in shaping the treatment volume. Survival of cultured cells has been used as a biological dosimeter to test the isoeffectiveness of the pion dose distributions, which must be shaped in depth to compensate for the depth-dependent LET distribution. Isoeffectiveness across the treatment field has also been verified using this system, which involves irradiating cells supported in a gelatin matrix. The response of pig skin to pion irradiation at TRIUMF has provided a check on the in vivo RBE for acute effects derived from our earlier studies with mouse foot. In addition, the pig skin reactions have been followed for several months to assess the later dermal response. The RBE of our pion beam relative to 270 kVp X rays is approximately 1.5 for both the acute epidermal and the later dermal responses. PMID:3937169
In vitro and in vivo studies of the TRIUMF pion therapy beam
Skarsgard, L.D.; Douglas, B.G.; Denekamp, J.; Chaplin, D.J.; Lam, G.K.; Harrison, R.W.; Kornelsen, R.O.; Palcic, B.
1985-01-01
Patient treatments at TRIUMF (Tri-University Meson Facility, Vancouver, B. C.) use a moving spot raster scan technique where the pion range is modulated in depth for each position of the moving spot. The spot scans in a stepwise fashion and can produce any desired field shape. This approach provides very good dose uniformity across the treatment field and allows maximum flexibility in shaping the treatment volume. Survival of cultured cells has been used as a biological dosimeter to test the isoeffectiveness of the pion dose distributions, which must be shaped in depth to compensate for the depth-dependent LET distribution. Isoeffectiveness across the treatment field has also been verified using this system, which involves irradiating cells supported in a gelatin matrix. The response of pig skin to pion irradiation at TRIUMF has provided a check on the in vivo RBE for acute effects derived from our earlier studies with mouse foot. In addition, the pig skin reactions have been followed for several months to assess the later dermal response. The RBE of our pion beam relative to 270 kVp X rays is approximately 1.5 for both the acute epidermal and the later dermal responses.
Short-range NN and N. Delta. correlations in pion double charge exchange (DCX)
Johnson, M.B.
1990-01-01
I will review several important results related to the short-range nucleon-nucleon and delta-nucleon interaction that have been obtained from recent studies of pion double charge exchange in selected nuclei. 32 refs., 5 figs., 3 tabs.
A Precision Measurement Of The Neutral Pion Lifetime: The PRIMEX Experiment
Miskimen, Rory
2008-10-13
The PRIMEX collaboration at Jefferson Lab is completing an experimental analysis to obtain a precision measurement of the neutral pion lifetime. Results from the experiment will be presented and comparisons made with the chiral anomaly prediction and NLO calculations. An extension of the experiment to 12 GeV for measurements of the {eta} and {eta}' radiative widths is discussed.
Revisiting the pion leading-twist distribution amplitude within the QCD background field theory
NASA Astrophysics Data System (ADS)
Zhong, Tao; Wu, Xing-Gang; Wang, Zhi-Gang; Huang, Tao; Fu, Hai-Bing; Han, Hua-Yong
2014-07-01
We study the pion leading-twist distribution amplitude (DA) within the framework of Shifman-Vainshtein-Zakharov sum rules under the background field theory. To improve the accuracy of the sum rules, we expand both the quark propagator and the vertex (z.D↔)n of the correlator up to dimension-six operators in the background field theory. The sum rules for the pion DA moments are obtained, in which all condensates up to dimension-six have been taken into consideration. Using the sum rules, we obtain ⟨ξ2⟩|1 GeV=0.338±0.032, ⟨ξ4⟩|1GeV=0.211±0.030 and ⟨ξ6⟩|1GeV=0.163±0.030. It is shown that the dimension-six condensates shall provide sizable contributions to the pion DA moments. We show that the first Gegenbauer moment of the pion leading-twist DA is a2π|1 GeV=0.403±0.093, which is consistent with those obtained in the literature within errors but prefers a larger central value as indicated by lattice QCD predictions.
Ogawa, Y.; Goodman, G.B.; Chaplin, D.J.; Grulkey, W.; Lam, G.K. )
1990-06-01
Female C3H mice aged 8-10 weeks with transplanted KHT sarcoma or SCCVII tumor were used to investigate the antitumor effect of SPG (Sonifilan, Schizophyllan) alone and in combination with local irradiation of pions with 4 fractions of 400 cGy (total 1600 cGy). Daily doses of 10 mg/kg of SPG were given intramuscularly to the mice bearing KHT sarcoma for 14 consecutive days from day 7, and to mice bearing SCCVII tumor for 20 consecutive days from day 7 and thereafter three times a week for another 2 weeks. The antitumor effect was evaluated by the changes in tumor volume, survival curves, and the number of pulmonary metastatic nodules on the surface of the lungs. SPG failed to exert any antitumor effect and any life-prolonging effect for the KHT sarcoma. As for SCCVII tumor, in the group treated with pions and SPG, tumor growth decreased significantly (p less than 0.01) compared with the group treated with pion only, and life prolonging effect and metastasis-suppressing effect were also observed (p less than 0.04). In conditions of minimal residual disease brought about by pion irradiation, the adjuvant effect of a Biological Response Modifier (BRM) SPG may prove to be a promising method of cancer therapy for some tumors.
Pion-nucleon charge exchange amplitudes above 2 GeV
NASA Astrophysics Data System (ADS)
Huang, F.; Sibirtsev, A.; Krewald, S.; Hanhart, C.; Haidenbauer, J.; Meißner, U.-G.
2009-04-01
The amplitudes for the pion-nucleon charge exchange reaction of the Karlsruhe-Helsinki and the George-Washington-University partial-wave analyses are compared with those of a Regge-cut model with the aim to explore the possibility to provide high-energy constraints for theoretical baryon resonance analyses in the energy region above 2GeV.
Pion content of the nucleon in polarized semi-inclusive DIS
Melnitchouk, W.; Thomas, A.W.
1994-04-01
An explicit pionic component of the nucleon may be identified by measuring polarized {Delta}{sup ++} fragments produced in deep-inelastic scattering (DIS) off polarized protons. The pion-exchange model predicts highly correlated polarizations of the {Delta}{sup ++} and target proton, in marked contrast with the competing diquark fragmentation process.
Yields of p, d, t formed in stopped pion absorption by intranuclear clusters
NASA Astrophysics Data System (ADS)
Chernyshev, B. A.; Gurov, Yu B.; Korotkova, L. Yu; Lapushkin, S. V.; Leonova, T. I.; Pritula, R. V.; Schurenkova, T. D.
2016-02-01
Results of the study of spectra and yields of p, d, t formed in stopped pion absorption by nuclei are presented. Data on charged particle formation have been obtained for 17 isotopes in wide atomic mass range (6 < A < 209). Empirical model was proposed to describe A- dependences of primary p, d, t yields.
Determination of the pion-nucleon coupling constant and scattering lengths
NASA Astrophysics Data System (ADS)
Ericson, T. E.; Loiseau, B.; Thomas, A. W.
2002-07-01
We critically evaluate the isovector Goldberger-Miyazawa-Oehme (GMO) sum rule for forward πN scattering using the recent precision measurements of π-p and π-d scattering lengths from pionic atoms. We deduce the charged-pion-nucleon coupling constant, with careful attention to systematic and statistical uncertainties. This determination gives, directly from data, g2c(GMO)/ 4π=14.11+/-0.05(statistical)+/-0.19(systematic) or f2c/4π=0.0783(11). This value is intermediate between that of indirect methods and the direct determination from backward np differential scattering cross sections. We also use the pionic atom data to deduce the coherent symmetric and antisymmetric sums of the pion-proton and pion-neutron scattering lengths with high precision, namely, (aπ-p+aπ-n)/2=[- 12+/-2(statistical)+/-8(systematic)]×10-4 m-1π and (aπ-p-aπ- n)/2=[895+/-3(statistical)+/-13 (systematic)]×10-4 m-1π. For the need of the present analysis, we improve the theoretical description of the pion-deuteron scattering length.
Pion's valence-quark GPD and its extension beyond DGLAP region
NASA Astrophysics Data System (ADS)
Mezrag, Cédric; Moutarde, Hervé; Rodríguez-Quintero, José
2016-03-01
We briefly report on a recent computation, with the help of a fruitful algebraic model, sketching the pion valence dressed-quark generalized parton distribution and, very preliminary, discuss on a possible avenue to get reliable results in both Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) and Efremov-Radyushkin-Brodsky-Lepage (ERBL) kinematial regions.
Parameterization of spectral distributions for pion and kaon production in proton-proton collisions
NASA Technical Reports Server (NTRS)
Schneider, John P.; Norbury, John W.; Cucinotta, Frank A.
1995-01-01
Accurate semi-empirical parameterizations of the energy-differential cross sections for charged pion and kaon production from proton-proton collisions are presented at energies relevant to cosmic rays. The parameterizations depend on the outgoing meson momentum and also the proton energy, and are able to be reduced to very simple analytical formulas suitable for cosmic-ray transport.
Pion condensation in a relativistic field theory consistent with bulk properties of nuclear matter
Banerjee, B.; Glendenning, N. K.; Gyulassy, M.
1981-05-01
Pion condensation is investigated in a self-consistent. relativistic mean field theory that is constrained to reproduce the bulk properties of nuclear matter. This constraint and self-consistency provide stringent constraints on the existence and energy of the condensate.
Next-to-leading-order correction to pion form factor in k{sub T} factorization
Li Hsiangnan; Shen Yuelong; Wang Yuming; Zou Hao
2011-03-01
We calculate the next-to-leading-order (NLO) correction to the pion electromagnetic form factor at leading twist in the k{sub T} factorization theorem. Partons off-shell by k{sub T}{sup 2} are considered in both quark diagrams and effective diagrams for the transverse-momentum-dependent pion wave function. The light-cone singularities in the transverse-momentum-dependent pion wave function are regularized by rotating the Wilson lines away from the light cone. The soft divergences from gluon exchanges among initial- and fal-state partons cancel exactly. We derive the infrared-finite k{sub T}-dependent NLO hard kernel for the pion electromagnetic form factor by taking the difference of the above two sets of diagrams. Varying the renormalization and factorization scales, we find that the NLO correction is smaller, when both the scales are set to the invariant masses of internal particles: it becomes lower than 40% of the leading-order contribution for momentum transfer squared Q{sup 2}>7 GeV{sup 2}. It is observed that the NLO leading-twist correction does not play an essential role in explaining the experimental data, but the leading-order higher-twist contribution does.
Ginsparg-Wilson pions scattering in a sea of staggered quarks
NASA Astrophysics Data System (ADS)
Chen, Jiunn-Wei; O'Connell, Donal; van de Water, Ruth; Walker-Loud, André
2006-04-01
We calculate isospin 2 pion-pion scattering in chiral perturbation theory for a partially quenched, mixed action theory with Ginsparg-Wilson valence quarks and staggered sea quarks. We point out that for some scattering channels, the power-law volume dependence of two-pion states in nonunitary theories such as partially quenched or mixed action QCD is identical to that of QCD. Thus one can extract infinite-volume scattering parameters from mixed action simulations. We then determine the scattering length for both 2 and 2+1 sea quarks in the isospin limit. The scattering length, when expressed in terms of the pion mass and the decay constant measured on the lattice, has no contributions from mixed valence-sea mesons, thus it does not depend upon the parameter, CMix, that appears in the chiral Lagrangian of the mixed theory. In addition, the contributions which nominally arise from operators appearing in the mixed action O(a2mq) Lagrangian exactly cancel when the scattering length is written in this form. This is in contrast to the scattering length expressed in terms of the bare parameters of the chiral Lagrangian, which explicitly exhibits all the sicknesses and lattice spacing dependence allowed by a partially quenched mixed action theory. These results hold for both 2 and 2+1 flavors of sea quarks.
Ginsparg-Wilson pions scattering in a sea of staggered quarks
Chen, J.-W.; O'Connell, Donal; Van de Water, Ruth; Walker-Loud, Andre
2006-04-01
We calculate isospin 2 pion-pion scattering in chiral perturbation theory for a partially quenched, mixed action theory with Ginsparg-Wilson valence quarks and staggered sea quarks. We point out that for some scattering channels, the power-law volume dependence of two-pion states in nonunitary theories such as partially quenched or mixed action QCD is identical to that of QCD. Thus one can extract infinite-volume scattering parameters from mixed action simulations. We then determine the scattering length for both 2 and 2+1 sea quarks in the isospin limit. The scattering length, when expressed in terms of the pion mass and the decay constant measured on the lattice, has no contributions from mixed valence-sea mesons, thus it does not depend upon the parameter, C{sub Mix}, that appears in the chiral Lagrangian of the mixed theory. In addition, the contributions which nominally arise from operators appearing in the mixed action O(a{sup 2}m{sub q}) Lagrangian exactly cancel when the scattering length is written in this form. This is in contrast to the scattering length expressed in terms of the bare parameters of the chiral Lagrangian, which explicitly exhibits all the sicknesses and lattice spacing dependence allowed by a partially quenched mixed action theory. These results hold for both 2 and 2+1 flavors of sea quarks.
A new muon-pion collection and transport system design using superconducting solenoids based on CSNS
NASA Astrophysics Data System (ADS)
Xiao, Ran; Liu, Yan-Fen; Xu, Wen-Zhen; Ni, Xiao-Jie; Pan, Zi-Wen; Ye, Bang-Jiao
2016-05-01
A new muon and pion capture system is proposed for the China Spallation Neutron Source (CSNS), currently under construction. Using about 4% of the pulsed proton beam (1.6 GeV, 4 kW and 1 Hz) of CSNS to bombard a cylindrical graphite target inside a superconducting solenoid, both surface muons and pions can be acquired. The acceptance of this novel capture system - a graphite target wrapped up by a superconducting solenoid - is larger than the normal muon beam lines using quadrupoles at one side of the separated muon target. The muon and pion production at different capture magnetic fields was calculated using Geant4. The bending angle of the capture solenoid with respect to the proton beam was also optimized in simulation to achieve more muons and pions. Based on the layout of the muon experimental area reserved at the CSNS project, a preliminary muon beam line was designed with multi-purpose muon spin rotation areas (surface, decay and low-energy muons). Finally, high-flux surface muons (108/s) and decay muons (109/s) simulated by G4beamline will be available at the end of the decay solenoid based on the first phase of CSNS. This collection and transport system will be a very effective beam line at a proton current of 2.5 μA. Supported by National Natural Science Foundation of China (11527811)
Measurement of Neutrino-Induced Coherent Pion Production and the Diffractive Background in MINERvA
NASA Astrophysics Data System (ADS)
Gomez, Alicia; Minerva Collaboration
2015-04-01
Neutrino-induced coherent charged pion production is a unique neutrino-nucleus scattering process in which a muon and pion are produced while the nucleus is left in its ground state. The MINERvA experiment has made a model-independent differential cross section measurement of this process on carbon by selecting events with a muon and a pion, no evidence of nuclear break-up, and small momentum transfer to the nucleus | t | . A similar process which is a background to the measurement on carbon is diffractive pion production off the free protons in MINERvA's scintillator. This process is not modeled in the neutrino event generator GENIE. At low | t | these events have a similar final state to the aforementioned process. A study to quantify this diffractive event contribution to the background is done by emulating these diffractive events by reweighting all other GENIE-generated background events to the predicted | t | distribution of diffractive events, and then scaling to the diffractive cross section.
Dehnhard, D.
1980-03-01
The elastic and inelastic scattering of ..pi../sup +/ and ..pi../sup -/ by /sup 13/C, /sup 16/O, and /sup 17/O was studied at pion energies close to the (3,3) resonance. Data were taken at the Los Alamos Meson Physics Facility. Large asymmetries were observed, two of which are consistent with pure neutron and pure proton excitations. Transitions to strongly excited states of /sup 13/C are in strikingly good agreement with theoretical predictions of Lee and Kurath. In sharp contrast, strong disagreements are found for the weakly excited states. The asymmetries for /sup 16/O + ..pi../sup + -/ were interpreted as due to isospin mixing between the excited states. High-resolution data for (t,t') and (/sup 3/He,/sup 3/He') on /sup 13/C were taken to supplement the pion work. Asymmetries were found for the relative cross sections for some states. In studies of the heavy-ion-nucleus potential the effect of potential resonances on the elastic scattering of /sup 16/O + /sup 28/Si was found to be small. A close similarity between the elastic exchange amplitude at 180/sup 0/ and the effect of the parity dependence on the elastic amplitude was found. Fits to the new data at 40 and 41.226 MeV required the use of a composite absorptive potential. The surface derivative part of this potential can be deduced from a coupled-channels calculation. 17 figures.
Fluctuations of the number of neutral pions at high multiplicity in pp interactions at 50 GeV
Ryadovikov, V. N.
2012-08-15
Results obtained by measuring fluctuations of the number of neutral pions in the SERP-E-190 Experiment (Thermalization Project) upon irradiating a liquid-hydrogen target of the SVD-2 setup with a beam of 50-GeV protons are presented. A simulation of the detection of photons from the decay of neutral pions with the aid of an electromagnetic calorimeter revealed a linear relation between the number of detected photons and the mean number of neutral pions in an event. After the introduction of corrections for the loss of charged tracks because of a limited acceptance of the setup, trigger operation, and the efficiency of the data-treatment system, distributions of the number of neutral pions, N{sub 0}, were obtained for each value of the total number of particles in an event, N{sub tot} = N{sub ch} + N{sub 0}. The fluctuation parameter {omega} = D/ Left-Pointing-Angle-Bracket N{sub 0} Right-Pointing-Angle-Bracket was measured. In the region N{sub tot} > 22, fluctuations of the number of neutral pions increase, which, within statistical models (GCE, CE, MCE), indicates that the system involving a large number of pions approaches the pion-condensate state. This effect was observed for the first time.
NASA Astrophysics Data System (ADS)
Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahn, S. U.; Aimo, I.; Aiola, S.; Ajaz, M.; Akindinov, A.; Alam, S. N.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Almaraz, J. R. M.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; Andrei, C.; Andronic, A.; Anguelov, V.; Anielski, J.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Armesto, N.; Arnaldi, R.; Arsene, I. C.; Arslandok, M.; Audurier, B.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Bach, M.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Baldisseri, A.; Baltasar Dos Santos Pedrosa, F.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Barth, K.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Belmont, R.; Belmont-Moreno, E.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biswas, R.; Biswas, S.; Bjelogrlic, S.; Blair, J. T.; Blanco, F.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Bossú, F.; Botta, E.; Böttger, S.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Butt, J. B.; Buxton, J. T.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Carnesecchi, F.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Cavicchioli, C.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Cerkala, J.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Chunhui, Z.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa Del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; de, S.; de Caro, A.; de Cataldo, G.; de Cuveland, J.; de Falco, A.; de Gruttola, D.; De Marco, N.; de Pasquale, S.; Deisting, A.; Deloff, A.; Dénes, E.; D'Erasmo, G.; di Bari, D.; di Mauro, A.; di Nezza, P.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Dobrowolski, T.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Drozhzhova, T.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Engel, H.; Erazmus, B.; Erdemir, I.; Erhardt, F.; Eschweiler, D.; Espagnon, B.; Estienne, M.; Esumi, S.; Eum, J.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabbietti, L.; Fabris, D.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Felea, D.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Feuillard, V. J. G.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fiore, E. M.; Fleck, M. G.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Gasik, P.; Germain, M.; Gheata, A.; Gheata, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-Dziadus, E.; Glässel, P.; Goméz Coral, D. M.; Gomez Ramirez, A.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Graczykowski, L. K.; Graham, K. L.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Grosse-Oetringhaus, J. F.; Grossiord, J.-Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gulkanyan, H.; Gunji, T.; Gupta, A.; Gupta, R.; Haake, R.
2016-03-01
Transverse momentum (pT) spectra of pions, kaons, and protons up to pT=20 GeV/c have been measured in Pb-Pb collisions at √{sNN}=2.76 TeV using the ALICE detector for six different centrality classes covering 0%-80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at pT≈3 GeV/c in central Pb-Pb collisions that decreases for more peripheral collisions. For pT>10 GeV/c , the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10%-20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched jet. For pT<10 GeV/c , the data provide important constraints for models aimed at describing the transition from soft to hard physics.
Search for Charged Current Coherent Pion Production on Carbon in a Few-GeV Neutrino Beam
Hiraide, K.; Alcaraz-Aunion, J.L.; Brice, S.J.; Bugel, Leonard G.; Catala-Perez, J.; Cheng, G.; Conrad, J.M.; Djurcic, Zelimir; Dore, U.; Finley, David A.; Franke, A.J.; /Columbia U. /Banca di Roma /Frascati
2008-11-01
The SciBooNE Collaboration has performed a search for charged current coherent pion production from muon neutrinos scattering on carbon, nu{sub {mu}}{sup 12}C- {yields} {mu}{sup 12}Cpi{sup +}, with two distinct data samples. No evidence for coherent pion production is observed. We set 90% confidence level upper limits on the cross section ratio of charged current coherent pion production to the total charged current cross section at 0.67 x 10{sup -2} at mean neutrino energy 1.1 GeV and 1.36 x 10{sup -2} at mean neutrino energy 2.2 GeV.
Azimuthal dependence of pion source radii in Pb+Au collisions at 158A GeV/c
Adamova, D.; Kushpil, V.; Sumbera, M.; Agakichiev, G.; Belaga, V.; Fomenko, K.; Panebrattsev, Y.; Petchenova, O.; Shimansky, S.; Yurevich, V.; Andronic, A.; Braun-Munzinger, P.; Garabatos, C.; Hering, G.; Holeczek, J.; Maas, A.; Marin, A.; Miskowiec, D.; Rak, J.; Sako, H.
2008-12-15
We present results of a two-pion correlation analysis performed with the Pb+Au collision data collected by the upgraded CERES experiment in the fall of 2000. The analysis was done in bins of the reaction centrality and the pion azimuthal emission angle with respect to the reaction plane. The pion source, deduced from the data, is slightly elongated in the direction perpendicular to the reaction plane, similarly as was observed at the Brookhaven National Laboratory Alternating Gradient Synchrotron and Relativistic Heavy Ion Collider.
Neutral pion production in the [sup 16]O+[sup 27]Al reaction at 94 MeV/nucleon
Badala, A.; Barbera, R.; Palmeri, A.; Pappalardo, G.S.; Riggi, F.; Russo, A.C.; Agodi, C.; Alba, R.; Bellia, G.; Coniglione, R.; Del Zoppo, A.; Finocchiaro, P.; Maiolino, C.; Migneco, E.; Piattelli, P.; Russo, G.; Sapienza, P.; Peghaire, A. Dipartimento di Fisica, Universita di Catania, Corso Italia 57, I95129 Catania Istituto Nazionale di Fisica Nucleare, Laboratorio Nazionale del Sud, Catania Grand Accelerateur National d'Ions Lourds, Caen )
1993-01-01
The production of neutral pions in the reaction [sup 16]O+[sup 27]Al at 94 MeV/nucleon was studied with a multidetector, which includes 180 BaF[sub 2] modules. Kinetic energy spectra for several laboratory angles were measured. The total cross section for neutral pion production was deduced. Results were compared with previous findings on charged pions from the same reaction at the same energy and with the prediction of a dynamical model based on the numerical solution of the Boltzmann-Nordheim-Vlasov equation.
Computed Pion Yields from a Tantalum Rod Target: Comparing MARS15 and GEANT4 Across Proton Energies
NASA Astrophysics Data System (ADS)
Brooks, S. J.; Walaron, K. A.
2006-05-01
The choice of proton driver energy is an important variable in maximising the pion flux available in later stages of the neutrino factory. Simulations of pion production using a range of energies are presented and cross-checked for reliability between the codes MARS15 and GEANT4. The distributions are combined with postulated apertures for the pion decay channel and muon front-end to estimate the usable muon flux after capture losses. Resolution of discrepancies between the codes awaits experimental data in the required energy range.
Present constraints on the H-dibaryon at the physical point from Lattice QCD
Beane, S. R.; Chang, E.; Detmold, W.; Joo, B.; Lin, H. -W.; Luu, T. C.; Orginos, K.; Parreno, A.; Savage, M. J.; Torok, A.; Walker-Loud, A.
2011-11-10
The current constraints from Lattice QCD on the existence of the H-dibaryon are discussed. With only two significant Lattice QCD calculations of the H-dibaryon binding energy at approximately the same lattice spacing, the form of the chiral and continuum extrapolations to the physical point are not determined. In this brief report, an extrapolation that is quadratic in the pion mass, motivated by low-energy effective field theory, is considered. An extrapolation that is linear in the pion mass is also considered, a form that has no basis in the effective field theory, but is found to describe the light-quark mass dependence observed in Lattice QCD calculations of the octet baryon masses. In both cases, the extrapolation to the physical pion mass allows for a bound H-dibaryon or a near-threshold scattering state.
Present constraints on the H-dibaryon at the physical point from Lattice QCD
Beane, S. R.; Chang, E.; Detmold, W.; Joo, B.; Lin, H. -W.; Luu, T. C.; Orginos, K.; Parreno, A.; Savage, M. J.; Torok, A.; et al
2011-11-10
The current constraints from Lattice QCD on the existence of the H-dibaryon are discussed. With only two significant Lattice QCD calculations of the H-dibaryon binding energy at approximately the same lattice spacing, the form of the chiral and continuum extrapolations to the physical point are not determined. In this brief report, an extrapolation that is quadratic in the pion mass, motivated by low-energy effective field theory, is considered. An extrapolation that is linear in the pion mass is also considered, a form that has no basis in the effective field theory, but is found to describe the light-quark mass dependencemore » observed in Lattice QCD calculations of the octet baryon masses. In both cases, the extrapolation to the physical pion mass allows for a bound H-dibaryon or a near-threshold scattering state.« less
Coherent neutrinoproduction of photons and pions in a chiral effective field theory for nuclei
NASA Astrophysics Data System (ADS)
Zhang, Xilin; Serot, Brian D.
2012-09-01
Background: The neutrinoproduction of photons and pions from nucleons and nuclei is relevant to the background analysis in neutrino-oscillation experiments [for example, the MiniBooNE; MiniBooNE Collaboration, A. A. Aquilar-Arevalo , Phys. Rev. Lett.0031-900710.1103/PhysRevLett.100.032301 100, 032301 (2008)]. The production from nucleons and incoherent production with Eν⩽0.5GeV have been studied in B. D. Serot and X. Zhang, Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.86.015501 86, 015501 (2012); and X. Zhang and B. D. Serot, Phys. Rev. C1110-865710.1103/PhysRevC.86.035502 86, 035502 (2012).Purpose: Study coherent productions with Eν⩽0.5GeV. Also address the contributions of two contact terms in neutral current (NC) photon production that are partially related to the proposed anomalous ω(ρ), Z boson, and photon interactions.Methods: We work in the framework of a Lorentz-covariant effective field theory (EFT), which contains nucleons, pions, the Δ (1232) (Δs), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields, and incorporates a nonlinear realization of (approximate) SU(2)L⊗SU(2)R chiral symmetry. A revised version of the so-called “optimal approximation” is applied, where one-nucleon interaction amplitude is factorized out and the medium-modifications and pion wave function distortion are included. The calculation is tested against the coherent pion photoproduction data.Results: The computation shows an agreement with the pion photoproduction data, although precisely determining the Δ modification is entangled with one mentioned contact term. The uncertainty in the Δ modification leads to uncertainties in both pion and photon neutrinoproductions. In addition, the contact term plays a significant role in NC photon production.Conclusions: First, the contact term increases NC photon production by ˜10% assuming a reasonable range of the contact coupling, which however seems not significant enough to explain the Mini
Bose-Einstein correlations between two neutral pions from photoproduction below 1.2 GeV
NASA Astrophysics Data System (ADS)
He, Qinghua; Hashimoto, Ryo; Ishikawa, Takatsugu; Masumoto, Shinichi; Miyabe, Manabu; Muramatsu, Norihito; Shimizu, Hajime; Tajima, Yasuhisa; Tsuchikawa, Yusuke; Yamazaki, Hirohito; Yamazaki, Ryuji; Forest Collaboration
2014-09-01
For the first time, we studied the space-time properties of the excited nucleons in the non-perturbative QCD region, via Bose-Einstein correlations (BEC) between two neutral pions from photoproduction off the proton/deuteron at incident photon energies below 1.2 GeV. In order to measure the Bose-Einstein correlations of two pions, an event mixing technique was developed and proved to be effective. The experiment was carried out at the Research Center for Electron Photon Science (ELPH) at Tohoku University. A 4 π electromagnetic calorimeter complex, named FOREST, was employed to detect neutral pions decaying into photons as well as some charged particles in the final state. In this work, we present the results of the spatial extension of the reaction region obtained from the BEC analysis. In addition, the BEC analysis provides useful information about the underlying mechanism of double neutral pion photoproduction. Preliminary results related to this study will be given.
Zhang Weining; Yang Zhitao; Ren Yanyu
2009-10-15
We examine the characteristic quantities of pion-emitting sources extracted by model-independent imaging analysis in relativistic heavy ion collisions. The moments of the spatial separation of pion pair emission can provide the characteristic information about the source geometry and coherence. They are better for describing the non-Gaussian sources with granular and core-halo structures. An improved granular source model of quark-gluon plasma droplets can reproduce the main characteristics of the two-pion correlation functions and source functions in the experiment of {radical}(s{sub NN})=200 GeV Au+Au collisions. The transverse-momentum dependence of the normalized first-order moments of the separation for the granular source is consistent with that of the usual interferometry results of source radii, after taking into account the Lorentz contraction in the direction of the transverse momentum of the pion pair.
Not Available
1992-12-31
This report summarizes investigations of various pion-nucleus interactions and nucleon-nucleus charge-exchange reactions. The work was carried out with the LAMPF accelerator at the Los Alamos National Laboratory and the cyclotrons at the Paul Scherrer Institute (PSI) near Zurich, Switzerland, and at Indiana University (IUCF), as a collaborative effort among several laboratories and universities. The experimental activity at LAMPF involved measurements of new data on pion double-charge-exchange scattering, some initial work on a new Neutral Meson Spectrometer system, a search for deeply-bound pionic atoms, measurements of elastic scattering, and studies of the (n,p) reaction on various nuclei. At PSI measurements of pion quasielastic scattering were carried out, with detection of the recoil proton. Work on the analysis of data from a previous experiment at PSI on pion absorption in nuclei was continued. This experiment involved using a detector system that covered nearly the full solid angle.
Pion Production from 5-15 GeV Beam for the Neutrino Factory Front-End Study
Prior, Gersende
2010-03-30
For the neutrino factory front-end study, the production of pions from a proton beam of 5-8 and 14 GeV kinetic energy on a Hg jet target has been simulated. The pion yields for two versions of the MARS15 code and two different field configurations have been compared. The particles have also been tracked from the target position down to the end of the cooling channel using the ICOOL code and the neutrino factory baseline lattice. The momentum-angle region of pions producing muons that survived until the end of the cooling channel has been compared with the region covered by HARP data and the number of pions/muons as a function of the incoming beam energy is also reported.
A study of longitudinal charged-pion electroproduction in D, {sup 3}He, and {sup 4}He
Jackson, H.E.; Coulter, K.P.; Geesaman, D.F.
1995-08-01
Recent studies of pion electroproduction on the deuteron carried out by the ANL group at ALS, Saclay, show that even in the weakly-bound deuteron, multinucleon processes alter the electroproduction amplitudes in the forward direction. The data provide the first experimental indications for a significant change in the pion-nucleon coupling for nucleons bound in nuclei. It is clear that forward-angle electroproduction may be a sensitive probe of the properties of the pion coupling in the nuclear medium. At CEBAF, we will study longitudinal charged-pion electroproduction (in the excitation region below the delta isobar) along the direction of the momentum transfer where the charge scattering process dominates. Direct comparison of the cross section per nucleon in deuterium and the helium isotopes with the experimental value for the free nucleon will provide estimates of the strength of the nuclear pion field. A Rosenbluth separation of the longitudinal and transverse cross sections will be performed for four-momentum transfers of 2.5 and 10 fm{sup -2}. Measurements for a number of light nuclei will provide useful data on the sensitivity of longitudinal electroproduction to nuclear binding effects. If current conceptions of pion-exchange currents in nuclei are correct, longitudinal electroproduction will be suppressed at the lower momentum transfer and enhanced at the higher momentum transfer by multinucleon processes. If on the other hand, as suggested by recent data from Drell-Yan studies of antiquark structure functions, there is no such enhancement, a reformulation of pion exchange models of the medium- and short-range properties of nuclear forces will be required. Our proposal to carry out such a series of measurements at CEBAF using the coincident-pair spectrometer system planned for Hall C was approved. Pions will be observed in the short-orbit spectrometer (SOS) which will serve as the second arm.
NASA Astrophysics Data System (ADS)
Song, Taesoo; Ko, Che Ming
2015-01-01
Using the relativistic Vlasov-Uehling-Uhlenbeck (RVUU) equation based on mean fields from the nonlinear relativistic NLρ and NLρ δ models, which have same nuclear equation of state and symmetry energy but different symmetry energy slope parameters, we study the effect of medium modification of the pion-production threshold on the total pion yield and the π-/π+ ratio in Au+Au collisions. We find that the in-medium threshold effect enhances both the total pion yield and the π-/π+ ratio, compared to those without this effect. Furthermore, including the medium modification of the pion-production threshold leads to a larger π-/π+ ratio for the NLρ δ model with a larger symmetry energy parameter than the NLρ model with a smaller symmetry energy parameter, opposite to that found without the in-medium threshold effect. To reproduce the total pion yield measured by the FOPI Collaboration, we introduce a density-dependent cross section for Δ baryon production from nucleon-nucleon collisions, which suppresses the total pion yield but hardly changes the π-/π+ ratio. Because of the small difference in the stiffness of their symmetry energies, the π-/π+ ratios obtained from both the NLρ and NLρ δ models are consistent with the FOPI data within the experimental errors.
1993-09-30
This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991-94 under a grant from the U.S. Department of Energy. Most of these studies involved investigations of various pion-nucleus interactions and nucleon-nucleus charge-exchange reactions. The work was carried out with the LAMPF accelerator at the Los Alamos National Laboratory and the cyclotrons at the Paul Scherrer Institute (PSI) near Zurich, Switzerland, at Indiana University (IUCF), and at TRIUMF in Vancouver, Canada, as collaborative efforts among several laboratories and universities. We have also worked on plans and preparations for new experiments involving studies of the quark structure of nucleons and nuclei, which would be carried out at Fermilab (FNAL), near Chicago, and at the HERA facility at the DESY laboratory in Hamburg, Germany. The NMSU personnel included two faculty members, five postdoctoral research associates, nine graduate students, and one undergraduate student.
Mesic molecular effects in the capture of negative pions stopped in gaseous hydrogen isotopes
NASA Astrophysics Data System (ADS)
Aniol, K. A.; Measday, D. F.; Hasinoff, M. D.; Roser, H. W.; Bagheri, A.; Entezami, F.; Virtue, C.; Stadlbauer, J. M.; Horváth, D.; Salomon, M.; Robertson, B. C.
1983-11-01
The influence of molecular structure on the nuclear capture probability of stopped negative pions has been observed by comparing the π0 gamma-ray spectrum from π- mesons stopped in HD gas to that from a mixture of equal amounts of H2 plus D2. The fraction of stopped pions that are captured by a proton in the H2+D2 mixture is fH2D2=0.417+/-0.004, while for HD it is fHD=0.338+/-0.008, independent of the gas pressure between 6 and 90 atm. The ratio, fH2D2fHD, of the fractions is 1.23+/-0.03.
Neutral-pion-decay gamma rays from the Galaxy and the interstellar gas content
NASA Technical Reports Server (NTRS)
Stecker, F. W.
1973-01-01
Knowledge of the total gamma-ray production rate per H atom from the decay of neutral pions produced in interstellar cosmic-ray interactions is essential for determining the possible amount of interstellar H2. This production rate is recalculated here using the latest accelerator data on neutral pion production in p-p interactions up to about 1500 GeV. A simple but accurate approximation used here resolves the past disagreement over the magnitude of this rate. An upper limit is obtained of (1.51 plus or minus 0.23) times 10 to the -25th power/sec, consistent with the observed upper limit of 1.6 times 10 to the -25th power/sec.
High-energy gamma-ray emission from pion decay in a solar flare magnetic loop
NASA Technical Reports Server (NTRS)
Mandzhavidze, Natalie; Ramaty, Reuven
1992-01-01
The production of high-energy gamma rays resulting from pion decay in a solar flare magnetic loop is investigated. Magnetic mirroring, MHD pitch-angle scattering, and all of the relevant loss processes and photon production mechanisms are taken into account. The transport of both the primary ions and the secondary positrons resulting from the decay of the positive pions, as well as the transport of the produced gamma-ray emission are considered. The distributions of the gamma rays as a function of atmospheric depth, time, emission angle, and photon energy are calculated and the dependence of these distributions on the model parameters are studied. The obtained angular distributions are not sufficiently anisotropic to account for the observed limb brightening of the greater than 10 MeV flare emission, indicating that the bulk of this emission is bremsstrahlung from primary electrons.
Appearance of p-odd nuclear forces in photoproduction of pions on /sup 6/Li
Rekalo, M.P.
1986-01-01
This paper studies P-odd effects in the photoproduction of pions on Li-6 nuclei, ..gamma.. + Li-6 ..-->.. ..pi../sup +/ + He-6. Collisions of linearly and circularly polarized photons with a polarized nuclear target are studied, and in addition both vectorial and tensorial polarization are taken into account. It is shown that in the general case P-odd effects in ..gamma.. + Li-6..--> pi../sup +/ + He-6 are characterized by 18 real structure functions, which determine different P-odd asymmetries in the angular distribution of the pions. The structure functions in their turn depend on different products of three p-even and three p-odd amplitudes of the process.
Rotating band pion production targets for muon colliders and neutrino factories
NASA Astrophysics Data System (ADS)
King, B. J.
2000-08-01
An update is presented on a conceptual design for a pion production target station using a rotating cupronickel band and that was originally proposed for use at a muon collider facility with a 4 MW pulsed proton beam. After reviewing the salient design features and motivations for this target, ongoing studies are described that are attempting to benchmark the thermal stresses and radiation damage on the target band using data from the Fermilab antiproton source and other operating targets. Possible parameter optimizations and alternative technologies for the rotating band are surveyed, including discussion on the the various proton beam parameters that might be encountered for rotating band targets at either muon colliders or neutrino factories. Finally, an outline is proposed for a possible R&D path towards capability for the actual construction of rotating band pion production targets.
Chiral effective-field theory in the Delta(1232) region : II. radiative pion photoproduction
Vladimir Pascalutsa; Marc Vanderhaeghen
2007-10-12
We present a theoretical study of the radiative pion photoproduction on the nucleon ($\\gamma N \\rightarrow \\pi N \\gamma'$) in the $\\De$-resonance region, with the aim to determine the magnetic dipole moment (MDM) of the $\\Delta^+(1232)$. The study is done within the framework of chiral effective-field theory where the expansion is performed (to next-to-leading order) in the $\\delta$ power-counting scheme which is an extension of chiral perturbation theory to the $\\Delta$-resonance energy region. We present in detail the results for the absorptive part of the $\\Delta$ MDM, as well as a sensitivity study for the radiative pion photoproduction observables on the real part of the $\\Delta$ MDM. We find that an asymmetry for circular polarization of the photon beam may provide a model-independent way to measure the $\\Delta$ MDM.
Single-Spin Asymmetries AULsinϕh in Semi-Inclusive Pions Production
NASA Astrophysics Data System (ADS)
Lu, Zhun; Mao, Wenjuan
2016-02-01
The single-spin asymmetry AULsinϕh of charged and neutral pion production in semi-inclusive deep-inelastic scattering on longitudinally polarized nucleon targets is studied. We particularly consider the effects of the twist-3 transverse-momentum dependent distribution functions fL⊥ and hL, which are calculated in two different spectator-diquark models. We estimate the asymmetry for π+, π‑ and π0 produced off the proton target at HERMES and compare the results with the HERMES measurements. We also predict the same asymmetric moment for different pions at the kinematics of CLAS 5.5 GeV on a proton target, as well as at COMPASS on a deuteron target for comparison.
Sivers asymmetries for inclusive pion and kaon production in deep-inelastic scattering
Ellis, John; Hwang, Dae Sung; Kotzinian, Aram
2009-10-01
We calculate the Sivers distribution functions induced by the final-state interaction due to one-gluon exchange in diquark models of a nucleon structure, treating the cases of scalar and axial-vector diquarks with both dipole and Gaussian form factors. We use these distribution functions to calculate the Sivers single-spin asymmetries for inclusive pion and kaon production in deep-inelastic scattering. We compare our calculations with the results of HERMES and COMPASS, finding good agreement for {pi}{sup +} production at HERMES, and qualitative agreement for {pi}{sup 0} and K{sup +} production. Our predictions for pion and kaon production at COMPASS could be probed with increased statistics. The successful comparison of our calculations with the HERMES data constitutes prima facie evidence that the quarks in the nucleon have some orbital angular momentum in the infinite-momentum frame.
Reanalysis of bubble chamber measurements of muon-neutrino induced single pion production
NASA Astrophysics Data System (ADS)
Wilkinson, Callum; Rodrigues, Philip; Cartwright, Susan; Thompson, Lee; McFarland, Kevin
2014-12-01
There exists a long-standing disagreement between bubble chamber measurements of the single pion production channel νμp →μ-p π+ from the Argonne and Brookhaven National Laboratories. We digitize and reanalyze data from both experiments to produce cross-section ratios for various interaction channels, for which the flux uncertainties cancel, and find good agreement between the experiments. By multiplying the cross-section ratio by the well-understood charged-current quasielastic cross section on free nucleons, we extract single-pion production cross sections which do not depend on the flux normalization predictions. The νμp →μ-p π+ cross sections we extract show good agreement between the ANL and BNL data sets.
Pion nucleus single charge exchange reactions above the. delta. (1232) resonance
Rokni, S.H.
1987-06-01
Forward-angle differential cross sections for the (..pi../sup +/, ..pi../sup 0/) reaction leading to the Isobaric Analog State in the residual nuclei at 300, 425, 500 and 550 MeV have been measured. Targets ranged in mass from /sup 7/Li to /sup 208/Pb. A description of the experimental setup and the analysis is presented. The 0/sup 0/ cross sections are found to rise markedly between 300 and 425 MeV, contrary to the extrapolation from the lower energy data and to the behavior of the free pion-nucleon single charge exchange process. The angular distributions are sharply forward peaked. Systematics of the data indicate increased volume penetration with increasing pion beam energy. The cross sections are compared with the results of Glauber model calculations indicating the significance of higher order processes even at these energies. 67 refs., 40 figs., 22 tabs.
The atmospheric charged kaon/pion ratio using seasonal variation methods
NASA Astrophysics Data System (ADS)
Grashorn, E. W.; de Jong, J. K.; Goodman, M. C.; Habig, A.; Marshak, M. L.; Mufson, S.; Osprey, S.; Schreiner, P.
2010-04-01
Observed since the 1950s, the seasonal effect on underground muons is a well studied phenomenon. The interaction height of incident cosmic rays changes as the temperature of the atmosphere changes, which affects the production height of mesons (mostly pions and kaons). The decay of these mesons produces muons that can be detected underground. The production of muons is dominated by pion decay, and previous work did not include the effect of kaons. In this work, the methods of Barrett and MACRO are extended to include the effect of kaons. These efforts give rise to a new method to measure the atmospheric K/π ratio at energies beyond the reach of current fixed target experiments. These methods were applied to data from the MINOS far detector. A method is developed for making these measurements at other underground detectors, including OPERA, Super-K, IceCube, Baksan and the MINOS near detector.
Weak quasielastic production of hyperons and threshold production of two pions
NASA Astrophysics Data System (ADS)
Singh, S. K.; Athar, M. Sajjad; Alam, M. Rafi; Chauhan, Shikha; Hernández, E.; Nieves, J.; Valverde, M.; Vacas, M. J. Vicente
2015-10-01
We have studied quasielastic charged current hyperon production induced by v¯μ on free nucleon and the nucleons bound inside the nucleus and the results are presented for several nuclear targets like 40Ar, 56Fe and 208Pb. The hyperon-nucleon transition form factors are determined from neutrino-nucleon scattering and semileptonic decays of neutron and hyperons using SU(3) symmetry. The nuclear medium effects(NME) due to Fermi motion and final state interaction(FSI) effect due to hyperon-nucleon scattering have been taken into account. Also we have studied two pion production at threshold induced by neutrinos off nucleon targets. The contribution of nucleon, pion, and contact terms are calculated using Lagrangian given by nonlinear σ model. The contribution of the Roper resonance has also been taken into account. The numerical results for the cross sections are presented and compared with the experimental results from ANL and BNL.
A relativistic meson-exchange model of pion-nucleon scattering
Lee, T.S.H.; Hung, C.T.; Yang, S.N.
1995-08-01
Pion-nucleon scattering is investigated using the Kadshevsky three-dimensional reduction of the Bethe-Salpeter equation. The resulting potential includes the direct and crossed N and {Delta} terms, and the t-channel {sigma}- and {rho}-exchange terms. The nucleon-pole condition is imposed to define the renormalization of the nucleon mass and the {pi}NN coupling constant. A mixture of the scalar and vector {sigma}{pi}{pi} couplings is introduced to simulate the broad width of the s-wave correlated two-pion exchange mechanism. Good descriptions of the {pi}N phase shifts up to 400 MeV have been obtained in all S- and P-waves. The off-shell behavior for our model differs significantly from that obtained using different reductions. A paper describing our results was published.
Inelastic-interaction mean free path of negative pions in tungsten
NASA Technical Reports Server (NTRS)
Cheshire, D. L.; Huggett, R. W.; Jones, W. V.; Rountree, S. P.; Schmidt, W. K. H.; Kurz, R. J.; Bowen, T.; Delise, D. A.; Krider, E. P.; Orth, C. D.
1975-01-01
The inelastic-interaction mean free paths (lambda) of 5-, 10-, and 15-GeV/c pions have been measured by determining the distribution of first-interaction locations in a modular tungsten-scintillator ionization spectrometer. In addition to commonly used interaction signatures of a few (2-5) particles in two or three consecutive modules, a chi-squared distribution is employed to calculate the probability that the first interaction occurred at a specific depth in the spectrometer. This latter technique seems to be more reliable than use of the simpler criteria. No significant dependence of lambda on energy has been observed. In tungsten, lambda for pions is 206 (plus or minus 6) g/sq cm.
Pion cloud and sea quark flavor asymmetry in the impact parameter representation
Strikman, Mark; Weiss, Christian
2008-07-01
We study large-distance contributions to the nucleon parton densities in the transverse coordinate (impact parameter) representation based on generalized parton distributions (GPDs). Chiral dynamics generates a distinct component of the partonic structure, located at momentum fractions x ~< M_pi / M_N and transverse distances b ~ 1/M_pi. We analyze the phenomenological "pion cloud" model of the flavor asymmetry dbar(x) - ubar(x) and quantify what fraction of the calculated asymmetry results from the universal large-distance region. Our findings indicate that a two-component picture of the nucleon's partonic structure -- a "core" antiquark distribution at b < b_core ~ 0.55 fm which vanishes at x -> 0, and the universal large-distance pion cloud at b > b_core -- could naturally account for the x-dependence of the measured asymmetry.
Charged-Current Neutral Pion production at SciBooNE
Catala-Perez, J.; /Valencia U., IFIC
2009-10-01
SciBooNE, located in the Booster Neutrino Beam at Fermilab, collected data from June 2007 to August 2008 to accurately measure muon neutrino and anti-neutrino cross sections on carbon below 1 GeV neutrino energy. SciBooNE is studying charged current interactions. Among them, neutral pion production interactions will be the focus of this poster. The experimental signature of neutrino-induced neutral pion production is constituted by two electromagnetic cascades initiated by the conversion of the {pi}{sup 0} decay photons, with an additional muon in the final state for CC processes. In this poster, I will present how we reconstruct and select charged-current muon neutrino interactions producing {pi}{sup 0}'s in SciBooNE.
Pion-nucleon scattering in the Skyrme model and the P-wave Born amplitudes
NASA Astrophysics Data System (ADS)
Hayashi, A.; Saito, S.; Uehara, M.
1991-03-01
We treat fluctuating pion fields around a rotating Skyrmion by means of Dirac's quantization method. The rotational collective motion of the Skyrmion is described by collective coordinates, and conventional gauge-fixing conditions are imposed. Taking into account all the relevant terms at the tree level appearing in the Hamiltonian, we show that pion-nucleon scattering amplitudes exhibit the P-wave Born amplitudes attributed to the Yukawa coupling of order √Nc , which is consistent with the prediction of chiral symmetry such as the Adler-Weisberger relation. This resolves the difficulty that the Skyrme model predicts a wrong Nc dependence for the coupling of order N-3/2c.
Nonmonotonic Target Excitation Dependence of Pion Clans in Relativistic Nucleus-Nucleus Collisions
NASA Astrophysics Data System (ADS)
Ghosh, Dipak; Deb, Argha; Dutta, Srimonti
Target excitation dependence of fluctuation of produced pions (i.e. classifying data of the fluctuation pattern on pions on the basis of the number of gray tracks) is studied for nucleus-nucleus collisions at different projectile energies. In each set the experimental multiplicity distribution is compared with the negative binomial distribution (NBD), which is found to describe the experimental distribution quite well. Target excitation dependence is studied in respect of the clan model parameters bar {n}c and bar {N}, which are extracted from the NBD fit parameters bar {n} and k. A detailed comparison between different interactions at the same energy and the same interactions at different energies is also drawn. A nonmonotonic dependence of D2/bar {n} on
Quark degrees of freedom in the production of soft pion jets
Okorokov, V. A. E-mail: Okorokov@bnl.gov
2015-05-15
Experimental results obtained by studying the properties of soft jets in the 4-velocity space at √s ∼ 2 to 20 GeV are presented. The changes in the mean distance from the jet axis to the jet particles, the mean kinetic energy of these particles, and the cluster dimension in response to the growth of the collision energy are consistent with the assumption that quark degrees of freedom manifest themselves in processes of pion-jet production at intermediate energies. The energy at which quark degrees of freedom begin to manifest themselves experimentally in the production of soft pion jets is estimated for the first time. The estimated value of this energy is 2.8 ± 0.6 GeV.
Pion-to-Photon Transition Distribution Amplitudes in the Non-Local Chiral Quark Model
NASA Astrophysics Data System (ADS)
Kotko, P.; Praszałowicz, M.
2009-01-01
We apply the non-local chiral quark model to study vector and axial pion-to-photon transition amplitudes that are needed as a nonperturbative input to estimate the cross-section of pion annihilation into the real and virtual photon. We use a simple form of the non-locality that allows to perform all calculations in the Minkowski space and guaranties polynomiality of the TDAs. We note only residual dependence on the precise form of the cut-off function, however vector TDA that is symmetric in skewedness parameter in the local quark model is no longer symmetric in the non-local case. We calculate also the transition form-factors and compare them with existing experimental parametrizations.
Sivers asymmetries for inclusive pion and kaon production in deep-inelastic scattering
NASA Astrophysics Data System (ADS)
Ellis, John; Hwang, Dae Sung; Kotzinian, Aram
2009-10-01
We calculate the Sivers distribution functions induced by the final-state interaction due to one-gluon exchange in diquark models of a nucleon structure, treating the cases of scalar and axial-vector diquarks with both dipole and Gaussian form factors. We use these distribution functions to calculate the Sivers single-spin asymmetries for inclusive pion and kaon production in deep-inelastic scattering. We compare our calculations with the results of HERMES and COMPASS, finding good agreement for π+ production at HERMES, and qualitative agreement for π0 and K+ production. Our predictions for pion and kaon production at COMPASS could be probed with increased statistics. The successful comparison of our calculations with the HERMES data constitutes prima facie evidence that the quarks in the nucleon have some orbital angular momentum in the infinite-momentum frame.
Polarization analysis of vector-meson production in pion-nucleon interactions
NASA Astrophysics Data System (ADS)
Arash, Firooz; Habibi, Mohammad F.
1993-07-01
In view of the growing (though still incomplete) set of data on vector-meson production in pion-nucleon interactions, the polarization structure of this reaction is presented, together with polarization tests of one-particle-exchange processes in the s and t channels, as well as polarization tests for the Skyrmion model. The amplitude-observable relations are exhibited in the helicity, transversity, and planar-transverse frames. The desirable direction of future experimental programs is also outlined.
Belyaev, I. M. Golubkov, D. Yu. Egorychev, V. Yu. Polikarpov, S. M. Savrina, D. V.
2015-12-15
The calibration of the LHCb electromagnetic calorimeter is a multistep procedure aimed at reconstructing photon and electron energies to a precision not poorer than 2%. A method based on measuring the neutral-pion invariantmass is applied at the last step of this procedure. A regular application of this method makes it possible to improve substantially the resolution for particles that decay through channels featuring electrons and photons in the final state.
Nuclear Targets for a Precision Measurement of the Neutral Pion Radiative Width
Martel, Philippe; Clinton, Eric; McWilliams, R.; Lawrence, Dave; Miskimen, Rory; Ahmidouch, Abdellah; Ambrozewicz, Pawel; Asaturyan, Arshak; Baker, O.; Benton, LaRay; Bernstein, Aron; Cole, Philip; Collins, Patrick; Dale, Daniel; Danagoulian, Samuel; Davidenko, G.; Demirchyan, Raphael; Deur, Alexandre; DOLGOLENKO, A.; Dzyubenko, Georgiy; Evdokimov, Anatoly; Feng, JIng; Gabrielyan, Marianna; Gan, Liping; Gasparian, Ashot; Glamazdin, Oleksandr; Goryachev, Vladimir; Gyurjyan, Vardan; Hardy, K.; Ito, Mark; Khandaker, Mahbubul; Kingsberry, Paul; Kolarkar, Ameya; Konchatnyi, Mykhailo; Korchin, O.; Korsch, Wolfgang; Kowalski, Stanley; Kubantsev, Mikhail; Kubarovsky, Valery; LARIN, Ilya; MATVEEV, V.; McNulty, Dustin; Milbrath, Brian; Minehart, Ralph; Mochalov, Vasiliy; Mtingwa, Sekazi; Nakagawa, Itaru; Overby, Steven; Pasyuk, Evgueni; Payen, Marvin; Pedroni, Ronald; Prok, Yelena; Ritchie, Barry; Salgado, Carlos; Sitnikov, Anatoly; Sober, Daniel; Stephens, W.; Teymurazyan, Aram; Underwood, Jarreas; VASILIEV, A.; VEREBRYUSOV, V.; Vishnyakov, Vladimir; Wood, Michael
2009-12-01
A technique is presented for precision measurements of the area densities, density * T, of approximately 5% radiation length carbon and 208Pb targets used in an experiment at Jefferson Laboratory to measure the neutral pion radiative width. The precision obtained in the area density for the carbon target is +/- 0.050%, and that obtained for the lead target through an x-ray attenuation technique is +/- 0.43%.
Nuclear targets for a precision measurement of the neutral pion radiative width
NASA Astrophysics Data System (ADS)
Martel, P.; Clinton, E.; McWilliams, R.; Lawrence, D.; Miskimen, R.; Ahmidouch, A.; Ambrozewicz, P.; Asratyan, A.; Baker, K.; Benton, L.; Bernstein, A.; Cole, P.; Collins, P.; Dale, D.; Danagoulian, S.; Davidenko, G.; Demirchyan, R.; Deur, A.; Dolgolenko, A.; Dzyubenko, G.; Evdokimov, A.; Feng, J.; Gabrielyan, M.; Gan, L.; Gasparian, A.; Glamazdin, O.; Goryachev, V.; Gyurjyan, V.; Hardy, K.; Ito, M.; Khandaker, M.; Kingsberry, P.; Kolarkar, A.; Konchatnyi, M.; Korchin, O.; Korsch, W.; Kowalski, S.; Kubantsev, M.; Kubarovsky, V.; Larin, I.; Matveev, V.; McNulty, D.; Milbrath, B.; Minehart, R.; Mochalov, V.; Mtingwa, S.; Nakagawa, I.; Overby, S.; Pasyuk, E.; Payen, M.; Pedroni, R.; Prok, Y.; Ritchie, B.; Salgado, C.; Sitnikov, A.; Sober, D.; Stephens, W.; Teymurazyan, A.; Underwood, J.; Vasiliev, A.; Verebryusov, V.; Vishnyakov, V.; Wood, M.
2009-12-01
A technique is presented for precision measurements of the area densities, ρT, of approximately 5% radiation length carbon and 208Pb targets used in an experiment at Jefferson Laboratory to measure the neutral pion radiative width. The precision obtained in the area density for the carbon target is ±0.050%, and that obtained for the lead target through an X-ray attenuation technique is ±0.43%.
Observation of pion-related effects in the photofission of preactinide nuclei
Arruda-Neto, J.D.T.; Saito, T.; Sugawara, M.; Tamae, T.; Miyase, H.; Abe, K.; Takahisa, K.; Konno, O.; Oikawa, M. ); Simionatto, S. )
1993-10-01
The absolute electrofission cross sections of Au and Ta were measured in the range 25--180 MeV. The deduced photofission cross section shows, for both Au and Ta, a pronounced dip around the photopion threshold ([similar to]140 MeV). This ([gamma],[ital f]) dip is interpreted as a consequence of a probable photopion absorption in a stopped pion regime.''
Measurement of Charged Current Charged Single Pion Production in SciBooNE
Hiraide, K.
2008-10-01
The SciBooNE experiment is designed to measure neutrino cross sections on carbon around one GeV region. Charged current single charged pion production is a dominant background process for {nu}{sub {mu}} to {nu}{sub x} oscillation experiments with a few-GeV neutrino beam, and thus a precision measurement of the cross section is essential. This article reports preliminary results on this process from SciBooNE.
Enrico Fermi: The First Chain Reactor (with Film) and Pion-Proton Scattering
Martin, Ron
2003-01-08
A twenty minute film will be shown depicting the first nuclear chain reactor at the University of Chicago on December 2, 1942. The film was made of a re-enactment in 1952 and is narrated by Arthur Compton and Enrico Fermi. After the film, Ronald Martin will talk about his experiences on pion-proton scattering with Enrico Fermi at the Chicago synchrocyclotron in the fifties.
On the potential role of the Collins effect in A_N in pp --> pion X
Anselmino, Mauro; Boglione, Mariaelena; D'Alesio, Umberto; Leader, Elliot; Melis, Stefano; Murgia, Francesco; Prokudin, Alexey
2013-10-01
Transverse single spin asymmetries in pp --> pion X processes, while on a quite firm ground experimentally, are still a much debated phenomenological issue. We consider them in a transverse momentum dependent factorization scheme. After revisiting a previous result, we give new estimates of the Collins contribution by adopting the latest information on the Collins and transversity functions, as extracted from SIDIS and e+e- data.