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.
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.
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.
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.
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.
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.
Chemical nonequilibrium for interacting bosons: Applications to the pion gas
NASA Astrophysics Data System (ADS)
Fernández-Fraile, D.; Gómez Nicola, A.
2009-09-01
We consider an interacting pion gas in a stage of the system evolution where thermal but not chemical equilibrium has been reached, i.e., for temperatures between thermal and chemical freeze-out Tther
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.
HBT Pion Interferometry with Phenomenological Mean Field Interaction
NASA Astrophysics Data System (ADS)
Hattori, K.
2010-11-01
To extract information on hadron production dynamics in the ultrarelativistic heavy ion collision, the space-time structure of the hadron source has been measured using Hanbury Brown and Twiss interferometry. We study the distortion of the source images due to the effect of a final state interaction. We describe the interaction, taking place during penetrating through a cloud formed by evaporating particles, in terms of a one-body mean field potential localized in the vicinity of the source region. By adopting the semiclassical method, the modification of the propagation of an emitted particle is examined. In analogy to the optical model applied to nuclear reactions, our phenomenological model has an imaginary part of the potential, which describes the absorption in the cloud. In this work, we focus on the pion interferometry and mean field interaction obtained using a phenomenological pipi forward scattering amplitude in the elastic channels. The p-wave scattering wit h rho meson resonance leads to an attractive mean field interaction, and the presence of the absorptive part is mainly attributed to the formation of this resonance. We also incorporate a simple time dependence of the potential reflecting the dynamics of the evaporating source. Using the obtained potential, we examine how and to what extent the so-called HBT Gaussian radius is varied by the modification of the propagation.
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.
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- 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.
Nucleon-nucleon interaction with one-pion exchange and instanton-induced interactions
NASA Astrophysics Data System (ADS)
Vanamali, C. S.; Kumar, K. B. Vijaya
2016-11-01
Singlet (S10) and triplet (S31) nucleon-nucleon potentials are obtained in the framework of the SU(2) nonrelativistic quark model using the resonating-group method in the Born-Oppenheimer approximation. The full Hamiltonian used in the investigation includes the kinetic energy, two-body confinement potential, one-gluon-exchange potential (OGEP), one-pion exchange potential (OPEP), and instanton induced interaction (III), which includes the effect of quark exchange between the nucleons. The contribution of the OGEP, III, and OPEP to the nucleon-nucleon adiabatic potential is discussed.
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.
Multi-Pion Systems in Lattice QCD and the Three-Pion Interaction
Silas Beane; William Detmold; Thomas Luu; Konstantinos Orginos; Assumpta Parreno; Martin Savage; Aaron Torok
2007-10-04
The ground-state energies of 2, 3, 4 and 5 Π+’s in a spatial-volume V ~ (2.5 fm)3 are computed with lattice QCD. By eliminating the leading contribution from three- Π+ interactions, particular combinations of these n- Π+ ground-state energies provide precise extractions of the Π+ Π+ scattering length that are in agreement with that obtained from calculations involving only two Π+’s. The three- Π+ interaction can be isolated by forming other combinations of the n- Π+ ground-state energies, and we find a result that is consistent with a repulsive three-Π+ interaction for mΠ ≲ 350 MeV.
Ratio of Pion Kaon Production in Proton Carbon Interactions
Lebedev, Andrey V.
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^{+}/π^{+}, K^{-}/π^{-}, K^{-}/K^{+}, and π^{-}/π^{+} 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.
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- 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.
Possibility of measuring Adler angles in charged current single pion neutrino-nucleus interactions
NASA Astrophysics Data System (ADS)
Sánchez, F.
2016-05-01
Uncertainties in modeling neutrino-nucleus interactions are a major contribution to systematic errors in long-baseline neutrino oscillation experiments. Accurate modeling of neutrino interactions requires additional experimental observables such as the Adler angles which carry information about the polarization of the Δ resonance and the interference with nonresonant single pion production. The Adler angles were measured with limited statistics in bubble chamber neutrino experiments as well as in electron-proton scattering experiments. We discuss the viability of measuring these angles in neutrino interactions with nuclei.
CP violation and kaon-pion interactions in B→Kπ+π- decays
NASA Astrophysics Data System (ADS)
El-Bennich, B.; Furman, A.; Kamiński, R.; Leśniak, L.; Loiseau, B.; Moussallam, B.
2009-05-01
We study CP violation and the contribution of the strong kaon-pion interactions in the three-body B→Kπ+π- decays. We extend our recent work on the effect of the two-pion S- and P-wave interactions to that of the corresponding kaon-pion ones. The weak amplitudes have a first term derived in QCD factorization and a second one as a phenomenological contribution added to the QCD penguin amplitudes. The effective QCD coefficients include the leading order contributions plus next-to-leading order vertex and penguins corrections. The matrix elements of the transition to the vacuum of the kaon-pion pairs, appearing naturally in the factorization formulation, are described by the strange Kπ scalar (S-wave) and vector (P-wave) form factors. These are determined from Muskhelishvili-Omn e s coupled channel equations using experimental kaon-pion T-matrix elements, together with chiral symmetry and asymptotic QCD constraints. From the scalar form factor study, the modulus of the K0*(1430) decay constant is found to be (32±5)MeV. The additional phenomenological amplitudes are fitted to reproduce the Kπ effective mass and helicity angle distributions, the B→K*(892)π branching ratios and the CP asymmetries of the recent data from Belle and BABAR collaborations. We use also the new measurement by the BABAR group of the phase difference between the B0 and Bmacr 0 decay amplitudes to K*(892)π. Our predicted B±→K0*(1430)π±, K0*(1430)→K±π∓ branching fraction, equal to (11.6±0.6)×10-6, is smaller than the result of the analyzes of both collaborations. For the neutral B0 decays, the predicted value is (11.1±0.5)×10-6. In order to reduce the large systematic uncertainties in the experimental determination of the B→K0*(1430)π branching fractions, a new parametrization is proposed. It is based on the Kπ scalar form factor, well constrained by theory and experiments other than those of B decays.
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.
Gamberg, Leonard; Schlegel, Marc
2010-01-18
In the factorized picture of semi-inclusive hadronic processes the naive time reversal-odd parton distributions exist by virtue of the gauge link which renders it color gauge invariant. The link characterizes the dynamical effect of initial/final-state interactions of the active parton due soft gluon exchanges with the target remnant. Though these interactions are non-perturbative, studies of final-state interaction have been approximated by perturbative one-gluon approximation in Abelian models. We include higher-order contributions by applying non-perturbative eikonal methods incorporating color degrees of freedom in a calculation of the Boer-Mulders function of the pion. Lastly, using this framework we explore under what conditions the Boer Mulders function can be described in terms of factorization of final state interactions and a spatial distribution in impact parameter space.
Gamberg, Leonard; Schlegel, Marc
2010-01-18
In the factorized picture of semi-inclusive hadronic processes the naive time reversal-odd parton distributions exist by virtue of the gauge link which renders it color gauge invariant. The link characterizes the dynamical effect of initial/final-state interactions of the active parton due soft gluon exchanges with the target remnant. Though these interactions are non-perturbative, studies of final-state interaction have been approximated by perturbative one-gluon approximation in Abelian models. We include higher-order contributions by applying non-perturbative eikonal methods incorporating color degrees of freedom in a calculation of the Boer-Mulders function of the pion. Lastly, using this framework we explore under what conditionsmore » the Boer Mulders function can be described in terms of factorization of final state interactions and a spatial distribution in impact parameter space.« less
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)
Le, Trung; Minerva Collaboration
2014-09-01
MINERvA is a neutrino scattering experiment which uses the intense neutrino beam from the NuMI beam line at FNAL. The detector employs high spatial resolution, is fully active, and designed to study interactions of neutrinos using different nuclei. We present the differential cross sections for single neutral pion produced by charged-current interactions of anti-neutrinos in plastic scintillator. We also compare the differential cross sections to predictions by the GENIE event generator.
NASA Astrophysics Data System (ADS)
Kullenberg, C. T.; Mishra, S. R.; Seaton, M. B.; Kim, J. J.; Tian, X. C.; Scott, A. M.; Kirsanov, M.; Petti, R.; Alekhin, S.; Astier, P.; Autiero, D.; Baldisseri, A.; Baldo-Ceolin, M.; Banner, M.; Bassompierre, G.; Benslama, K.; Besson, N.; Bird, I.; Blumenfeld, B.; Bobisut, F.; Bouchez, J.; Boyd, S.; Bueno, A.; Bunyatov, S.; Camilleri, L.; Cardini, A.; Cattaneo, P. W.; Cavasinni, V.; Cervera-Villanueva, A.; Challis, R.; Chukanov, A.; Collazuol, G.; Conforto, G.; Conta, C.; Contalbrigo, M.; Cousins, R.; Degaudenzi, H.; De Santo, A.; Del Prete, T.; Di Lella, L.; do Couto e Silva, E.; Dumarchez, J.; Ellis, M.; Feldman, G. J.; Ferrari, R.; Ferrère, D.; Flaminio, V.; Fraternali, M.; Gaillard, J.-M.; Gangler, E.; Geiser, A.; Geppert, D.; Gibin, D.; Gninenko, S.; Godley, A.; Gomez-Cadenas, J.-J.; Gosset, J.; Gößling, C.; Gouanère, M.; Grant, A.; Graziani, G.; Guglielmi, A.; Hagner, C.; Hernando, J.; Hurst, P.; Hyett, N.; Iacopini, E.; Joseph, C.; Juget, F.; Kent, N.; Klimov, O.; Kokkonen, J.; Kovzelev, A.; Krasnoperov, A.; Kulagin, S.; Lacaprara, S.; Lachaud, C.; Lakić, B.; Lanza, A.; La Rotonda, L.; Laveder, M.; Letessier-Selvon, A.; Levy, J.-M.; Ling, J.; Linssen, L.; Ljubičić, A.; Long, J.; Lupi, A.; Lyubushkin, V.; Marchionni, A.; Martelli, F.; Méchain, X.; Mendiburu, J.-P.; Meyer, J.-P.; Mezzetto, M.; Moorhead, G. F.; Naumov, D.; Nédélec, P.; Nefedov, Yu.; Nguyen-Mau, C.; Orestano, D.; Pastore, F.; Peak, L. S.; Pennacchio, E.; Pessard, H.; Placci, A.; Polesello, G.; Pollmann, D.; Polyarush, A.; Poulsen, C.; Popov, B.; Rebuffi, L.; Rico, J.; Riemann, P.; Roda, C.; Rubbia, A.; Salvatore, F.; Samoylov, O.; Schahmaneche, K.; Schmidt, B.; Schmidt, T.; Sconza, A.; Sevior, M.; Sillou, D.; Soler, F. J. P.; Sozzi, G.; Steele, D.; Stiegler, U.; Stipčević, M.; Stolarczyk, Th.; Tareb-Reyes, M.; Taylor, G. N.; Tereshchenko, V.; Toropin, A.; Touchard, A.-M.; Tovey, S. N.; Tran, M.-T.; Tsesmelis, E.; Ulrichs, J.; Vacavant, L.; Valdata-Nappi, M.; Valuev, V.; Vannucci, F.; Varvell, K. E.; Veltri, M.; Vercesi, V.; Vidal-Sitjes, G.; Vieira, J.-M.; Vinogradova, T.; Weber, F. V.; Weisse, T.; Wilson, F. F.; Winton, L. J.; Wu, Q.; Yabsley, B. D.; Zaccone, H.; Zuber, K.; Zuccon, P.
2009-11-01
We present a study of exclusive neutral pion production in neutrino-nucleus Neutral Current interactions using data from the NOMAD experiment at the CERN SPS. The data correspond to 1.44 ×106 muon-neutrino Charged Current interactions in the energy range 2.5 ⩽Eν ⩽ 300 GeV. Neutrino events with only one visible π0 in the final state are expected to result from two Neutral Current processes: coherent π0 production, ν + A → ν + A +π0 and single π0 production in neutrino-nucleon scattering. The signature of coherent π0 production is an emergent π0 almost collinear with the incident neutrino while π0's produced in neutrino-nucleon deep inelastic scattering have larger transverse momenta. In this analysis all relevant backgrounds to the coherent π0 production signal are measured using data themselves. Having determined the backgrounds, and using the Rein-Sehgal model for the coherent π0 production to compute the detection efficiency, we obtain 4630 ± 522 (stat) ± 426 (syst) corrected coherent-π0 events with Eπ0 ⩾ 0.5 GeV. We measure σ (νA → νAπ0) = [ 72.6 ± 8.1 (stat) ± 6.9 (syst) ] ×10-40 cm2 /nucleus. This is the most precise measurement of the coherent π0 production to date.
Eberly, Brandon M.
2014-01-01
Precise knowledge of neutrino-nucleus interactions is increasingly important as neutrino oscillation measurements transition into the systematics-limited era. In addition to modifying the initial interaction, the nuclear medium can scatter and absorb the interaction by-products through final state interactions, changing the types and kinematic distributions of particles seen by the detector. Recent neutrino pion production data from MiniBooNE is inconsistent with the final state interaction strength predicted by models and theoretical calculations, and some models fit best to the MiniBooNE data only after removing final state interactions entirely. This thesis presents a measurement of dσ/dT_{π} and dσ/dθ_{π} for muon-neutrino charged current charged pion production in the MINER A scintillator tracker. MINER A is a neutrino-nucleus scattering experiment installed in the few-GeV NuMI beam line at Fermilab. The analysis is limited to neutrino energies between 1.5-10 GeV. Dependence on invariant hadronic mass W is studied through two versions of the analysis that impose the limits W < 1.4 GeV and W < 1.8 GeV. The lower limit on W increases compatibility with the MiniBooNE pion data. The shapes of the differential cross sections, which depend strongly on the nature of final state interactions, are compared to Monte Carlo and theoretical predictions. It is shown that the measurements presented in this thesis favor models that contain final state interactions. Additionally, a variety of neutrino-nucleus interaction models are shown to successfully reproduce the thesis measurements, while simultaneously failing to describe the shape of the MiniBooNE data.
Single neutral pion production by charged-current νbarμ interactions on hydrocarbon at
NASA Astrophysics Data System (ADS)
Le, T.; Palomino, J. L.; Aliaga, L.; Altinok, O.; Bercellie, A.; Bodek, A.; Bravar, A.; Brooks, W. K.; Butkevich, A.; Martinez Caicedo, D. A.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Devan, J.; Dytman, S. A.; Díaz, G. A.; Eberly, B.; Felix, J.; Fields, L.; Fine, R.; Gago, A. M.; Gallagher, H.; Gran, R.; Harris, D. A.; Higuera, A.; Hurtado, K.; Kordosky, M.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Miller, J.; Morfín, J. G.; Mousseau, J.; Nelson, J. K.; Norrick, A.; Osta, J.; Paolone, V.; Park, J.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ransome, R. D.; Ray, H.; Ren, L.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Schmitz, D. W.; Sobczyk, J. T.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Yepes-Ramirez, H.; Zavala, G.; Zhang, D.; Ziemer, B. P.
2015-10-01
Single neutral pion production via muon antineutrino charged-current interactions in plastic scintillator (CH) is studied using the MINERvA detector exposed to the NuMI low-energy, wideband antineutrino beam at Fermilab. Measurement of this process constrains models of neutral pion production in nuclei, which is important because the neutral-current analog is a background for νbare appearance oscillation experiments. The differential cross sections for π0 momentum and production angle, for events with a single observed π0 and no charged pions, are presented and compared to model predictions. These results comprise the first measurement of the π0 kinematics for this process.
CP violation and kaon-pion interactions in B{yields}K{pi}{sup +}{pi}{sup -} decays
El-Bennich, B.; Furman, A.; Loiseau, B.; Moussallam, B.
2009-05-01
We study CP violation and the contribution of the strong kaon-pion interactions in the three-body B{yields}K{pi}{sup +}{pi}{sup -} decays. We extend our recent work on the effect of the two-pion S- and P-wave interactions to that of the corresponding kaon-pion ones. The weak amplitudes have a first term derived in QCD factorization and a second one as a phenomenological contribution added to the QCD penguin amplitudes. The effective QCD coefficients include the leading order contributions plus next-to-leading order vertex and penguins corrections. The matrix elements of the transition to the vacuum of the kaon-pion pairs, appearing naturally in the factorization formulation, are described by the strange K{pi} scalar (S-wave) and vector (P-wave) form factors. These are determined from Muskhelishvili-Omnes coupled channel equations using experimental kaon-pion T-matrix elements, together with chiral symmetry and asymptotic QCD constraints. From the scalar form factor study, the modulus of the K{sub 0}*(1430) decay constant is found to be (32{+-}5) MeV. The additional phenomenological amplitudes are fitted to reproduce the K{pi} effective mass and helicity angle distributions, the B{yields}K*(892){pi} branching ratios and the CP asymmetries of the recent data from Belle and BABAR collaborations. We use also the new measurement by the BABAR group of the phase difference between the B{sup 0} and B{sup 0} decay amplitudes to K*(892){pi}. Our predicted B{sup {+-}}{yields}K{sub 0}*(1430){pi}{sup {+-}}, K{sub 0}*(1430){yields}K{sup {+-}}{pi}{sup {+-}} branching fraction, equal to (11.6{+-}0.6)x10{sup -6}, is smaller than the result of the analyzes of both collaborations. For the neutral B{sup 0} decays, the predicted value is (11.1{+-}0.5)x10{sup -6}. In order to reduce the large systematic uncertainties in the experimental determination of the B{yields}K{sub 0}{sup *}(1430){pi} branching fractions, a new parametrization is proposed. It is based on the K{pi} scalar form
CP violation and kaon-pion interactions in B {r_arrow} K {pi}{sup +}{pi}{sup -} decays.
El-Bennich, B.; Furman, A.; Kaminski, R.; Lesniak, L.; Loiseau, B.; Moussallam, B.; Physics; Univ. Pierre et Marie Curie; ul. Bronowicka; Polish Academy of Sciences; Univ. Paris-Sud
2009-01-01
We study CP violation and the contribution of the strong kaon-pion interactions in the three-body B {yields} Kpi{sup +}pi{sup -} decays. We extend our recent work on the effect of the two-pion S- and P-wave interactions to that of the corresponding kaon-pion ones. The weak amplitudes have a first term derived in QCD factorization and a second one as a phenomenological contribution added to the QCD penguin amplitudes. The effective QCD coefficients include the leading order contributions plus next-to-leading order vertex and penguins corrections. The matrix elements of the transition to the vacuum of the kaon-pion pairs, appearing naturally in the factorization formulation, are described by the strange Kpi scalar (S-wave) and vector (P-wave) form factors. These are determined from Muskhelishvili-Omnes coupled channel equations using experimental kaon-pion T-matrix elements, together with chiral symmetry and asymptotic QCD constraints. From the scalar form factor study, the modulus of the K*{sub 0}(1430) decay constant is found to be (32 {+-} 5) MeV. The additional phenomenological amplitudes are fitted to reproduce the Kpi effective mass and helicity angle distributions, the B {yields} K*(892)pi branching ratios and the CP asymmetries of the recent data from Belle and BABAR collaborations. We use also the new measurement by the BABAR group of the phase difference between the B{sup 0} and [overline B]{sup 0} decay amplitudes to K*(892)pi. Our predicted B{sup {+-}} {yields} K*{sub 0}(1430)pi{sup {+-}}, K*{sub 0}(1430) {yields} K{sup {+-}}pi{sup {-+}} branching fraction, equal to (11.6 {+-} 0.6) x 10{sup -6}, is smaller than the result of the analyzes of both collaborations. For the neutral B{sup 0} decays, the predicted value is (11.1 {+-} 0.5) x 10{sup -6}. In order to reduce the large systematic uncertainties in the experimental determination of the B {yields} K*{sub 0}(1430)pi branching fractions, a new parametrization is proposed. It is based on the Kpi scalar
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.
Measurements of cross sections and charged pion spectra in proton-carbon interactions at 31 GeV/c
NASA Astrophysics Data System (ADS)
Abgrall, N.; Aduszkiewicz, A.; Andrieu, B.; Anticic, T.; Antoniou, N.; Argyriades, J.; Asryan, A. G.; Baatar, B.; Blondel, A.; Blumer, J.; Bogusz, M.; Boldizsar, L.; Bravar, A.; Brooks, W.; Brzychczyk, J.; Bubak, A.; Bunyatov, S. A.; Busygina, O.; Cetner, T.; Choi, K.-U.; Christakoglou, P.; Chung, P.; Czopowicz, T.; Davis, N.; Diakonos, F.; di Luise, S.; Dominik, W.; Dumarchez, J.; Engel, R.; Ereditato, A.; Esposito, L. S.; Feofilov, G. A.; Fodor, Z.; Ferrero, A.; Fulop, A.; Garrido, X.; Gaździcki, M.; Golubeva, M.; Grebieszkow, K.; Grzeszczuk, A.; Guber, F.; Hakobyan, H.; Hasegawa, T.; Igolkin, S.; Ivanov, A. S.; Ivanov, Y.; Ivashkin, A.; Kadija, K.; Kapoyannis, A.; Katryńska, N.; Kiełczewska, D.; Kikola, D.; Kim, J.-H.; Kirejczyk, M.; Kisiel, J.; Kobayashi, T.; Kochebina, O.; Kolesnikov, V. I.; Kolev, D.; Kondratiev, V. P.; Korzenev, A.; Kowalski, S.; Kuleshov, S.; Kurepin, A.; Lacey, R.; Lagoda, J.; Laszlo, A.; Lyubushkin, V. V.; Mackowiak, M.; Majka, Z.; Malakhov, A. I.; Marchionni, A.; Marcinek, A.; Maris, I.; Marin, V.; Matulewicz, T.; Matveev, V.; Melkumov, G. L.; Meregaglia, A.; Messina, M.; Mrówczyński, St.; Murphy, S.; Nakadaira, T.; Naumenko, P. A.; Nishikawa, K.; Palczewski, T.; Palla, G.; Panagiotou, A. D.; Peryt, W.; Petukhov, O.; Płaneta, R.; Pluta, J.; Popov, B. A.; Posiadała, M.; Puławski, S.; Rauch, W.; Ravonel, M.; Renfordt, R.; Robert, A.; Röhrich, D.; Rondio, E.; Rossi, B.; Roth, M.; Rubbia, A.; Rybczyński, M.; Sadovsky, A.; Sakashita, K.; Sekiguchi, T.; Seyboth, P.; Shibata, M.; Sissakian, A. N.; Skrzypczak, E.; Słodkowski, M.; Sorin, A. S.; Staszel, P.; Stefanek, G.; Stepaniak, J.; Strabel, C.; Ströbele, H.; Susa, T.; Szaflik, P.; Szuba, M.; Tada, M.; Taranenko, A.; Tsenov, R.; Ulrich, R.; Unger, M.; Vassiliou, M.; Vechernin, V. V.; Vesztergombi, G.; Wilczek, A.; Włodarczyk, Z.; Wojtaszek, A.; Yi, J.-G.; Yoo, I.-K.; Zipper, W.
2011-09-01
Interaction cross sections and charged pion spectra in p+C interactions at 31 GeV/c were measured with the large-acceptance NA61/SHINE spectrometer at the CERN SPS. These data are required to improve predictions of the neutrino flux for the T2K long-baseline neutrino oscillation experiment in Japan. A set of data collected during the first NA61/SHINE run in 2007 with an isotropic graphite target with a thickness of 4% of a nuclear interaction length was used for the analysis. The measured p+C inelastic and production cross sections are 257.2 ± 1.9 ± 8.9 and 229.3 ± 1.9 ± 9.0 mb, respectively. Inclusive production cross sections for negatively and positively charged pions are presented as functions of laboratory momentum in ten intervals of the laboratory polar angle covering the range from 0 up to 420 mrad. The spectra are compared with predictions of several hadron production models.
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.
Willocq, S.
1992-05-01
The coherent production of single pions and and {rho} mesons in charged current interactions of neutrinos and antineutrinos on neon nuclei has been studied. The data were obtained using the Fermilab 15-foot Bubble Chamber, filled with a heavy Ne-H{sub 2} mixture and exposed to the Quadrupole Triplet neutrino beam produced by 800 GeV protons from the Tevatron. The average beam energy was 86 GeV. In a sample of 330000 frames, 1032 two-prong {nu}{sub {mu}} + {bar {nu}}{sub {mu}} charged current interactions were selected. The goal of this study was to investigate the low Q{sup 2} high {nu} region where the hadron dominance model can be tested. In this model, the vector and axial-vector parts of the weak hadronic current are dominated by the {rho} and a{sub 1} mesons respectively. Moreover, the Partially Conserved Axial Current (PCAC) hypothesis can be tested by studying the coherent production of single pions.
Charged pion production in νμ interactions on hydrocarbon at ⟨Eν⟩=4.0 GeV
NASA Astrophysics Data System (ADS)
Eberly, B.; Aliaga, L.; Altinok, O.; Barrios Sazo, M. G.; Bellantoni, L.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Bustamante, M. J.; Butkevich, A.; Martinez Caicedo, D. A.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Datta, M.; Devan, J.; Díaz, G. A.; Dytman, S. A.; Felix, J.; Fields, L.; Fine, R.; Fiorentini, G. A.; Gago, A. M.; Galindo, R.; Gallagher, H.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Hurtado, K.; Kafka, T.; Kleykamp, J.; Kordosky, M.; Le, T.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Muhlbeier, T.; Naples, D.; Nelson, J. K.; Norrick, A.; Osta, J.; Palomino, J. L.; Paolone, V.; Park, J.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ransome, R. D.; Ray, H.; Ren, L.; Rodrigues, P. A.; Ruterbories, D.; Salazar, G.; Schellman, H.; Schmitz, D. W.; Simon, C.; Sobczyk, J. T.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Wospakrik, M.; Zavala, G.; Zegarra, A.; Zhang, D.; Ziemer, B. P.; Minerva Collaboration
2015-11-01
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. 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.
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.
NASA Astrophysics Data System (ADS)
Batyunya, B. V.; Boguslavsky, I. V.; Gramenitsky, I. M.; Lednický, R.; Tikhonova, L. A.; Valkárová, A.; Vrba, V.; Zlatanov, Z.; Levonian, S. V.; Ermilova, D. I.; Filippova, V. V.; Takibaev, Z. S.; Temiraliev, T.; Dumbrajs, S.; Ervanne, J.; Hannula, E.; Villanen, P.; Dementiev, R. K.; Korzhavina, I. A.; Leikin, E. M.; Rud, V. I.; Suk, M.; Herynek, I.; Reimer, P.; Řídký, J.; Šimák, V.; Khudzadze, A. M.; Kuratashvili, G. O.; Topuriya, T. P.; Tsintsadze, V. D.
1981-05-01
The Bose-Einstein interference effect is studied using 7333 events of ¯pp-interactions with n ch≧6 at 22·4 GeV/c. An essential dependence of the strength of this effect on the pion pair velocity is observed. An indication is obtained that processes with essentially different time characteristics (τ<1 fm and τ>2 fm) contribute to ¯pp-interactions at 22·4 GeV/c. The interpretation based on abundant resonance production in high energy collisions is discussed.
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.
Exclusive measurements of pion nucleon going to pion pion nucleon
NASA Astrophysics Data System (ADS)
Kermani, Mohammad Arjomand
The pion induced pion production reactions π±p/toπ±π+n were studied at projectile incident energies of 223, 243, 264, 284, and 305 MeV. The Canadian High Acceptance Orbit Spectrometer (CHAOS) was used to detected the charged particles, which originated from the interaction of the incident pion beam with a cryogenic liquid hydrogen target. The experimental results are presented in the form of single, double and triple differential cross sections. Total cross sections obtained by integrating the differential quantities are also reported. The experimental data, namely the π-p/toπ-π+n double differential cross sections, were used as input to the Chew-Low extrapolation procedure which was utilized to determine on-shell π+π- elastic scattering cross sections in the near threshold region. The Chew-Low results (the extrapolated πpi cross sections) were then used in a dispersion analysis (Roy equations) to obtain the πpi isospin zero S-wave scattering length. We find a00=0.209/pm 0.011μ-1. In addition, the invariant mass distributions from the (π+π-) channel were fitted to determine the model parameters for the extended model of Oset and Vicente-Vacas. We find that the model parameters obtained from fitting the (π+π-) data do not describe the invariant mass distributions in the (π+π+) channel.
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.
Parity-violating two-pion exchange nucleon-nucleon interaction
Kaiser, N.
2007-10-15
We calculate in chiral perturbation theory the parity-violating two-pion exchange nucleon-nucleon potentials at leading one-loop order. At a distance of r=m{sub {pi}}{sup -1}{approx_equal}1.4 fm they amount to about {+-}16% of the parity-violating 1{pi} exchange potential. We evaluate also the parity-violating effects arising from 2{pi} exchange with excitation of virtual {delta}(1232) isobars. These come out to be relatively small in comparison with those from diagrams with only nucleon intermediate states. The reason for this behavior, which is opposite that of the parity-conserving case, is the blocking of the dominant isoscalar central channel by CP invariance. Furthermore, we calculate the T matrix related to the iteration of the parity-violating 1{pi} exchange with the parity-conserving one. The analytical results presented in this work can be easily implemented into calculations of parity-violating nuclear observables.
High-energy pion-nucleus scattering at LAMPF
Morris, C.L.
1993-01-01
Recent data obtained for pion-nucleus interactions above the [triangle](1232) is presented. The expected long mean-free path at pion energies above the [3,3] resonance is demonstrated in elastic scattering. Evidence for unexpected nuclear transparency for outgoing pions at resonance energies is presented. A new technique measuring virtual [triangle] components of the nuclear wave function is suggested.
High-energy pion-nucleus scattering at LAMPF
Morris, C.L.
1993-02-01
Recent data obtained for pion-nucleus interactions above the {triangle}(1232) is presented. The expected long mean-free path at pion energies above the [3,3] resonance is demonstrated in elastic scattering. Evidence for unexpected nuclear transparency for outgoing pions at resonance energies is presented. A new technique measuring virtual {triangle} components of the nuclear wave function is suggested.
NASA Astrophysics Data System (ADS)
Mattingly, Margarita Claudia Krieghoff
The space-time development of hadron-nucleus interactions is examined using bubble chamber and downstream particle identifier data from the hybrid spectrometer of Fermilab experiment E597. 5583 events representing 12 interactions are studied with conventional and fractal techniques. Comparisons are made to simulated events from the Lund Monte Carlo FRITIOF 1.6. Multiplicities are studied conventionally. Negative binomial descriptions of produced particle multiplicities are interpreted in terms of clusters and cascading and in terms of partial stimulated emission; forward-backward correlations, in terms of short- and long-range correlations and multiple scattering. Multiplicities are consistent with a multiple collision view of multiparticle production mechanisms and are investigated in terms of the number of collisions nu. Rapidity density fluctuations are studied fractally. The possibility of new dynamics is considered on the basis of event-by-event studies of spike phenomena, intermittency, and fractal dimensions. Results from these exploratory studies are consistent with predictions made for quark-gluon plasma transitions. 131 spike events are analyzed; intermittency is investigated with normalized factorial moments and cumulants; and fractal dimensions and correlations dimensions are calculated. Seagull effects and production region sizes from Bose-Einstein pion interferometry are also considered.
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.
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.
Chiral pions in a magnetic background
NASA Astrophysics Data System (ADS)
Colucci, G.; Fraga, E. S.; Sedrakian, A.
2014-01-01
We investigate the modification of the pion self-energy at finite temperature due to its interaction with a low-density, isospin-symmetric nuclear medium embedded in a constant magnetic background. To one loop, for fixed temperature and density, we find that the pion effective mass increases with the magnetic field. For the π-, interestingly, this happens solely due to the trivial Landau quantization shift ∼|eB|, since the real part of the self-energy is negative in this case. In a scenario in which other charged particle species are present and undergo an analogous trivial shift, the relevant behavior of the effective mass might be determined essentially by the real part of the self-energy. In this case, we find that the pion mass decreases by ∼10% for a magnetic field |eB|∼mπ2, which favors pion condensation at high density and low temperatures.
NASA Astrophysics Data System (ADS)
Abgrall, N.; Aduszkiewicz, A.; Ali, Y.; Anticic, T.; Antoniou, N.; Baatar, B.; Bay, F.; Blondel, A.; Blumer, J.; Bogomilov, M.; Bravar, A.; Brzychczyk, J.; Bunyatov, S. A.; Busygina, O.; Christakoglou, P.; Czopowicz, T.; Davis, N.; Debieux, S.; Dembinski, H.; Diakonos, F.; Luise, S. Di; Dominik, W.; Drozhzhova, T.; Dumarchez, J.; Dynowski, K.; Engel, R.; Ereditato, A.; Feofilov, G. A.; Fodor, Z.; Fulop, A.; Gaździcki, M.; Golubeva, M.; Grebieszkow, K.; Grzeszczuk, A.; Guber, F.; Haesler, A.; Hasegawa, T.; Hierholzer, M.; Idczak, R.; Igolkin, S.; Ivashkin, A.; Joković, D.; Kadija, K.; Kapoyannis, A.; Kaptur, E.; Kiełczewska, D.; Kirejczyk, M.; Kisiel, J.; Kiss, T.; Kleinfelder, S.; Kobayashi, T.; Kolesnikov, V. I.; Kolev, D.; Kondratiev, V. P.; Korzenev, A.; Kovesarki, P.; Kowalski, S.; Krasnoperov, A.; Kurepin, A.; Larsen, D.; László, A.; Lyubushkin, V. V.; Maćkowiak-Pawłowska, M.; Majka, Z.; Maksiak, B.; Malakhov, A. I.; Manić, D.; Marcinek, A.; Marin, V.; Marton, K.; Mathes, H.-J.; Matulewicz, T.; Matveev, V.; Melkumov, G. L.; Mrówczyński, St.; Murphy, S.; Nakadaira, T.; Nirkko, M.; Nishikawa, K.; Palczewski, T.; Palla, G.; Panagiotou, A. D.; Paul, T.; Pistillo, C.; Peryt, W.; Petukhov, O.; Płaneta, R.; Pluta, J.; Popov, B. A.; Posiadała, M.; Puławski, S.; Puzović, J.; Rauch, W.; Ravonel, M.; Redij, A.; Renfordt, R.; Robert, A.; Röhrich, D.; Rondio, E.; Roth, M.; Rubbia, A.; Rustamov, A.; Rybczyński, M.; Sadovsky, A.; Sakashita, K.; Savić, M.; Schmidt, K.; Sekiguchi, T.; Seyboth, P.; Sgalaberna, D.; Shibata, M.; Sipos, R.; Skrzypczak, E.; Słodkowski, M.; Staszel, P.; Stefanek, G.; Stepaniak, J.; Ströbele, H.; Šuša, T.; Szuba, M.; Tada, M.; Tereshchenko, V.; Tolyhi, T.; Tsenov, R.; Turko, L.; Ulrich, R.; Unger, M.; Vassiliou, M.; Veberič, D.; Vechernin, V. V.; Vesztergombi, G.; Vinogradov, L.; Wilczek, A.; Włodarczyk, Z.; Wojtaszek-Szwarc, A.; Wyszyński, O.; Zambelli, L.; Zipper, W.
2014-03-01
We present experimental results on inclusive spectra and mean multiplicities of negatively charged pions produced in inelastic p+p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 GeV/ c ( 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively). The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN super proton synchrotron. Two-dimensional spectra are determined in terms of rapidity and transverse momentum. Their properties such as the width of rapidity distributions and the inverse slope parameter of transverse mass spectra are extracted and their collision energy dependences are presented. The results on inelastic p+p interactions are compared with the corresponding data on central Pb+Pb collisions measured by the NA49 experiment at the CERN SPS. The results presented in this paper are part of the NA61/SHINE ion program devoted to the study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter. They are required for interpretation of results on nucleus-nucleus and proton-nucleus collisions.
Status of Pion Decay Experiments
NASA Astrophysics Data System (ADS)
Numao, T.
2016-11-01
The branching ratio of pion decays, {Re/}_μ = Γ ({{{π }}^ + } \\to {e^ + }ν + {e^ + }{{ν γ }})/Γ ({{{π }}^ + } \\to {{{μ }}^ + }ν + {{{μ }}^ + }ν {{γ }}), has provided a sensitive test of electron-muon universality in weak interactions. The uncertainty of the Standard Model prediction is at a 0.01% level. Although a recent measurement, Re /μ = (1.2344 ± 0.0023(stat) ± 0.0019(syst)) × 10-4, reduced the experimental uncertainty by a factor of two, there is room for improvement by more than an order of magnitude. The status of two {{{π }}^ + } \\to {e^ + }ν experiments at TRIUMF and PSI as well as related pion decay experiments is presented.
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.
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.
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.
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
NASA Astrophysics Data System (ADS)
Boehnlein, David Jude
1990-01-01
K^- p interactions at 8 GeV/c have been produced at Brookhaven National Laboratory's Multi-Particle Spectrometer to study the final state K ^+{| K^0}pi^ - in the mass range 1-2 GeV/c^2. A total of 1711 events have been produced in the reaction K^- pto(K^+{| K^0}pi^-) + Y where Y is a neutral baryon with strangeness -1. The Y's identified include the Lambda(1115), Sigma(1192), Sigma (1385), and Lambda(1530). We see no clear signals for the resonances D(1285), E(1420), and D^'(1520). Upper limits for the production cross sections of these mesons are computed. Through comparison with data obtained in the reaction pi^- pto( K^+{| K^0}pi ^-) + n we find that the production cross sections for the D(1285) and E(1420) are at least an order of magnitude smaller for the K^{-}p interactions than for the pi^ {-}p interactions, while that of the D^'(1530) may be of the same order of magnitude for both interactions, indicating the possibility of a significant s{| s} component. Also, a Partial Wave Analysis shows some evidence of an interference of 1^{++} and 1^{+-} J^{PG} states near 1.4 GeV/c^2. The 1^{+-} wave appears to be the strongest in this mass region.
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
The pion: an enigma within the Standard Model
Horn, Tanja; Roberts, Craig D.
2016-05-27
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
Pion production in high-energy neutrino reactions with nuclei
NASA Astrophysics Data System (ADS)
Mosel, U.
2015-06-01
Background: A quantitative understanding of neutrino interactions with nuclei is needed for precision era neutrino long baseline experiments (MINOS, NOvA, DUNE) which all use nuclear targets. Pion production is the dominant reaction channel at the energies of these experiments. Purpose: Investigate the influence of nuclear effects on neutrino-induced pion production cross sections and compare predictions for pion-production with available data. Method: The Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) model is used for the description of all incoherent channels in neutrino-nucleus reactions. Results: Differential cross sections for charged and neutral pion production for the MINER ν A neutrino and antineutrino flux are calculated. An estimate for the coherent cross section is obtained from a comparison of data with theoretical results for incoherent cross sections. The invariant mass (W ) distribution of the Δ resonances produced is analyzed. Conclusions: Final state interactions affect the pion kinetic energy spectra significantly. The data for charged pion production at MINER ν A are compatible with the results of calculations using elementary data taken from an old Argonne National Laboratory experiment. Remaining differences for charged pion production can be attributed to coherent production; the data for antineutrino induced neutral pion production, where no coherent contribution is present, are reproduced quite well. The analysis of W distributions shows that sharp cuts on experimentally reconstructed invariant masses lead to shape distortions of the true W distributions for nuclear targets.
D Meson Production in Negative Pion-Proton and Proton-Proton Interactions at 360 Gev/c
NASA Astrophysics Data System (ADS)
van Immerseel, Marina
The aim of the NA16 experiment is to study charm production in (pi)('-)p and pp interactions at 360 GeV/c. The possibility of direct observation and interpretation of the charmed particle decays is chosen. Therefore, the experimental set-up is composed of a high resolution hydrogen bubble chamber LEBC coupled to the European Hybrid Spectrometer EHS. In this experiment 56 D mesons are identified. The neutral and charged D lifetimes are found to be respectively. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). The ratio of the charged over the neutral D meson lifetime is thus. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). This supports the idea that the weak decay of a charmed particle cannot be described by simple spectator diagrams wherein the light quarks, bound to the c-quark, do not participate actively in the decay. Processes in which the heavy charm quark and the light quark annihilate have to be included and this implies that a charmed particle cannot be described simply by its valence quarks. The D meson production in both (pi)('-)p and pp interactions is studied. In principle, this opens the possibility to check the relevance. of the different QCD diagrams for charm production. The inclusive single D/(')D cross section for x(,F) > 0 in (pi)('-)p interactions is found to be. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). whereas the D(')D pair cross section for all x(,F) in pp interactions has the same magnitude,. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). These charm yields are in agreement with production models including as well quark-antiquark and gluon-gluon fusion as charm excitation diagrams. The x(,F) distributions of the D mesons produced in both (pi)('-)p and pp interactions are flatter than predicted by the fusion models, indicating that the charm excitation processes are important. In addition, also the characteristics of the D(')D pairs seem to support the idea that more production mechanisms than qq and gg fusion
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.
Medium Effects of Low Energy Pions
NASA Astrophysics Data System (ADS)
Friedman, E.
2004-03-01
Fits of pion--nucleus potentials to large sets of pionic atom data reveal departures of parameter values from the corresponding free π N parameters. These medium effects can be quantitatively reproduced by a chiral-motivated model where the pion decay constant is modified in the medium or by including the empirical on-shell energy dependence of the amplitudes. No consistency is obtained between pionic atoms and the free π N interaction when an extreme off-shell chiral model is used. The role of the size of data sets is briefly discussed.
Pion Induced Pion Production on Deuterium.
NASA Astrophysics Data System (ADS)
Sossi, Vesna
This thesis describes measurements of the pion induced pion production reaction pi^+ d to pi^{+} pi^{-}p p performed with a 280 MeV incident pi^{+} beam at TRIUMF. The data are compared with an improved version of the Oset and Vicente-Vacas theoretical model (12). The goal of the experiment and of the analysis was to provide a larger body of data for the free reaction and to test the validity of theoretical models. In the process, the ability to determine the values of the coupling constants C, f_Delta, g _{N*Delta_tau} within such a model framework would be explored. The knowledge of the precise value of these coupling constants would constrain N^* decay branching ratios and other pion induced reaction mechanisms like Double Charge Exchange. A previous experiment (23) had indicated that the pion induced pion production on deuterium is essentially a quasifree process with the reaction occurring on the neutron leaving the proton merely a spectator. The main difference with respect to the free reaction is the effect of Fermi motion of the neutron. Although we were interested in studying the free reaction (pi^ {-}p to pi^ {+}pi^{-}n), we chose a deuterium target so that the experiment could be run with a pi^+beam, since the pi^- beam flux is about 6 times lower than the flux of the positive pion beam at 280 MeV, the energy at which our experiment was performed. Such a flux would have required a much longer running time for the experiment in order to achieve the same statistical accuracy. The quasifree nature of the process was also confirmed in our experiment. This experiment involved a coincidence measurement of the quasifree process and as such provided four-fold differential cross section spectra of the reaction thus allowing for a microscopic comparison between data and theoretical models. In the theoretical description we incorporated additional amplitudes for the N^* to N(pipi)_{p-wave} diagrams required to describe the reaction cross section at T_pi = 280 Me
NASA Astrophysics Data System (ADS)
Lomon, Earle L.; Pacetti, Simone
2016-09-01
The pion electromagnetic form factor and two-pion production in electron-positron collisions are simultaneously fitted by a vector dominance model evolving to perturbative QCD at large momentum transfer. This model was previously successful in simultaneously fitting the nucleon electromagnetic form factors (spacelike region) and the electromagnetic production of nucleon-antinucleon pairs (timelike region). For this pion case dispersion relations are used to produce the analytic connection of the spacelike and timelike regions. The fit to all the data is good, especially for the newer sets of timelike data. The description of high-q2 data, in the timelike region, requires one more meson with ρ quantum numbers than listed in the 2014 Particle Data Group review.
Longitudinal Lelectroproduction of Charged Pions on Hydrogen, Deuterium, and Helium 3
Gaskell, David
2001-03-22
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.
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.
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.
NASA Astrophysics Data System (ADS)
Cecile, D. J.
In Quantum Chromodynamics (QCD), the pions are the lightest bound states. Current lattice QCD calculations are not able to study pions at realistic masses due to algorithmic difficulties. Instead, lattice studies are limited to unphysically large pion masses, and Chiral Perturbation Theory (ChPT) is often relied upon to extrapolate lattice results to the phenomenological regime and to the chiral limit, where quarks are massless. One of the outstanding problems in the field is to determine the range of quark masses where ChPT is valid and to understand the nonperturbative physics that may cause ChPT to break down. Given the difficulty of studying QCD, it is interesting and useful to construct a lattice field theory model of pions, which would allow a direct lattice calculation without the need for chiral extrapolations. This model can be used to evaluate the reliability of chiral extrapolations as applied to lattice data in the context of a lattice field theory that is exactly solvable numerically even at small quark masses and in the chiral limit. In this light, to create a model of pions of two-flavor Quantum Chromodynamics (QCD), a lattice field theory involving two flavors of staggered quarks interacting strongly with Abelian gauge fields is constructed. In the chiral limit, this theory exhibits a SUL(2) x SU R(2) x UA(1) symmetry. The UA(1) symmetry can be broken by introducing a four-fermion term into the action, thereby incorporating the physics of the QCD anomaly. To qualify as a meaningful model of QCD, this lattice model must exhibit spontaneous chiral symmetry breaking and confinement and must have a continuum limit. An interesting mechanism is introduced to address the continuum limit. In particular, an extra dimension allows one to tune a fictitious temperature in order to access a phase of broken symmetry and to find a range where the pion decay constant is much smaller than the lattice cutoff, i.e. Fpi ≪1a . Unlike lattice QCD, a major advantage of
Bush, S.E.; Smith, A.R.; Zink, S.
1982-12-01
Clinical investigations of pi meson radiotherapy were conducted by the Cancer Research and Treatment Center of the University of New Mexico and the Los Alamos National Laboratory from 1974 until 1982. Two hundred and thirty patients have been treated for a variety of locally advanced primary and metastatic neoplasms. One hundred and ninety-six patients have been followed for a minimum of 18 months. Crude survival data range from 11% for unresectable pancreatic carcinoma to 82% for Stages C and D1 adenocarcinoma of the prostate. Acute tolerance of normal tissues is approximately 4500 pion rad in 36 fractions over 7 weeks. Severe chronic reactions have appeared with increasing frequency after doses in excess of 4000 pion rad.
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)
Abe, K.; Andreopoulos, C.; Antonova, M.; Aoki, S.; Ariga, A.; Assylbekov, S.; Autiero, D.; Barbi, M.; Barker, G. J.; Barr, G.; Bartet-Friburg, P.; Batkiewicz, M.; Berardi, V.; Berkman, S.; Bhadra, S.; Blondel, A.; Bolognesi, S.; Bordoni, S.; Boyd, S. B.; Brailsford, D.; Bravar, A.; Bronner, C.; Buizza Avanzini, M.; Calland, R. G.; Cao, S.; Caravaca Rodríguez, J.; Cartwright, S. L.; Castillo, R.; Catanesi, M. G.; Cervera, A.; Cherdack, D.; Chikuma, N.; Christodoulou, G.; Clifton, A.; Coleman, J.; Collazuol, G.; Cremonesi, L.; Dabrowska, A.; De Rosa, G.; Dealtry, T.; Denner, P. F.; Dennis, S. R.; Densham, C.; Dewhurst, D.; Di Lodovico, F.; Di Luise, S.; Dolan, S.; Drapier, O.; Duffy, K. E.; Dumarchez, J.; Dytman, S.; Dziewiecki, M.; Emery-Schrenk, S.; Ereditato, A.; Feusels, T.; Finch, A. J.; Fiorentini, G. A.; Friend, M.; Fujii, Y.; Fukuda, D.; Fukuda, Y.; Furmanski, A. P.; Galymov, V.; Garcia, A.; Giffin, S. G.; Giganti, C.; Gizzarelli, F.; Gonin, M.; Grant, N.; Hadley, D. R.; Haegel, L.; Haigh, M. D.; Hamilton, P.; Hansen, D.; Hara, T.; Hartz, M.; Hasegawa, T.; Hastings, N. C.; Hayashino, T.; Hayato, Y.; Helmer, R. L.; Hierholzer, M.; Hillairet, A.; Himmel, A.; Hiraki, T.; Hirota, S.; Hogan, M.; Holeczek, J.; Horikawa, S.; Hosomi, F.; Huang, K.; Ichikawa, A. K.; Ieki, K.; Ikeda, M.; Imber, J.; Insler, J.; Intonti, R. A.; Irvine, T. J.; Ishida, T.; Ishii, T.; Iwai, E.; Iwamoto, K.; Izmaylov, A.; Jacob, A.; Jamieson, B.; Jiang, M.; Johnson, S.; Jo, J. H.; Jonsson, P.; Jung, C. K.; Kabirnezhad, M.; Kaboth, A. C.; Kajita, T.; Kakuno, H.; Kameda, J.; Karlen, D.; Karpikov, I.; Katori, T.; Kearns, E.; Khabibullin, M.; Khotjantsev, A.; Kielczewska, D.; Kikawa, T.; Kim, H.; Kim, J.; King, S.; Kisiel, J.; Knight, A.; Knox, A.; Kobayashi, T.; Koch, L.; Koga, T.; Konaka, A.; Kondo, K.; Kopylov, A.; Kormos, L. L.; Korzenev, A.; Koshio, Y.; Kropp, W.; Kudenko, Y.; Kurjata, R.; Kutter, T.; Lagoda, J.; Lamont, I.; Larkin, E.; Lasorak, P.; Laveder, M.; Lawe, M.; Lazos, M.; Lindner, T.; Liptak, Z. J.; Litchfield, R. P.; Li, X.; Longhin, A.; Lopez, J. P.; Ludovici, L.; Lu, X.; Magaletti, L.; Mahn, K.; Malek, M.; Manly, S.; Marino, A. D.; Marteau, J.; Martin, J. F.; Martins, P.; Martynenko, S.; Maruyama, T.; Matveev, V.; Mavrokoridis, K.; Ma, W. Y.; Mazzucato, E.; McCarthy, M.; McCauley, N.; McFarland, K. S.; McGrew, C.; Mefodiev, A.; Mezzetto, M.; Mijakowski, P.; Minamino, A.; Mineev, O.; Mine, S.; Missert, A.; Miura, M.; Moriyama, S.; Mueller, Th. A.; Murphy, S.; Myslik, J.; Nakadaira, T.; Nakahata, M.; Nakamura, K. G.; Nakamura, K.; Nakamura, K. D.; Nakayama, S.; Nakaya, T.; Nakayoshi, K.; Nantais, C.; Nielsen, C.; Nirkko, M.; Nishikawa, K.; Nishimura, Y.; Nowak, J.; O'Keeffe, H. M.; Ohta, R.; Okumura, K.; Okusawa, T.; Oryszczak, W.; Oser, S. M.; Ovsyannikova, T.; Owen, R. A.; Oyama, Y.; Palladino, V.; Palomino, J. L.; Paolone, V.; Patel, N. D.; Pavin, M.; Payne, D.; Perkin, J. D.; Petrov, Y.; Pickard, L.; Pickering, L.; Pinzon Guerra, E. S.; Pistillo, C.; Popov, B.; Posiadala-Zezula, M.; Poutissou, J.-M.; Poutissou, R.; Przewlocki, P.; Quilain, B.; Radicioni, E.; Ratoff, P. N.; Ravonel, M.; Rayner, M. A. M.; Redij, A.; Reinherz-Aronis, E.; Riccio, C.; Rojas, P.; Rondio, E.; Roth, S.; Rubbia, A.; Rychter, A.; Sacco, R.; Sakashita, K.; Sánchez, F.; Sato, F.; Scantamburlo, E.; Scholberg, K.; Schoppmann, S.; Schwehr, J.; Scott, M.; Seiya, Y.; Sekiguchi, T.; Sekiya, H.; Sgalaberna, D.; Shah, R.; Shaikhiev, A.; Shaker, F.; Shaw, D.; Shiozawa, M.; Shirahige, T.; Short, S.; Smy, M.; Sobczyk, J. T.; Sorel, M.; Southwell, L.; Stamoulis, P.; Steinmann, J.; Stewart, T.; Suda, Y.; Suvorov, S.; Suzuki, A.; Suzuki, K.; Suzuki, S. Y.; Suzuki, Y.; Tacik, R.; Tada, M.; Takahashi, S.; Takeda, A.; Takeuchi, Y.; Tanaka, H. K.; Tanaka, H. A.; Terhorst, D.; Terri, R.; Thakore, T.; Thompson, L. F.; Tobayama, S.; Toki, W.; Tomura, T.; Touramanis, C.; Tsukamoto, T.; Tzanov, M.; Uchida, Y.; Vacheret, A.; Vagins, M.; Vallari, Z.; Vasseur, G.; Wachala, T.; Wakamatsu, K.; Walter, C. W.; Wark, D.; Warzycha, W.; Wascko, M. O.; Weber, A.; Wendell, R.; Wilkes, R. J.; Wilking, M. J.; Wilkinson, C.; Wilson, J. R.; Wilson, R. J.; Yamada, Y.; Yamamoto, K.; Yamamoto, M.; Yanagisawa, C.; Yano, T.; Yen, S.; Yershov, N.; Yokoyama, M.; Yoshida, K.; Yuan, T.; Yu, M.; Zalewska, A.; Zalipska, J.; Zambelli, L.; Zaremba, K.; Ziembicki, M.; Zimmerman, E. D.; Zito, M.; Żmuda, J.; T2K Collaboration
2016-06-01
We report the measurement of muon neutrino charged-current interactions on carbon without pions in the final state at the T2K beam energy using 5.734 ×1020 protons on target. For the first time the measurement is reported as a flux-integrated, double-differential cross section in muon kinematic variables (cos θμ, pμ), without correcting for events where a pion is produced and then absorbed by final state interactions. Two analyses are performed with different selections, background evaluations and cross-section extraction methods to demonstrate the robustness of the results against biases due to model-dependent assumptions. The measurements compare favorably with recent models which include nucleon-nucleon correlations but, given the present precision, the measurement does not distinguish among the available models. The data also agree with Monte Carlo simulations which use effective parameters that are tuned to external data to describe the nuclear effects. The total cross section in the full phase space is σ =(0.417 ±0.047 (syst ) ±0.005 (stat ) )×10-38 cm2 nucleon-1 and the cross section integrated in the region of phase space with largest efficiency and best signal-over-background ratio (cos θμ>0.6 and pμ>200 MeV ) is σ =(0.202 ±0.036 (syst ) ±0.003 (stat ) )×10-38 cm2 nucleon-1 .
Pion-pair formation and the pion dispersion relation in a hot pion gas
NASA Astrophysics Data System (ADS)
Alm, T.; Chanfray, G.; Schuck, P.; Welke, G.
1997-02-01
The possibility of pion-pair formation in a hot pion gas, based on the bosonic gap equation, is pointed out and discussed in detail. The critical temperature for condensation of pion pairs (Evans-Rashid transition) is determined as a function of the pion density. As for fermions, this phase transition is signated by the appearance of a pole in the two-particle propagator. In Bose systems there exists a second, lower critical temperature, associated with the appearance of the single-particle condensate. Between the two critical temperatures the pion dispersion relation changes from the usual quasiparticle dispersion to a Bogoliubov-like dispersion relation at low momenta. This generalizes the non-relativistic result for an attractive Bose gas by Evans et al. Possible consequences for the inclusive pion spectra measured in heavy-ion collisions at ultra-relativistic energies are discussed.
Amplitude analysis of resonant production in three pions
Jackura, Andrew; Mikhasenko, Mikhail; Szczepaniak, Adam
2016-11-29
We present some results on the analysis of three pion resonances. The analyses are motivated by the recent release of the largest data set on diffractively produced three pions by the COMPASS collaboration. We construct reaction amplitudes that satisfy fundamental $S$-matrix principles, which allows the use of models that have physical constraints to be used in fitting data. The models are motivated by the isobar model that satisfy unitarity constraints. The model consist of a Deck production amplitude with which final state interactions are constrained by unitarity. We employ the isobar model where two of the pions form a quasi-stable particle. The analysis is performed in the high-energy, single Regge limit. We specifically discuss the examples of the three pion $J^{PC}=2^{-+}$ resonance in the $\\rho\\pi$ and $f_2\\pi$ channels.
Amplitude analysis of resonant production in three pions
NASA Astrophysics Data System (ADS)
Jackura, Andrew; Mikhasenko, Mikhail; Szczepaniak, Adam
2016-11-01
We present some results on the analysis of three pion resonances. The analyses are motivated by the recent release of the largest data set on diffractively produced three pions by the COMPASS collaboration. We construct reaction amplitudes that satisfy fundamental S -matrix principles, which allows the use of models that have physical constraints to be used in fitting data. The models are motivated by the isobar model that satisfy unitarity constraints. The model consist of a Deck production amplitude with which final state interactions are constrained by unitarity. We employ the isobar model where two of the pions form a quasi-stable particle. The analysis is performed in the high-energy, single Regge limit. We specifically discuss the examples of the three pion JPC = 2-+ resonance in the ρπ and f2π channels.
Charged- and neutral-pion production in the S-matrix approach
Malafaia, V.; Pena, M. T.; Elster, Ch.; Adam, J. Jr.
2006-10-15
The S-matrix approach is used to calculate both charged- and neutral-pion production in nucleon-nucleon (NN) scattering near threshold. The irreducible pion-rescattering diagram, direct production mechanism, {delta} isobars in intermediate states, and Z diagrams mediated by heavy isoscalar mesons are included in the calculation. For the NN distortions, we considered a realistic interaction, within the Bonn family of potentials, which describes the nucleonic inelasticities above the pion production energy threshold.
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.
Vector meson condensation in a pion superfluid
NASA Astrophysics Data System (ADS)
Brauner, Tomáš; Huang, Xu-Guang
2016-11-01
We revisit the suggestion that charged ρ -mesons undergo Bose-Einstein condensation in isospin-rich nuclear matter. Using a simple version of the Nambu-Jona-Lasinio (NJL) model, we conclude that ρ -meson condensation is either avoided or postponed to isospin chemical potentials much higher than the ρ -meson mass as a consequence of the repulsive interaction with the preformed pion condensate. In order to support our numerical results, we work out a linear sigma model for pions and ρ -mesons, showing that the two models lead to similar patterns of medium dependence of meson masses. As a byproduct, we analyze in detail the mapping between the NJL model and the linear sigma model, focusing on conditions that must be satisfied for a quantitative agreement between the models.
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)
Binding energy of the X (3872 ) at unphysical pion masses
NASA Astrophysics Data System (ADS)
Baru, V.; Epelbaum, E.; Filin, A. A.; Gegelia, J.; Nefediev, A. V.
2015-12-01
The chiral extrapolation of the X (3872 ) binding energy is investigated using the modified Weinberg formulation of chiral effective field theory for the D D¯* scattering. Given its explicit renormalizability, this approach is particularly useful to explore the interplay of the long- and short-range D D¯* forces in the X (3872 ) from studying the light-quark (pion) mass dependence of its binding energy. In particular, the parameter-free leading-order calculation shows that the X pole disappears for unphysically large pion masses. On the other hand, without contradicting the naive dimensional analysis, the higher-order pion-mass-dependent contact interaction can change the slope of the binding energy at the physical point, yielding the opposite scenario of a more strongly bound X at pion masses larger than its physical value. An important role of the pion dynamics and of the three-body D D ¯π effects for chiral extrapolations of the X pole is emphasized. The results of the present study should be of practical value for lattice simulations since they provide a nontrivial connection between lattice points at unphysical pion masses and the physical world.
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.
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.
An Overview of CC Coherent Pion Production
NASA Astrophysics Data System (ADS)
Williams, Zachary
2017-01-01
Neutrino cross-sections are a critical component to any neutrino measurement. With the modern neutrino experiments aiming to measure precision parameters, such as those in long-baseline oscillation experiments, the need for a detailed understanding of neutrino interactions has become even more important. Within this landscape remains a number of experimental challenges in the regime of low energy neutrino cross-sections. This talk will give an overview of recent publications on Charged Current-Coherent Pion Production (CC-Coh Pion) results from a number of experimental collaborations. Specifically, the lack of observation from the SciBooNE and T2K collaborations to observe CC-Coh Pion below one GeV in contrast to the observation of this signature at higher energies by other experiments. The work presented here is a part of the beginning steps to a reanalysis of the SciBooNE data using a modern neutrino generator in order to better understand the previous results. There will be included details of a liquid Argon purification system that is being built at UTA, and of plans for a ``Baby Time Projection Chamber (TPC)'' which will also be built at UTA, and the instrumentation and detector methods used in their construction. The closing is a look to the future for a new analysis at low neutrino energies utilizing Liquid Argon Time Projection Chambers (LArTPCs) based at Fermilab.
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.
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.
Abelian anomaly and neutral pion production
NASA Astrophysics Data System (ADS)
Roberts, Craig
2011-04-01
The process γ* γ -->π0 is fascinating because in order to explain the associated transition form factor within the Standard Model on the full domain of momentum transfer, one must combine, using a single internally-consistent framework, an explanation of the essentially nonperturbative Abelian anomaly with the features of perturbative QCD. The case for attempting this has received a significant boost with the publication of data from the BaBar Collaboration [Phys. Rev. D 80, 052002 (2009)] because, while they agree with earlier experiments on their common domain of squared-momentum-transfer [CELLO - Z. Phys. C 49, 401 (1991); CLEO - Phys. Rev. D 57, 33 (1998)], the BaBar data are unexpectedly far above the prediction of perturbative QCD at larger values of Q2. I will elucidate the sensitivity of the γ* γ -->π0 transition form factor, Gγ* γπ(Q2) , to the pointwise behaviour of the interaction between quarks; and use existing Dyson-Schwinger equation calculations of this and the kindred γ*γ* -->π0 form factor to characterize the Q2-dependence of Gγ* γπ(Q2) . It will become apparent that in fully-self-consistent treatments of pion: static properties; and elastic and transition form factors, the asymptotic limit of the product Q2Gγ* γπ0(Q2) , which is determined a priori by the interaction employed, is not exceeded at any finite value of spacelike momentum transfer: the product is a monotonically-increasing concave function. Studies exist which interpret the BaBar data as an indication that the pion's distribution amplitude, φπ(x) , deviates dramatically from its QCD asymptotic form, indeed, that φπ(x) = constant, or is at least flat and nonvanishing at x = 0 , 1 . I will explain that such a distribution amplitude characterises an essentially-pointlike pion; and show that, when used in a fully-consistent treatment, it produces results for pion elastic and transition form factors that are in striking disagreement with experiment. A bound-state pion
Quark dynamics and pion-nucleon coupling
NASA Astrophysics Data System (ADS)
Weise, W.; Werner, E.
1981-05-01
In the framework of nonperturbative QCD phenomenology we discuss: (1) The elementary process for the creation of color-singlet qq-pairs inside a hadron. (2) The interaction of the qq-pair with the surrounding quark-gluon medium. An important consequence of these discussions is that meson emission takes place preferentially, if the primary qq-pair is created in the surface region of the hadron. For the case of pseudoscalar coupling we employ PCAC to obtain the coupling of the qq-pair to the pion. The resulting form and coupling strength of the πNN vertex is consistent with the phenomenological OPEP.
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.
Pion electric polarizability from lattice QCD
Alexandru, Andrei; Lujan, Michael; Freeman, Walter; Lee, Frank
2016-01-22
Electromagnetic polarizabilities are important parameters for understanding the interaction between photons and hadrons. For pions these quantities are poorly constrained experimentally since they can only be measured indirectly. New experiments at CERN and Jefferson Lab are planned that will measure the polarizabilities more precisely. Lattice QCD can be used to compute these quantities directly in terms of quark and gluons degrees of freedom, using the background field method. We present results for the electric polarizability for two different quark masses, light enough to connect to chiral perturbation theory. These are currently the lightest quark masses used in polarizability studies.
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.
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.
{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.
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.
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.
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 (-)}.
NASA Astrophysics Data System (ADS)
Uribe Duque, Jorge
We have measured low relative momentum correlations between like sign pions produced in the reactions pp to pp(pi^+,pi^ {-})^{n} with n ranging from 2 to 6. The data sample consisted of 0.93 times10^6 fully reconstructed exclusive interactions, with incident proton momentum of 27.5 GeV/c, recorded by experiment E766 at the AGS in Brookhaven National Laboratory. By parametrizing the correlation with a function of Q^2 representing the dynamics of the reaction and the correlation itself, it was shown that the Q^2 scale does not depend on the final state multiplicity and has a value of 1.08 fermi. The "strength" of the correlation does depend on multiplicity. For negative pions the "strength" is 26% larger than for positive pions.
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.
Scrutinizing the pion condensed phase
NASA Astrophysics Data System (ADS)
Carignano, Stefano; Lepori, Luca; Mammarella, Andrea; Mannarelli, Massimo; Pagliaroli, Giulia
2017-02-01
When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero-momentum state forming a superfluid. Chiral perturbation theory provides a very powerful tool for studying this phase. However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic. We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework. As a first step, we perform a low-density expansion of the chiral Lagrangian valid close to the onset of the Bose-Einstein condensation. We obtain an effective theory that can be mapped to a Gross-Pitaevskii Lagrangian in which, remarkably, all the coefficients depend on the isospin chemical potential. The low-density expansion becomes unreliable deep in the pion condensed phase. For this reason, we develop an alternative field expansion deriving a low-energy Lagrangian analog to that of quantum magnets. By integrating out the "radial" fluctuations we obtain a soft Lagrangian in terms of the Nambu-Goldstone bosons arising from the breaking of the pion number symmetry. Finally, we test the robustness of the second-order transition between the normal and the pion condensed phase when next-to-leading-order chiral corrections are included. We determine the range of parameters for turning the second-order phase transition into a first-order one, finding that the currently accepted values of these corrections are unlikely to change the order of the phase transition.
Pion production: A probe for coherence in medium-energy heavy-ion collisions
NASA Astrophysics Data System (ADS)
Stachel, J.; Braun-Munzinger, P.; Freifelder, R. H.; Paul, P.; Sen, S.; Deyoung, P.; Zhang, P. H.; Awes, T. C.; Obenshain, F. E.; Plasil, F.; Young, G. R.; Fox, R.; Ronningen, R.
1986-04-01
The production of neutral pions has been studied in reactions of 35 MeV/nucleon 14N+ 27Al,Ni,W and 25 MeV/nucleon 16O+ 27Al,Ni. Inclusive pion differential distributions dσ/dTπ, dσ/dΩ, dσ/dy, dσ/dp⊥, and d2σ/dy dp⊥ have been measured by detecting the two pion-decay γ rays in a setup of 20 lead glass Cˇerenkov detector telescopes. Special care was taken to understand and suppress background events. Effects of pion reabsorption are discussed and it is found that the cross sections presented here are substantially affected by such final state interactions. The comparatively large experimental cross sections and the shape of the spectral distributions cannot be accounted for in single nucleon-nucleon collision or statistical models; they rather call for a coherent pion production mechanism.
I=2 pion scattering length from two-pion wave functions
Aoki, S.; Iwasaki, Y.; Kanaya, K.; Yamazaki, T.; Fukugita, M.; Ishikawa, K-I.; Okawa, M.; Ishizuka, N.; Kuramashi, Y.; Ukawa, A.; Yoshie, T.; Kaneko, T.
2005-05-01
We calculate the two-pion wave function in the ground state of the I=2 S-wave system and find the interaction range between two pions, which allows us to examine the validity of the necessary condition for the finite-volume method for the scattering length proposed by Luescher. We work in the quenched approximation employing a renormalization group improved gauge action for gluons and an improved Wilson action for quarks at 1/a=1.207(12) GeV on 16{sup 3}x80, 20{sup 3}x80, and 24{sup 3}x80 lattices. We conclude that the necessary condition is satisfied within the statistical errors for the lattice sizes L{>=}24 (3.92 fm) when the quark mass is in the range that corresponds to m{sub {pi}}{sup 2}=0.273-0.736 GeV{sup 2}. We obtain the scattering length with a smaller statistical error from the wave function than from the two-pion time correlator.
Pion-induced pion production on deuterium: a quasifree process
NASA Astrophysics Data System (ADS)
Sossi, V.; Iqbal, M. J.; Johnson, R. R.; Jones, G.; Pavan, M.; Rozon, F. M.; Sevior, M.; Vetterli, D.; Weber, P.; Sheffer, G.; Smith, G. R.; Camerini, P.; Grion, N.; Rui, R.; Stevenson, N. R.; Vicente-Vacas, M. J.
1992-10-01
A detailed experimental analysis of the π+d → π+π-pp in-plane coincidence data first presented by Rui et al. is compared to an expanded version of the Oset and Vicente-Vacas model for pion-induced pion production on a free nucleon. This extended model averages over Fermi motion to describe the assumed quasifree nature of the process occurring on the deuteron and includes nine additional diagrams to account for the N∗ → N(ππ) p-wave reaction channels. Experimental effects such as pion energy loss in the target and in the detectors, pion decay and muon detection are investigated and incorporated into the comparison of experimental data and theory. Inclusion of Fermi motion was found to be essential to provide good agreement between data and model confirming the quasifree nature of the reaction. When compared to the total-cross-section measurements of Manley et al., the free-reaction model yields a model-dependent estimate of the overall strength of the diagram containing the N∗ → N(ππ) s-wave vertex.
In-Medium Pion Valence Distribution Amplitude
NASA Astrophysics Data System (ADS)
Tsushima, K.; de Melo, J. P. B. C.
2017-03-01
After a brief review of the quark-based model for nuclear matter, and some pion properties in medium presented in our previous works, we report new results for the pion valence wave function as well as the valence distribution amplitude in medium, which are presented in our recent article. We find that both the in-medium pion valence distribution and the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.
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.
Dipole polarizabilities of charged pions
NASA Astrophysics Data System (ADS)
Fil'kov, L. V.; Kashevarov, V. L.
2017-01-01
We discuss main experimental works, where dipole polarizabilities of charged pions have been determined. Possible reasons for the differences between the experimental data are discussed. In particular, it is shown that the account of the -meson gives a significant correction to the value of the polarizability obtained in the latest experiment of the COMPASS collaboration.
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)
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
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.
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.
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.
NASA Astrophysics Data System (ADS)
Boos, E. G.; Ermilova, D. I.; Samojlov, V. V.; Temiraliev, T.; Batyunya, B. V.; Boguslavsky, I. V.; Dashian, N. B.; Gramenitsky, I. M.; Lednický, R.; Levonian, S. V.; Tikhonova, L. A.; Valkárová, A.; Vrba, V.; Zlatanov, Z.; Dumbrajs, S.; Ervanne, J.; Hannula, E.; Villanen, P.; Dementiev, R. K.; Korzhavina, I. A.; Leikin, E. M.; Rud, V. I.; Herynek, I.; Křepelová, O.; Reimer, P.; Řídký, J.; Šimák, V.; Suk, M.; Khudzadze, A. M.; Kuratashvili, G. O.; Topuriya, T. P.; Tsintsadze, V. D.; Alma-Ata-Dubna-Helsinki-Moscow-Prague-Tbilisi Collaboration
1980-11-01
New results on the inclusive and semi-inclusive production of π+ mesons and protons in the whole phase space are given for about 2.2 · 10 4 inelastic overlinepp interactions at 22.4 GeV/ c. A method of statistical separation for spectra of particles of the same charge which are produced in CP-symmetrical reactions is discussed in detail. Experimental data are compared with quark-parton model predictions.
Measurement of Charged Current Coherent Pion Production by Neutrinos on Carbon at MINER$\
Mislivec, Aaron Robert
2017-01-01
Neutrino-nucleus coherent pion production is a rare neutrino scattering process where the squared four-momentum transferred to the nucleus is small, a lepton and pion are produced in the forward direction, and the nucleus remains in its initial state. This process is an important background in neutrino oscillation experiments. Measurements of coherent pion production are needed to constrain models which are used to predict coherent pion production in oscillation experiments. This thesis reports measurements of νµ and νµ charged current coherent pion production on carbon for neutrino energies in the range 2 < Eν < 20 GeV. The measurements were made using data from MINERνA, which is a dedicated neutrino-nucleus scattering experiment that uses a fi scintillator tracking detector in the high-intensity NuMI neutrino beam at Fermilab. Coherent interactions were isolated from the data using only model-independent signatures of the reaction, which are a forward muon and pion, no evidence of nuclear breakup, and small four-momentum transfer to the nucleus. The measurements were compared to the coherent pion production model used by oscillation experiments. The data and model agree in the total interaction rate and are similar in the dependence of the interaction rate on the squared four- momentum transferred from the neutrino. The data and model disagree significantly in the pion kinematics. The measured νµ and νµ interaction rates are consistent, which supports model predictions that the neutrino and antineutrino interaction rates are equal.
Three pion nucleon coupling constants
NASA Astrophysics Data System (ADS)
Ruiz Arriola, E.; Amaro, J. E.; Navarro Pérez, R.
2016-08-01
There exist four pion nucleon coupling constants, fπ0pp, - fπ0nn, fπ+pn/2 and fπ-np/2 which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion-nucleon-nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination fp2 = 0.0759(4),f 02 = 0.079(1),f c2 = 0.0763(6), based on a partial wave analysis of the 3σ self-consistent nucleon-nucleon Granada-2013 database comprising 6713 published data in the period 1950-2013.
Pion single charge exchange in three body nuclei at intermediate energies
Dowell, Marla 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, π^{+}n → π^{0} p or π^{-} p → π^{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 Δ-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--^{3}He and ^{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 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.
Gauged linear sigma model and pion-pion scattering
Fariborz, Amir H.; Schechter, Joseph; Shahid, M. Naeem
2009-12-01
A simple gauged linear sigma model with several parameters to take the symmetry breaking and the mass differences between the vector meson and the axial vector meson into account is considered here as a possibly useful 'template' for the role of a light scalar in QCD as well as for (at a different scale) an effective Higgs sector for some recently proposed walking technicolor models. An analytic procedure is first developed for relating the Lagrangian parameters to four well established (in the QCD application) experimental inputs. One simple equation distinguishes three different cases: i. QCD with axial vector particle heavier than vector particle, ii. possible technicolor model with vector particle heavier than the axial vector one, iii. the unphysical QCD case where both the Kawarabayashi-Suzuki-Riazuddin-Fayazuddin and Weinberg relations hold. The model is applied to the s-wave pion-pion scattering in QCD. Both the near threshold region and (with an assumed unitarization) the 'global' region up to about 800 MeV are considered. It is noted that there is a little tension between the choice of 'bare' sigma mass parameter for describing these two regions. If a reasonable 'global' fit is made, there is some loss of precision in the near threshold region.
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.
The classical pion field in a nucleus
NASA Astrophysics Data System (ADS)
Ripka, Georges
2008-12-01
A self-consistent symmetry arises when the nucleon angular momentum j and the isospin t are coupled to a grand spin G. Closed G shells become sources of a classical pion field with a hedgehog shape. Although the amplitude of the pion field, as measured by the chiral angle, is small, it is found to perturb significantly the energies of the nucleon orbits.
Pion masses in quasiconformal gauge field theories
Dietrich, Dennis D.; Jaervinen, Matti
2009-03-01
We study modifications to Weinberg-like sum rules in quasiconformal gauge field theories. Beyond the two Weinberg sum rules and the oblique S parameter, we study the pion mass and the X parameter. Especially, we evaluate the pion mass for walking technicolor theories, in particular, minimal walking technicolor, and find contributions of the order of up to several hundred GeV.
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.
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.
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
Fate of pion condensation in quark matter: From the chiral limit to the physical pion mass
Abuki, H.; Anglani, R.; Pellicoro, M.; Ruggieri, M.; Gatto, R.
2009-02-01
We study aspects of the pion condensation in two-flavor neutral quark matter using the Nambu-Jona-Lasinio model of QCD at finite density. We investigate the role of electric charge neutrality, and explicit symmetry breaking via quark mass, both of which control the onset of the charged pion ({pi}{sup c}) condensation. We show that the equality between the electric chemical potential and the in-medium pion mass, {mu}{sub e}=M{sub {pi}{sup -}}, as a threshold, persists even for a composite pion system in the medium, provided the transition to the pion condensed phase is of the second order. Moreover, we find that the pion condensate in neutral quark matter is extremely fragile with respect to the symmetry breaking effect via a current quark mass m, and is ruled out for m larger than the order of 10 keV.
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.
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.
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.
Valence-quark distributions in the pion
Hecht, M. B.; Roberts, C. D.; Schmidt, S. M.
2001-02-01
We calculate the pion's valence-quark momentum-fraction probability distribution using a Dyson-Schwinger equation model. Valence quarks with an active mass of 0.30 GeV carry 71% of the pion's momentum at a resolving scale q{sub 0}=0.54 GeV=1/(0.37 fm). The shape of the calculated distribution is characteristic of a strongly bound system and, evolved from q{sub 0} to q=2 GeV, it yields first, second, and third moments in agreement with lattice and phenomenological estimates, and valence-quarks carrying 49% of the pion's momentum. However, pointwise there is a discrepancy between our calculated distribution and that hitherto inferred from parametrizations of extant pion-nucleon Drell-Yan data.
Low energy theorems in pion production
Holstein, B.R. |
1992-09-01
Considerable activity-both theoretical and experimental-has recently taken place involving the threshold and near threshold of pion photo- and electroproduction. This activity is herein summarized and a program for future work is outlined.
Low energy theorems in pion production
Holstein, B.R. . Dept. of Physics and Astronomy Washington Univ., Seattle, WA . Inst. for Nuclear Theory)
1992-01-01
Considerable activity-both theoretical and experimental-has recently taken place involving the threshold and near threshold of pion photo- and electroproduction. This activity is herein summarized and a program for future work is outlined.
Model selection for pion photoproduction
NASA Astrophysics Data System (ADS)
Landay, J.; Döring, M.; Fernández-Ramírez, C.; Hu, B.; Molina, R.
2017-01-01
Partial-wave analysis of meson and photon-induced reactions is needed to enable the comparison of many theoretical approaches to data. In both energy-dependent and independent parametrizations of partial waves, the selection of the model amplitude is crucial. Principles of the S matrix are implemented to a different degree in different approaches; but a many times overlooked aspect concerns the selection of undetermined coefficients and functional forms for fitting, leading to a minimal yet sufficient parametrization. We present an analysis of low-energy neutral pion photoproduction using the least absolute shrinkage and selection operator (LASSO) in combination with criteria from information theory and K -fold cross validation. These methods are not yet widely known in the analysis of excited hadrons but will become relevant in the era of precision spectroscopy. The principle is first illustrated with synthetic data; then, its feasibility for real data is demonstrated by analyzing the latest available measurements of differential cross sections (d σ /d Ω ), photon-beam asymmetries (Σ ), and target asymmetry differential cross sections (d σT/d ≡T d σ /d Ω ) in the low-energy regime.
Model selection for pion photoproduction
Landay, J.; Doring, M.; Fernandez-Ramirez, C.; ...
2017-01-12
Partial-wave analysis of meson and photon-induced reactions is needed to enable the comparison of many theoretical approaches to data. In both energy-dependent and independent parametrizations of partial waves, the selection of the model amplitude is crucial. Principles of the S matrix are implemented to a different degree in different approaches; but a many times overlooked aspect concerns the selection of undetermined coefficients and functional forms for fitting, leading to a minimal yet sufficient parametrization. We present an analysis of low-energy neutral pion photoproduction using the least absolute shrinkage and selection operator (LASSO) in combination with criteria from information theory andmore » K-fold cross validation. These methods are not yet widely known in the analysis of excited hadrons but will become relevant in the era of precision spectroscopy. As a result, the principle is first illustrated with synthetic data; then, its feasibility for real data is demonstrated by analyzing the latest available measurements of differential cross sections (dσ/dΩ), photon-beam asymmetries (Σ), and target asymmetry differential cross sections (dσT/d≡Tdσ/dΩ) in the low-energy regime.« less
PLIAC: A Pion Linac facility for 1-GEV pion physics at LAMPF
Spalek, G.; Thiessen, H.A.
1991-01-01
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 an rf particle separator, all beams produced by PILAC will be free of electron (or positron) and proton contamination.
PLIAC: A Pion Linac facility for 1-GEV pion physics at LAMPF
Spalek, G.; 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 an rf particle separator, all beams produced by PILAC will be free of electron (or positron) and proton contamination.
JLAB CLAS Results on Pion Production from Nuclear Target
NASA Astrophysics Data System (ADS)
Lee, Hyupwoo; Manly, Steven
Preliminary results on single 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, carbon, iron, and lead targets. The motivation for this work is to provide distributions useful for tuning the hadronic final state interaction models used in extracting results from current and next generation neutrino oscillation experiments.
Longitudinal Electroproduction of Charged Pions from
David Gaskell; Abdellah Ahmidouch; Pawel Ambrozewicz; H. Anklin; John Arrington; K. Assamagan; Steven Avery; Kevin Bailey; Oliver K. Baker; Shelton Beedoe; Elizabeth Beise; Herbert Breuer; D. S. Brown; Roger Carlini; Jinseok Cha; Nicholas Chant; Anthony Cowley; Samuel Danagoulian; D. De Schepper; Jim Dunne; Dipangkar Dutta; Rolf Ent; Liping Gan; Ashot Gasparian; Donald Geesaman; Ron Gilman; Charles Glashausser; Paul Gueye; M. Harvey; O. Hashimoto; Wendy Hinton; G. Hofman; Ceasar Jackson; Hal Jackson; Cynthia Keppel; Ed Kinney; Doug Koltenuk; G. Kyle; Allison Lung; David Mack; D. McKee; Joseph Mitchell; Hamlet Mkrtchyan; B. Mueller; Gabriel Niculescu; Ioana Niculescu; Tom O'Neill; V. Papavassiliou; Dave Potterveld; Juerg Reinhold; Philip Roos; Reyad Sawafta; Ralph Segel; Stepan Stepanyan; Vardan Tadevosyan; T. Takahashi; Liguang Tang; B. Terburg; D. Van Westrum; J. Volmer; T. P. Welch; Stephen Wood; Lulin Yuan; Ben Zeidman; Beni Zihlmann
2001-11-12
Separated longitudinal and transverse cross sections for charged pion electroproduction from {sup 1}H, {sup 2}H, and {sup 3}He were measured at Q{sup 2} = 0.4 (GeV/c){sup 2} for two values of the invariant mass, {bar W} = 1.15 GeV and {bar W} = 1.60 GeV, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in {sup 3>}He at {bar W} = 1.60 GeV. The {bar W} = 1.15 GeV results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production.
Pion Charge Exchange Cross Section on Liquid Argon
NASA Astrophysics Data System (ADS)
Nelson, Kevin; LArIAT (FNAL T-1034) Collaboration
2017-01-01
The observation of neutrino oscillations allows charge parity violation to be probed in the neutrino sector. Detectors with high calorimetric energy resolution and high spatial resolution will provide precise measurements of neutrino oscillations. By measuring small π+/- cross sections for individual interaction channels, specifically charge exchange, we will make a measurement in the first of its kind on liquid Argon and demonstrate the physics capabilities of a relatively new detector technology: the Liquid Argon Time Projection Chamber (LAr TPC). This analysis will report on the thin slab cross section measurement technique and the Monte Carlo cross section measurements in the energy range of 0.2 - 1.0 GeV. This analysis is the first iteration in classifying charge exchange events from a sample of incident pions, and it aims to identify events in which a π0 was produced without any charged pions leaving the interaction vertex. We will also report on the methodology and efficiency of this algorithm in identifying particles and their interactions in liquid argon. This analysis will inform a future measurement of the π+/- charge exchange cross section on liquid argon. This work was supported in part by the National Science Foundation under Grant No. PHY-1359364.
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.
Effects of chiral imbalance and magnetic field on pion superfluidity and color superconductivity
NASA Astrophysics Data System (ADS)
Cao, Gaoqing; Zhuang, Pengfei
2015-11-01
The effects of chiral imbalance and external magnetic field on pion superfluidity and color superconductivity are investigated in extended Nambu-Jona-Lasinio models. We take the Schwinger approach to treat the interaction between the charged pion condensate and magnetic field at finite isospin density and include simultaneously the chiral imbalance and magnetic field at finite baryon density. For the superfluidity, the chiral imbalance and magnetic field lead to catalysis and inverse catalysis effects, respectively. For the superconductivity, the chiral imbalance enhances the critical baryon density, and the magnetic field results in a de Haas-van Alphan oscillation on the phase transition line.
Partial wave analysis of 3 π with pion and photon beams
NASA Astrophysics Data System (ADS)
Jackura, Andrew; Mikhasenko, Mikhail; Szczepaniak, Adam; Ketzer, Bernhard; Joint Physics Analysis Center Collaboration
2016-09-01
We present some results on the analysis of 3 π resonances from peripheral scattering of pions off of nuclear targets. The analysis is motivated by the recent release of the largest data set on diffractively produced three pions by the COMPASS collaboration. The model emphasizes the 3 π production process and their final state interactions which satisfy S-matrix principles. We apply our model to fit partial wave intensities and relative phases from COMPASS in the JPC =2-+ sector and search for resonances. We then discuss the extension of our formalism to photon beams to be used in the GlueX experiment.
Relativistic O(q{sup 4}) two-pion exchange nucleon-nucleon potential: parametrized version
R. Higa; M. R. Robilotta; C. A. da Rocha
2005-01-01
The chiral two-pion exchange nucleon-nucleon interaction has nowadays a rather firm conceptual basis, but depends on low-energy constants, which may be extracted from fits to data. In order to facilitate this kind of application, we present here a parametrized version of our relativistic expansion of this component of the force to O(q{sup 4}), performed recently.
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.
nuSTORM Pion Beamline Design Update
Liu, A.; Bross, A.; Neuffer, D.; Lee, S. Y.
2013-09-01
A facility producing neutrinos from muons that decay in a racetrack ring can provide extremely well understood neutrino beams for oscillation physics and the search for sterile neutrinos. The “neutrinos from STORed Muons” (nuSTORM) facility based on this idea has been introduced by Bross, Neuffer et al. The design of the nuSTORM facility and the particle tracking have been presented in the paper of Liu, et al. This paper demonstrates the recent optimization results of the pion beamline, with G4beamline simulations. The optimum choice of pion beam center momentum, a new algorithm on fitting bivariate Gaussian distribution to the pion phase space data at the downstream side of the horn, and the comparison of the beamline performance with the optics designed based on Graphite and Inconel targets are also described.
Low-energy theorems for pion photoproduction from nuclei and pion-nucleus coupling constants
Radutskii, G.M.; Serdyutskii, V.A.
1982-10-01
New low-energy theorems for pion photoproduction in light nuclei are derived using a model that allows one to extract all the information contained in the current algebra and the CVC and PCAC hypotheses. From the comparison with the experimental total cross sections for threshold photoproduction of charged pions on the nuclei /sup 6/Li, /sup 12/C, and /sup 14/N, the values of the pion-nucleus coupling constants are obtained and the magnitude of the electric quadrupole moment of the /sup 12/N nucleus is predicted.
NASA Astrophysics Data System (ADS)
Kocić, Aleksander
1988-06-01
We discuss the origin of the pion mass using a simple model of the QCD vacuum as a condensate of overlapping quark-antiquark pairs. We analyze the relationship between local conservation of the axial current and the nonzero current quark mass. Away from the chiral limit, we find that the pion mass comes from a change in the geometry of the overlap of condensed pairs. We wish to thank Lee Brekke, Vijay Pandharipande, and Bob Thews for their interest and useful discussions. We acknowledge the hospitality of the Physics Department of the University of Illinois where part of this work was done.
Pion absorption on 3He at low energies
NASA Astrophysics Data System (ADS)
Hahn, H.; Altman, A.; Ashery, D.; Gefen, G.; Gill, D. R.; Johnson, R. R.; Levy-Nathansohn, R.; Moinester, M. A.; Sevior, M.; Trelle, R. P.
1996-03-01
The reactions 3He(π+,pp)p and 3He(π-,pn)n were studied at 37.0 MeV by coincidence detection of two nucleons. The differential cross sections were separated to two-nucleon (σ2N), three-nucleon (σ3N), and final-state interaction (σFSI) components. For π+, the σ2N angular distribution is symmetric about 90°, and the total cross section is 1.5 times the cross section measured for d(π+,pp). For π-, the angular distribution is asymmetric (backward peaked). The asymmetry increases with decreasing energy, indicating increasing pion s-wave contribution at lower energies. The fraction of the cross section induced by s-wave pions as calculated by a partial wave amplitude analysis is 13%. The measured total cross sections are σ2N(π-)=0.85+/-0.08 mb and σ2N(π+)=7.9+/-0.5 mb; σ3N(π-)=1.6+/-0.7 mb and σ3N(π+)=1.3+/-0.3 mb. A new evaluation of σ3N at Tπ=62.5 and 82.8 MeV is given, using data from an earlier experiment. The cross sections leading to the two-nucleon final-state interaction at Tπ=37.0 MeV are also estimated.
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.
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.
Exclusive electroproduction of two pions at HERA
NASA Astrophysics Data System (ADS)
Abramowicz, H.; Abt, I.; Adamczyk, L.; Adamus, M.; Aggarwal, R.; Antonelli, S.; Antonioli, P.; Antonov, A.; Arneodo, M.; Ashery, D.; Aushev, V.; Aushev, Y.; Bachynska, O.; Bamberger, A.; Barakbaev, A. N.; Barbagli, G.; Bari, G.; Barreiro, F.; Bartosik, N.; Bartsch, D.; Basile, M.; Behnke, O.; Behr, J.; Behrens, U.; Bellagamba, L.; Bertolin, A.; Bhadra, S.; Bindi, M.; Blohm, C.; Bokhonov, V.; Bołd, T.; Bondarenko, K.; Boos, E. G.; Borras, K.; Boscherini, D.; Bot, D.; Brock, I.; Brownson, E.; Brugnera, R.; Brümmer, N.; Bruni, A.; Bruni, G.; Brzozowska, B.; Bussey, P. J.; Bylsma, B.; Caldwell, A.; Capua, M.; Carlin, R.; Catterall, C. D.; Chekanov, S.; Chwastowski, J.; Ciborowski, J.; Ciesielski, R.; Cifarelli, L.; Cindolo, F.; Contin, A.; Cooper-Sarkar, A. M.; Coppola, N.; Corradi, M.; Corriveau, F.; Costa, M.; D'Agostini, G.; Dal Corso, F.; del Peso, J.; Dementiev, R. K.; De Pasquale, S.; Derrick, M.; Devenish, R. C. E.; Dobur, D.; Dolgoshein, B. A.; Dolinska, G.; Doyle, A. T.; Drugakov, V.; Durkin, L. S.; Dusini, S.; Eisenberg, Y.; Ermolov, P. F.; Eskreys, S.; Fang, S.; Fazio, S.; Ferrando, J.; Ferrero, M. I.; Figiel, J.; Forrest, M.; Foster, B.; Gach, G.; Galas, A.; Gallo, E.; Garfagnini, A.; Geiser, A.; Gialas, I.; Gladilin, L. K.; Gladkov, D.; Glasman, C.; Gogota, O.; Golubkov, Yu. A.; Göttlicher, P.; Grabowska-Bołd, I.; Grebenyuk, J.; Gregor, I.; Grigorescu, G.; Grzelak, G.; Gueta, O.; Gurvich, E.; Guzik, M.; Gwenlan, C.; Haas, T.; Hain, W.; Hamatsu, R.; Hart, J. C.; Hartmann, H.; Hartner, G.; Hilger, E.; Hochman, D.; Hori, R.; Horton, K.; Hüttmann, A.; Ibrahim, Z. A.; Iga, Y.; Ingbir, R.; Ishitsuka, M.; Jakob, H.-P.; Januschek, F.; Jones, T. W.; Jüngst, M.; Kadenko, I.; Kahle, B.; Kananov, S.; Kanno, T.; Karshon, U.; Karstens, F.; Katkov, I. I.; Kaur, M.; Kaur, P.; Keramidas, A.; Khein, L. A.; Kim, J. Y.; Kisielewska, D.; Kitamura, S.; Klanner, R.; Klein, U.; Koffeman, E.; Kooijman, P.; Korol, Ie.; Korzhavina, I. A.; Kotański, A.; Kötz, U.; Kowalski, H.; Kuprash, O.; Kuze, M.; Lee, A.; Levchenko, B. B.; Levy, A.; Libov, V.; Limentani, S.; Ling, T. Y.; Lisovyi, M.; Lobodzinska, E.; Lohmann, W.; Löhr, B.; Lohrmann, E.; Long, K. R.; Longhin, A.; Lontkovskyi, D.; Lukina, O. Yu.; Maeda, J.; Magill, S.; Makarenko, I.; Malka, J.; Mankel, R.; Margotti, A.; Marini, G.; Martin, J. F.; Mastroberardino, A.; Mattingly, M. C. K.; Melzer-Pellmann, I.-A.; Mergelmeyer, S.; Miglioranzi, S.; Mohamad Idris, F.; Monaco, V.; Montanari, A.; Morris, J. D.; Mujkic, K.; Musgrave, B.; Nagano, K.; Namsoo, T.; Nania, R.; Nigro, A.; Ning, Y.; Nobe, T.; Noor, U.; Notz, D.; Nowak, R. J.; Nuncio-Quiroz, A. E.; Oh, B. Y.; Okazaki, N.; Oliver, K.; Olkiewicz, K.; Onishchuk, Yu.; Papageorgiu, K.; Parenti, A.; Paul, E.; Pawlak, J. M.; Pawlik, B.; Pelfer, P. G.; Pellegrino, A.; Perlański, W.; Perrey, H.; Piotrzkowski, K.; Pluciński, P.; Pokrovskiy, N. S.; Polini, A.; Proskuryakov, A. S.; Przybycień, M.; Raval, A.; Reeder, D. D.; Reisert, B.; Ren, Z.; Repond, J.; Ri, Y. D.; Robertson, A.; Roloff, P.; Rubinsky, I.; Ruspa, M.; Sacchi, R.; Salii, A.; Samson, U.; Sartorelli, G.; Savin, A. A.; Saxon, D. H.; Schioppa, M.; Schlenstedt, S.; Schleper, P.; Schmidke, W. B.; Schneekloth, U.; Schönberg, V.; Schörner-Sadenius, T.; Schwartz, J.; Sciulli, F.; Shcheglova, L. M.; Shehzadi, R.; Shimizu, S.; Singh, I.; Skillicorn, I. O.; Słomiński, W.; Smith, W. H.; Sola, V.; Solano, A.; Son, D.; Sosnovtsev, V.; Spiridonov, A.; Stadie, H.; Stanco, L.; Stern, A.; Stewart, T. P.; Stifutkin, A.; Stopa, P.; Suchkov, S.; Susinno, G.; Suszycki, L.; Sztuk-Dambietz, J.; Szuba, D.; Szuba, J.; Tapper, A. D.; Tassi, E.; Terrón, J.; Theedt, T.; Tiecke, H.; Tokushuku, K.; Tomalak, O.; Tomaszewska, J.; Tsurugai, T.; Turcato, M.; Tymieniecka, T.; Vázquez, M.; Verbytskyi, A.; Viazlo, O.; Vlasov, N. N.; Volynets, O.; Walczak, R.; Wan Abdullah, W. A. T.; Whitmore, J. J.; Wiggers, L.; Wing, M.; Wlasenko, M.; Wolf, G.; Wolfe, H.; Wrona, K.; Yagües-Molina, A. G.; Yamada, S.; Yamazaki, Y.; Yoshida, R.; Youngman, C.; Żarnecki, A. F.; Zawiejski, L.; Zenaiev, O.; Zeuner, W.; Zhautykov, B. O.; Zhmak, N.; Zhou, C.; Zichichi, A.; Zolkapli, Z.; Zolko, M.; Zotkin, D. S.
2012-01-01
The exclusive electroproduction of two pions in the mass range 0.4< M ππ <2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb-1. The analysis was carried out in the kinematic range of 2< Q 2<80 GeV2, 32< W<180 GeV and | t|<0.6 GeV2, where Q 2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, | F( M ππ )|, assuming that the studied mass range includes the contributions of the ρ, ρ' and ρ'' vector-meson states. The masses and widths of the resonances were obtained and the Q 2 dependence of the cross-section ratios σ( ρ'→ ππ)/ σ( ρ) and σ( ρ''→ ππ)/ σ( ρ) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e + e -→ π + π -.
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.
The pion: an enigma within the Standard Model
Horn, Tanja; Roberts, Craig D.
2016-05-27
Almost 50 years after the discovery of gluons & quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: neutrons, protons, and the pions that bind them. QCD is characterised by two emergent phenomena: confinement & dynamical chiral symmetry breaking (DCSB). They are expressed with great force in the character of the pion. In turn, pion properties suggest that confinement & DCSB are closely connected. As both a Nambu-Goldstone boson and a quark-antiquark bound-state, the pion is unique in Nature. Developing an understanding of its properties is thus critical to revealing basic features of the Standard Model. We describe experimental progress in this direction, made using electromagnetic probes, highlighting both improvements in the precision of charged-pion form factor data, achieved in the past decade, and new results on the neutral-pion transition form factor. Both challenge existing notions of pion structure. We also provide a theoretical context for these empirical advances, first explaining how DCSB works to guarantee that the pion is unnaturally light; but also, nevertheless, ensures the pion is key to revealing the mechanisms that generate nearly all the mass of hadrons. Our discussion unifies the charged-pion elastic and neutral-pion transition form factors, and the pion's twist-2 parton distribution amplitude. It also indicates how studies of the charged-kaon form factor can provide significant contributions. Importantly, recent predictions for the large-$Q^2$ behaviour of the pion form factor can be tested by experiments planned at JLab 12. Those experiments will extend precise charged-pion form factor data to momenta that can potentially serve in validating factorisation theorems in QCD, exposing the transition between the nonperturbative and perturbative domains, and thereby reaching a goal that has long driven hadro-particle physics.
Energy dependence of pion and kaon production in central Pb+Pb collisions
NASA Astrophysics Data System (ADS)
Afanasiev, S. V.; Anticic, T.; Barna, D.; Bartke, J.; Barton, R. A.; Behler, M.; Betev, L.; Białkowska, H.; Billmeier, A.; Blume, C.; Blyth, C. O.; Boimska, B.; Botje, M.; Bracinik, J.; Bramm, R.; Brun, R.; Bunčić, P.; Cerny, V.; Cramer, J. G.; Csató, P.; Dinkelaker, P.; Eckhardt, V.; Filip, P.; Fodor, Z.; Foka, P.; Freund, P.; Friese, V.; Gál, J.; Gaździcki, M.; Georgopoulos, G.; Gładysz, E.; Hegyi, S.; Höhne, C.; Igo, G.; Jones, P. G.; Kadija, K.; Karev, A.; Kolesnikov, V. I.; Kollegger, T.; Kowalski, M.; Kraus, I.; Kreps, M.; van Leeuwen, M.; Lévai, P.; Malakhov, A. I.; Margetis, S.; Markert, C.; Mayes, B. W.; Melkumov, G. L.; Mischke, A.; Molnár, J.; Nelson, J. M.; Pálla, G.; Panagiotou, A. D.; Perl, K.; Petridis, A.; Pikna, M.; Pinsky, L.; Pühlhofer, F.; Reid, J. G.; Renfordt, R.; Retyk, W.; Roland, C.; Roland, G.; Rybicki, A.; Sammer, T.; Sandoval, A.; Sann, H.; Schmitz, N.; Seyboth, P.; Siklér, F.; Sitar, B.; Skrzypczak, E.; Squier, G. T.; Stock, R.; Ströbele, H.; Susa, T.; Szentpétery, I.; Sziklai, J.; Trainor, T. A.; Varga, D.; Vassiliou, M.; Veres, G. I.; Vesztergombi, G.; Vranić, D.; Wetzler, A.; Whitten, C.; Yoo, I. K.; Zaranek, J.; Zimányi, J.
2002-11-01
Measurements of charged pion and kaon production in central Pb+Pb collisions at 40, 80, and 158 A GeV are presented. These are compared with data at lower and higher energies as well as with results from p+p interactions. The mean pion multiplicity per wounded nucleon increases approximately linearly with s1/4NN with a change of slope starting in the region 15-40 A GeV. The change from pion suppression with respect to p+p interactions, as observed at low collision energies, to pion enhancement at high energies occurs at about 40A GeV. A nonmonotonic energy dependence of the ratio of K+ to π+ yields is observed, with a maximum close to 40A GeV and an indication of a nearly constant value at higher energies. The measured dependences may be related to an increase of the entropy production and a decrease of the strangeness to entropy ratio in central Pb+Pb collisions in the low SPS energy range, which is consistent with the hypothesis that a transient state of deconfined matter is created above these energies. Other interpretations of the data are also discussed.
Impact of pion dynamics on nuclear shell structure
NASA Astrophysics Data System (ADS)
Litvinova, Elena
2015-10-01
Spin-isospin response in exotic nuclear systems is investigated. It is found that in some nuclei excitations with pionic quantum numbers (0-, 1+, 2-, …) 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- components of the spin-dipole resonance in 78Ni and 132Sn 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 100Sn is discussed.
Quark mean field model with pion and gluon corrections
NASA Astrophysics Data System (ADS)
Xing, Xueyong; Hu, Jinniu; Shen, Hong
2016-10-01
The properties of nuclear matter and finite nuclei are studied within the quark mean field (QMF) model by taking the effects of pions and gluons into account at the quark level. The nucleon is described as the combination of three constituent quarks confined by a harmonic oscillator potential. To satisfy the spirit of QCD theory, the contributions of pions and gluons on the nucleon structure are treated in second-order perturbation theory. In a nuclear many-body system, nucleons interact with each other by exchanging mesons between quarks. With different constituent quark mass, mq, we determine three parameter sets for the coupling constants between mesons and quarks, named QMF-NK1, QMF-NK2, and QMF-NK3, by fitting the ground-state properties of several closed-shell nuclei. It is found that all of the three parameter sets can give a satisfactory description of properties of nuclear matter and finite nuclei, moreover they also predict a larger neutron star mass around 2.3 M⊙ without hyperon degrees of freedom.
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.
Nuclear collective flow and charged-pion emission in Ne-nucleus collisions at E/A = 800 MeV
NASA Technical Reports Server (NTRS)
Gosset, J.; Valette, O.; Babinet, R.; Alard, J. P.; Augerat, J.
1989-01-01
Triple-differential cross sections of charged pions were measured for collisions of Ne projectiles at E/A = 800 MeV with NaF, Nb, and Pb targets. The reaction plane was estimated event by event from the light-baryon momentum distribution. For heavy targets, preferential emission of charged pions away from the interaction zone toward the projectile side was observed in the transverse direction. Such a preferential emission, which is not predicted by cascade calculations, may be attributed to a stronger pion absorption by the heavier spectator remnant.
The First Pion-Ar Cross-Section Measurement with the LArIAT Experiment
Nutini, Irene
2016-01-01
A complete understanding of neutrinos properties requires a study and a characterization of the interactions of the daughter particles created in a neutrino-nucleus interaction. The Liquid Argon In A Testbeam (LArIAT) experiment is a small-scale liquid argon detector situated in the Fermilab Test Beam Facility. The LArIAT experiment is exposed to a tertiary beam comprised of mostly pions along with a mix of muons, protons, kaons, and electrons. LArIAT's goal is to characterize the response of the LArTPC to known incoming charged particles and measure their interactions in Argon, in order to understand their cross-sections and to help developing and tuning simulations and reconstruction algorithms for LArTPC neutrino experiments. The world's rst measurement of a pion cross-section on an Argon target, made with the LArIAT detector, is presented here.
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 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.; 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
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 than $\\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.
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}
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 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.
Chiral nontopological solitons with perturbative quantum pions
NASA Astrophysics Data System (ADS)
Williams, A. G.; Dodd, L. R.
1988-04-01
We investigate chiral extensions of a broad class of nontopological soliton bag models. Chiral symmetry is restored in a nonlinear realization through the introduction of an elementary pion field. We show in particular that it is consistent to treat the pions as a perturbative quantum field, as is done in the cloudy-bag model. The cloudy-bag model is recovered as a limiting case. A careful comparison is made between predictions of chiral extensions of the Friedberg-Lee and the Nielsen-Patkos color-dielectric nontopological soliton models and the cloudy-bag model. Once the overall distance scale is fixed we find relative insensitivity to the detailed choice of nontopological soliton parameters. We investigate two versions of chiral nontopological solitons, analogous to the surface- and volume-coupled cloudy-bag model, and discuss their relation to current algebra.
Transversity from two pion interference fragmentation
She Jun; Huang Yang; Barone, Vincenzo; Ma Boqiang
2008-01-01
We present calculation on the azimuthal spin asymmetries for pion pair production in semi-inclusive deep inelastic scattering (SIDIS) process at both HERMES and COMPASS kinematics, with transversely polarized proton, deuteron, and neutron targets. We calculate the asymmetry by adopting a set of parametrization of the interference fragmentation functions and two different models for the transversity. We find that the result for the proton target is insensitive to the approaches of the transversity but more helpful to understand the interference fragmentation functions. However, for the neutron target, which can be obtained through using deuteron and {sup 3}He targets, we find different predictions for different approaches to the transversity. Thus probing the two pion interference fragmentation from the neutron can provide us more interesting information on the transversity.
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.
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.
Faessler, A.; Kovalenko, S.; Simkovic, F.; Schwieger, J.; Kovalenko, S.; Simkovic, F.; Simkovic, F.
1997-01-01
We present a new contribution of the R-parity-violating (R/{sub p}) supersymmetry (SUSY) to neutrinoless double beta decay (0{nu}{beta}{beta}) via the pion exchange between decaying neutrons. The pion coupling to the final state electrons is induced by the R/{sub p} SUSY interactions. We have found this pion-exchange mechanism to dominate over the conventional two-nucleon one. The latter corresponds to direct interaction between quarks from two decaying neutrons without any light hadronic mediator like {pi} meson. The constraints on the certain R/{sub p} SUSY parameters are extracted from the current experimental 0{nu}{beta}{beta}-decay half-life limit. These constraints are significantly stronger than those previously known or expected from the ongoing accelerator experiments. {copyright} {ital 1997} {ital The American Physical Society}
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.
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.
A Study of Charged Current Single Charged Pion Productions on Carbon in a Few-GeV Neutrino Beam
Hiraide, Katsuki
2009-01-01
Understanding single charged pion production via neutrino-nucleus charged current interaction in the neutrino energy region of a few GeV is essential for future neutrino oscillation experiments since this process is a dominant background for v_{μ} → v_{x} oscillation measurements. There are two contributions to this process: single pion production via baryonic resonance (v_{μ}N → μ^{-} Nπ^{+}) and coherent pion production interacting with the entire nucleus (v_{μ}A → μ^{-} Aπ^{+}), where N is nucleon in the nucleus and A is the nucleus. The purpose of the study presented in this thesis is a precise measurement of charged current single charged pion productions, resonant and coherent pion productions, with a good final state separation in the neutrino energy region of a few GeV. In this thesis, we focus on the study of charged current coherent pion production from muon neutrinos scattering on carbon, v_{μ} ^{12}C → μ^{-12}Cπ^{+}, in the SciBooNE experiment. This is motivated by the fact that without measuring this component first, the precise determination of resonant pion production cross section can not be achieved since the contribution of coherent pion production in the region of small muon scattering angle is not small. Furthermore, the coherent process is particularly interesting because it is deeply rooted in fundamental physics via Adler's partially conserved axial-vector current theorem. We took data from June 2007 until August 2008, in both the neutrino and antineutrino beam. In total, 2.52 x 10^{20} protons on target were collected. We have performed a search for charged current coherent pion production by using SciBooNE's full neutrino data set, corresponding to 0.99 x 10^{20} protons on target. No evidence for coherent pion production is observed. We set 90% confidence level upper limits on the cross section ratio of charged
NASA Astrophysics Data System (ADS)
Dingus, Peter John
From over 300,000 hadronic events gathered by the BC72/73 collaboration, which directed a 20GeV photon beam onto a liquid hydrogen target, the reaction gamma p to pp ^' was isolated in the channels gamma p to p2pi^+2pi^- and gamma p to ppi^+pi^-2pi^0 . Subsequently various Monte Carlo models of the rho^' decaying into four pions in the charge states 2pi^+2 pi^- and pi^+ pi^-2pi^0 were fit to the data in all pertinent kinematic variables along with the decay angular distributions and various assumed backgrounds that had not been disentangled. The results of this analysis are: (1) The Photoproduced rho^' conserves S channel helicity, this is shown by an analysis of the angle Phi, as described in the text, and by the Density Matrix Elements, (DME), of the rho^' in the channel gamma p to p2pi^+2pi^-. The DMEs, through the Parity Asymmetry, also show the rho^' production to be mostly due to natural parity exchange in the t channel. (2) The dominant decay mode of the rho^' is via rho^' to pi A_1, this is shown by the absence of a rho^0 signal in the channel gamma p to ppi^+pi ^-2pi^0 and by the approximate equality of the rho^' cross sections in the two channels. The rho ^' cross section in the channel gamma p to p2pi^+2pi^- is measured to be 0.944 +/- 0.05 mu b and the rho^' cross section in the channel gamma p to ppi^+ pi^-2pi^0 is measured to be 1.19 +/- 0.089mu b. (3) The rho^' mass and width in the channel gamma p to p2pi^+2 pi^- are determined to be 1.20 +/- 0.05GeV and 0.535 +/- 0.04GeV respectively. In the channel gamma p to ppi^+ pi^-2pi^0 the rho^' mass and width are determined to be 1.25 +/- 0.1GeV and 0.53 +/- 0.06GeV respectively.
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.
NEGATIVE PION PHOTOPRODUCTION FROM BISMUTH ACCOMPANIED BY NEUTRON EMISSION,
BISMUTH, PIONS, EMISSIVITY, BREMSSTRAHLUNG, NUCLEI, ALPHA PARTICLE DETECTORS, PROTON REACTIONS, RADIOACTIVITY, PHOTONUCLEAR REACTIONS, POLONIUM , NUCLEAR STRUCTURE, MATHEMATICAL MODELS, PROBABILITY, SURFACES, DISTRIBUTION.
Pion production via isobar giant resonance formation and decay
NASA Technical Reports Server (NTRS)
Townsend, L. W.; Deutchman, P. A.; Madigan, R. L.; Norbury, J. W.
1984-01-01
A spin, isotopic-spin formalism for the production of pions due to decays of isobar giant resonances formed in peripheral heavy-ion collisions is presented. The projectile nucleus isobar giant resonance state is assumed to coherently form and then incoherently decay to produce the pions. Total spin and isotopic spin for the system are conserved through the concomitant excitation of the target nucleus to an isobaric analog giant resonance state. Comparisons of the predicted total pion cross sections, over a range of energies, are made with heavy-ion pion data.
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.
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 pion(0) produced in interstellar cosmic ray interactions is essential for determining the possible amount of interstellar H2. This production rate is recalculated using the latest accelerator data on pion(0) production in pp interactions up to approximately 300 GeV. A simple but accurate approximation resolves the past disagreement over the magnitude of this rate. An upper limit is obtained of (1.51 + or - 0.23) x 10 to the minus 25th power/sec. consistent with the observed upper limit of 1.6 x 10 to the minus 25th power/sec.
Pions in nuclei and manifestations of supersymmetry in neutrinoless double beta decay
NASA Astrophysics Data System (ADS)
Faessler, Amand; Kovalenko, Sergey; Šimkovic, Fedor
1998-12-01
We examine the pion realization of the short-ranged supersymmetric (SUSY) mechanism of neutrinoless double beta decay (0νββ decay). It originates from the R-parity violating quark-lepton interactions of the SUSY extensions of the standard model of the electroweak interactions. We argue that pions are dominant SUSY mediators in 0νββ decay. The corresponding nuclear matrix elements for potentially 0νββ-decaying isotopes are calculated within the proton-neutron renormalized quasiparticle random-phase approximation (pn-RQRPA). We define those isotopes which are most sensitive to the SUSY signal and provide an outlook on the present experimental situation with the 0νββ-decay searches for SUSY. Upper limits on the R-parity violating first-generation Yukawa coupling λ'111 are derived from various 0νββ experiments.
NASA Astrophysics Data System (ADS)
Mannheim, Karl
There has been a dramatic revolution in gamma-ray astronomy throughout the last few years. Beginning with the discovery made by the spark chamber EGRET on board the Compton Gamma Ray Observatory that AGN with jets are the most powerful quasi-steady gamma-ray sources in the Universe, air-Cerenkov telescopes have soon after succeeded in detecting gamma-rays up to TeV energies. In the last year, it has become clear that these AGN emit photons even up to 10 TeV and more. This is a strong indication for proton acceleration going on in them, since protons owing to their large mass suffer weaker energy losses than electrons and can thus reach higher energies. Nucleons escaping from the AGN jets contribute to the local flux of cosmic rays at highest energies. If AGN produce the diffuse gamma-ray background, they would also be able to produce all the cosmic rays above the ankle in the local spectrum. The majority of AGN resides at large distances, indicated by their cosmological redshifts, and can therefore not be seen through the fog of electron-positron pairs which they produce interacting with diffuse infrared radiation from the era of galaxy formation. To observe the cosmic accelerators at large redshifts, neutrino observations are required. It is important to understand the astrophysical neutrino sources in order to be able to recognize signatures of new physics, e.g. due to decaying or annihilating particles from the early phases of the Universe.
Charged pion production in {sub 44}{sup 96}Ru+{sub 44}{sup 96}Ru collisions at 400A and 1528A MeV
Hong, B.; Sim, K.S.; Kim, Y.J.; Herrmann, N.; Stockmeier, M.R.; Benabderrahmane, M. L.; Mangiarotti, A.; Merschmeyer, M.; Pelte, D.; Andronic, A.; Gobbi, A.; Hartmann, O.N.; Hildenbrand, K.D.; Koczon, P.; Kress, T.; Leifels, Y.; Reisdorf, W.; Schuettauf, A.; Xiao, Z.G.; Barret, V.
2005-03-01
We present transverse momentum and rapidity spectra of charged pions in central Ru+Ru collisions at 400A and 1528A MeV. The data exhibit enhanced production at low transverse momenta compared to expectations from a thermal model that includes the decay of {delta}(1232) resonances and thermal pions. Modifications of the {delta} spectral function and the Coulomb interaction are necessary to describe the detailed shape of the transverse momentum spectra. Within the framework of the thermal model, the freeze-out radii of pions are similar at both beam energies. The isospin quantum molecular dynamics model reproduces the shapes of the transverse momentum and rapidity spectra of pions, but the predicted absolute yields are larger than in the measurements, especially at lower beam energy.
Photoproduction of neutral pions off protons
NASA Astrophysics Data System (ADS)
Crede, V.; Sparks, N.; Wilson, A.; Anisovich, A. V.; Bacelar, J. C. S.; Bantes, R.; Bartholomy, O.; Bayadilov, D.; Beck, R.; Beloglazov, Y. A.; Castelijns, R.; Dutz, H.; Elsner, D.; Ewald, R.; Frommberger, F.; Funke, Chr.; Gregor, R.; Gridnev, A.; Gutz, E.; Hillert, W.; Hoffmeister, P.; Jaegle, I.; Junkersfeld, J.; Kalinowsky, H.; Kammer, S.; Klein, Frank; Klein, Friedrich; Klempt, E.; Kotulla, M.; Krusche, B.; Löhner, H.; Lopatin, I. V.; Lugert, S.; Menze, D.; Mertens, T.; Messchendorp, J. G.; Metag, V.; Nanova, M.; Nikonov, V. A.; Novinski, D.; Novotny, R.; Ostrick, M.; Pant, L. M.; van Pee, H.; Pfeiffer, M.; Roy, A.; Sarantsev, A. V.; Schadmand, S.; Schmidt, C.; Schmieden, H.; Schoch, B.; Shende, S.; Sokhoyan, V.; Süle, A.; Sumachev, V. V.; Szczepanek, T.; Thoma, U.; Trnka, D.; Varma, R.; Walther, D.; Wendel, Ch.
2011-11-01
Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector in the reaction γp→pπ0 for photon energies between 0.85 and 2.50 GeV. The π0 mesons are observed in their dominant neutral decay mode: π0→γγ. For the first time, the differential cross sections cover the very forward region, θc.m.<60∘. A partial-wave analysis of these data within the Bonn-Gatchina framework observes the high-mass resonances G17(2190), D13(2080), and D15(2070).
Pions in large N quantum chromodynamics.
Weinberg, Steven
2010-12-31
An effective field theory of quarks, gluons, and pions, with the number N of colors treated as large, is proposed as a basis for calculations of hadronic phenomena at moderate energies. The qualitative consequences of the large N limit are similar though not identical to those in pure quantum chromodynamics, but because constituent quark masses appear in the effective Lagrangian, the 't Hooft coupling in the effective theory need not be strong at moderate energies. To leading order in 1/N the effective theory is renormalizable, with only a finite number of terms in the Lagrangian.
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
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
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
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 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.
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.
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.
B Meson Decays to Deuterium Pion and Deuterium Pion-Pion
NASA Astrophysics Data System (ADS)
Ball, Steven Lee
The decays | B to Dpi and | B to Dpipi are observed in data taken by the ARGUS detector at the e^{+}e^{-} storage ring DORIS II. The data sample includes 100 pb^{-1} collected at the Upsilon(4S) resonance and 31 pb^{-1} continuum data taken at a center-of-mass energy just below the Upsilon(4S). The decays of | B to Drho ^{-} are observed for the first time. We find:eqalign{&bullet BR(B^- to D^0rho^ -) = (2.0 +/- 0.7 +/- 0.7)%cr&bullet BR(| B^0 to D^+rho ^-) = (2.7 +/- 1.0 +/- 1.0)%.cr }These branching ratios are substantially larger than those for the decays | B to Dpi^{-}, for which we find: eqalign{&bullet BR(B ^- to D^0pi^-) = (0.19 +/- 0.10 +/- 0.06)%cr&bullet BR(| B^0 to D^+pi ^-) = (0.35 +/- 0.14 +/- 0.12)%. cr}Suggestive, yet inconclusive evidence is found for the existence of the decays | B to D``rho(1600)^{-} ". An upper limit of 0.3% at a 90% confidence level is found for the "color-suppressed" decay | B^0 to D^0rho^0. The measured branching ratios of the decays | B to Dpi, Dpipi are consistent with other measurements and with theoretical predictions based upon a spectator decay model. Strong effects appear to be minor in B decays beyond the confinement in hadrons, whereas dynamical effects of the V - A weak interaction are quite pronounced.
Pion contamination in the MICE muon beam
Adams, D.; Alekou, A.; Apollonio, M.; ...
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
Vector and Axial Vector Pion Form Factors
NASA Astrophysics Data System (ADS)
Vitz, Michael; PEN Collaboration
2015-04-01
Radiative pion decay π+ -->e+ νγ (RPD) provides critical input to chiral perturbation theory (χPT). Aside from the uninteresting ``inner bremsstrahlung'' contribution from QED, the RPD rate contains ``structure dependent'' terms given by FV and FA, the vector and axial-vector pion form factors, respectively. The two appear in the decay rate in combinations FV -FA and FV +FA , i.e., in the so-called SD- and SD+ terms, respectively. The latter has been measured to high precision by the PIBETA collaboration. We report on the analysis of new data, measured by the PEN collaboration in runs between 2008 and 2010 at the Paul Scherrer Institute, Switzerland. We particularly focus on the possibility of improvement in the determination of the SD- term. Precise determinations of FV and FA test the validity of the CVC hypothesis, provide numerical input for the l9 +l10 terms in the χPT lagrangian, and constrain potential non-(V - A) terms, such as a possible tensor term FT. NSF grants PHY-0970013, 1307328, and others.
Formation of Deeply Bound Pionic Atoms and Pion Properties in Nuclei
NASA Astrophysics Data System (ADS)
Ikeno, Natsumi; Yamagata-Sekihara, Junko; Nagahiro, Hideko; Hirenzaki, Satoru
We report the recent theoretical studies for the formation of deeply bound pionic atoms. It is important to know the pion properties in nuclei since they are believed to provide valuable information on the aspects of the symmetry of strong interaction at finite density. In order to deduce precise information on the pion properties in nuclei from observables of the deeply bound pionic atom, we consider the pionic atom formation on the even-even and neutron-odd nucleus targets. Furthermore, we also calculate the formation spectra using the Green's function method. Theoretical results using the Green's function method will be necessary to investigate the high precision data which will be obtained in near future.
NASA Astrophysics Data System (ADS)
Ross, M. Alan
1991-02-01
The first nuclear physics experiment at the IUCF Cooler is a measurement of the p+ptop+p+ pi^0 cross section near threshold. The Cooler, together with a thin internal H_2 gas jet target, allows for a precise cross section measurement by providing well-defined interaction energies and by eliminating background from p-nucleus pion production which has a much lower threshold. A cylindrically symmetric detector system has been installed in one of the straight sections of the ring and is used to detect the coincident protons in the exit channel with good energy and angular resolution. The mass of the unobserved is then deduced. Elastically scattered protons were detected at the same time and by the same detector as pion production events. Elastic scattering was used for normalization to obtain an absolute p+p top+p+pi^0 cross section.
NASA Astrophysics Data System (ADS)
Cozma, M. D.
2017-01-01
The charged pion multiplicity ratio in intermediate-energy heavy-ion collisions, a probe of the density dependence of symmetry energy above the saturation point, has been proven in a previous study to be extremely sensitive to the strength of the isovector Δ (1232 ) potential in nuclear matter. As there is no knowledge, either from theory or experiment, about the magnitude of this quantity, the extraction of constraints on the slope of the symmetry energy at saturation by using exclusively the mentioned observable is hindered at present. It is shown that, by including the ratio of average pT of charged pions
Three-nucleon force the {Delta}-mechanism for pion production and pion absorption
Pena, M.T. |; Sauer, P.U.; Stadler, A. |; Kortemeyer, G.
1993-05-18
The description of the three-nucleon system in terms of nucleon and {Delta} degrees of freedom is extended to allow for explicit pion production (absorption) from single dynamic {Delta} de-excitation (excitation) processes. This mechanism yields an energy dependent effective three-body hamiltonean. The Faddeev equations for the trinucleon bound state are solved with a force model that has already been tested in the two-nucleon system above pion-production threshold. The binding energy and other bound state properties are calculated. The contribution to the effective three-nucleon force arising from the pionic degrees of freedom is evaluated. The validity of previous coupled-channel calculations with explicit but stable A isobar components in the wavefunction is studied.
Neutrinos from PIon Beam Line, nuPIL
Lagrange, J. B.; Pasternak, J.; Bross, A.; Liu, A.
2016-05-05
LBNF-DUNE (Long Baseline Neutrino Facilities - Deep Underground Neutrino Experiment) is a project based at Fermilab to study neutrino oscillations. The current baseline regarding the neutrino production considers the conventional approach: a high energy proton beam hits a target, producing pions that are collected by a horn and that decay in a decay pipe. An alternative solution, called nuPIL (neutrinos from a Pion beam Line) consists of using a beam line to guide the pions to clean the beam and to put instrumentation to monitor it. This paper presents the concept and the first preliminary results.
Form factors in the radiative pion decay
NASA Astrophysics Data System (ADS)
Mateu, V.; Portolés, J.
2007-10-01
We perform an analysis of the form factors that rule the structure-dependent amplitude in radiative pion decay. The resonance contributions to π→eνeγ decays are computed through the proper construction of the vector and axial-vector form factors by setting the QCD driven asymptotic properties of the three-point Green functions
Pions near the chiral critical point
NASA Astrophysics Data System (ADS)
Hippert, M.; Fraga, E. S.; Santos, E. M.
2016-04-01
It is an exciting possibility that the QCD critical point can be found in ultrarelativistic heavy-ion collision experiments (HICs). While quantities such as some event-by-event moments of specific observables should display strong non-monotonic behavior near the critical point and could, hence, be used as signatures of criticality, it is not clear that this behavior could effectively be observed in the highly non-ideal scenario of HICs. We here employ Monte Carlo simulations to test second-order moments of pion observables as possible signatures of the critical point while taking into account some realistic ingredients, similar to the ones found in HICs. We make use of simplified models to introduce spurious contributions and dynamical effects.
Nuclear effects in neutrino production of pions
NASA Astrophysics Data System (ADS)
Schmidt, Iván; Siddikov, M.
2015-04-01
In this paper we study nuclear effects in the neutrino production of pions. We found that in a Bjorken kinematics, for moderate xB accessible in ongoing and forthcoming neutrino experiments, the cross section is dominated by the incoherent contribution; the coherent contribution becomes visible only for small |t |≲1 /RA2, which requires xB≲0.1 . Our results could be relevant to the kinematics of the ongoing MINERvA experiment in the middle-energy regime. We provide a code which could be used for the evaluation of the neutrino induced deeply virtual meson production observables using different parametrizations of generalized parton distributions and different models of nuclear structure.
In-medium pion valence distributions in a light-front model
NASA Astrophysics Data System (ADS)
de Melo, J. P. B. C.; Tsushima, K.; Ahmed, I.
2017-03-01
Pion valence distributions in nuclear medium and vacuum are studied in a light-front constituent quark model. The in-medium input for studying the pion properties is calculated by the quark-meson coupling model. We find that the in-medium pion valence distribution, as well as the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.
Can one distinguish τ-neutrinos from antineutrinos in neutral-current pion production processes?
NASA Astrophysics Data System (ADS)
Hernández, E.; Nieves, J.; Valverde, M.
2007-04-01
A potential way to distinguish τ-neutrinos from antineutrinos, below the τ-production threshold, but above the pion production one, is presented. It is based on the different behavior of the neutral-current pion production off the nucleon, depending on whether it is induced by neutrinos or antineutrinos. This procedure for distinguishing τ-neutrinos from antineutrinos neither relies on any nuclear model, nor it is affected by any nuclear effect (distortion of the outgoing nucleon waves, etc.). We show that neutrino-antineutrino asymmetries occur both in the totally integrated cross sections and in the pion azimuthal differential distributions. To define the asymmetries for the latter distributions we just rely on Lorentz-invariance. All these asymmetries are independent of the lepton family and can be experimentally measured by using electron or muon neutrinos, due to the lepton family universality of the neutral-current neutrino interaction. Nevertheless and to estimate their size, we have also used the chiral model of [E. Hernández, J. Nieves, M. Valverde, arxiv:hep-ph/0701149] at intermediate energies. Results are really significant since the differences between neutrino and antineutrino induced reactions are always large in all physical channels.
Pion and σ-meson Properties in a Strong Magnetic Field
NASA Astrophysics Data System (ADS)
Zhang, Rui; Fu, Wei-Jie; Liu, Yu-Xin
2015-09-01
With the Nambu-Jona-Lasinio (NJL) model we calculate the properties of pion and σ-meson at finite temperature and finite magnetic field. The obtained temperature and magnetic field strength dependence of the constituent quark mass M, the pion and σ-meson masses and the neutral pion decay constant indicates that, in the simple four fermion interaction model, there exists the magnetic catalysis effect. It also shows that the Gell-Mann-Oakes-Renner relation is violated obviously with the increasing of the temperature, and the effect of the magnetic field becomes pronounced only around the critical temperature. The deviation of the critical temperatures obtained with different criteria indicates that the chiral phase transition driven by the temperature in the magnetic field strength region we have considered is in fact a crossover. Supported by the National Natural Science Foundation of China under Grant Nos. 10935001, 11175004, and 11435001, and the National Key Basic Research Program of China under Grant Nos. G2013CB834400 and G2015CB856900
Pair counting, pion-exchange forces and the structure of light nuclei
Wiringa, R.B.
2006-03-15
A simple but useful guide for understanding the structure of light nuclei is presented. It is based on counting the number of interacting pairs in different spin-isospin (S,T) states for a given spatial symmetry and estimating the overall binding according to the sum of {sigma}{sub i}{center_dot}{sigma}{sub j}{tau}{sub i}{center_dot}{tau}{sub j} expectation values, as suggested by one-pion exchange. Applied to s- and p-shell nuclei, this simple picture accounts for the relative stability of nuclei as A increases and as T changes across isobars, the saturation of nuclear binding in the p shell, and the tendency to form d,t, or {alpha} subclusters there. With allowance for pairwise tensor and spin-orbit forces, which are also generated or boosted by pion exchange, the model explains why mixing of different spatial symmetries in ground states increases as T increases across isobars and why, for states of the same spatial symmetry, the ones with greater S are lower in the spectrum. The ordering of some sd-shell intruder levels can also be understood. The success of this simple model supports the idea that one-pion exchange is the dominant force controlling the structure of light nuclei.
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.
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.
Pion form factor in the NLC QCD SR approach
Bakulev, A. P. Pimikov, A. V.; Stefanis, N. G.
2010-06-15
We present results of a calculation of the electromagnetic pion form factor within the framework of QCD sum rules with nonlocal condensates and using a perturbative spectral density which includes O({alpha}{sub s}) contributions.
Roy-Steiner-equation analysis of pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Meißner, U.-G.; Ruiz de Elvira, J.; Hoferichter, M.; Kubis, B.
2017-03-01
Low-energy pion-nucleon scattering is relevant for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the long-range part of two-pion-exchange potentials and three-nucleon forces in Chiral Effective Field Theory. In this talk, we show how the fruitful combination of dispersion-theoretical methods, in particular in the form of Roy-Steiner equations, with modern high-precision data on hadronic atoms allows one to determine the pion-nucleon scattering amplitudes at low energies with unprecedented accuracy. Special attention will be paid to the extraction of the pion-nucleon σ-term, and we discuss in detail the current tension with recent lattice results, as well as the determination of the low-energy constants of chiral perturbation theory.
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.
Pion Production from Proton Synchrotron Radiation in Strong Magnetic Fields
NASA Astrophysics Data System (ADS)
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field. In this study we find that the decay width satisfies a robust scaling relation. 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. Then, we present the resultant pion intensity and angular distributions for realistic magnetic field strengths.
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.
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.
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.
Onset of quark-hadron duality in pion electroproduction.
Navasardyan, T; Adams, G S; Ahmidouch, A; Angelescu, T; Arrington, J; Asaturyan, R; Baker, O K; Benmouna, N; Bertoncini, C; Blok, H P; Boeglin, W U; Bosted, P E; Breuer, H; Christy, M E; Connell, S H; Cui, Y; Dalton, M M; Danagoulian, S; Day, D; Dodario, T; Dunne, J A; Dutta, D; El Khayari, N; Ent, R; Fenker, H C; Frolov, V V; Gan, L; Gaskell, D; Hafidi, K; Hinton, W; Holt, R J; Horn, T; Huber, G M; Hungerford, E; Jiang, X; Jones, M; Joo, K; Kalantarians, N; Kelly, J J; Keppel, C E; Kubarovski, V; Li, Y; Liang, Y; Malace, S; Markowitz, P; McGrath, E; McKee, P; Meekins, D G; Mkrtchyan, H; Moziak, B; Niculescu, G; Niculescu, I; Opper, A K; Ostapenko, T; Reimer, P; Reinhold, J; Roche, J; Rock, S E; Schulte, E; Segbefia, E; Smith, C; Smith, G R; Stoler, P; Tadevosyan, V; Tang, L; Ungaro, M; Uzzle, A; Vidakovic, S; Villano, A; Vulcan, W F; Wang, M; Warren, G; Wesselmann, F; Wojtsekhowski, B; Wood, S A; Xu, C; Yuan, L; Zheng, X; Zhu, H
2007-01-12
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-->pion production mechanisms.
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.
Production and decay of baryonic resonances in pion induced reactions
NASA Astrophysics Data System (ADS)
Przygoda, Witold
2016-11-01
Pion induced reactions give unique opportunities for an unambiguous description of baryonic resonances and their coupling channels. A systematic energy scan and high precision data, in conjunction with a partial wave analysis, allow for the study of the excitation function of the various contributions. A review of available world data unravels strong need for modern facilities delivering measurements with a pion beam. Recently, HADES collaboration collected data in pion-induced reactions on light (12C) and heavy (74W) nuclei at a beam momentum of 1.7 GeV/c dedicated to strangeness production. It was followed by a systematic scan at four different pion beam momenta (0.656, 0.69, 0.748 and 0.8 GeV/c) in π- - p reaction in order to tackle the role of N(1520) resonance in conjunction with the intermediate ρ production. First results on exclusive channels with one pion (π- p) and two pions (nπ+π-, pπ-π0) in the final state are discussed.
Pion production in heavy ion reactions near absolute thresholds
Stachel, J.; Braun-Munzinger, P.; Paul, P.; Zhang, P.H.; Obenshain, F.E.; Plasil, F.; Young, G.R.
1984-01-01
Pion production in heavy ion collisions at energies below the free nucleon-nucleon threshold, i.e., at energies, where the pion mass exceeds the kinetic energy of a projectile nucleon in the zero momentum frame, has been discussed for a long time in terms of probing the intrinsic Fermi motion in the projectile and target nuclei. However, as the beam energy is lowered, this process gets more and more unlikely and below a certain energy it should not be observed anymore. In a sharp cut-off Fermi gas model this occurs at E/sub lab/=50 MeV/u. However, as long as the total center of mass energy exceeds the pion mass, pions still can be produced by a cooperative sharing of the beam energy of several (or all) projectile nucleons. The experiments presented here are meant to extend the experimental information into that kinematic domain and represent the up to now lowest beam energy, where pion production has been identified unambiguously. The production of a pion of 100 MeV kinematic energy with a 35 MeV/u /sup 14/N beam requires Fermi momenta as high as approx.350 MeV/c or alternatively 60% of the total beam energy. The information from the present experiments together with the results of previous experiments at higher beam energies of 44 MeV/u and 60 to 84 MeV/u allows one to distinguish between the alternative production mechanisms.
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.
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.
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.
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.
Production spectrum of gamma rays in interstellar space through neutral pion decay
NASA Technical Reports Server (NTRS)
Stephens, S. A.; Badhwar, G. D.
1981-01-01
A simple representation is obtained of the observed invariant cross section for the production of neutral pions in proton-proton collisions. Using this representation, the differential and integral production spectra of gamma rays in the galaxy are calculated from interactions of cosmic ray nuclei with interstellar gas. It is shown that the uncertainties in deducing interstellar proton spectrum by demodulating the observed spectrum have only a limited effect on the gamma ray spectrum. Also determined is the gamma ray production spectrum through bremsstrahlung process for a typical interstellar electron spectrum derived from the radio spectrum in the galaxy.
Two-pion exchange contributions to the relativistic NN kernel: Peripheral scattering
Cozma, M. D.; Scholten, O.; Timmermans, R. G. E.; Tjon, J. A.
2007-01-15
The relativistic one-boson-exchange model for NN scattering is extended by including two-pion exchange (TPE) contributions in the kernel. We develop the formalism for the evaluation of the TPE diagrams within the relativistic quasipotential approach. The peripheral partial waves in elastic NN scattering are studied within this model. The TPE interactions contain a strongly attractive isoscalar-scalar component which requires a low value of the cutoff parameter: {lambda}=650-800 MeV. With this prescription, the peripheral waves can be reasonably described.
a Phenomenological Determination of the Pion-Nucleon Scattering Lengths from Pionic Hydrogen
NASA Astrophysics Data System (ADS)
Ericson, T. E. O.; Loiseau, B.; Wycech, S.
A model independent expression for the electromagnetic corrections to a phenomenological hadronic pion-nucleon (πN) scattering length ah, extracted from pionic hydrogen, is obtained. In a non-relativistic approach and using an extended charge distribution, these corrections are derived up to terms of order α2 log α in the limit of a short-range hadronic interaction. We infer ahπ ^-p=0.0870(5)m-1π which gives for the πNN coupling through the GMO relation g2π ^± pn/(4π )=14.04(17).
Meson spectroscopy in diffractive dissociation of high-energetic pions at COMPASS
Friedrich, Jan
2011-07-15
COMPASS at CERN uses hadron and muon beams with up to 200 GeV/c momentum, produced from the SPS proton beam, for investigations in hadron structure and spectroscopy. From a pilot run with a 190 GeV/c pion beam on a lead target, various results are presented. In the region of low momentum transfer, interference of photon-exchange and strong production of the a{sub 1}(1260) and a{sub 2}(1320) resonances is observed, revealing the different nature of the two interactions.
Two-body pion absorption on {sup 3}He at threshold
Lee, T.S.H.; Kiang, L.L.; Riska, D.O.
1995-08-01
We showed that a drastic reduction of the ratio of the rates of the reactions {sup 3}He({pi}{sup -},nn) and {sup 3}He({pi}{sup -},np) for stopped pions is obtained once the effect of the short-range two-nucleon components of the axial charge operator for nuclear systems is taken into account. In a calculation using realistic models of nucleon-nucleon interactions in the construction of these short-range components of the axial charge operator, the predicted ratios can be brought to within 10-20% of the empirical value. A paper describing our results was published.
Pion single charge exchange scattering from 3He at 285, 428, and 525 MeV
NASA Astrophysics Data System (ADS)
Källne, J.; Altemus, R.; Gugelot, P. C.; McCarthy, J. S.; Minehart, R. C.; Orphanos, L.; Gram, P. A. M.; Höistad, B.; Morris, C. L.; Wadlinger, E. A.; Perdrisat, C. F.
1982-02-01
We have measured the cross section of 3He(π-,π0)3H at T=285, 428, and 525 MeV for angles in the range of 60°<~θ<~135° covering the momentum transfer range 0.5<~q<~1.0 GeV/c. Comparison is made with Glauber model calculations to discuss the sensitivity to nuclear structure and pion-nucleus interaction effects. NUCLEAR REACTIONS π-+3He-->3H+π0, T=285, 428, and 525 MeV, θπ0~70-140° measured σ(θt,Tπ). Analysis based on optical and Glauber model predictions.
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% .
Matthews, Scott K.
1993-11-01
Several experiments have measured nominally-charge-symmetric scattering of pions from tritium (^{3}H) and ^{3}He. These experiments have covered incident pion energies from 142 MeV to 295 MeV and scattering angles up to 110° in the laboratory. The results have been used to study charge-symmetry breaking and nuclear scattering systematics. In the work I have extended these measurements to angles near 180° for pion energies of 142 MeV, 180 MeV, 220 MeV, and 256 MeV, which bracket the Δ_{33} pion-nucleon resonance. This is the most extensive set of πT and π^{3}He data in this kinematical region. It will allow tests of scattering theory of pion-nucleus interactions and charge-symmetry breaking in back-angle scattering, and, within the limits of these two theories, it may help improve our understanding of the structure of these nuclei.
Clark, J.L.
1980-01-01
Carrier-free radiochemical techniques have been used to measure cross sections for the double charge exchange reactions of the type /sup 209/Bi(pi/sup +/, pi/sup -/xn)/sup 209-x/At for 100, 180, and 300 MeV incident pions. The observed formation of astatine products with mass numbers ranging from 208 to 205 is interpreted as evidence of processes in which energy deposited in the initial double charge exchange interaction is subsequently dissipated through neutron evaporation. The excitation functions for these reactions are seen to rise rapidly with decreasing incident pion energy with the maximum results for this study at 100 MeV. The astatine production cross secions measured for these positive pion irradiations of thick bismuth targets must be corrected for secondary processes, particularly the pion induced production of fast alpha particles which can contribute to the total cross sections through reactions like /sup 209/Bi(alpha,xn)/sup 213-x/At. The importance of these secondary contributions was studied through a series of negative pion irradiations of bismuth in which secondary pathways furnish the only means of producing astatine. The failure of evaporation calculations to reproduce the astatine product mass yields observed in these secondary studies suggests that direct mechanisms for energetic complex particle formation are quite important. Values for the alpha decay branches of /sup 207/At, /sup 208/At, and /sup 209/At were determined through a study of the electron capture and alpha decay characteristics of chemically purified astatine fractions.
Sadler, M.E.; Isenhower, L.D.
1992-02-15
This report discusses research on the following topics: pion-nucleon interactions; detector tomography facility; nuclear dependence of charm and beauty quark production and a study of two-prong decays of neutral D and B mesons; N* collaboration at CEBAF; and pilac experiments. (LSP)
Parton Distributions in the pion from lattice QCD
W. Detmold; Wally Melnitchouk; Anthony Thomas
2003-03-01
We analyze the moments of parton distribution functions in the pion calculated in lattice QCD, paying particular attention to their chiral extrapolation. Using the lowest three non-trivial moments calculated on the lattice, we assess the accuracy with which the x-dependence of both the valence and sea quark distributions in the pion can be extracted. The resulting valence quark distributions at the physical pion mass are in fair agreement with existing Drell-Yan data, but the statistical errors are such that one cannot yet confirm (or rule out) the large-x behavior expected from hadron helicity conservation in perturbative QCD. One can expect, however, that the next generation of calculations in lattice QCD will allow one to extract parton distributions with a level of accuracy comparable with current experiments.
Low energy analyzing powers in pion-proton elastic scattering
NASA Astrophysics Data System (ADS)
Meier, R.; Cröni, M.; Bilger, R.; van den Brandt, B.; Breitschopf, J.; Clement, H.; Comfort, J. R.; Denz, H.; Erhardt, A.; Föhl, K.; Friedman, E.; Gräter, J.; Hautle, P.; Hofman, G. J.; Konter, J. A.; Mango, S.; Pätzold, J.; Pavan, M. M.; Wagner, G. J.; von Wrochem, F.
2004-05-01
Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS and a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π+p scattering, and at 67.3 and 87.2 MeV for π-p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.
Magnetic catalysis of a finite-size pion condensate
NASA Astrophysics Data System (ADS)
Ayala, Alejandro; Mercado, Pedro; Villavicencio, C.
2017-01-01
We study the Bose-Einstein condensation of a finite-size pion gas subject to the influence of a magnetic field. We find the expressions for the critical chemical potential and temperature for the onset of condensation. We show that for values of the external magnetic flux larger than the elemental flux, the critical temperature is larger than the one obtained by considering only finite-size effects. We use experimentally reported values of pion source sizes and multiplicities at Large Hadron Collider (LHC) energies to show that if the magnetic flux, produced initially in peripheral heavy-ion collisions, is at least partially preserved up to the hadronic phase, the combined finite-size and magnetic field effects give rise to a critical temperature above the kinetic freeze-out temperature. We discuss the implications for the evolution of the pion system created in relativistic heavy-ion collisions.
Pion Inelastic Scattering to the First Three Excited States of Lithium-6.
1984-12-01
extremely useful hadronic probe due to resulting theoretical simplifications in the analysis of pion- nucleus scattering data, and the ability to perform... hadronic probe such as the proton. (2) The pion possesses spin zero. As a boson, it can be absorbed by clusters of nucleons in the nucleus , and pion...treatment of pion- nucleus scattering as is the case for other hadronic probes such as protons and alpha particles. (4) Lastly, the total w+p and r-p cross
Valence-quark distribution functions in the kaon and pion
Chen, Chen; Chang, Lei; Roberts, Craig D.; Wan, Shaolong; Zong, Hong-Shi
2016-04-18
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.
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$.
Beam Spin Asymmetry Measurements for Two Pion Photoproduction at CLAS
Anderson, Mark D.
2015-09-01
The overarching goal of this analysis, and many like it, is to develop our understanding of the strong force interactions within the nucleon by examining the nature of their excitation spectra. As the resonances of these spectra have very short lifetimes (tau = 1x10^{-23} s) and often have very similar masses, it is often impossible to directly observe resonances in the excitation spectra of nucleons. Polarization observables allow us to study the resonances by looking at how they affect the spin state of final state particles. The beam asymmetry is a polarization observable that allows us to detect the sensitivity of these resonances, and other transition mechanisms, to the electric vector orientation of incident photons. Presented in this thesis are first measurements of the beam asymmetries in the resonant region for the reaction channel pgamma p --> p π^{+} π^{-}focusing on the intermediate mesonic states rho^0 and f^0, and the final state pions. The analysis used data from the g8b experiment undertaken at the Thomas Jefferson National Accelerator Facility (JLab), the first experiment at JLab to use a linearly polarized photon beam. Using the coherent Bremsstrahlung facility and the CLAS detector of Hall B at JLab allowed for many multi-channel reactions to be detected and the first measurements of many polarization observables including those presented here. A brief overview of the theoretical framework used to undertake this analysis is given, followed by a description of the experimental details of the facilities used, then a description of the calibration of the Bremsstrahlung tagging facility which the author undertook, and finally the analysis is presented and the resulting measurements.
Exclusive near threshold two-pion production with the MOMO experiment at COSY
NASA Astrophysics Data System (ADS)
Bavink, S.; Bellemann, F.; Berg, A.; Bisplinghoff, J.; Bohlscheid, G.; Ernst, J.; Henrich, C.; Hinterberger, F.; Ibald, R.; Jahn, R.; Jarczyk, L.; Joosten, R.; Kozela, A.; Machner, H.; Magiera, A.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Munkel, J.; Neumann-Cosel, P. v.; Rosendaal, D.; Rossen, P. v.; Schnitker, H.; Scho, K.; Smyrski, J.; Strzalkowski, A.; Tölle, R.; Wurzinger, R.
1998-03-01
Near threshold two pion production via the reaction pd → 3Heπ +π - was measured kinematically complete with the MOMO experiment at COSY. A remarkable deviation of the obtained two pion invariant mass spectra from phase space as well as a predominant back to back and sidewise emission of the two pions was observed.
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.
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.
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.
Tensor polarization in pion-deuteron elastic scattering
Holt, R.J.
1983-01-01
The angular dependence of the tensor polarization t/sub 20//sup lab/ of recoiling deuterons in ..pi..-d elastic scattering was measured as a function of incident pion energy in the range 134 to 256 MeV. No evidence was found for rapid energy or angular dependences in t/sub 20//sup lab/. The results agree most favorably with theoretical calculations in which the P/sub 11/ ..pi..-N amplitude has been removed altogether. This agreement is consistent with a small effect of pion absorption on the elastic channel. 14 references.
Measurement of the Charged Pion Electromagnetic Form Factor
J. Volmer; David Abbott; H. Anklin; Chris Armstrong; John Arrington; K. Assamagan; Steven Avery; Oliver K. Baker; Henk Blok; C. Bochna; Ed Brash; Herbert Breuer; Nicholas Chant; Jim Dunne; Tom Eden; Rolf Ent; David Gaskell; Ron Gilman; Kenneth Gustafsson; Wendy Hinton; Garth Huber; Hal Jackson; Mark K. Jones; Cynthia Keppel; P.H. Kim; Wooyoung Kim; Andi Klein; Doug Koltenuk; Meme Liang; George Lolos; Allison Lung; David Mack; D. McKee; David Meekins; Joseph Mitchell; H. Mkrtchian; B. Mueller; Gabriel Niculescu; Ioana Niculescu; D. Pitz; D. Potterveld; Liming Qin; Juerg Reinhold; I.K. Shin; Stepan Stepanyan; V. Tadevosian; L.G. Tang; R.L.J. van der Meer; K. Vansyoc; D. Van Westrum; Bill Vulcan; Stephen Wood; Chen Yan; W.X. Zhao; Beni Zihlmann
2001-02-26
Separated longitudinal and transverse structure functions for the reaction 1H(e,eprime pi+)n were measured in the momentum transfer region Q2=0.6-1.6 (GeV/c)**2 at a value of the invariant mass W=1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parameterization fitted to very low Q2 elastic data.
Effective pion mass term and the trace anomaly
NASA Astrophysics Data System (ADS)
Golterman, Maarten; Shamir, Yigal
2017-01-01
Recently, we developed an effective theory of pions and a light dilatonic meson for gauge theories with spontaneously broken chiral symmetry that are close to the conformal window. The pion mass term in this effective theory depends on an exponent y . We derive the transformation properties under dilatations of the renormalized fermion mass and use this to rederive y =3 -γm* , where γm* is the fixed-point value of the mass anomalous dimension at the sill of the conformal window. This value for y is consistent with the trace anomaly of the underlying near-conformal gauge theory.
Critique of a pion exchange model for interquark forces
NASA Astrophysics Data System (ADS)
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.
Effects of pion-fold-pion diagrams in the energy-independent nucleon-nucleon potential
NASA Astrophysics Data System (ADS)
de Guzman, G.; Kuo, T. T. S.; Holinde, K.; Machleidt, R.; Faessler, A.; Müther, H.
1985-10-01
Based on a T-matrix equivalence theory, an energy-independent or locally energy-dependent nucléon-nucléon potential VNN derived from meson exchanges is studied. The potential, given as a series expansion of folded diagrams, is independent of the asymptotic energy of the scattering nucleons. It is, however, locally energy dependent in the sense that its matrix elements < a| VNN| b> depend on the energies associated with its bra and ket states a and b. Our formulation makes use of right-hand-side on-shell T-matrix equivalence of the field-theoretical and potential descriptions when limited to the space of neutrons and protons only. This preserves not only scattering (e.g. phase shifts, projections of wave functions) but also bound-state properties. The matrix elements of V were calculated for two potential models, one based on one-pion exchange (OPEP) and the other on one-boson exchange (OBEP) using {π, ρ, σ, ω, δ, η }. Three types of phase-shift calculations have been carried out to study the viability of constructing an energy-independent potential using the folded-diagram expansion: (A) NN phase shifts for an energy-dependent OPEP and OBEP. For the OBEP we used parameters adjusted to fit experimental data. (B) The same phase shifts for the energy-independent case for both OPEP and OBEP. (C) Repetition of (B) with effects of the two-pion folded diagrams included. Our results show two important points: (i) folded diagrams are of essential importance, and (ii) the first-order folded diagrams contain the dominant effect and the neglect of terms with more than two folds can be regarded as a good approximation. The effects of folded diagrams are large especially for low partial waves and high energies. For high partial waves ( J greater than 2) the folded terms are negligible, and the phase shifts given by (A), (B) and (C) practically coincide.
Minimally nonlocal nucleon-nucleon potentials with chiral two-pion exchange including Δ resonances
Piarulli, M.; Girlanda, L.; Schiavilla, R.; ...
2015-02-26
In this study, we construct a coordinate-space chiral potential, including Δ-isobar intermediate states in its two-pion-exchange component up to order Q3 (Q denotes generically the low momentum scale). The contact interactions entering at next-to-leading and next-to-next-to-next-to-leading orders (Q2 and Q4, respectively) are rearranged by Fierz transformations to yield terms at most quadratic in the relative momentum operator of the two nucleons. The low-energy constant multiplying these contact interactions are fitted to the 2013 Granada database, consisting of 2309 pp and 2982 np data (including, respectively, 148 and 218 normalizations) in the laboratory-energy range 0–300 MeV. For the total 5291 $pp$more » and $np$ data in this range, we obtain a Χ2 /datum of roughly 1.3 for a set of three models characterized by long- and short-range cutoffs, RL and RS respectively, ranging from (RL,RS)=(1.2,0.8) fm down to (0.8,0.6) fm. The long-range (short-range) cutoff regularizes the one- and two-pion exchange (contact) part of the potential.« less
Limiting temperature of pion gas with the van der Waals equation of state
NASA Astrophysics Data System (ADS)
Poberezhnyuk, R. V.; Vovchenko, V.; Anchishkin, D. V.; Gorenstein, M. I.
2016-09-01
The grand canonical ensemble formulation of the van der Waals equation of state that includes the effects of Bose statistics is applied to the equilibrium system of interacting pions. If the attractive interaction between pions is large enough, a limiting temperature T 0 emerges, i.e., no thermodynamical equilibrium is possible at T\\gt {T}0. The system pressure p, particle number density n, and energy density ε remain finite at T={T}0, whereas for T near T 0 both the specific heat C={{d}}\\varepsilon /{{d}}T and the scaled variance of particle number fluctuations ω [N] are proportional to {({T}0-T)}-1/2 and, thus, go to infinity at T\\to {T}0. The limiting temperature also corresponds to the softest point of the equation of state, i.e., the speed of sound squared {c}s2={{d}}p/{{d}}\\varepsilon goes to zero as {({T}0-T)}1/2. Very similar thermodynamical behavior takes place in the Hagedorn model for the special choice of a power, namely {m}-4, in the pre-exponential factor of the mass spectrum ρ (m).
Biernat, Elmar P.; Gross, Franz; Peña, M. T.; ...
2015-10-26
The pion form factor is calculated in the framework of the charge-conjugation invariant covariant spectator theory. This formalism is established in Minkowski space, and the calculation is set up in momentum space. In a previous calculation we included only the leading pole coming from the spectator quark (referred to as the relativistic impulse approximation). In this study we also include the contributions from the poles of the quark which interacts with the photon and average over all poles in both the upper and lower half-planes in order to preserve charge conjugation invariance (referred to as the C-symmetric complete impulse approximation).more » We find that for small pion mass these contributions are significant at all values of the four-momentum transfer Q2 but, surprisingly, do not alter the shape obtained from the spectator poles alone.« less
Biernat, Elmar P.; Gross, Franz; Peña, M. T.; Stadler, Alfred
2015-10-26
The pion form factor is calculated in the framework of the charge-conjugation invariant covariant spectator theory. This formalism is established in Minkowski space, and the calculation is set up in momentum space. In a previous calculation we included only the leading pole coming from the spectator quark (referred to as the relativistic impulse approximation). In this study we also include the contributions from the poles of the quark which interacts with the photon and average over all poles in both the upper and lower half-planes in order to preserve charge conjugation invariance (referred to as the C-symmetric complete impulse approximation). We find that for small pion mass these contributions are significant at all values of the four-momentum transfer Q^{2} but, surprisingly, do not alter the shape obtained from the spectator poles alone.
NASA Astrophysics Data System (ADS)
Wickremasinghe, Don Athula Abeyarathna
The prediction of the muon neutrino flux from a 71.0 cm long beryllium target for the MiniBooNE experiment is based on a measured pion production cross section which was taken from a short beryllium target (2.0 cm thick - 5% nuclear interaction length) in the Hadron Production (HARP) experiment at CERN. To verify the extrapolation to our longer target, HARP also measured the pion production from 20.0 cm and 40.0 cm beryllium targets. The measured production yields on targets of 50% and 100% nuclear interaction lengths in the kinematic rage of momentum from 0.75 GeV/c to 6.5 GeV/c and the range of angle from 30 mrad to 210 mrad are presented along with an update of the short target cross sections. The best fitted extended Sanford-Wang (SW) model parameterization for updated short beryllium target positive pion production cross section is presented. Yield measurements for all three targets are also compared with that from the Monte Carlo predictions in the MiniBooNE experiment for different SW parameterization. The comparisons of muon neutrino flux predictions for updated SW model is presented.
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.
Anomalous electrodynamics of neutral pion matter in strong magnetic fields
NASA Astrophysics Data System (ADS)
Brauner, Tomáš; Kadam, Saurabh V.
2017-03-01
The ground state of quantum chromodynamics in sufficiently strong external magnetic fields and at moderate baryon chemical potential is a chiral soliton lattice (CSL) of neutral pions [1]. We investigate the interplay between the CSL structure and dynamical electromagnetic fields. Our main result is that in presence of the CSL background, the two physical photon polarizations and the neutral pion mix, giving rise to two gapped excitations and one gapless mode with a nonrelativistic dispersion relation. The nature of this mode depends on the direction of its propagation, interpolating between a circularly polarized electromagnetic wave [2] and a neutral pion surface wave, which in turn arises from the spontaneously broken translation invariance. Quite remarkably, there is a neutral-pion-like mode that remains gapped even in the chiral limit, in seeming contradiction to the Goldstone theorem. Finally, we have a first look at the effect of thermal fluctuations of the CSL, showing that even the soft nonrelativistic excitation does not lead to the Landau-Peierls instability. However, it leads to an anomalous contribution to pressure that scales with temperature and magnetic field as T 5/2( B/f π )3/2.
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.
Resonance production and decay in pion induced collisions with HADES
NASA Astrophysics Data System (ADS)
Scozzi, Federico
2017-03-01
The main goal of the High Acceptance Di-Electron experiment (HADES) at GSI is the study of hadronic matter in the 1-3.5 GeV/nucleon incident energy range. HADES results on e+ e- production in proton-nucleus reactions and in nucleus-nucleus collisions demonstrate a strong enhancement of the dilepton yield relative to a reference spectrum obtained from elementary nucleon-nucleon reactions. These observations point to a strong modification of the in-medium ρ spectral function driven by the coupling of the ρ to baryon-resonance hole states. However, to scrutinize this conjecture, a precise study of the role of the ρ meson in electromagnetic baryon-resonance transitions in the time-like region is mandatory. In order to perform this study, HADES has started a dedicated pion-nucleon programme. For the first time a combined measurement of hadronic and dielectron final states have been performed in π--N reactions at four different pion beam momenta (0.656, 0.69, 0.748 and 0.8 GeV/c). First results on exclusive channels with one pion π--p and two pions (nπ+π-, pπ-π0) in the final state, which are currently analysed within the partial wave analysis (PWA) framework of the Bonn-Gatchina group, are discussed. Finally first results for the dielectron analysis will be shown.
Recent results on SIDIS from pion production at CLAS
P. Rossi
2011-10-01
Novel view on QCD dynamics inside hadrons is offered by the transverse momentum dependent parton distributions and fragmentation functions. They can be accessed in Semi-Inclusive Deep Inelastic Scattering (SIDIS) experiments. Recent results on SIDI S from pion production at CLAS is presented in this talk.
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.
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.
NASA Astrophysics Data System (ADS)
Roginsky, Jacob
1987-09-01
In 1982 Gotta et al^1, experimentally observed the branching ratios for n + D, n + D^', where D ^' represents the virtual S _{0} np state, and the probability density for three-body (n + n + p) events following absorption of stopped (pi) ^{-} in ^3He. The purpose of the thesis was to calculate theoretically the particle spectrum following the absorption, using the two-nucleon model of pion absorption ^2 and to compare it to the results obtained in the Gotta experiment. The ^3 He pionic atom is unique in that it is the simplest nucleus which provides an opportunity for the verification of the two-nucleon absorption model. For this calculation the effective two-nucleon Hamiltonian^{3,4,5} was chosen as the T-matrix for low energy pion scattering from one nucleon followed by absorption on the second nucleon. The constants g_{0} and g _1 are obtained from the corresponding two-nucleon interaction processes resulting in the pion production with the first one corresponding to the spin triplet and the second to the spin singlet nucleon interactions. The initial bound-state momentum-space wave function was chosen ^6 to be consistent with the charge radius of the ^3He nucleus and to have the correct singularities generated by the asymptotic two- and three-body channels. The final-state wave functions are characterized by non-interacting n + D, non-interacting n + D^', and a non-interacting n + n + p states (when the energy is roughly equally shared between the nucleons). The results of the calculation turned out to be in a fairly good agreement with those obtained in ^1. The branching ratio of singlet deuteron rate of transition to the corresponding rate into deuteron differed from the result in the former by less than one percent. As a check some of the results obtained in ^6 were reproduced, giving a very good agreement with it as well. The calculation indicates that the two-nucleon absorption model gives a good result when used for a simple system like ^3He. Those
Pion-photon reactions and chiral dynamics in Primakoff processes at COMPASS
Friedrich, Jan Michael
2016-01-22
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.
Nuclear fragmentation and charge-exchange reactions induced by pions in the Δ -resonance region
NASA Astrophysics Data System (ADS)
Feng, Zhao-Qing
2016-11-01
The dynamics of the nuclear fragmentations and the charge exchange reactions in pion-nucleus collisions near the Δ (1232) resonance energies has been investigated within the Lanzhou quantum molecular dynamics transport model. An isospin-, momentum-, and density-dependent pion-nucleon potential is implemented in the model, which influences the pion dynamics, in particular the kinetic energy spectra, but weakly impacts the fragmentation mechanism. The absorption process in pion-nucleon collisions to form the Δ (1232) resonance dominates the heating mechanism of the target nucleus. The excitation energy transferred to the target nucleus increases with the pion kinetic energy and is similar for both π-- and π+-induced reactions. The magnitude of fragmentation of the target nucleus weakly depends on the pion energy. The isospin ratio in the pion double-charge exchange is influenced by the isospin ingredient of target nucleus.
Universal correlations in pion-less EFT with the resonating group model: three and four nucleons
NASA Astrophysics Data System (ADS)
Kirscher, J.; Grießhammer, H. W.; Shukla, D.; Hofmann, H. M.
A systematic connection between QCD and nuclear few- and many-body properties in the form of the Effective Field Theory "without pions" is applied to $A\\le 6$ nuclei to determine its range of applicability. We present results at next-to-leading order for the Tjon correlation and for a correlation between the singlet S-wave $^3$He-neutron scattering length and the triton binding energy. In the A=6 sector we performed leading order calculations for the binding energy and the charge and matter radii of the halo nucleus $^6$He. Also at leading order, the doublet S-wave 4-He-neutron phase shifts are compared with R-matrix data. These analysis provide evidence for a sufficiently fast convergence of the effective field theory, in particular, our results in $A\\le 4$ predict an expansion parameter of about 1/3, and they converge to data within the predicted uncertainty band at this order. A properly adjusted three-body contact force which we include together with the Coulomb interaction in all calculations is found to correctly renormalize the pion-less theory at leading- and next-to-leading order, i.e. the power counting does not require four-body forces at the respective order.
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.
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.
Pion Electroproduction form Helium 3, Deuterium, and Hydrogen
Avery, Stephen Milton
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.
Axial transition form factors and pion decay of baryon resonances
Julia-Diaz, B.; Riska, D.O.; Coester, F.
2004-10-01
The pion decay constants of the lowest orbitally excited states of the nucleon and the {delta}(1232) along with the corresponding axial transition form factors are calculated with Poincare covariant constituent-quark models with instant, point, and front forms of relativistic kinematics. The model wave functions are chosen such that the calculated electromagnetic and axial form factors of the nucleon represent the empirical values in all three forms of kinematics, when calculated with single-constituent currents. The pion decay widths calculated with the three forms of kinematics are smaller than the empirical values. Front and instant form kinematics provide a similar description, with a slight preference for front form, while the point form values are significantly smaller in the case of the lowest positive parity resonances.
Glauber gluons in pion-induced Drell-Yan processes
NASA Astrophysics Data System (ADS)
Chang, Chun-peng; Li, Hsiang-nan
2013-10-01
We point out that the existence of Glauber gluons in the kT factorization theorem can account for the violation of the Lam-Tung relation, namely, the anomalous lepton angular distribution observed in pion-induced Drell-Yan processes. The emission of a final-state parton, that balances the lepton-pair transverse momentum, causes the responsible spin-transverse-momentum correlation in the Glauber-gluon background. It is argued that the Glauber effect is significant in the pion due to its unique role of being a Nambu-Goldstone boson and a qqbar bound state simultaneously. This mechanism is compared to other resolutions in the literature by means of vacuum effects and Boer-Mulders functions. We propose to discriminate the above resolutions by measuring the ppbar Drell-Yan process at GSI and J-PARC.
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.
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.
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 .
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
Julien, J.; Bellini, V.; Bolore, M.; Charlot, X.; Girard, J.; Pappalardo, G.S.; Poitou, J.; Roussel, L.
1984-02-01
A scintillator range telescope was designed to detect pions in a very intense background of charged particles (ca 5000 ps) and to identify pion charge in the 15-90 MeV range. Such a telescope has a solid angle of 20 msr and allows the simultaneous detection of a wide pion momentum range on the order of 70 MeV/c to 200 MeV/c for both pions plus and pions minus. Several angles can be simultaneously studied with three telescopes. The pion energy resolution of ca 3 MeV is less, however, than the corresponding 0.5 MeV of a magnetic spectrometer. The accuracy of the R ratio depends on the accuracy of the pion plus identification method. This identification is based on the detection of particles generated by the pion plus-to-muon-to-tau decay sequence with a mean life of 26 ns. One method relies on the fast recovery time of the associated electronics by using an appropriate delayed coincidence between poin plus and muon plus signals. The low efficiency of such a method does not permit the determination of the pion minus contribution. In order to improve the charge identification of pions, the authors use a new approach in their experiments, based on the measurement of the charge of the particle pulses within different time gates. This paper presents the principles of this approach. Three gates--a prompt, a normal, and a delayed gate-and their respective charge analyzers are used in the discussion.
Freeze-out radii extracted from three-pion cumulants in pp, p-Pb and Pb-Pb collisions at the LHC
NASA Astrophysics Data System (ADS)
Abelev, B.; Adam, J.; Adamová, D.; Aggarwal, M. M.; Agnello, M.; Agostinelli, A.; Agrawal, N.; Ahammed, Z.; Ahmad, N.; Ahmed, I.; Ahn, S. U.; Ahn, S. A.; Aimo, I.; Aiola, S.; Ajaz, M.; Akindinov, A.; Alam, S. N.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alici, A.; Alkin, A.; 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.; Arbor, N.; Arcelli, S.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I. C.; Arslandok, M.; Augustinus, A.; Averbeck, R.; Awes, T. C.; 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.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartke, J.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batyunya, B.; Batzing, P. C.; Baumann, C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bellwied, R.; Belmont-Moreno, E.; Belmont, R.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Berger, M. E.; 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.; Bjelogrlic, S.; Blanco, F.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Bogolyubsky, M.; Böhmer, F. V.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Bossú, F.; Botje, M.; Botta, E.; Böttger, S.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Castillo Castellanos, J.; Casula, E. A. R.; Catanescu, V.; Cavicchioli, C.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Chang, B.; Chapeland, S.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Chochula, P.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; 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.; Cortese, P.; Cortés Maldonado, I.; Cosentino, M. R.; Costa, F.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dainese, A.; Dang, R.; Danu, A.; Das, D.; Das, I.; Das, K.; Das, S.; Dash, A.; Dash, S.; De, S.; Delagrange, H.; Deloff, A.; Dénes, E.; D'Erasmo, G.; De Caro, A.; de Cataldo, G.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; de Rooij, R.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Di Bari, D.; Di Liberto, S.; Di Mauro, A.; Di Nezza, P.; Djuvsland, Ø.; Dobrin, A.; Dobrowolski, T.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Dørheim, S.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Dutta Majumdar, A. K.; Ehlers, R. J.; Elia, D.; Engel, H.; Erazmus, B.; Erdal, H. A.; Eschweiler, D.; Espagnon, B.; Esposito, M.; Estienne, M.; Esumi, S.; Evans, D.; Evdokimov, S.; Fabris, D.; Faivre, J.; Falchieri, D.; Fantoni, A.; Fasel, M.; Fehlker, D.; Feldkamp, L.; Felea, D.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Floratos, E.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Garishvili, I.; Gerhard, J.; Germain, M.; Gheata, A.; Gheata, M.; Ghidini, B.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Gladysz-Dziadus, E.; Glässel, P.; Gomez Ramirez, A.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Graczykowski, L. K.; 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.; Guilbaud, M.; Gulbrandsen, K.; Gulkanyan, H.; Gumbo, M.; Gunji, T.; Gupta, A.; Gupta, R.; Khan, K. H.; Haake, R.; Haaland, Ø.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hanratty, L. D.; Hansen, A.; Harris, J. W.; Hartmann, H.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Heide, M.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Hess, B. A.; Hetland, K. F.; Hippolyte, B.; Hladky, J.; Hristov, P.; Huang, M.; Humanic, T. J.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Ilkiv, I.; Inaba, M.; Innocenti, G. M.; Ionita, C.; Ippolitov, M.; Irfan, M.; Ivanov, M.; Ivanov, V.; Jachołkowski, A.; Jacobs, P. M.; Jahnke, C.; Jang, H. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jung, H.; Jusko, A.; Kadyshevskiy, V.; Kalcher, S.; Kalinak, P.; Kalweit, A.; Kamin, J.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karpechev, E.; Kebschull, U.; Keidel, R.; Khan, M. M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, B.; Kim, D. W.; Kim, D. J.; Kim, J. S.; Kim, M.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, J.; Klein-Bösing, C.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobdaj, C.; Köhler, M. K.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Konevskikh, A.; Kovalenko, V.; Kowalski, M.; Kox, S.; Koyithatta Meethaleveedu, G.; Kral, J.; Králik, I.; Kramer, F.; Kravčáková, A.; Krelina, M.; Kretz, M.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kučera, V.; Kucheriaev, Y.; Kugathasan, T.; Kuhn, C.; Kuijer, P. G.; Kulakov, I.; Kumar, J.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kushpil, S.; Kweon, M. J.; Kwon, Y.; Ladron de Guevara, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lara, C.; Lardeux, A.; Lattuca, A.; La Pointe, S. L.; La Rocca, P.; Lea, R.; Lee, G. R.; Legrand, I.; Lehnert, J.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; Leoncino, M.; León Monzón, I.; Lévai, P.; Li, S.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loggins, V. R.; Loginov, V.; Lohner, D.; Loizides, C.; Lopez, X.; López Torres, E.; Lu, X.-G.; Luettig, P.; Lunardon, M.; Luparello, G.; Luzzi, C.; Ma, R.; Maevskaya, A.; Mager, M.; Mahapatra, D. P.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manceau, L.; Manko, V.; Manso, F.; Manzari, V.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Marín, A.; Markert, C.; Marquard, M.; Martashvili, I.; Martin, N. A.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martin Blanco, J.; Martynov, Y.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzoni, M. A.; Meddi, F.; Menchaca-Rocha, A.; Mercado Pérez, J.; Meres, M.; Miake, Y.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mlynarz, J.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Morando, M.; Moreira De Godoy, D. A.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Müller, H.; Munhoz, M. G.; Murray, S.; Musa, L.; Musinsky, J.; Nandi, B. K.; Nania, R.; Nappi, E.; Nattrass, C.; Nayak, K.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Nicassio, M.; Niculescu, M.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Nilsen, B. S.; Noferini, F.; Nomokonov, P.; Nooren, G.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Okatan, A.; Olah, L.; Oleniacz, J.; Oliveira Da Silva, A. C.; Onderwaater, J.; Oppedisano, C.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Sahoo, P.; Pachmayer, Y.; Pachr, M.; Pagano, P.; Paić, G.; Painke, F.; Pajares, C.; Pal, S. K.; Palmeri, A.; Pant, D.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Patalakha, D. I.; Paticchio, V.; Paul, B.; Pawlak, T.; Peitzmann, T.; Pereira Da Costa, H.; Pereira De Oliveira Filho, E.; Peresunko, D.; Pérez Lara, C. E.; Pesci, A.; Peskov, V.; Pestov, Y.; Petráček, V.; Petran, M.; Petris, M.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Pohjoisaho, E. H. O.; Polichtchouk, B.; Poljak, N.; Pop, A.; Porteboeuf-Houssais, S.; Porter, J.; Potukuchi, B.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Rauf, A. W.; Razazi, V.; Read, K. F.; Real, J. S.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reicher, M.; Reidt, F.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Rettig, F.; Revol, J.-P.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Rivetti, A.; Rocco, E.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohni, S.; Rohr, D.; Röhrich, D.; Romita, R.; Ronchetti, F.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, R.; Sahu, P. K.; Saini, J.; Sakai, S.; Salgado, C. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Sanchez Castro, X.; Sánchez Rodríguez, F. J.; Šándor, L.; Sandoval, A.; Sano, M.; Santagati, G.; Sarkar, D.; Scapparone, E.; Scarlassara, F.; Scharenberg, R. P.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schuchmann, S.; Schukraft, J.; Schulc, M.; Schuster, T.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Segato, G.; Seger, J. E.; Sekiguchi, Y.; Selyuzhenkov, I.; Seo, J.; Serradilla, E.; Sevcenco, A.; Shabetai, A.; Shabratova, G.; Shahoyan, R.; Shangaraev, A.; Sharma, N.; Sharma, S.; Shigaki, K.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Singaraju, R.; Singh, R.; Singha, S.; Singhal, V.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Skjerdal, K.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Søgaard, C.; Soltz, R.; Song, J.; Song, M.; Soramel, F.; Sorensen, S.; Spacek, M.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Srivastava, B. K.; Stachel, J.; Stan, I.; Stefanek, G.; Steinpreis, M.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Stolpovskiy, M.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Sultanov, R.; Šumbera, M.; Susa, T.; Symons, T. J. M.; Szabo, A.; Szanto de Toledo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Takahashi, J.; Tangaro, M. A.; Tapia Takaki, J. D.; Tarantola Peloni, A.; Tarazona Martinez, A.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terrevoli, C.; Thäder, J.; Thomas, D.; Tieulent, R.; Timmins, A. R.; Toia, A.; Torii, H.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ulery, J.; Ullaland, K.; Uras, A.; Usai, G. L.; Vajzer, M.; Vala, M.; Valencia Palomo, L.; Vallero, S.; Vande Vyvre, P.; Vannucci, L.; Van Der Maarel, J.; Van Hoorne, J. W.; van Leeuwen, M.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vechernin, V.; Veldhoen, M.; Velure, A.; Venaruzzo, M.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Vyushin, A.; Wagner, B.; Wagner, J.; Wagner, V.; Wang, M.; Wang, Y.; Watanabe, D.; Weber, M.; Wessels, J. P.; Westerhoff, U.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, G.; Wilkinson, J.; Williams, M. C. S.; Windelband, B.; Winn, M.; Xiang, C.; Yaldo, C. G.; Yamaguchi, Y.; Yang, H.; Yang, P.; Yang, S.; Yano, S.; Yasnopolskiy, S.; Yi, J.; Yin, Z.; Yoo, I.-K.; Yushmanov, I.; Zaccolo, V.; Zach, C.; Zaman, A.; Zampolli, C.; Zaporozhets, S.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, F.; Zhou, Y.; Zhou, Zhuo; Zhu, H.; Zhu, J.; Zhu, X.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zoccarato, Y.; Zyzak, M.
2014-12-01
In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose-Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e.g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correlations in pp, p-Pb and Pb-Pb collisions at the LHC with ALICE. At similar multiplicity, the invariant radii extracted in p-Pb collisions are found to be 5-15% larger than those in pp, while those in Pb-Pb are 35-55% larger than those in p-Pb. Our measurements disfavor models which incorporate substantially stronger collective expansion in p-Pb as compared to pp collisions at similar multiplicity.
Monte Carlo simulation of virtual Compton scattering below pion threshold
NASA Astrophysics Data System (ADS)
Janssens, P.; Van Hoorebeke, L.; Fonvieille, H.; D'Hose, N.; Bertin, P. Y.; Bensafa, I.; Degrande, N.; Distler, M.; Di Salvo, R.; Doria, L.; Friedrich, J. M.; Friedrich, J.; Hyde-Wright, Ch.; Jaminion, S.; Kerhoas, S.; Laveissière, G.; Lhuillier, D.; Marchand, D.; Merkel, H.; Roche, J.; Tamas, G.; Vanderhaeghen, M.; Van de Vyver, R.; Van de Wiele, J.; Walcher, Th.
2006-10-01
This paper describes the Monte Carlo simulation developed specifically for the Virtual Compton Scattering (VCS) experiments below pion threshold that have been performed at MAMI and JLab. This simulation generates events according to the (Bethe-Heitler + Born) cross-section behaviour and takes into account all relevant resolution-deteriorating effects. It determines the "effective" solid angle for the various experimental settings which are used for the precise determination of the photon electroproduction absolute cross-section.
Pion Interferometry in AU+AU Collisions at the AGS
Lee, J. H.
1999-01-09
Two-pion Bose-Einstein correlations have been studied using the BNL-E866 Forward Spectrometer in 11.6 A {center_dot} GeV/c Au + Au collisions. The data were analyzed using three-dimensional correlation parameterizations to study transverse momentum-dependent source parameters. The freeze-out time and the duration of emission were derived from the source radii parameters.
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.
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.
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.
Pion masses in two-flavor QCD with η condensation.
Aoki, Sinya; Creutz, Michael
2014-04-11
We investigate some aspects of two-flavor QCD with mu≠md at low energy, using the leading order chiral perturbation theory including anomaly effects. While nothing special happens at mu=0 for the fixed md≠0, the neutral pion mass becomes zero at two critical values of mu, between which the neutral pion field condenses, leading to a spontaneously CP broken phase, the so-called Dashen phase. We also show that the "topological susceptibility" in the chiral perturbation theory diverges at these two critical points. We briefly discuss a possibility that mu=0 can be defined by the vanishing the "topological susceptibility. We finally analyze the case of mu=md=m with θ=π, which is equivalent to mu=-md=-m with θ=0 by the chiral rotation. In this case, the η condensation occurs at small m, violating the CP symmetry spontaneously. Deep in the η condensation phase, three pions become Nambu-Goldstone bosons, but they show unorthodox behavior at small m that mπ2=O(m2), which, however, is shown to be consistent with the chiral Ward-Takahashi identities.
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.
Pion structure function from leading neutron electroproduction and SU(2) flavor asymmetry
NASA Astrophysics Data System (ADS)
McKenney, J. R.; Sato, Nobuo; Melnitchouk, W.; Ji, Chueng-Ryong
2016-03-01
We examine the efficacy of pion exchange models to simultaneously describe leading neutron electroproduction at HERA and the d ¯ -u ¯ flavor asymmetry in the proton. A detailed χ2 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 ×10-4≲xπ≲0.05 at a scale of Q2=10 GeV2 . Based on the fit results, we provide estimates for leading proton structure functions in upcoming tagged deep-inelastic scattering experiments at Jefferson Lab on the deuteron with forward protons.
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 the $\\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.
Pion structure function from leading neutron electroproduction and SU(2) flavor asymmetry
McKenney, Joshua R.; Sato Gonzalez, Nobuo; Melnitchouk, Wally; Ji, Chueng-Ryong
2016-03-01
We examine the efficacy of pion exchange models to simultaneously describe leading neutron electroproduction at HERA and the $\\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$. Based on the fit results, we provide estimates for leading proton structure functions in upcoming tagged deep-inelastic scattering experiments at Jefferson Lab on the deuteron with forward protons.
Chaoticity parameter λ in two-pion interferometry in an expanding boson gas model
Liu, Jie; Ru, Peng; Zhang, Wei-Ning; ...
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
Measurements of pion production in eA with the CLAS detector
NASA Astrophysics Data System (ADS)
Manly, S.; Lee, H.
2015-05-01
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. Selected distributions in W, Q2, pπ, and θπ are shown for data produced using deuterium, carbon, iron and lead 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 final state interaction models in order to reduce uncertainties in the results extracted from current and next-generation neutrino oscillation experiments.
Measurements of pion production in eA with the CLAS detector
Manly, S.; Lee, H.
2015-05-15
Preliminary results on semi-inclusive charged pion production in eA collisions at E{sub beam}=5 GeV/c{sup 2} 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. Selected distributions in W, Q{sup 2}, p{sub π}, and θ{sub π} are shown for data produced using deuterium, carbon, iron and lead 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 final state interaction models in order to reduce uncertainties in the results extracted from current and next-generation neutrino oscillation experiments.
NASA Astrophysics Data System (ADS)
Fanelli, C.; Cisbani, E.; Hamilton, D. J.; Salmé, G.; Wojtsekhowski, B.; Ahmidouch, A.; Annand, J. R. M.; Baghdasaryan, H.; Beaufait, J.; Bosted, P.; Brash, E. J.; Butuceanu, C.; Carter, P.; Christy, E.; Chudakov, E.; Danagoulian, S.; Day, D.; Degtyarenko, P.; Ent, R.; Fenker, H.; Fowler, M.; Frlez, E.; Gaskell, D.; Gilman, R.; Horn, T.; Huber, G. M.; de Jager, C. W.; Jensen, E.; Jones, M. K.; Kelleher, A.; Keppel, C.; Khandaker, M.; Kohl, M.; Kumbartzki, G.; Lassiter, S.; Li, Y.; Lindgren, R.; Lovelace, H.; Luo, W.; Mack, D.; Mamyan, V.; Margaziotis, D. J.; Markowitz, P.; Maxwell, J.; Mbianda, G.; Meekins, D.; Meziane, M.; Miller, J.; Mkrtchyan, A.; Mkrtchyan, H.; Mulholland, J.; Nelyubin, V.; Pentchev, L.; Perdrisat, C. F.; Piasetzky, E.; Prok, Y.; Puckett, A. J. R.; Punjabi, V.; Shabestari, M.; Shahinyan, A.; Slifer, K.; Smith, G.; Solvignon, P.; Subedi, R.; Wesselmann, F. R.; Wood, S.; Ye, Z.; Zheng, X.
2015-10-01
Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The wide-angle Compton scattering polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of θcmp=70 ° . The longitudinal transfer KLL, measured to be 0.645 ±0.059 ±0.048 , where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is ˜3 times larger than predicted by the generalized-parton-distribution-based calculations, which indicates a significant unknown contribution to the scattering amplitude.
Fanelli, C; Cisbani, E; Hamilton, D J; Salmé, G; Wojtsekhowski, B; Ahmidouch, A; Annand, J R M; Baghdasaryan, H; Beaufait, J; Bosted, P; Brash, E J; Butuceanu, C; Carter, P; Christy, E; Chudakov, E; Danagoulian, S; Day, D; Degtyarenko, P; Ent, R; Fenker, H; Fowler, M; Frlez, E; Gaskell, D; Gilman, R; Horn, T; Huber, G M; de Jager, C W; Jensen, E; Jones, M K; Kelleher, A; Keppel, C; Khandaker, M; Kohl, M; Kumbartzki, G; Lassiter, S; Li, Y; Lindgren, R; Lovelace, H; Luo, W; Mack, D; Mamyan, V; Margaziotis, D J; Markowitz, P; Maxwell, J; Mbianda, G; Meekins, D; Meziane, M; Miller, J; Mkrtchyan, A; Mkrtchyan, H; Mulholland, J; Nelyubin, V; Pentchev, L; Perdrisat, C F; Piasetzky, E; Prok, Y; Puckett, A J R; Punjabi, V; Shabestari, M; Shahinyan, A; Slifer, K; Smith, G; Solvignon, P; Subedi, R; Wesselmann, F R; Wood, S; Ye, Z; Zheng, X
2015-10-09
Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The wide-angle Compton scattering polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of θ_{cm}^{p}=70°. The longitudinal transfer K_{LL}, measured to be 0.645±0.059±0.048, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is ~3 times larger than predicted by the generalized-parton-distribution-based calculations, which indicates a significant unknown contribution to the scattering amplitude.
Fanelli, Cristiano V.
2015-10-06
Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The WACS polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of θ^{P}_{cm} = 70°. The longitudinal transfer K_{LL}, measured to be 0.645 ± 0.059 ± 0.048, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is ~3 times larger than predicted by the GPD-based calculations, which indicates a significant unknown contribution to the scattering amplitude.
Fanelli, Cristiano V.
2015-10-06
Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The WACS polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of θPcm = 70°. The longitudinal transfer KLL, measured to be 0.645 ± 0.059 ± 0.048, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton.more » However, the observed value is ~3 times larger than predicted by the GPD-based calculations, which indicates a significant unknown contribution to the scattering amplitude.« less
Impact of nucleon-nucleon bremsstrahlung rates beyond one-pion exchange
NASA Astrophysics Data System (ADS)
Bartl, A.; Bollig, R.; Janka, H.-T.; Schwenk, A.
2016-10-01
Neutrino-pair production and annihilation through nucleon-nucleon bremsstrahlung is included in current supernova simulations by rates that are based on the one-pion-exchange approximation. Here we explore the consequences of bremsstrahlung rates based on modern nuclear interactions for proto-neutron star cooling and the corresponding neutrino emission. We find that despite a reduction of the bremsstrahlung emission by a factor of 2-5 in the neutrinospheric region, models with the improved treatment exhibit only ≲5 % changes of the neutrino luminosities and an increase of ≲0.7 MeV of the average energies of the radiated neutrino spectra, with the largest effects for the antineutrinos of all flavors and at late times. Overall, the proto-neutron star cooling evolution is slowed down modestly by ≲0.5 - 1 s .
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.
Towards a model of pion generalized parton distributions from Dyson-Schwinger equations
Moutarde, H.
2015-04-10
We compute the pion quark Generalized Parton Distribution H{sup q} and Double Distributions F{sup q} and G{sup q} in a coupled Bethe-Salpeter and Dyson-Schwinger approach. We use simple algebraic expressions inspired by the numerical resolution of Dyson-Schwinger and Bethe-Salpeter equations. We explicitly check the support and polynomiality properties, and the behavior under charge conjugation or time invariance of our model. We derive analytic expressions for the pion Double Distributions and Generalized Parton Distribution at vanishing pion momentum transfer at a low scale. Our model compares very well to experimental pion form factor or parton distribution function data.
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.
FFAG Beam Line for nuPIL - Neutrinos from PIon Beam Line
Lagrange, Jean-Baptiste; Pasternak, Jaroslaw; Bross, Alan; Liu, Ao; Appleby, Robert; Tygier, Sam
2016-06-01
The Long Baseline Neutrino Facilities (LBNF) program aims to deliver a neutrino beam for the Deep Underground Neutrino Experiment (DUNE). The current baseline for LBNF is a conventional magnetic horn and decay pipe system. Neutrinos from PIon beam Line (nuPIL) is a part of the optimization effort to optimize the LBNF. It consists of a pion beam line after the horn to clean the beam of high energy protons and wrong-sign pions before transporting them into a decay beam line, where instrumentation could be implemented. This paper focuses on the FFAG solution for this pion beam line. The resulting neutrino flux is also presented.
Measurement of Neutral Current Neutral Pion Production on Carbon in a Few-GeV Neutrino Beam
Kurimoto, Yoshinori
2010-01-01
Understanding of the π^{0} production via neutrino-nucleus neutral current interaction in the neutrino energy region of a few GeV is essential for the neutrino oscillation experiments. In this thesis, we present a study of neutral current π^{0} production from muon neutrinos scattering on a polystyrene (C_{8}H_{8}) target in the SciBooNE experiment. All neutrino beam data corresponding to 0.99 × 10^{20} protons on target have been analyzed. We have measured the cross section ratio of the neutral current π^{0} production to the total charge current interaction and the π^{0} kinematic distribution such as momentum and direction. We obtain [7.7 ± 0.5(stat.) ± 0.5(sys.)] × 10^{-2} as the ratio of the neutral current neutral pion production to total charged current cross section; the mean energy of neutrinos producing detected neutral pions is 1.1 GeV. The result agrees with the Rein- Sehgal model, which is generally used for the Monte Carlo simulation by many neutrino oscillation experiments. We achieve less than 10 % uncertainty which is required for the next generation search for ν_{µ} → ν_{e} oscillation. The spectrum shape of the π^{0} momentum and the distribution of the π0 emitted angle agree with the prediction, which means that not only the Rein-Sehgal model but also the intra-nuclear interaction models describe our data well. We also measure the ratio of the neutral current coherent pion production to total charged current cross section to be (1.17 ± 0.23 ) × 10^{-2} based on the Rein and Sehgal model. The result gives the evidence for non-zero coherent pion production via neutral current interaction at the mean neutrino energy of 1.0 GeV.
Photocouplings at the pole from pion photoproduction
Ronchen, D.; Doring, M.; Huang, F.; ...
2014-06-24
The reactions γp → π0p and γp → π+n are analyzed in a semi-phenomenological approach up to E ~ 2.3 GeV. Fits to differential cross section and single and double polarization observables are performed. A good overall reproduction of the available photoproduction data is achieved. The Julich2012 dynamical coupled-channel model -which describes elastic πN scattering and the world data base of the reactions πN → ηN, KΛ, and KΣ at the same time– is employed as the hadronic interaction in the final state. Furthermore, the framework guarantees analyticity and, thus, allows for a reliable extraction of resonance parameters in termsmore » of poles and residues. In particular, the photocouplings at the pole can be extracted and are presented.« less
Photocouplings at the pole from pion photoproduction
Ronchen, D.; Doring, M.; Huang, F.; Haberzettl, H.; Haidenbauer, J.; Hanhart, C.; Krewald, S.; MeiBner, U. -G.; Nakayama, K.
2014-06-24
The reactions γp → π^{0}p and γp → π^{+}n are analyzed in a semi-phenomenological approach up to E ~ 2.3 GeV. Fits to differential cross section and single and double polarization observables are performed. A good overall reproduction of the available photoproduction data is achieved. The Julich2012 dynamical coupled-channel model -which describes elastic πN scattering and the world data base of the reactions πN → ηN, KΛ, and KΣ at the same time– is employed as the hadronic interaction in the final state. Furthermore, the framework guarantees analyticity and, thus, allows for a reliable extraction of resonance parameters in terms of poles and residues. In particular, the photocouplings at the pole can be extracted and are presented.
Sadler, M.E.; Isenhower, L.D.
1992-02-15
This report discusses research on the following topics: pion-nucleon interactions; detector tomography facility; nuclear dependence of charm and beauty quark production and a study of two-prong decays of neutral D and B mesons; N* collaboration at CEBAF; and pilac experiments. (LSP)
A Pion Production and Capture System for a 4 MW Target Station
Ding, X.; Kirk, H.; Berg, J.S.
2010-06-01
A study of a pion production and capture system for a 4 MW target station for a neutrino factory or muon collider is presented. Using the MARS code, we simulate the pion production produced by the interaction of a free liquid mercury jet with an intense proton beam. We study the variation of meson production with the direction of the proton beam relative to the target. We also examine the influence on the meson production by the focusing of the proton beam. The energy deposition in the capture system is determined and the shielding required in order to avoid radiation damage is discussed. The exploration for the multiple proton beam entry directions relative to mercury jet in the 8GeV proton beam case demonstrates that an asymmetric layout is required in order to achieve the same beam/jet crossing angle at the jet axis. We find a correlation between the distance of beam relative to the jet and the meson production. The peak meson production is 8% higher than for the lowest case. The examination of the influence on the meson production by the focusing of the proton beam shows the meson production loss is negligible (<1%) for a beta function to be 0.3m or higher for the proton beam. By investigating the energy deposition in the target/capture system, we see that the bulk of 4-MW proton beam power is deposited in the water cooled tungsten-carbide (WC) shielding, the mercury jet and the capture beam pipe. In addition, high power deposition in the first superconducting coil causes an issue for its operation and life time. Enhanced shielding is necessary to lower the radiation damage.
Target dependence of clan model parameters at Dubna energy-chaotic pion production
NASA Astrophysics Data System (ADS)
Bhattacharyya, Swarnapratim; Haiduc, Maria; Neagu, Alina Tania; Firu, Elena
2013-02-01
A detailed study of clan model parameters and their target dependence has been carried out in the light of void probability scaling for heavy (AgBr) and light (CNO) groups of targets present in the nuclear emulsion using 22Ne (at an incident momentum of 4.1 GeV/c), 28Si (at an incident momentum of 4.5 GeV/c), 16O (at an incident momentum of 4.5 GeV/c) and 32S (at an incident momentum of 4.5 GeV/c) projectiles. The variation of scaled rap-gap probability with the single moment combination has been studied for all of the interactions. The experimental points are found to lie approximately on the NBD curve for all of the interactions, indicating a scaling behavior. According to the two-source model of particle production, in the case of 32S-AgBr interactions at 4.5 GeV/c, the pion production mechanism has been found to be almost chaotic. On the contrary, for all of the other interactions at 4.1-4.5 GeV/c, pion production is predominantly chaotic. Average clan multiplicities (\\overline N) for all of the interactions are found to increase with the increase in the pseudo-rapidity interval Δη. The values of \\overline N for the AgBr target are larger than those for the CNO target. The average number of particles per clan (\\overline n_c) increases initially with the increase in pseudo-rapidity interval. An approximate saturation of the values of \\overline n_c is observed for 22Ne and 16O projectiles around Δη = 6. With the increase in projectile size, the saturation of \\overline n_c seems to be wiped out. It can also be observed from the tables that for a particular target the average number of particles per clan (\\overline n_c) increases with the increase in the size of the projectile nucleus. A comparison with the results of the SPS data has also been presented.
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.
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.
Pion transition form factor through Dyson-Schwinger equations
NASA Astrophysics Data System (ADS)
Raya, Khépani
2016-10-01
In the framework of Dyson-Schwinger equations (DSE), we compute the γ*γ→π0 transition form factor, G(Q2). For the first time, in a continuum approach to quantun chromodynamics (QCD), it was possible to compute G(Q2) on the whole domain of space-like momenta. Our result agrees with CELLO, CLEO and Belle collaborations and, with the well- known asymptotic QCD limit, 2ƒπ. Our analysis unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA) and elastic electromagnetic form factor.
Neutral pion form factor measurement by the NA62 experiment
NASA Astrophysics Data System (ADS)
Pepe, Monica
2017-03-01
The NA62 experiment at CERN collected a large sample of charged kaon decays with a highly efficient trigger for decays into electrons in 2007. A measurement of the electromagnetic transition form factor slope of the neutral pion in the time-like region from about one million fully reconstructed π0 Dalitz decays is presented. The limits on dark photon production from a sample of about 1.7 × 107 π0 Dalitz decays collected in 2003-2004 by the earlier kaon experiment at CERN NA48/2 are also reported.
Superluminal Neutrinos at OPERA Confront Pion Decay Kinematics
Cowsik, Ramanath; Nussinov, Shmuel; Sarkar, Utpal
2011-12-16
Violation of Lorentz invariance (VLI) has been suggested as an explanation of the superluminal velocities of muon neutrinos reported by OPERA. In this Letter, we show that the amount of VLI required to explain this result poses severe difficulties with the kinematics of the pion decay, extending its lifetime and reducing the momentum carried away by the neutrinos. We show that the OPERA experiment limits {alpha}=(v{sub {nu}}-c)/c<4x10{sup -6}. We then take recourse to cosmic-ray data on the spectrum of muons and neutrinos generated in Earth's atmosphere to provide a stronger bound on VLI: (v-c)/c<10{sup -12}.
Measurement of double-radiative pion capture on hydrogen
NASA Astrophysics Data System (ADS)
Tripathi, Sugata
The first measurement of double radiative pion capture on hydrogen is presented. The experiment was conducted at the TRIUMF cyclotron using the RMC spectrometer, and detected gamma-ray coincidences following pi - stops in liquid hydrogen. The branching ratio for the double radiative capture reaction was found to be (3.05 +/- 0.27 (stat.) +/- 0.31 (syst.)) x 10-5. The measured branching ratio and angle-energy distributions support the theoretical prediction of a dominant contribution from the pi-pi + → gammagamma annihilation mechanism.
Superluminal neutrinos at OPERA confront pion decay kinematics.
Cowsik, Ramanath; Nussinov, Shmuel; Sarkar, Utpal
2011-12-16
Violation of Lorentz invariance (VLI) has been suggested as an explanation of the superluminal velocities of muon neutrinos reported by OPERA. In this Letter, we show that the amount of VLI required to explain this result poses severe difficulties with the kinematics of the pion decay, extending its lifetime and reducing the momentum carried away by the neutrinos. We show that the OPERA experiment limits α=(ν(ν)-c)/c<4×10(-6). We then take recourse to cosmic-ray data on the spectrum of muons and neutrinos generated in Earth's atmosphere to provide a stronger bound on VLI: (ν-c)/c<10(-12).
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.
Loop corrections to pion and kaon neutrino production
NASA Astrophysics Data System (ADS)
Siddikov, Marat; Schmidt, Iván
2017-01-01
In this paper, we study the next-to-leading-order corrections to deeply virtual pion and kaon production in neutrino experiments. We estimate these corrections in the kinematics of the minerva experiment at Fermilab, and find that they are sizable and increase the leading-order cross section by up to a factor of 2. We provide a computational code which can be used for the evaluation of the cross sections, taking into account these corrections and employing various generalized parton distribution models.
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.
Exclusive near threshold two-pion production with the MOMO experiment at COSY
NASA Astrophysics Data System (ADS)
Bavink, S.; Bellemann, F.; Berg, A.; Bisplinghoff, J.; Bohlscheid, G.; Ernst, J.; Henrich, C.; Hinterberger, F.; Ibald, R.; Jahn, R.; Jarczyk, L.; Joosten, R.; Kozela, A.; Machner, H.; Magiera, A.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Munkel, J.; Neumann-Cosel, P. v.; Rosendaal, D.; Rossen, P. v.; Schnitker, H.; Scho, K.; Smyrski, J.; Strzalkowski, A.; Tölle, R.; Wurzinger, R.
1997-05-01
Near threshold two pion production via the reaction pd→3Heπ+π- was measured kinematically complete with the MOMO experiment at COSY. A remarkable deviation of the obtained two pion invariant mass spectra from phase space as well as a predominant sidewise and back to back emission of the two mesons was observed.
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.
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
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.
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.
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.
NASA Astrophysics Data System (ADS)
Pasquini, B.; Schweitzer, P.
2014-07-01
At leading twist the transverse momentum dependent parton distributions of the pion consist of two functions, the unpolarized f1,π(x,k⊥2) and the Boer-Mulders function h1,π⊥(x ,k⊥2). We study both functions within a light-front constituent model of the pion, comparing the results with different pion models and the corresponding nucleon distributions from a light-front constituent model. After evolution from the model scale to the relevant experimental scales, the results for the collinear pion valence parton distribution function f1,π(x) are in very good agreement with available parametrizations. Using the light-front constituent model results for the Boer-Mulders functions of the pion and nucleon, we calculate the coefficient ν in the angular distribution of Drell-Yan dileptons produced in pion-nucleus scattering, which is responsible for the violation of the Lam-Tung relation. We find a good agreement with the data, and carefully discuss the range of applicability of our approach.
Wickremasinghe, Don Athula Abeyarathna
2015-07-01
The prediction of the muon neutrino flux from a 71.0 cm long beryllium target for the MiniBooNE experiment is based on a measured pion production cross section which was taken from a short beryllium target (2.0 cm thick - 5% nuclear interaction length) in the Hadron Production (HARP) experiment at CERN. To verify the extrapolation to our longer target, HARP also measured the pion production from 20.0 cm and 40.0 cm beryllium targets. The measured production yields, d^{2}N^{π±} (p; θ )=dpd Ω, on targets of 50% and 100% nuclear interaction lengths in the kinematic rage of momentum from 0.75 GeV/c to 6.5 GeV/c and the range of angle from 30 mrad to 210 mrad are presented along with an update of the short target cross sections. The best fitted extended Sanford-Wang (SW) model parameterization for updated short beryllium target π^{+} production cross section is presented. Yield measurements for all three targets are also compared with that from the Monte Carlo predictions in the MiniBooNE experiment for different SW parameterization. The comparisons of v_{μ} flux predictions for updated SW model is presented.
Piarulli, M.; Girlanda, L.; Schiavilla, R.; Pérez, R. Navarro; Amaro, J. E.; Arriola, E. Ruiz
2015-02-26
In this study, we construct a coordinate-space chiral potential, including Δ-isobar intermediate states in its two-pion-exchange component up to order Q^{3} (Q denotes generically the low momentum scale). The contact interactions entering at next-to-leading and next-to-next-to-next-to-leading orders (Q^{2} and Q^{4}, respectively) are rearranged by Fierz transformations to yield terms at most quadratic in the relative momentum operator of the two nucleons. The low-energy constant multiplying these contact interactions are fitted to the 2013 Granada database, consisting of 2309 pp and 2982 np data (including, respectively, 148 and 218 normalizations) in the laboratory-energy range 0–300 MeV. For the total 5291 $pp$ and $np$ data in this range, we obtain a Χ^{2} /datum of roughly 1.3 for a set of three models characterized by long- and short-range cutoffs, R_{L} and R_{S} respectively, ranging from (R_{L},R_{S})=(1.2,0.8) fm down to (0.8,0.6) fm. The long-range (short-range) cutoff regularizes the one- and two-pion exchange (contact) part of the potential.
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.
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.
Neutrino-induced one-pion production revisited: The νμn →μ-n π+ channel
NASA Astrophysics Data System (ADS)
Hernández, E.; Nieves, J.
2017-03-01
Understanding single pion production reactions on free nucleons is the first step towards a correct description of these processes in nuclei, which are important for signal and background contributions in current and near future accelerator neutrino oscillation experiments. In this work, we reanalyze our previous studies of neutrino-induced one-pion production on nucleons for outgoing π N invariant masses below 1.4 GeV. Our motivation is to get a better description of the νμn →μ-n π+ cross section, for which current theoretical models give values significantly below data. This channel is very sensitive to the crossed Δ (1232 ) contribution and thus, to spin 1 /2 components in the Rarita-Schwinger Δ propagator. We show how these spin 1 /2 components are nonpropagating and give rise to contact interactions. In this context, we point out that the discrepancy with experiment might be corrected by the addition of appropriate extra contact terms and argue that this procedure will provide a natural solution to the νμn →μ-n π+ puzzle. To keep our model simple, in this work, we propose to change the strength of the spin 1 /2 components in the Δ propagator and use the νμn →μ-n π+ data to constraint its value. With this modification, we now find a good reproduction of the νμn →μ-n π+ cross section without affecting the good results previously obtained for the other channels. We also explore how this change in the Δ propagator affects our predictions for pion photoproduction and find also a better agreement with experiment than with the previous model.
NASA Astrophysics Data System (ADS)
Kahrimanis, George Peter
1995-01-01
Pion-nucleus scattering at energies above the Delta(1232) resonance has been studied intensively using both pi^+ and pi^- beams on ^{12}C, ^{40}Ca, ^{90}Zr, and ^{208}Pb. The present data provide an opportunity to study the interaction of pions with nuclei at energies above the Delta(1232), where conventional second-order corrections should be small. The results are compared with other data sets at similar energies, and with four theoretical calculations: one employing a momentum-space microscopic optical model, another in the eikonal approach, an application of the Kemmer-Duffin-Petiau wave equation with the Relativistic Impulse Approximation, and one based on the Non-Relativistic Impulse Approximation. The comparisons show certain persistent features, such as a smaller effective radius of strong absorption than in the region of the Delta(1232), as expected, but still larger than these calculations predict.
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; Calderón de la Barca Sánchez, 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; Mora Corral, 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; Lednický, R; Leontiev, V M; LeVine, M J; Li, Q; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Z; Liu, Q J; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Ludlam, T; Lynn, D; Ma, J; Ma, Y G; Magestro, D; Majka, R; Margetis, S; Markert, C; Martin, L; Marx, J; Matis, H S; Matulenko, Yu A; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Messer, M; Miller, M L; Milosevich, Z; Minaev, N G; Mitchell, J; Molnar, L; Moore, C F; Morozov, V; de Moura, M M; Munhoz, M G; Nelson, J M; Nevski, P; Nikitin, V A; Nogach, L V; Norman, B; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Paic, G; Pandey, S U; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Perevoztchikov, V; Peryt, W; Petrov, V A; Picha, R; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potrebenikova, E; Prindle, D; Pruneau, C; Putschke, J; Rai, G; Rakness, G; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Rykov, V; Sakrejda, I; Salur, S; Sandweiss, J; Savin, I; Schambach, J; Scharenberg, R P; Schmitz, N; Schroeder, L S; Schweda, K; Seger, J; Seyboth, P; Shahaliev, E; Shestermanov, K E; Shimanskii, S S; Simon, F; Skoro, G; Smirnov, N; Snellings, R; Sorensen, P; Sowinski, J; Spinka, H M; Srivastava, B; Stephenson, E J; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Struck, C; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; Szanto de Toledo, A; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Thein, D; Thomas, J H; Thompson, M; Timoshenko, S; Tokarev, M; Tonjes, M B; Trainor, T A; Trentalange, S; Tribble, R E; Trofimov, V; Tsai, O; Ullrich, T; Underwood, D G; Van Buren, G; Vander Molen, A M; Vasiliev, A N; Vigdor, S E; Voloshin, S A; Vznuzdaev, M; Wang, F; Wang, Y; Ward, H; Watson, J W; Wells, R; Westfall, G D; Whitten, C; Wieman, H; Willson, R; Wissink, S W; Witt, R; Wood, J; Xu, N; Xu, Z; Yakutin, A E; Yamamoto, E; Yang, J; Yepes, P; Yurevich, V I; Zanevski, Y V; Zborovský, I; Zhang, H; Zhang, W M; Zoulkarneev, R; Zoulkarneeva, J; Zubarev, A N
2003-12-31
Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory, Au+Au collisions at sqrt[s(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 freeze-out. 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.
Online-Analysis of Hits in the Belle-II Pixeldetector for Separation of Slow Pions from Background
NASA Astrophysics Data System (ADS)
Baehr, S.; Sander, O.; Heck, M.; Pulvermacher, C.; Feindt, M.; Becker, J.
2015-12-01
The impending Upgrade of the Belle experiment is expected to increase the generated data set by a factor of 50. This means that for the planned pixel detector, which is the closest to the interaction point, the data rates are going to increase to up to 28 Gbit/s. Combined with data generated by the other detectors, this rate is too big to efficiently send out to offline processing. In order to reduce the data rates online data reduction schemes, in which background is detected and rejected, are going to be employed. In this paper, an approach for efficient online data reduction for the planned pixel detector of Belle-II is presented. Its central part is the NeuroBayes algorithm, which is based on multivariate analysis. It allows the identification of signal and background by analyzing clusters of hits in the pixel detector on FPGAs. The algorithm is leveraging the fact that hits of signal particles can have very different characteristics, compared to background, when passing through the pixel detector. The applicability and advantages in performance are shown through the D* decay. In Belle-II, these decays produce pions with such a small transversal momentum, that they barely escape the pixel detector itself. In a common approach like an extrapolation of tracks from outer detectors to RoIs, these pions are simply lost, since they do not reach all necessary layers of the detector. However, cluster analysis is able to identify and separate these pions from the background, thus keeping their data. For that characteristics of corresponding hits, like the total amount of charge deposited in the pixels, are used for separation. The capability for effective data reduction is underlined by a background reduction of at least 90% and signal efficiency of 95%, for slow pions. An implementation of the algorithm for usage on Virtex-6 FPGAs that are used at the pixel detector was performed. It is shown that the resulting implementation succeeds in replicating the efficiency of
Low-energy chiral two-pion exchange potential with statistical uncertainties
NASA Astrophysics Data System (ADS)
Pérez, R. Navarro; Amaro, J. E.; Arriola, E. Ruiz
2015-05-01
We present a new phenomenological nucleon-nucleon (N N ) chiral potential fitted to 925 p p and 1743 n p scattering data selected from the Granada-2013 N N database up to a laboratory energy of 125 MeV with 20 short-distance parameters and three chiral constants c1,c3, and c4 with χ2/ν =1.02 . Special attention is given to testing the normality of the residuals which allows for a sound propagation of statistical errors from the experimental data to the potential parameters, phase shifts, scattering amplitudes, and counterterms. This fit allows for a new determination of the chiral constants c1,c3, and c4 compatible with previous determinations from N N data. This new interaction is found to be softer than other high-quality potentials by undertaking a Weinberg eigenvalue analysis. We further explore the interplay between the error analysis and the assumed form of the short-distance interaction. The present work shows that it is possible to fit N N scattering with a two-pion exchange (TPE) chiral potential fulfilling all necessary statistical requirements up to 125 MeV and shows unequivocal nonvanishing D -wave short-distance pieces.
A Measurement of Neutrino-Induced Charged-Current Neutral Pion Production
Nelson, Robert H.
2010-01-01
This work presents the first comprehensive measurement of neutrino-induced charged-current neutral pion production (CCπ^{0}) off a nuclear target. The Mini Booster Neutrino Experiment (MiniBooNE) and Booster Neutrino Beam (BNB) are discussed in detail. MiniBooNE is a high-statistics (~ 1, 000, 000 interactions) low-energy (E_{v}ϵ 2 0.5 - 2.0 GeV) neutrino experiment located at Fermilab. The method for selecting and reconstructing CCπ^{0} events is presented. The π^{0} and μ^{-} are fully reconstructed in the final state allowing for the measurement of, among other things, the neutrino energy. The total observable CCπ^{0} cross-section is presented as a function of neutrino energy, along with five differential cross-sections in terms of the final state kinematics and Q^{2}. The results are combined to yield a flux-averaged total cross-section of <σ>_{Φ} = (9.2 ± 0.3_{stat.} ± 1.5_{syst.}) × 10^{-39} cm^{2}/CH_{2} at energy 965 MeV. These measurements will aid future neutrino experiments with the prediction of their neutrino interaction rates.
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.
Matching lightcone and anomaly-sum-rule predictions for the pion-photon transition form factor
NASA Astrophysics Data System (ADS)
Oganesian, A. G.; Pimikov, A. V.; Stefanis, N. G.; Teryaev, O. V.
2016-03-01
The pion-photon transition form factor is studied by employing two types of sum rules: light cone sum rules (LCSR) and anomaly sum rules (ASR). By comparing the predictions for the pion-photon transition form factor, obtained from these two approaches, the applicability limit of the LCSRs at low momenta is determined. Reciprocally, the ASR threshold dependence on the momentum was extracted using our LCSR-based method in combination with two different types of pion distribution amplitudes and found that at higher Q2 it approaches a constant.
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.
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.
In-Medium Isovector πN Amplitude from Low-Energy Pion Scattering
NASA Astrophysics Data System (ADS)
Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Meier, R.; Wagner, G. J.; Yaari, G.
2004-09-01
Differential cross sections for elastic scattering of 21.5MeV positive and negative pions by Si, Ca, Ni, and Zr have been measured as part of a study of the pion-nucleus potential across the threshold. The “anomalous” repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.
Adolph, C.; Akhunzyanov, R.; Alexeev, M. G.; ...
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.
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}}).
Roy-Steiner equations for pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Ditsche, C.; Hoferichter, M.; Kubis, B.; Meissner, U. G.
Starting from hyperbolic dispersion relations for the invariant amplitudes of pion-nucleon scattering together with crossing symmetry and unitarity, one can derive a closed system of integral equations for the partial waves of both the s-channel (pi N --> pi N) and the t-channel (pi pi --> Nbar N) reaction, called Roy-Steiner equations. After giving a brief overview of the Roy-Steiner system for pi N scattering, we demonstrate that the solution of the t-channel subsystem, which represents the first step in solving the full system, can be achieved by means of Muskhelishvili-Omn\\`es techniques. In particular, we present results for the P-waves featuring in the dispersive analysis of the electromagnetic form factors of the nucleon.
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.
Beam-spin asymmetries from semi-inclusive pion electroproduction
NASA Astrophysics Data System (ADS)
Gohn, W.; Avakian, H.; Joo, K.; Ungaro, M.; Adhikari, K. P.; Aghasyan, M.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Biselli, A. S.; Bono, J.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Cole, P. L.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Djalali, C.; Doughty, D.; Dupre, R.; El Alaoui, A.; El Fassi, L.; Eugenio, P.; Fedotov, G.; Fleming, J. A.; Forest, T.; Garçon, M.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Gothe, R. W.; Griffioen, K. A.; Guegan, B.; Guo, L.; Hafidi, K.; Hanretty, C.; Harrison, N.; Hattawy, Mohammad; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jo, H. S.; Keller, D.; Khandaker, M.; Khetarpal, P.; Kim, W.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Lenisa, P.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Movsisyan, A.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Peng, P.; Phillips, J. J.; Pisano, S.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Prok, Y.; Puckett, A. J. R.; Raue, B. A.; Ripani, M.; Ritchie, B. G.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Simonyan, A.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stoler, P.; Strakovsky, I. I.; Stepanyan, S.; Strauch, S.; Tang, W.; Tkachenko, S.; Vernarsky, B.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zonta, I.; CLAS Collaboration
2014-04-01
We have measured the moment ALUsinϕ corresponding to the polarized electron beam-spin asymmetry in semi-inclusive deep inelastic scattering. ALUsinϕ 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 (π+, π0 and π-) were measured simultaneously over a large range of kinematics within the virtuality range Q2≈ 1.0-4.5 GeV2. The observable was measured with better than 1% statistical precision over a large range of z, PT, xB, and Q2, 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 π- sinϕ moment.
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.
Pion and photon production in heavy ion collisions
Gabor,D.
2008-03-16
Measurement of neutral pions and direct photons are closely connected experimentally, on the other hand they probe quite different aspects of relativistic heavy ion collisions. In this short review of the {pi}{sup 0} results from the PHENIX experiment at RHIC our focus is on the {phi}-integrated nuclear modification factor, its energy and system size dependence, and the impact of these results on parton energy loss models. We also discuss the current status of high p{sub T} and thermal direct photon measurements both in p+p and Au+Au collisions. Recognizing the advantages of measuring not only the 'signal', but also all the 'references' needed for proper interpretation in the same experiments (with same or similar systematics) we argue that RHIC should regularly include d+A and even d+d collisions into its system size and energy scan.
New studies of allowed pion and muon decays
NASA Astrophysics Data System (ADS)
Počanić, D.; Palladino, A.; Alonzi, L. P.; Baranov, V. A.; Bertl, W.; Bychkov, M.; Bystritsky, Yu. M.; Frlež, E.; Kalinnikov, V. A.; Khomutov, N. V.; Korenchenko, A. S.; Korenchenko, S. M.; Korolija, M.; Kozlowski, T.; Kravchuk, N. P.; Kuchinsky, N. A.; Lehman, M. C.; Mekterović, D.; Munyangabe, E.; Mzhavia, D.; Robmann, P.; Rozhdestvensky, A. M.; Shkarovskiy, S. N.; Straumann, U.; Supek, I.; Truöl, P.; Tsamalaidze, Z.; van der Schaaf, A.; Velicheva, E. P.; Volnykh, V. P.
2013-10-01
Building on the rare pion and muon decay results of the PIBETA experiment, the PEN collaboration has undertaken a precise measurement of Bπe2≡Re/μπ, the π+ → e+ν(γ) decay branching ratio, at the Paul Scherrer Institute, to reduce the present 40× experimental precision lag behind theory to ˜6 - 7×. Because of large helicity suppression, Re/μπ is uniquely sensitive to contributions from non-(V - A) physics, making this decay a particularly suitable subject of study. Even at current precision, the experimental value of Bπe2 provides the most accurate test of lepton universality available. During runs in 2008-10, PEN has accumulated over 2 × 107 πe2 events; a comprehensive maximum-likelihood analysis is currently under way. The new data will also lead to improved precision of the earlier PIBETA results on radiative π and μ decays.
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.
NASA Astrophysics Data System (ADS)
Flores, Christopher E.
2016-12-01
The Beam Energy Scan (BES) at the Relativistic Heavy-Ion Collider was proposed to characterize the properties of the medium produced in heavy-ion interactions over a broad range of baryon chemical potential. The aptitude of the STAR detector for mid-rapidity measurements has previously been leveraged to measure identified particle yields and spectra to extract bulk properties for the BES energies for | y | ≤ 0.1. However, to extract information on expansion dynamics and full phase space particle production, it is necessary to study identified particle rapidity density distributions. We present the first rapidity density distributions of identified pions from Au+Au collisions at √{sNN} = 7.7 , 11.5, and 19.6 GeV from the BES program as measured by the STAR detector. We use these distributions to obtain the full phase space yields of the pions to provide additional information of the system's chemistry. Further, we report the width of the rapidity density distributions compared to the width expected from Landau hydrodynamics. Finally, we interpret the results as a function of collision energy and discuss them in the context of previous energy scans done at the AGS and SPS.
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
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
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 mass $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.
Exclusive Single Pion Electroproduction off the Proton: Results from CLAS
NASA Astrophysics Data System (ADS)
Park, Kijun
2016-11-01
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 mass 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 Δ (1232)3/2^+, N(1440)1/2^+, N(1520)3/2^-, and N(1535)1/2^- states. In addition, we recently published the differential cross sections and helicity amplitudes of the reaction γ ^*p→ nπ ^+ at higher W (1.6-2.0 GeV) which are the N(1675)5/2^-, N(1680)5/2^+, and N(1710)1/2^+ states. These excited states with isospin 1/2 and with masses near 1.7 GeV can be accessed in single nπ ^+ production as there are no isospin 3/2 states present in this mass range with the same spin-parity assignments. I will briefly discuss these states from CLAS results of the single charged pion electroproduction data.
Palamara, Ornella
2016-12-29
Results from the analysis of charged current pion-less (CC 0-pion) muon neutrino events in argon collected by the ArgoNeuT experiment on the NuMI beam at Fermilab are presented and compared with predictions from Monte Carlo simulations. A novel analysis method, based on the reconstruction of exclusive topologies, fully exploiting the Liquid argon Time Projection Chamber (LAr TPC) technique capabilities, is used to analyze the events, characterized by the presence at the vertex of a leading muon track eventually accompanied by one or more highly ionizing tracks, and study nuclear effects in neutrino interactions on argon nuclei. Multiple protons accompanying the leading muon are visible in the ArgoNeuT events, and measured with a proton reconstruction threshold of 21 MeV kinetic energy. As a result, measurements of (anti-)neutrino CC 0-pion inclusive and exclusive cross sections on argon nuclei are reported. Prospects for future, larger mass LAr TPC detectors are discussed.
Palamara, Ornella
2016-12-29
Results from the analysis of charged current pion-less (CC 0-pion) muon neutrino events in argon collected by the ArgoNeuT experiment on the NuMI beam at Fermilab are presented and compared with predictions from Monte Carlo simulations. A novel analysis method, based on the reconstruction of exclusive topologies, fully exploiting the Liquid argon Time Projection Chamber (LAr TPC) technique capabilities, is used to analyze the events, characterized by the presence at the vertex of a leading muon track eventually accompanied by one or more highly ionizing tracks, and study nuclear effects in neutrino interactions on argon nuclei. Multiple protons accompanying themore » leading muon are visible in the ArgoNeuT events, and measured with a proton reconstruction threshold of 21 MeV kinetic energy. As a result, measurements of (anti-)neutrino CC 0-pion inclusive and exclusive cross sections on argon nuclei are reported. Prospects for future, larger mass LAr TPC detectors are discussed.« less
McGivern, C. L.; Le, T.; Eberly, B.; ...
2016-09-06
Separate samples of charged-current pion production events representing two semi-inclusive channels νμ–CC(π+) and ν¯μ–CC(π0) have been obtained using neutrino and antineutrino exposures of the MINERvA detector. Distributions in kinematic variables based upon μ±-track reconstructions are analyzed and compared for the two samples. The differential cross sections for muon production angle, muon momentum, and four-momentum transfer Q2 are reported, and cross sections versus neutrino energy are obtained. Comparisons with predictions of current neutrino event generators are used to clarify the role of the Δ(1232) and higher-mass baryon resonances in CC pion production and to show the importance of pion final-state interactions.more » For the νμ–CC(π+) [ν¯μ–CC(π0)] sample, the absolute data rate is observed to lie below (above) the predictions of some of the event generators by amounts that are typically 1-to- 2σ. Furthermore, the generators are able to reproduce the shapes of the differential cross sections for all kinematic variables of either data set.« less
NASA Astrophysics Data System (ADS)
McGivern, C. L.; Le, T.; Eberly, B.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; Carneiro, M. F.; Christy, M. E.; da Motta, H.; Dytman, S. A.; Díaz, G. A.; Endress, E.; Felix, J.; Fields, L.; Fine, R.; Galindo, R.; Gallagher, H.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Hurtado, K.; Kiveni, M.; Kleykamp, J.; Kordosky, M.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; Martinez Caicedo, D. A.; McFarland, K. S.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Naples, D.; Nelson, J. K.; Norrick, A.; Nuruzzaman; Paolone, V.; Park, J.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ransome, R. D.; Ray, H.; Ren, L.; Rimal, D.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Schmitz, D. W.; Simon, C.; Solano Salinas, C. J.; Sánchez Falero, S.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Wospakrik, M.; Zhang, D.; Minerva Collaboration
2016-09-01
Separate samples of charged-current pion production events representing two semi-inclusive channels νμ-CC (π+) and ν¯ μ-CC (π0) have been obtained using neutrino and antineutrino exposures of the MINERvA detector. Distributions in kinematic variables based upon μ±-track reconstructions are analyzed and compared for the two samples. The differential cross sections for muon production angle, muon momentum, and four-momentum transfer Q2 are reported, and cross sections versus neutrino energy are obtained. Comparisons with predictions of current neutrino event generators are used to clarify the role of the Δ (1232 ) and higher-mass baryon resonances in CC pion production and to show the importance of pion final-state interactions. For the νμ-CC (π+) [ν¯ μ-CC (π0) ] sample, the absolute data rate is observed to lie below (above) the predictions of some of the event generators by amounts that are typically 1-to- 2 σ . However the generators are able to reproduce the shapes of the differential cross sections for all kinematic variables of either data set.
Pion-nucleon scattering: from chiral perturbation theory to Roy-Steiner equations
NASA Astrophysics Data System (ADS)
Kubis, Bastian; Hoferichter, Martin; de Elvira, Jacobo Ruiz; Meißner, Ulf-G.
2016-11-01
Ever since Weinberg's seminal predictions of the pion-nucleon scattering amplitudes at threshold, this process has been of central interest for the study of chiral dynamics involving nucleons. The scattering lengths or the pion-nucleon σ-term are fundamental quantities characterizing the explicit breaking of chiral symmetry by means of the light quark masses. On the other hand, pion-nucleon dynamics also strongly affects the long-range part of nucleon-nucleon potentials, and hence has a far-reaching impact on nuclear physics. We discuss the fruitful combination of dispersion-theoretical methods, in the form of Roy-Steiner equations, with chiral dynamics to determine pion-nucleon scattering amplitudes at low energies with high precision.
The Exclusive Drell-Yan Process and Deeply Virtual Pion Production
NASA Astrophysics Data System (ADS)
Kroll, Peter
In this talk it is reported on analyses of p → lπ+n and π-p → l+l-n within the handbag approach. It is argued that recent measurements of hard pion production performed by HERMES and CLAS clearly indicate the occurrence of strong contributions from transversely polarized photons. The γ T* to π transitions are described by the transversity GPDs accompanied by twist-3 pion wave functions. The experiments also require strong contributions from the pion pole which can be modeled as classical one-pion exchange. With these extensions the handbag approach leads to results on cross sections and spin asymmetries in fair agreement with experiment. This approach is also used for an estimate of the partial cross sections for the exclusive Drell-Yan process.
Studying ρ-N couplings with HADES in pion-induced reactions
NASA Astrophysics Data System (ADS)
Scozzi, Federico
2016-11-01
The High-Acceptance Di-Electron Spectrometer (HADES) operates at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt with pion, proton and heavyion beams provided by the synchrotron SIS18. In summer 2014, HADES took data using a pion beam on carbon and polyethylene targets. A large part of the data was taken at a pion beam momentum of 0.69 GeV/c in order to explore di-pion and di-electron production in the second resonance region and the sub-threshold coupling of the ρ to baryonic resonances. In this contribution lepton identification will be discussed as well the purity of reconstructed e+e-. Finally we will show the preliminary di-electon raw spectra.
Using a New Smearing Technique to Find Moments of the Quark Distribution Amplitude of the Pion
H. L. L. Roberts, David Richards, Christopher Thomas
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.
Two-pion exchange NN potential from Lorentz-invariant $\\chi$EFT
Higa, Renato; Robilotta, Manoel; da Rocha, Carlos A
2006-10-12
We outline the progress made in the past five years by the Sao Paulo group in the development of a two-pion exchange nucleon-nucleon potential within a Lorentz-invariant framework of (baryon) chiral perturbation theory.
Minkowski space pion model inspired by lattice QCD running quark mass
NASA Astrophysics Data System (ADS)
Mello, Clayton S.; de Melo, J. P. B. C.; Frederico, T.
2017-03-01
The pion structure in Minkowski space is described in terms of an analytic model of the Bethe-Salpeter amplitude combined with Euclidean Lattice QCD results. The model is physically motivated to take into account the running quark mass, which is fitted to Lattice QCD data. The pion pseudoscalar vertex is associated to the quark mass function, as dictated by dynamical chiral symmetry breaking requirements in the limit of vanishing current quark mass. The quark propagator is analyzed in terms of a spectral representation, and it shows a violation of the positivity constraints. The integral representation of the pion Bethe-Salpeter amplitude is also built. The pion space-like electromagnetic form factor is calculated with a quark electromagnetic current, which satisfies the Ward-Takahashi identity to ensure current conservation. The results for the form factor and weak decay constant are found to be consistent with the experimental data.
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.
Total pion-proton cross section from the new LHCf data on leading neutrons spectra
NASA Astrophysics Data System (ADS)
Ryutin, R. A.
2017-02-01
In the light of the latest data by the LHCf collaboration of the LHC on leading neutrons spectra it is possible to obtain total pion-proton cross sections in the TeV energy region. In this work the exact extraction procedure is shown. Final results for the pion-proton cross section are collected at several different values of the colliding energy and compared with some popular theoretical predictions. The errors of the results are estimated.
Criteria and techniques for three-dimensional treatment planning with pions
Berardo, P.; Zink, S.; Paciotti, M.; Bradbury, J.
1981-01-01
The ability to predict a pion dose distribution in a patient is a major objective of the clinical trials at LAMPF. Accurate predictions are essential for evaluation of pion therapy. But accuracy must be in the context of clinical utility. That is, reasonable approximations must be made in calculational methods so that treatment planning can proceed in a timely and efficient manner. A few of the techniques and current developments used to achieve that objective are presented here.
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.
NASA Astrophysics Data System (ADS)
Anikina, M. Kh.; Belyaev, A. V.; Golokhvastov, A. I.; Lukstins, J.; Troyan, A. Yu.; Troyan, Yu. A.
2009-03-01
By the method of interference correlations, it was directly proven for the first time that the pion-production volume in neutron-proton ( np) interactions at primary momenta in the range 3.8-5.2 GeV/ c is not constant. It was shown that the interference patterns for np and MgMg interactions are identical. It was established that the rate of expansion of the pion-production volume does not depend on the type of interacting particles (from np and e + e - to PbPb collisions) or on their primary energy (from 3.4 to 200 GeV). It was found that the determination of dimensions is possible only for individual approximately stationary volume elements in their rest frame. A change in the kinematical properties of the subensemble under analysis leads to changes both in the size of the respective element and in its shape.
Resonance Production and Decay in Proton and Pion Induced Collisions with HADES
NASA Astrophysics Data System (ADS)
Przygoda, Witold
Resonance production and decay in proton-proton collisions at kinetic beam energies of 1.25 and 3.5 GeV as well as π- - p reactions at four different pion beam momenta (0.656, 0.69, 0.748, and 0.8 GeV/c) are investigated. Exclusive channels with one pion in the final state (npπ+ and ppπ0) in the pp collisions were put to extended studies based on various observables in the framework of a one-pion exchange model and with solutions obtained within the framework of a partial wave analysis (PWA) of the Bonn-Gatchina group. In the case of the 3.5 GeV data, the study of the ppe+e- channel gave insight on the dielectron production from N* and Δ in the second and third resonance regions. We show that the measured dielectron invariant mass distribution cannot be explained by a point-like resonance-γ* coupling. Comparison with various transport models unravels the ambiguities of the descriptions and the important role of the intermediate ρ production. To tackle this problem a systematic investigation focused on the role of N(1520) production and decay in pion induced reactions on polyethylene and carbon targets. First results on exclusive channels with one pion (π-p), two pions (nπ+π-) and dileptons (ne+e-) in the final state are presented.
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.
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.
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 structure function from leading neutron electroproduction and SU(2) flavor asymmetry
McKenney, Joshua R.; Sato, Nobuo; Melnitchouk, Wally; ...
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
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.
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.
Eta photoproduction in a combined analysis of pion- and photon-induced reactions
Ronchen, D.; Doring, M.; Haberzettl, H.; ...
2015-06-25
Themore » $$\\eta N$$ final state is isospin-selective and thus provides access to the spectrum of excited nucleons without being affected by excited $$\\Delta$$ states. To this end, the world database on eta photoproduction off the proton up to a center-of-mass energy of $$E\\sim 2.3$$ GeV is analyzed, including data on differential cross sections, and single and double polarization observables. resonance spectrum and its properties are determined in a combined analysis of eta and pion photoproduction off the proton together with the reactions $$\\pi N\\to \\pi N$$, $$\\eta N$$, $$K\\Lambda$$ and $$K\\Sigma$$. For the analysis, the so-called J\\"ulich coupled-channel framework is used, incorporating unitarity, analyticity, and effective three-body channels. Parameters tied to photoproduction and hadronic interactions are varied simultaneously. Furthermore, the influence of recent MAMI $T$ and $F$ asymmetry data on the eta photoproduction amplitude is discussed in detail.« less
Eta photoproduction in a combined analysis of pion- and photon-induced reactions
Ronchen, D.; Doring, M.; Haberzettl, H.; Haidenbauer, J.; MeiBner, U. -G.; Nakayama, K.
2015-06-25
The $\\eta N$ final state is isospin-selective and thus provides access to the spectrum of excited nucleons without being affected by excited $\\Delta$ states. To this end, the world database on eta photoproduction off the proton up to a center-of-mass energy of $E\\sim 2.3$ GeV is analyzed, including data on differential cross sections, and single and double polarization observables. The resonance spectrum and its properties are determined in a combined analysis of eta and pion photoproduction off the proton together with the reactions $\\pi N\\to \\pi N$, $\\eta N$, $K\\Lambda$ and $K\\Sigma$. For the analysis, the so-called J\\"ulich coupled-channel framework is used, incorporating unitarity, analyticity, and effective three-body channels. Parameters tied to photoproduction and hadronic interactions are varied simultaneously. Furthermore, the influence of recent MAMI $T$ and $F$ asymmetry data on the eta photoproduction amplitude is discussed in detail.
Universal Correlations in Pion-less EFT with the Resonating Group Model: Three and Four Nucleons
NASA Astrophysics Data System (ADS)
Kirscher, J.; Grießhammer, H. W.; Shukla, D.; Hofmann, H. M.
2010-04-01
A systematic connection between QCD and nuclear few- and many-body properties in the form of the Effective Field Theory “without pions” is applied to A ≤ 6 nuclei to determine its range of applicability. We present results at next-to-leading order for the Tjon correlation and for a correlation between the singlet S-wave 3 He-neutron scattering length and the triton binding energy. In the A = 6 sector we performed leading order calculations for the binding energy and the charge and matter radii of the halo nucleus 6He. Also at leading order, the doublet S-wave 4-He-neutron phase shifts are compared with R-matrix data. These analysis provide evidence for a sufficiently fast convergence of the effective field theory, in particular, our results in A ≤ 4 predict 1 an expansion parameter of about ?, and they converge to data within the predicted uncertainty band at this order. A properly adjusted three-body contact force which we include together with the Coulomb interaction in all calculations is found to correctly renormalize the pion-less theory at leading- and next-to-leading order, i.e., the power counting does not require four-body forces at the respective order.
Chiral nucleon-Δ using the coherent-pion pair approximation
NASA Astrophysics Data System (ADS)
Sayed Aly, Tarek; McNeil, J. A.
1996-10-01
Despite significant strides in the numerical assault on QCD, this candidate theory of the strong interactions remains a computational challenge and models incorporating its important symmetries remain attractive alternatives for gaining insight into the nucleon problem. One such class of models which does not incorporate confinement but does respect chiral symmetry is the Nambu-Jona-Lasinio model and in particular its bosonized variant, the linear sigma model using quarks and mesonic degrees of freedom. About a decade ago several groups made significant progress in understanding fundamental nucleon properties using such models. In this work we re-visit one such effort undertaken by K. Goeke et al.(K. Goeke, M. Harvey, F. Grümmer, and J. N. Urbano, Phys. Rev. D37), 754 (1988). who computed nucleon and Δ properties using the so-called coherent pair approximation to treat the quantum nature of the pion field in a more realistic fashion. In rederiving their equations we have discovered some discrepancies in the treatment of the coherent pair Fock states. In this work we present alternative equations for the coherent-pair states. Numerical work to evaluate the new equations for the nucleon-Δ sector are underway.
Pion-Mass Dependence of the Nucleon Polarisabilities: A Reappraisal
NASA Astrophysics Data System (ADS)
Phillips, Daniel R.; Griesshammer, Harald W.; McGovern, Judith A.
2014-09-01
The static electric and magnetic scalar dipole polarisabilities and the four spin polarisabilities parametrise the nucleon's two-photon response. At next-to-next-to-leading order in Chiral Effective Field Theory (χEFT) with dynamical Δ (1232) s, they have recently been extracted from Compton scattering data; ongoing experiments at HI γS, MAMI and MAXlab test proton-neutron differences and chiral symmetry breaking. Comparing lattice QCD simulations at pion masses mπ > 220 MeV to data and χEFT predictions requires a reliable extrapolation to the physical point. Since χEFT provides a systematically improvable, model-independent parametrisation of the polarisabilities, it is well-suited for that task. The relative theoretical uncertainties increase with increasing mπ: the magnitudes of the polarisabilities decrease; the χEFT expansion parameter itself increases; and the Δ (1232) becomes more important, leading to a re-ordering of contributions. After a review of χEFT, this presentation offers a method to quantitatively assess error-bands for chiral lattice extrapolations which can also be applied to other cases. Published errors appear to be underestimated. The static electric and magnetic scalar dipole polarisabilities and the four spin polarisabilities parametrise the nucleon's two-photon response. At next-to-next-to-leading order in Chiral Effective Field Theory (χEFT) with dynamical Δ (1232) s, they have recently been extracted from Compton scattering data; ongoing experiments at HI γS, MAMI and MAXlab test proton-neutron differences and chiral symmetry breaking. Comparing lattice QCD simulations at pion masses mπ > 220 MeV to data and χEFT predictions requires a reliable extrapolation to the physical point. Since χEFT provides a systematically improvable, model-independent parametrisation of the polarisabilities, it is well-suited for that task. The relative theoretical uncertainties increase with increasing mπ: the magnitudes of the
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.
The one-pion-exchange potential in the three-body model of nucleon-nucleon scattering
NASA Astrophysics Data System (ADS)
Garcilazo, Humberto
1981-02-01
We derive the one-pion-exchange potential in the three-body model of nucleon-nucleon scattering in which the nucleon is treated as a bound state of a pion and a nucleon, and show that it has the same form as the usual Yukawa OPEP derived from field theory, except that its range is energy dependent and it becomes complex above the pion-production threshold.
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
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 → π^{0} 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 z^{2}, they are parametrized through virtuality distribution amplitudes (VDA) Φ(x,σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z^{2}. 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. Furthermore, we discuss how one can generate high-k tails from primordial soft distributions.
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.
Roy-Steiner equations for pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Ditsche, C.; Hoferichter, M.; Kubis, B.; Meißner, U.-G.
2012-06-01
Starting from hyperbolic dispersion relations, we derive a closed system of Roy-Steiner equations for pion-nucleon scattering that respects analyticity, unitarity, and crossing symmetry. We work out analytically all kernel functions and unitarity relations required for the lowest partial waves. In order to suppress the dependence on the high energy regime we also consider once- and twice-subtracted versions of the equations, where we identify the subtraction constants with subthreshold parameters. Assuming Mandelstam analyticity we determine the maximal range of validity of these equations. As a first step towards the solution of the full system we cast the equations for the π π to overline N N partial waves into the form of a Muskhelishvili-Omnès problem with finite matching point, which we solve numerically in the single-channel approximation. We investigate in detail the role of individual contributions to our solutions and discuss some consequences for the spectral functions of the nucleon electromagnetic form factors.
Resonance effects in pion and kaon decay constants
NASA Astrophysics Data System (ADS)
Guo, Zhi-Hui; Sanz-Cillero, Juan José
2014-05-01
In this article we study the impact of the lightest vector and scalar resonance multiplets in the pion and kaon decay constants up to next-to-leading order in the 1/NC expansion, i.e., up to the one-loop level. The Fπ and FK predictions obtained within the framework of resonance chiral theory are confronted with lattice simulation data. The vector loops (and the ρ-ππ coupling GV in particular) are found to play a crucial role in the determination of the chiral perturbation theory couplings L4 and L5 at next-to-leading order in 1/NC. Puzzling, values of GV≲40 MeV seem to be necessary to agree with current phenomenological results for L4 and L5. Conversely, a value of GV≳60 MeV compatible with standard ρ -ππ determinations turns these chiral couplings negative. However, in spite of the strong anti-correlation with L4, the SU(3) chiral coupling F0 remains stable all the time and stays within the range 78˜86 MeV when GV is varied in a wide range, from 40 up to 70 MeV. Finally, we would like to remark that the leading order expressions used in this article for the η-η' mixing, mass splitting of the vector multiplet masses and the quark mass dependence of the ρ(770) mass are found in reasonable agreement with the lattice data.
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.
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.
New Results in Rare Allowed Muon and Pion Decays
NASA Astrophysics Data System (ADS)
Počanić, D.; Munyangabe, E.; Bychkov, M.; Alonzi, L. P.; Baranov, V. A.; Bertl, W.; Bystritsky, Yu. M.; Frlež, E.; Kalinnikov, V. A.; Khomutov, N. V.; Korenchenko, A. S.; Korenchenko, S. M.; Korolija, M.; Kozlowski, T.; Kravchuk, N. P.; Kuchinsky, N. A.; Lehman, M. C.; Mekterović, D.; Mzhavia, D.; Palladino, A.; Robmann, P.; Rozhdestvensky, A. M.; Supek, I.; Truöl, P.; Tsamalaidze, Z.; van der Schaaf, A.; Vandevender, B.; Velicheva, E. P.; Volnykh, V. P.
2014-12-01
Simple dynamics, few available decay channels, and highly controlled radiative and loop corrections, make pion and muon decays a sensitive means of exploring details of the underlying symmetries. We review the current status of the rare decays: π+ → e+ν (πe2), π+ → e+νγ (πe2γ), π+ → π0e+ν (πe3), and μ + -> e+ν \\bar {ν }γ . For the latter we report new preliminary values for the branching ratio B(Eγ > 10 MeV, θeγ > 30°) = 4.365 (9)stat (42)syst × 10-3, and the decay parameter \\bar {η } = 0.006 (17) stat (18) syst, both in excellent agreement with standard model predictions. We review recent measurements, particularly by the PIBETA and PEN experiments, and near-term prospects for improvement. These and other similar precise low energy studies complement modern collider results materially.
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.
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.
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}
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
Pion Interferometry in Au+Au and Cu+Cu Collisions at sqrt sNN = 62.4 and 200 GeV
STAR Collaboration; Abelev, B.I.
2009-08-24
We present a systematic analysis of two-pion interferometry in Au+Au collisions at {radical}sNN = 62.4 GeV and Cu+Cu collisions at {radical}sNN = 62.4 and 200 GeV using the STAR detector at RHIC. The multiplicity and transverse momentum dependences of the extracted correlation lengths (radii) are studied. The scaling with charged particle multiplicity of the apparent system volume at final interaction is studied for the RHIC energy domain. The multiplicity scaling of the measured correlation radii is found to be independent of colliding system and collision energy.
Coherent amplification of classical pion fields during the cooling of droplets of quark plasma
Abada, A.; Birse, M.C.
1997-06-01
In the framework of the linear {sigma} model, we study the time evolution of a system of classical {sigma} and pion fields coupled to quarks. For this purpose we solve numerically the classical transport equation for relativistic quarks coupled to the nonlinear Klein-Gordon equations for the meson fields. We examine evolution starting from variety of initial conditions corresponding to spherical droplets of hot quark matter, which might mimic the behavior of a quark plasma produced in high-energy nucleus-nucleus collisions. For large droplets we find a strong amplification of the pion field that oscillates in time. This leads to a coherent production of pions with a particular isospin and so would have similar observable effects to a disoriented chiral condensate which various authors have suggested might be a signal of the chiral phase transition. The mechanism for amplification of the pion field found here does not rely on this phase transition and is better thought of as a {open_quotes}pion laser{close_quotes} which is driven by large oscillations of the {sigma} field. {copyright} {ital 1997} {ital The American Physical Society}
NASA Astrophysics Data System (ADS)
Rodrigues, Philip; Wilkinson, Callum; McFarland, Kevin
2016-08-01
The longstanding discrepancy between bubble chamber measurements of ν _μ -induced single pion production channels has led to large uncertainties in pion production cross section parameters for many years. We extend the reanalysis of pion production data in deuterium bubble chambers where this discrepancy is solved (Wilkinson et al., PRD 90, 112017 2014) to include the ν _{μ }n→ μ -pπ 0 and ν _{μ }n→ μ -nπ + channels, and use the resulting data to fit the parameters of the GENIE pion production model. We find a set of parameters that can describe the bubble chamber data better than the GENIE default parameters, and provide updated central values and reduced uncertainties for use in neutrino oscillation and cross section analyses which use the GENIE model. We find that GENIE's non-resonant background prediction has to be significantly reduced to fit the data, which may help to explain the recent discrepancies between simulation and data observed by the MINERν A coherent pion and NOν A oscillation analyses.
Pion and kaon structure functions at 12 GeV JLab and EIC
NASA Astrophysics Data System (ADS)
Horn, Tanja
2017-01-01
Pions and kaons are, along with protons and neutrons, the main building blocks of nuclear matter. They are connected to the Goldstone modes of dynamical chiral symmetry breaking, the mechanism thought to generate all hadron mass in the visible universe. The distribution of the fundamental constituents, the quarks and gluons, is expected to be different in pions, kaons, and nucleons. However, experimental data are sparse. As a result, there has been persistent doubt about the behavior of the pion's valence quark structure function at large Bjorken-x and virtually nothing is known about the contribution of gluons. A 12 GeV JLab experiment using tagged DIS may contribute to the resolution of the former. The Electron-Ion Collider with an acceptance optimized for forward physics could provide access to structure functions over a larger kinematic region. This would allow for measurements testing if the origin of mass is encoded in the differences of gluons in pions, kaons, and nucleons, and measurements testing assumptions used in the extraction of structure functions and the pion and kaon form factors. Electroweak measurements at an EIC would also potentially allow to disentangle the role of quark flavors at high x. In this talk we will discuss the prospects of such measurements. Supported in part by NSF grants PHY-1306227 and PHY-1306418.
Universal correlations in pion-less EFT with the resonating group method: Three and four nucleons
NASA Astrophysics Data System (ADS)
Kirscher, J.; Grießhammer, H. W.; Shukla, D.; Hofmann, H. M.
2010-05-01
The Effective Field Theory “without pions” at next-to-leading order is used to analyze universal bound-state and scattering properties of the 3- and 4-nucleon system. Results of a variety of phase shift equivalent nuclear potentials are presented for bound-state properties of 3H and 4He , and for the singlet S -wave 3He -neutron scattering length a 0(3He-n) . The calculations are performed with the Refined Resonating Group Method and include a full treatment of the Coulomb interaction and the leading-order 3-nucleon interaction. The results compare favorably with data and values from AV18(+UIX) model calculations. A new correlation between a 0(3He-n) and the 3H binding energy is found. Furthermore, we confirm at next-to-leading order the correlations, already found at leading order, between the 3H binding energy and the 3H charge radius, and the Tjon line. With the 3H binding energy as input, we get predictions of the effective field theory “without pions” at next-to-leading order for the root mean square charge radius of 3H of (1.6±0.2) fm, for the 4He binding energy of (28±2.5) MeV, and for Re{ a 0(3He-n)} of (7.5±0.6) fm. Including the Coulomb interaction, the splitting in binding energy between 3H and 3He is found to be (0.66±0.03) MeV. The discrepancy to data of (0.10±0.03) MeV is model independently attributed to higher-order charge independence breaking interactions. We also demonstrate that different results for the same observable stem from higher-order effects, and carefully assess that numerical uncertainties are negligible. Our results demonstrate the convergence and usefulness of the pion-less theory at next-to-leading order in the 4He channel. We conclude that no 4-nucleon interaction is needed to renormalize the theory at next-to-leading order in the 4-nucleon sector.
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.
NASA Astrophysics Data System (ADS)
Brack, Jeffrey Thomas
Differential cross sections for elastic pi^{+/-}p scattering have been measured at TRIUMF for 10 incident pion energies in three separate experiments at 66.8 <= T_{pi} <= 138.8 MeV, Tpi = 66.8 MeV (pi^+p only), and 30 <= T_{pi} <= 66.8 MeV, using three independent techniques. Typical statistical accuracies are 1-3% and normalization uncertainties are 1.2-3.0%. Extensive experimental checks were employed to minimize systematic errors. Incident pion beam rates were varied by a factor of 5, target thickness was varied by a factor of 10, different target compositions were used (CH_2 and CH_{1.1 }), and derangements of the detector geometry tested the reproducibility of the cross sections under widely varying conditions. Three separate Monte Carlo routines were used. All measurements used solid targets. Thin scintillators and time-of-flight (TOF) techniques were used to count and identify particles incident on the targets and to detect the scattered pions. Recoil protons were detected in coincidence with the scattered pions in two of the three experiments. At the upper range of incident pion energies (66.8 to 138 MeV), a two-arm coincidence technique was used in which proton detection was similar to pion detection (TOF). At the three lowest incident pion energies, an active target technique was used in which the recoil particles were detected by means of the light generated within the CH_ {1.1} scintillator-target. These are the only elastic pip coincidence measurements by any experimental group below 140 MeV incident pion energy. At 66.8 MeV, a third technique was used in which no recoil particles were detected. At incident pion energies of 100 MeV and above, all pi^{+/-}p results from these three measurements are in good agreement with previous measurements, as are the pi ^-p results at all energies. However, while the pi^{+/-}p results of these three experiments are consistent within experimental error at the overlapping energy of 66.8 MeV, they are 10-25% lower than
Effects of nonlocal one-pion-exchange potential in the deuteron
NASA Astrophysics Data System (ADS)
Forest, J. L.
2000-03-01
The off-shell aspects of the one-pion-exchange potential (OPEP) are discussed. Relativistic Hamiltonians containing relativistic kinetic energy, relativistic OPEP with various off-shell behaviors, and Argonne v18 short-range parametrization are used to study the deuteron wave functions. The OPEP off-shell behaviors depend on whether a pseudovector or pseudoscalar pion-nucleon coupling is used and are characterized by a parameter μ. We study potentials having μ=-1, 0, and +1 and we find that they are nearly unitarily equivalent. We also find that a nonrelativistic Hamiltonian containing local potentials and nonrelativistic kinetic energy provides a good approximation to a Hamiltonian containing a relativistic OPEP based on pseudovector pion-nucleon coupling and relativistic kinetic energy.
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.}
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.
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.
Quantitative estimate of pion fluctuation and its multiplicity dependence in nuclear collisions
NASA Astrophysics Data System (ADS)
Ghosh, Dipak; Deb, Argha; Dutta, Srimonti
2009-02-01
This paper presents the results of an investigation on the multiplicity dependence of the fluctuation pattern of pions for the entire accelerator energy range from 2.1 to 200 AGeV. The data set for produced pions is divided into four sets depending on the number of shower tracks ns. Analysis is carried out in two-dimensional η-phi space with the Hurst exponent to take care of the anisotropy of the phase space. The Hurst exponent is extracted by fitting one-dimensional factorial moment saturation curves to Ochs' saturation formula. The values of the effective fluctuation strength α eff are estimated and multiplicity dependence is studied w.r.t. α eff and the Hurst exponent H. It is highly interesting to observe that both fluctuation strength and degree of anisotropy (characterized by H) depend on pion multiplicity. The multiplicity dependence is more pronounced at lower projectile energy. The results of the study are discussed in detail.
Search for deeply bound pionic states in 208Pb via radiative atomic capture of negative pions
NASA Astrophysics Data System (ADS)
Raywood, K. J.; Lange, J. B.; Jones, G.; Pavan, M.; Sevior, M. E.; Hutcheon, D. A.; Olin, A.; Ottewell, D.; Yen, S.; Lee, S. J.; Sim, K. S.; Altman, A.; Friedman, E.; Trudel, A.
1997-05-01
A search for narrow, deeply bound pionic atom states via atomic radiative capture of negative pions in a target of 208Pb was carried out for pion kinetic energies of 20 and 25 MeV. Although no clear signature of any such gamma ray emission could be observed in the data, fits of the gamma ray spectra between the energies of 12 and 42 MeV involving a quadratic background together with a pair of peaks (1s, 2p) whose relative intensity was taken from theory yielded an overall strength for the peaks which are consistent (to a 67% confidence level) with radiative capture whose integrated cross section is 20.0 +/- 10.0 μb/sr at 90° for 20 MeV incident pions. A lower probability (40% confidence level) result was obtained when the fit was carried out without the peaks included, just the continuum background.
Pion induced reaction with carbon and polyethylene targets obtained by HADES-GSI in 2014
NASA Astrophysics Data System (ADS)
Rodríguez-Ramos, Pablo
2016-08-01
In the summer of 2014, HADES was conducting measurements with secondary pion-beam using different targets. The program was devoted to measure dilepton radiation from baryonic resonances. In particular we investigated a sub-threshold coupling of ρ to baryonic resonances in the second resonance region (N(1520), N(1535)). Most of the beam time was dedicated to measurement of e+e- production from Polyethylene target at pion beam momentum of 0.69 GeV/c. In addition we run part of the time with pure carbon target. This allow us to study exclusive π- + p → ne-e+ channel. The normalization of spectra has been done using elastic scattering of pion on proton and carbon. The simulations of dilepton yields for π0, Δ and N(1520) Dalitz decay using PLUTO was carried out.
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.
Nonperturbative relativistic approach to pion form factors: Predictions for future JLab experiments
Krutov, A. F.; Troitsky, V. E.; Tsirova, N. A.
2009-11-15
Some predictions concerning possible results of the future experiments at the Thomas Jefferson National Accelerator Facility (JLab) on the pion form factor F{sub {pi}}(Q{sup 2}) are made. The calculations exploit the method proposed previously by the authors and based on the instant-form Poincare invariant approach to pions, considered as quark-antiquark systems. This model has predicted with surprising accuracy the values of F{sub {pi}}(Q{sup 2}), which were measured later in JLab experiments. The results are almost independent from the form of wave function. The pion mean square radius
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.
Precise π^-/π^+ Ratios from Exclusive Forward Pion Electroproduction on the Deuteron \\unboldmath
NASA Astrophysics Data System (ADS)
Mkrtchyan, Hamlet
1998-10-01
for the Charged Pion Form Factor (F_π) Collaboration at the Thomas Jefferson National Accelerator Facility (TJNAF). During the F_π experiment E93-021, forward charged pion electroproduction data were acquired on a Deuterium target over a -t range of 0.02-0.50 GeV^2. The goal of this experiment is to extract F_π(Q^2) from the pion pole-dominated forward longitudinal response, so a thorough understanding of the physics backgrounds is necessary. The cross-section ratio π^-/π^+ is sensitive to the reaction mechanism, and the longitudinal and transverse separated ratios are even more revealing. Preliminary ratios will be presented and compared with the recent Regge model calculations of Vanderhaeghen et al.
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.
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 most effectively in the combined studies of both the single and double pion photoproduction data are identified for future studies.
Double and single pion photoproduction within a dynamical coupled-channels model
Hiroyuki Kamano; Julia-Diaz, Bruno; Lee, T. -S. H.; ...
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
Anatomy of relativistic pion loop corrections to the electromagnetic nucleon coupling
Ji, Chueng-Ryong; Melnitchouk, Wally; Thomas, Anthony W.
2013-10-01
We present a relativistic formulation of pion loop corrections to the coupling of photons with nucleons on the light-front. Vertex and wave function renormalization constants are computed to lowest order in the pion field, including their nonanalytic behavior in the chiral limit, and studied numerically as a function of the ultraviolet cutoff. Particular care is taken to explicitly verify gauge invariance and Ward-Takahashi identity constraints to all orders in the m_\\pi expansion. The results are used to compute the chiral corrections to matrix elements of local operators, related to moments of deep-inelastic structure functions. Finally, comparisons of results for pseudovector and pseudoscalar coupling allows the resolution of a long-standing puzzle in the computation of pion cloud corrections to structure function moments.
PionX sites mark the X chromosome for dosage compensation.
Villa, Raffaella; Schauer, Tamas; Smialowski, Pawel; Straub, Tobias; Becker, Peter B
2016-09-08
The rules defining which small fraction of related DNA sequences can be selectively bound by a transcription factor are poorly understood. One of the most challenging tasks in DNA recognition is posed by dosage compensation systems that require the distinction between sex chromosomes and autosomes. In Drosophila melanogaster, the male-specific lethal dosage compensation complex (MSL-DCC) doubles the level of transcription from the single male X chromosome, but the nature of this selectivity is not known. Previous efforts to identify X-chromosome-specific target sequences were unsuccessful as the identified MSL recognition elements lacked discriminative power. Therefore, additional determinants such as co-factors, chromatin features, RNA and chromosome conformation have been proposed to refine targeting further. Here, using an in vitro genome-wide DNA binding assay, we show that recognition of the X chromosome is an intrinsic feature of the MSL-DCC. MSL2, the male-specific organizer of the complex, uses two distinct DNA interaction surfaces-the CXC and proline/basic-residue-rich domains-to identify complex DNA elements on the X chromosome. Specificity is provided by the CXC domain, which binds a novel motif defined by DNA sequence and shape. This motif characterizes a subclass of MSL2-binding sites, which we name PionX (pioneering sites on the X) as they appeared early during the recent evolution of an X chromosome in D. miranda and are the first chromosomal sites to be bound during de novo MSL-DCC assembly. Our data provide the first, to our knowledge, documented molecular mechanism through which the dosage compensation machinery distinguishes the X chromosome from an autosome. They highlight fundamental principles in the recognition of complex DNA elements by protein that will have a strong impact on many aspects of chromosome biology.
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
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.
Nucleon-to-Pion Transition Distribution Amplitudes: A Challenge for P¯ANDA
NASA Astrophysics Data System (ADS)
Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2014-06-01
Baryon-to-meson transition distribution amplitudes (TDAs) appear as building blocks in the collinear factorized description of amplitudes for a class of hard exclusive reactions, prominent examples being hard exclusive pion electroproduction off a nucleon in the backward region and baryon-antibaryon annihilation into a pion and a lepton pair or a charmonium. Baryon-to-meson TDAs extend both the concepts of generalized parton distributions and baryon distribution amplitudes encoding valuable complementary information on the hadronic structure. We review the basic properties of baryon-to-meson TDAs and discuss the perspectives for the experimental access with the P¯ANDA detector.
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.
Helicity Dependence of Single-Pion Photoproduction in the Δ-REGION
NASA Astrophysics Data System (ADS)
Preobrajenski, I.
2001-02-01
The helicity dependence of the γp → nπ+ and γp → pπ0 channels have been measured for incident photon energies from pion threshold to 800 MeV. We used the large acceptance detector DAPHNE with additional forward components, a newly developed frozen-spin target, and the tagged circularly polarized photon beam facility of the MAMI accelerator in Mainz. Preliminary results for the polarized total and differential cross sections of both single-pion channels are compared with partial wave analyses of HDT and SAID.
On the determination of the pion effective mass in nuclei from pionic atoms
NASA Astrophysics Data System (ADS)
Friedman, E.; Gal, A.
1998-07-01
The binding energies of the deeply bound 1s and 2p states in pionic atoms of 207Pb, recently established experimentally in the 208Pb(d,3He) reaction, have been used by several groups to derive the pion effective mass in nuclear matter. We show that these binding energies are fully consistent with `normal' pionic atoms and that the real part of the pion-nucleus potential at the center of 207Pb is 28+/-3 MeV and not 20 MeV as suggested previously.
Pion and eta production in elementary and heavy-ion collisions at SIS energies
NASA Astrophysics Data System (ADS)
Gumberidze, M.
2016-11-01
A main emphasis of the HADES program is on the dielectron signal from the early phase of heavy-ion collisions. We discuss the data with respect to the emission of charged hadrons, specifically the production of π+ and π- mesons, which are related to neutral pions representing a dominant contribution to the dielectron yield. In addition, inclusive pion production obtained with the photon-conversion method is disscused. Preliminary results from Au+Au at 1.23 AGeV are presented.
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.
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.
Progress of the Hypernuclear Decay Pion Spectroscopy Program at MAMI-C
NASA Astrophysics Data System (ADS)
Nagao, Sho; Achenbach, Patrick; Arai, Naoki; Ayerbe Gayoso, Carlos; Böhm, Ralph; Borodina, Olga; Bosnar, Damir; Bozsurt, Vakkas; Devenjak, Luka; Distler, Michael O.; Esser, Anselm; Fujita, Manami; Friščič, Ivica; Fujii, Yuu; Gogami, Toshiyuki; Gómez Rodríguez, Mar; Hirose, Satoshi; Kanda, Hiroki; Kaneta, Masashi; Kim, Eunhee; Kusaka, Junichiro; Margaryan, Amur; Merkel, Harald; Müller, Ulrich; Nakamura, Satoshi N.; Pochodzalla, Josef; Rappold, Christophe; Reinhold, Joerg; Saito, Takehiko R.; Sanchez Lorente, Alicia; Sánchez Majos, Salvador; Sören Schlimme, Björn; Schoth, Matthias; Schulz, Florian; Sfienti, Concettina; Širca, Simon; Takahashi, Yuta; Tang, Liguang; Thiel, Michaela; Tsukada, Kyo; Uchiyama, Daisuke
We have performed high resolution spectroscopies for binding energies of light Λ hypernuclei with newly established experimental technique "hypernuclear decay pion spectroscopy using electro-photo production". We identified successfully a first decay pion peak from Λ 4H in 2012 experiment. A spectrometer Kaos for K+ tagger was upgraded and suppressed large positron background using a lead wall in the experiment. We performed the next generation experiment with higher statistics in 2014. In this experiment, we achieved twice higher beam intensity and doubled the length of the beam-time with a lower background rate thanks to improvements for the lead wall and a trigger system.
Present Status of Single Pion Production in Neutrino-Nucleus Reactions
NASA Astrophysics Data System (ADS)
Alvarez-Ruso, L.; Hernández, E.; Nieves, J.; Vacas, M. J. Vicente
Some of the recent progress in the physics of pion production induced by neutrinos on nucleons and nuclei is reviewed from a theoretical perspective. The importance of Watson's theorem to reconcile ANL and BNL data with the off-diagonal Goldberger-Treiman relation for the Δ(1232) is discussed. The disagreement between MiniBooNE data and theoretical calculations is presented in the light of the new MINERvA data. The coherent pion production data on 12C obtained by MINERvA are also compared to different microscopic and PCAC models.
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.
On the effect of pion condensates on the spectrum of neutron stars
Kolevatov, S. S.; Andrianov, A. A.; Espriu, D.
2016-01-22
There is no precise theory describing the structure of neutron stars. However, inside such objects the baryon density is very high and a pion condensation may occur. These condensates, if they exist, might give a significant effect on a spectrum of neutron stars. We investigate this influence with a help of simplified model to give qualitative picture of the effect.
Parameterization of spectral distributions for pion and kaon production in proton-proton collisions.
Schneider, J P; Norbury, J W; Cucinotta, F A
1995-04-01
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.
Global extraction of the parton-to-pion fragmentation functions at NLO accuracy in QCD
NASA Astrophysics Data System (ADS)
Hernández-Pinto, R. J.; Epele, M.; de Florian, D.; Sassot, R.; Stratmann, M.
2016-10-01
In this review, we discuss the results on the parton-to-pion fragmentation functions obtained in a combined NLO fit to data of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and lepton-nucleon deep-inelastic scattering. A more complete discussion can be found in Ref. [1].
Cumulative production of pions by heavy baryonic resonances in proton-nucleus collisions
NASA Astrophysics Data System (ADS)
Motornenko, A.; Gorenstein, M. I.
2017-02-01
Pion production in proton-nucleus (p+A) collisions outside the kinematical boundary of proton-nucleon (p+N) reactions and the so-called cumulative effect are studied. Restrictions from energy-momentum conservation of the energy of pions emitted in the backward direction in the target rest frame are analyzed. It is assumed that the cumulative pions are produced in p+A reactions by heavy baryonic resonances. The baryonic resonances are first created in p+N reactions. Due to successive collisions with nuclear nucleons, the masses of these resonances may then increase and, simultaneously, their longitudinal velocities decrease. We also use the ultra relativistic quantum molecular dynamics model to reveal the key role of successive collisions of baryonic resonances with nuclear nucleons for cumulative pion production in p+A reactions. Further experimental studies of cumulative hadron production in p+A reactions at high collision energies are needed to search for heavy hadron-like objects and investigate their properties.
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.
Inelastic pion scattering to 2 1+ states of pre12C and 28Si
NASA Astrophysics Data System (ADS)
Amos, K.; Berge, L.
1983-08-01
Large basis, microscopic models of nuclear structure have been used to specify the “collective” form factors for inelastic scattering to the 2 1+ states in 12C and 28Si. They have been used in a Distorted Wave Impulse Approximation, with π-nucleon t-matrices fixed by elastic scattering analyses, to fit inelastic pion scattering data.
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.
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.
Reaction Mechanism for Forward Pion Electroproduction from π^-/π^+ ratios on the Deuteron
NASA Astrophysics Data System (ADS)
Assamagan, Ketevi
1998-04-01
for the Charged Pion Form Factor (F_π) Collaboration at the Thomas Jefferson National Accelerator Facility (E93-021). During the F_π experiment, forward pion electroproduction data were acquired on the deuteron for Q^2 = 0.6-1.6 at W = 1.95 for both π^+ and π^-. Measurements were made in Hall C with two beam energies at fixed momentum transfer in order to separate the longitudinal and transverse response functions. The ratio of π^-/π^+ production on the deuteron yields an important test of the reaction mechanism, and most systematic errors cancel in this ratio. Previous results using unseparated cross sections were consistent with pion pole dominance at low -t and s-channel quark knockout at higher -t. Ratios for the separated response functions should make more definitive conclusions possible. The F_π experiment will extract F_π(Q^2) from the pion-pole dominated longitudinal response. Reaction mechanism studies will help us to understand any longitudinal non-pole physics backgrounds which may become important at larger -t. The state of the analysis will be summarized as well as our improving knowledge of the reaction mechanism.
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.
Norbury, J W; Townsend, L W
1986-01-01
Using the Weizsacher-Williams method of virtual quanta, total cross section estimates for the photoproduction of neutral subthreshold pions in carbon-carbon collisions at incident energies below 300 MeV/nucleon are made. Comparisons with recent experimental data indicate that the photoproduction mechanism makes an insignificant contribution to these measured cross sections.
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.
NASA Astrophysics Data System (ADS)
Duncan, Fraser Andrew
There is considerable interest in the pn to pi^-pp reaction which can proceed by a nonresonant channel from the isospin 0 pn initial state (an NDelta intermediate state cannot be formed). This thesis describes a measurement of analyzing powers and triple differential cross sections for a subset of this reaction, pn to pi^-pp(^1S_0) by isolating the quasifree process in pd to pi^-ppp_{s}. The experimental arrangement selects the relative S-wave component of the outgoing "diproton". The experiment was done on TRIUMF beam line 1B using a LD_2 target; the pion was detected in a magnetic spectrometer, the two outgoing protons in a scintillator bar array. The spectator proton was undetected. Data were taken in August 1989 at 353, 403 and 440 MeV beam energies. Of these the 403 and 440 MeV data are analysed in this thesis and analyzing powers and triple differential cross sections as a function of pion scattering angle extracted at centre of mass kinetic energies, T_{CM}, of 55 and 70 MeV (corresponding to the 403 and 440 MeV beam energies respectively). Partial wave analysis of the data shows that, while the isospin 0 channel dominates the reaction, contributing approximately 75% of the cross section at the energies studied here, there are significant contributions from the s and d-wave pion, isospin 1 channels. Of particular importance is the contribution from the s-wave pion, isospin 1, channel whose interference with the isospin 0 channels produces the characteristic shapes of the cross sections and analyzing powers observed in the data. The d-wave pion, isospin 1 channels, are also required to fully explain the observed analyzing power distributions, and are essential for the T_{CM} = 70MeV data. Comparisons of the pion production data measured in this experiment with pion absorption measurements on ^3He, where the absorption process is pi^-pp(^1S_0) to pn, show a shift in the shape of the differential cross section which can be interpreted as due to differences in
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.
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.
NASA Astrophysics Data System (ADS)
Assylbekov, Shamil; Wilson, Robert; Wachala, Tomasz; T2K Collaboration
2015-04-01
This work describes the first neutrino cross-section measurement of charged-current (CC) single charged pion (1 π+) interaction channel on water as a target. There is some disagreement between measurements on carbon for this process, which effects the precision of neutrino oscillation results. P0D detector of the T2K experiment has been taking neutrino interaction data since 2009 in configurations with and without a water target. Using a statistical water-in/water-out event rate subtraction, a measurement of νμ-induced CC1π+ cross-section on water is reported to be σ = 1 . 10 .10-39 -32.38%+35.27% cm2 , integrated over the entire T2K energy range. The measurement is based on a sample of 2703 events selected from beam runs of 2 . 64 ×1020 protons-on-target with the P0D water-in configuration, and 2187 events selected from 3 . 71 ×1020 protons-on-target with the water-out configuration. The corresponding Monte Carlo (MC) simulation predicted numbers of background events to be 1387.2 and 1046.0 for the water-in and water-out configurations, respectively. Data favors a smaller cross-section when compared with the model, but within uncertainty is consistent with σ = 1 . 26 .10-39cm2 predicted by MC.
Medium Modification of Hadronic Interactions from Low Energy Experiments
NASA Astrophysics Data System (ADS)
Friedman, E.
Medium-modification of hadronic interactions is defined as the differences between hadron-hadron interaction in the nuclear medium and the corresponding interaction in free space. Deeply penetrating hadrons provide such information and we discuss here pionic atoms and scattering by nuclei of 21.5 MeV pions. Brief mention is made also of the interaction of 500-700 MeV/c K+ with nuclei.
Pion-Kaon correlations in central Au+Au collisions at square root [sNN] = 130 GeV.
Adams, J; Adler, C; Aggarwal, M M; Ahammed, Z; Amonett, J; Anderson, B D; Anderson, M; Arkhipkin, D; Averichev, G S; Badyal, S K; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellwied, R; Berger, J; Bezverkhny, B I; Bhardwaj, S; Bhaskar, P; Bhati, A K; 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; Calderón de la Barca Sánchez, M; Carroll, J; Castillo, J; Castro, M; Cebra, D; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, Y; Chernenko, S P; Cherney, M; Chikanian, A; Choi, B; Christie, W; Coffin, J P; Cormier, T M; Cramer, J G; Crawford, H J; Das, D; Das, S; Derevschikov, A A; Didenko, L; Dietel, T; Dong, X; Draper, J E; Du, F; Dubey, A K; Dunin, V B; Dunlop, J C; Dutta Majumdar, M R; Eckardt, V; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Fachini, P; Faine, V; Faivre, J; Fatemi, R; Filimonov, K; Filip, P; Finch, E; Fisyak, Y; Flierl, D; Foley, K J; Fu, J; Gagliardi, C A; Ganti, M S; Gutierrez, T D; Gagunashvili, N; Gans, J; Gaudichet, L; Germain, M; Geurts, F; Ghazikhanian, V; Ghosh, P; Gonzalez, J E; Grachov, O; Grigoriev, V; Gronstal, S; Grosnick, D; Guedon, M; Guertin, S M; Gupta, A; Gushin, E; 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; Huang, S L; 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; Koetke, D D; Kollegger, T; Konstantinov, A S; Kopytine, M; Kotchenda, L; Kovalenko, A D; Kramer, M; Kravtsov, P; Krueger, K; Kuhn, C; Kulikov, A I; Kumar, A; 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; Lednický, R; Leontiev, V M; LeVine, M J; Li, C; Li, Q; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Z; Liu, Q J; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Ludlam, T; Lynn, D; Ma, J; Ma, Y G; Magestro, D; Mahajan, S; Mangotra, L K; Mahapatra, D P; Majka, R; Manweiler, R; Margetis, S; Markert, C; Martin, L; Marx, J; Matis, H S; Matulenko, Yu A; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Messer, M; Miller, M L; Milosevich, Z; Minaev, N G; Mironov, C; Mishra, D; Mitchell, J; Mohanty, B; Molnar, L; Moore, C F; Mora-Corral, M J; Morozov, V; de Moura, M M; Munhoz, M G; Nandi, B K; Nayak, S K; Nayak, T K; Nelson, J M; Nevski, P; Nikitin, V A; Nogach, L V; Norman, B; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Paic, G; Pandey, S U; Pal, S K; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Perevoztchikov, V; Peryt, W; Petrov, V A; Phatak, S C; Picha, R; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potekhin, M; Potrebenikova, E; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Rai, G; Rakness, G; Raniwala, R; Raniwala, S; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Ruan, L J; Rykov, V; Sahoo, R; Sakrejda, I; Salur, S; Sandweiss, J; Savin, I; Schambach, J; Scharenberg, R P; Schmitz, N; Schroeder, L S; Schweda, K; Seger, J; Seliverstov, D; Seyboth, P; Shahaliev, E; Shao, M; Sharma, M; Shestermanov, K E; Shimanskii, S S; Singaraju, R N; Simon, F; Skoro, G; Smirnov, N; Snellings, R; Sood, G; Sorensen, P; Sowinski, J; Spinka, H M; Srivastava, B; Stanislaus, S; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Struck, C; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; Szanto de Toledo, A; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Thein, D; Thomas, J H; Tikhomirov, V; Tokarev, M; Tonjes, M B; Trainor, T A; Trentalange, S; Tribble, R E; Trivedi, M D; Trofimov, V; Tsai, O; Ullrich, T; Underwood, D G; Van Buren, G; VanderMolen, A M; Vasiliev, A N; Vasiliev, M; Vigdor, S E; Viyogi, Y P; Voloshin, S A; Waggoner, W; Wang, F; Wang, G; Wang, X L; Wang, Z M; Ward, H; Watson, J W; Wells, R; Westfall, G D; Whitten, C; Wieman, H; Willson, R; Wissink, S W; Witt, R; Wood, J; Wu, J; Xu, N; Xu, Z; Xu, Z Z; Yakutin, A E; Yamamoto, E; Yang, J; Yepes, P; Yurevich, V I; Zanevski, Y V; Zborovský, I; Zhang, H; Zhang, H Y; Zhang, W M; Zhang, Z P; Zołnierczuk, P A; Zoulkarneev, R; Zoulkarneeva, J; Zubarev, A N
2003-12-31
Pion-kaon correlation functions are constructed from central Au+Au STAR data taken at sqrt[s(NN)]=130 GeV by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The results suggest that pions and kaons are not emitted at the same average space-time point. Space-momentum correlations, i.e., transverse flow, lead to a space-time emission asymmetry of pions and kaons that is consistent with the data. This result provides new independent evidence that the system created at RHIC undergoes a collective transverse expansion.
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.
New Aspects of Experimental Study of the Pion-Nucleon Interaction in the Resonance Region
Sumachev, V.V.
2005-06-01
New experimental data that were obtained by the PNPI-ITEP Collaboration have resolved some discrete ambiguities in the partial-wave analysis (PWA). These results were used in the new FA02 PWA performed at George Washington University. At the same time, the FA02 PWA has revealed considerable fewer N* and {delta} resonances than those listed in the RPP tables. This circumstance aggravated the known problem of so-called missing resonances. The program for further measurements of the spin rotation parameters in elastic {pi}N scattering that are required to eliminate the remaining discrete PWA ambiguities is discussed.
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.
NASA Astrophysics Data System (ADS)
Feng, Zhao-Qing
2017-02-01
Within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model, pion dynamics in heavy-ion collisions near threshold energies and the emission of preequilibrium particles (nucleons and light complex fragments) have been investigated. A density, momentum and isospin-dependent pion-nucleon potential based on the Δ-hole model is implemented in the transport approach, which slightly leads to the increase of the π-/π+ ratio, but reduces the total pion yields. It is found that a bump structure of the π-/π+ ratio in the kinetic energy spectra appears at the pion energy close to the Δ (1232) resonance region. The yield ratios of neutrons to protons from the squeeze-out particles perpendicular to the reaction plane are sensitive to the stiffness of nuclear symmetry energy, in particular at the high-momentum (kinetic energy) tails.
πN TDAs from charmonium production in association with a forward pion at P̅ANDA
NASA Astrophysics Data System (ADS)
Ma, B.; Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2014-06-01
Charmonium production in association with a forward or backward pion in nucleon-antinucleon annihilation is one of the most promising reaction to access nucleon-to-pion transition distribution amplitudes (TDAs) at P̅ANDA. We briefly review the description of this reaction in terms of πN TDAs within the collinear factorization approach and present the first results of dedicated feasibility studies for the P̅ANDA experimental setup.
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.
FROM PIONS TO PROTON DECAY: Tales of the Unexpected
NASA Astrophysics Data System (ADS)
Perkins, D. H.
2005-12-01
This account recalls early observations of elementary particles from cosmic ray experiments, using the nuclear emulsion technique. Discoveries in this field in the 1940s and 50s led to the development of high energy particle accelerators and associated detectors, resulting eventually in the observation of the quark and lepton constituents of matter and of the fundamental interactions between them, as described in the Standard Model. The concept of unification of the fundamental interactions led to the prediction of proton decay, and although this has not been observed, the unwanted background due to atmospheric neutrino interactions led to the discovery of neutrino oscillations and neutrino mass, and the first indications of new physics beyond that of the Standard Model. In all this research, unexpected developments have often played an important role.
NASA Astrophysics Data System (ADS)
Avakyan, V. V.; Garyaka, A. P.; Zazyan, G. Z.
Fluctuations of the observable parameters of nuclear electromagnetic cascades induced by 0.5-5.0 TeV cosmic ray protons, neutrons and pions are studied by the ionization calorimeter of the PION setup. The distributions of the inelasticity coefficient Kpi0 are measured for pFe, nFe and (pi)Fe interactions and compared with the predictions of various models. The probability of the inelastic charge exchange reaction in the (pi)Fe interactions is defined.
Pion tensor force and nuclear binding energy in the relativistic Hartree-Fock formalism
NASA Astrophysics Data System (ADS)
Marcos, S.; López-Quelle, M.; Niembro, R.; Savushkin, L. N.
2014-03-01
The binding energies of several isotopic families are studied within the relativistic Hartree-Fock approximation with the pseudovector coupling for the πN vertex, to find out a suitable strength for the effective pion tensor force (EPTF). An approximation for determining separately the contributions of the central and tensor forces generated by pion is considered. The results for heavy nuclei indicate that a realistic strength for the EPTF is smaller than a half of that appearing in the OPEP. This conclusion also applies to the results for the single-particle energies. Besides, it has been found that there is a genuine relativistic contribution of the EPTF in nuclear matter which is small but significant.
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.
Measurement of the charged pion mass using a low-density target of light atoms
NASA Astrophysics Data System (ADS)
Trassinelli, M.; Anagnostopoulos, D. F.; Borchert, G.; Dax, A.; Egger, J.-P.; Gotta, D.; Hennebach, M.; Indelicato, P.; Liu, Y.-W.; Manil, B.; Nelms, N.; Simons, L. M.; Wells, A.
2016-11-01
We present a new evaluation of the negatively charged pion mass based on the simultaneous spectroscopy of pionic nitrogen and muonic oxygen transitions using a gaseous target composed by a N2/O2 mixture at 1.4 bar. We present the experimental set-up and the methods for deriving the pion mass value from the spatial separation from the 5g - 4f πN transition line and the 5g - 4f μO transition line used as reference. Moreover, we discuss the importance to use dilute targets in order to minimize the influence of additional spectral lines from the presence of remaining electrons during the radiative emission. The occurrence of possible satellite lines is investigated via hypothesis testing methods using the Bayes factor.
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.
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.
Pion mass dependence of the K l3 semileptonic scalar form factor within finite volume
NASA Astrophysics Data System (ADS)
Ghorbani, K.; Yazdanpanah, M. M.; Mirjalili, A.
2011-06-01
We calculate the scalar semileptonic kaon decay in finite volume at the momentum transfer t m =( m K - m π )2, using chiral perturbation theory. At first we obtain the hadronic matrix element to be calculated in finite volume. We then evaluate the finite size effects for two volumes with L=1.83 fm and L=2.73 fm and find that the difference between the finite volume corrections of the two volumes are larger than the difference as quoted in Boyle et al. (Phys. Rev. Lett. 100:141601, 2008). It appears then that the pion masses used for the scalar form factor in ChPT are large which result in large finite volume corrections. If appropriate values for pion mass are used, we believe that the finite size effects estimated in this paper can be useful for lattice data to extrapolate at large lattice size.
Pion interferometry at RHIC: porobing a thermalized quark-gluon plasma?
Soff, S; Bass, S A; Dumitru, A
2001-04-30
We calculate the Gaussian radius parameters of the pion-emitting source in high-energy heavy-ion collisions, assuming a first-order phase transition from a thermalized quark-gluon plasma (QGP) to a gas of hadrons. Such a model leads to a very long-lived dissipative hadronic rescattering phase which dominates the properties of the two-pion correlation functions. The radii are found to depend only weakly on the thermalization time tau(i), the critical temperature Tc (and thus the latent heat), and the specific entropy of the QGP. The model calculations suggest a rapid increase of R(out)/R(side) as a function of KT if a thermalized QGP were formed.
PION INTERFEREMETRY FROM P+P TO AU+AU IN STAR.
CHAJECKI, Z.
2005-08-15
The geometric substructure of the particle-emitting source has been characterized via two-particle interferometry by the STAR collaboration for all energies and colliding systems at RHIC. We present systematic studies of charged pion interferometry. The collective nature of the source is revealed through the m{sub T} dependence of HBT radii for all particle types. Preliminary results suggest a scaling in the pion HBT radii with overall system size, as central Au+Au collisions are compared to peripheral collisions as well as with Cu+Cu and even with d+Au and p+p collisions, naively suggesting comparable flow strength in all systems. To probe this issue in greater detail, multidimensional correlation functions are studied using a spherical decomposition method. This allows clear identification of source anisotropy and, for the light systems, the presence of significant long-range non-femtoscopic correlations.
Improved input for multi-reaction hadronic analyses from elastic pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Revier, Joseph; Roenchen, Deborah; Doering, Michael; Workman`, Ronald
2017-01-01
In the search for missing baryonic resonances, many analyses include data from a variety of pion and photon induced reactions. For elastic πN scattering, however, usually the partial waves of the SAID or other groups are fitted, instead of data. We provide the partial-wave covariance matrices needed to perform correlated χ2 fits, in which the obtained χ2 equals the actual χ2 up to non-linear and normalization corrections. For any analysis relying on partial waves extracted from elastic pion scattering, this is a prerequisite to assess the significance of resonance signals and to assign any uncertainty on results. The compilation of the necessary data to improve hadronic analyses is presented in detail. Supported by the U.S. Department of Energy Grant DE-SC0014133, contract DE-AC05-06OR23177, and by the National Science Foundation (CAREER grant No. 1452055, PIF Grant No. 1415459).
Covariant and self-consistent vertex corrections for pions and isobars in nuclear matter
Korpa, C. L.; Lutz, M. F. M.; Riek, F.
2009-08-15
We evaluate the pion and isobar propagators in cold nuclear matter self-consistently applying a covariant form of the isobar-hole model. Migdal's vertex correction effects are considered systematically in the absence of phenomenological soft form factors. Saturated nuclear matter is modeled by scalar and vector mean fields for the nucleon. It is shown that the short-range dressing of the {pi}N{delta} vertex has a significant effect on the pion and isobar properties. Using realistic parameters sets we predict a downward shift of about 50 MeV for the {delta} resonance at nuclear saturation density. The pionic soft modes are much less pronounced than in previous studies.
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.
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.
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
The HARP Collaboration has presented measurements of the double-differential {pi}{sup {+-}} production cross section in the range of momentum 100 MeV/c{<=}p{<=}800 MeV/c and angle 0.35 rad{<=}{theta}{<=}2.15 rad with proton beams hitting thin nuclear targets. In many applications the extrapolation to long targets is necessary. In this article the analysis of data taken with long (one interaction length) solid cylindrical targets made of carbon, tantalum, and lead is presented. The data were taken with the large-acceptance HARP detector in the T9 beam line of the CERN proton synchrotron. The secondary pions were produced by beams of protons with momenta of 5, 8, and 12GeV/c. The tracking and identification of the produced particles were performed using a small-radius cylindrical time projection chamber placed inside a solenoidal magnet. Incident protons were identified by an elaborate system of beam detectors. Results are obtained for the double-differential yields per target nucleon d{sup 2}{sigma}/dpd{theta}. The measurements are compared with predictions of the MARS and GEANT4 Monte Carlo simulations.
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.
2010-10-15
Measurements of the double-differential proton production cross-section d{sup 2{sigma}}/dpd{Omega} in the range of momentum 0.5 GeV/c{<=}p<8.0 GeV/c and angle 0.05 rad{<=}{theta}<0.25 rad in collisions of charged pions and protons on beryllium, carbon, aluminium, copper, tin, tantalum, and lead are presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN Proton Synchrotron. Incident particles were identified by an elaborate system of beam detectors and impinged on a target of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using the forward spectrometer of the HARP experiment. Results are obtained for the double-differential cross-sections mainly at four incident beam momenta (3,5,8, and 12 GeV/c). Measurements are compared with predictions of the geant4 and mars Monte Carlo generators.
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.
Pion single- and double-charge-exchange reactions at low energies
Baer, H.W.
1987-01-01
The general features of pion charge-exchange reactions at energies of 20 to 80 MeV leading to nuclear isobaric-analog states (IAS) and double-isobaric-analog states (DIAS) are reviewed. The recent progress achieved in understanding the role of short-range N-N correlations in the double-charge-exchange reactions is presented. 36 refs., 21 figs., 2 tabs.
Emergence of a nonuniform pion condensate in the (1 + 1)-dimensional Nambu-Jona-Lasinio model
Gubina, N. V. Zhukovsky, V. Ch.; Klimenko, K. G.; Kurbanov, S. G.
2013-11-15
The (1 + 1)-dimensional Nambu-Jona-Lasinio model describing the system of two-flavor quarks is studied in the limit of a large number of colors in the presence of a baryon chemical potential Micro-Sign and an isospin chemical potential Micro-Sign {sub I}. The possible formation of a nonuniform pion condensate in dense quark matter is considered for the cases of both the massive and the massless model.
LArIAT: Worlds First Pion-Argon Cross-Section
Hamilton, Pip
2016-11-02
The LArIAT experiment has performed the world's first measurement of the total charged-current pion cross-section on an argon target, using the repurposed ArgoNeuT detector in the Fermilab test beam. Presented here are the results of that measurement, along with an overview of the LArIAT experiment and details of the LArIAT collaboration's plans for future measurements.
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%.
Twist-3 Distribution Amplitudes of Pion in the Light-Front Quark Model
NASA Astrophysics Data System (ADS)
Choi, Ho-Meoyng; Ji, Chueng-Ryong
2017-03-01
We analyzed two twist-3 distribution amplitudes of pion, i.e. pseudoscalar φ ^P_{3;π }(x) and pseudotensor φ ^σ _{3;π }(x), within the LFQM. Our LFQM descriptions both for twist-3 φ ^P_{3;π } and φ ^σ _{3;π } obtained from the Gaussian radial wave function not only satisfy the fundamental constraint required from the isospin symmetry, but also reproduce exactly the asymptotic forms anticipated from QCD's conformal limit.
Measurement of the G double-polarisation observable in pion photoproduction
J. McAndrew, D. Watts, E. Pasyuk
2012-04-01
The g9a experiment using the CLAS detector in Hall B of Jefferson Lab will measure double-polarization observables using a polarized energy-tagged photon beam in conjunction with the frozen spin target, FROST. This contribution describes the extraction of the G double polarization observable in the single pion photoproduction using a linearly polarized photon beam in the energy range 730-2300 MeV and the longitudinally polarized frozen spin target, FROST.
Pion-Nucleus potentials in the energy range of 0-80 MeV
NASA Astrophysics Data System (ADS)
Meirav, O.; Friedman, E.; Altman, A.; Hannah, M.; Johnson, R. R.; Gill, D. R.
1987-12-01
Data for the elastic scattering of 30-80 MeV positive and negative pions by a wide range of nuclei is analysed with an Ericson-Ericson MSU type optical potential. By use of consistent sets of data for π+ and π- and of experimental results for total reaction cross sections we obtain for the first time optical potentials that describe well all the data without the need of introducing non-standard charge-dependent effects.
Implications of the pion-decay gamma emission and neutron observations with CORONAS-F/SONG
NASA Astrophysics Data System (ADS)
Kurt, V.; Yushkov, B.; Kudela, K.
2013-05-01
We analyzed the high-energy gamma and neutron emissions observed by the SONG instrument onboard the CORONAS-F satellite during August 25, 2001, October 28, 2003, November 4, 2003, and January 20, 2005 solar flares. These flares produced neutrons and/or protons recorded near Earth. The SONG response was consistent with detection of the pion-decay gamma emission and neutrons in these events. We compared time profiles of various electromagnetic emissions and showed that the maximum of the pion-decay-emission coincided in time best of all with the soft X-ray derivative, dISXR/dt, maximum. We evaluated the energy of accelerated ions and compared it with the energy deposited by accelerated electrons. The ion energy becomes comparable or even higher than the electron energy from a certain step of flare development. So the time profile of dISXR/dt is a superposition of energy deposited by both fractions of accelerated particles. This result allowed us to use a time profile of dISXR/dt as a real proxy of time behavior of the energy release at least during major flare analysis. In particular the time interval when the dISXR/dt value exceeds 0.9 of its maximum can be used as a unified reference point for the calculations of time delay between the high-energy proton acceleration and GLE onset. Analysis of the total set of pion-decay emission observations shows that such temporal closeness of pion-decay emission maximum and the soft X-ray derivative maximum is typical but not obligatory.
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.
Total Cross Section Parameterizations for Pion Production in Nucleon-Nucleon Collisions
NASA Technical Reports Server (NTRS)
Norbury, John W.
2008-01-01
Total cross section parameterizations for neutral and charged pion production in nucleon-nuelcon collisions are compared to an extensive set of experimental data over the projectile momentum range from threshold to 300 GeV. Both proton-proton and proton-neutron reactions are considered. Good agreement between parameterizations and experiment is found, and therefore the parameterizations will be useful for applications, such as transport codes.
NASA Astrophysics Data System (ADS)
Lukyanov, V. K.; Zemlyanaya, E. V.; Lukyanov, K. V.; Abdul-Magead, I. A. M.
2016-11-01
The folding-model optical potential is generalized in such a way as to apply it to calculating the cross sections for inelastic scattering of π ±-mesons on 28Si, 40Ca, 58Ni, and 208Pb nuclei at the energies of 162, 180, 226, and 291 MeV leading to the excitation of the 2+ and 3- collective states. In doing this, use is made of known nucleon-density distributions in nuclei and the pion-nucleon scattering amplitude whose parameters were obtained previously by fitting the elastic scattering cross sections for the same nuclei. Thus, the values of quadrupole ( β 2) and octupole ( β 3) deformations of nuclei appear here as the only adjustable parameters. The scattering cross section is calculated by solving the relativistic wave equation, whereby effects of relativization and distortion in the entrance and exit scattering channels are taken exactly into account. The cross sections calculated in this way for inelastic scattering are in good agreement with respective experimental data. The importance of the inclusion of in-medium effects in choosing parameters of the pion-nucleon amplitude is emphasized.
Exploring hadronization mechanisms via neutral pion electroproduction off D, C, Fe and Pb
NASA Astrophysics Data System (ADS)
Mineeva, Taisiya; Kyungseon Joo Team; William K. Brooks Team
2014-09-01
Propagation of partons inside a nuclear medium and formation of hadrons is a topic of interest to multiple communities. New data available from Drell-Yan measurements at Fermilab, heavy ion collisions in RHIC and LHC, SIDIS measurements from HERMES at DESY and Jefferson Lab all bring different types of information on short distance processes. The most direct information comes from SIDIS measurements, which have a unique ability to investigate time-dependence of hadronization by embedding it in the nuclei of varying size. This talk presents results on a series of SIDIS measurements of neutral pion multiplicities on carbon, iron, and lead nuclei normalized to deuterium. The experiment was performed at Thomas Jefferson National Accelerator facility utilizing a 5 GeV electron beam and CEBAF Large Acceptance Spectrometer in Hall B. The high statistics accumulated during the experiment allowed for a three-dimensional analysis of neutral pion attenuation studied as a function of leptonic and hadronic variables. Combined with existing data on charged pions, these data provide new insights into hadronization mechanisms.
NASA Astrophysics Data System (ADS)
Yao, De-Liang; Siemens, D.; Bernard, V.; Epelbaum, E.; Gasparyan, A. M.; Gegelia, J.; Krebs, H.; Meißner, Ulf-G.
2016-05-01
We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the S- and P -partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the D and F waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in order to determine the strangeness content of the nucleon, we calculate the octet baryon masses in the presence of decuplet resonances up to next-to-next-to-leading order in SU(3) baryon chiral perturbation theory. The octet baryon sigma terms are predicted as a byproduct of this calculation.
Consistent model for πN transition distribution amplitudes and backward pion electroproduction
NASA Astrophysics Data System (ADS)
Lansberg, J. P.; Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2012-03-01
The extension of the concept of generalized parton distributions leads to the introduction of baryon to meson transition distribution amplitudes (TDAs), nondiagonal matrix elements of the nonlocal three quark operator between a nucleon and a meson state. We present a general framework for modeling nucleon to pion (πN) TDAs. Our main tool is the spectral representation for πN TDAs in terms of quadruple distributions. We propose a factorized Ansatz for quadruple distributions with input from the soft-pion theorem for πN TDAs. The spectral representation is complemented with a D-term like contribution from the nucleon exchange in the cross channel. We then study backward pion electroproduction in the QCD collinear factorization approach in which the nonperturbative part of the amplitude involves πN TDAs. Within our two component model for πN TDAs, we update previous leading-twist estimates of the unpolarized cross section. Finally, we compute the transverse target single spin asymmetry as a function of skewness. We find it to be sizable in the valence region and sensitive to the phenomenological input of our πN TDA model.
Analyzing power in pion-proton bremsstrahlung, and the. Delta. sup ++ (1232) magnetic moment
Bosshard, A.; Amsler, C.; Doebeli, M.; Doser, M.; Schaad, M.; Riedlberger, J.; Truoel, P. ); Bistirlich, J.A.; Crowe, K.M.; Ljungfelt, S.; Meyer, C.A. ); van den Brandt, B.; Konter, J.A.; Mango, S.; Renker, D. ); Loude, J.F.; Perroud, J.P. ); Haddock, R.P. ); Sober, D.I. )
1991-10-01
We report on a first measurement of the polarized-target asymmetry of the pion-proton bremsstrahlung cross section ({pi}{sup +}{ital p}{r arrow}{pi}{sup {minus}}{ital p}{gamma}). As in previous cross section measurements the pion energy (298 MeV) and the detector geometry for this experiment was chosen to optimize the sensitivity to the radiation from the magnetic dipole moment of the {Delta}{sup ++}(1232) resonance {mu}{sub {Delta}}. Comparison to a recent isobar model for pion-nucleon bremsstrahlung yields {mu}{sub {Delta}}=(1.62{plus minus}0.18){mu}{sub {ital p}}, where {mu}{sub {ital p}} is the proton magnetic moment. Since the asymmetry depends less than the cross section on the choice of the other input parameters for the model, their uncertainties affect this analysis by less than the experimental error. However the theory fails to represent both the cross section and the asymmetry data at the highest photon energies. Hence further improvements in the calculations are needed before the model dependence of the magnetic moment analysis can be fully assessed. The present result agrees with bag-model corrections to the SU(6) prediction {mu}{sub {Delta}}=2{mu}{sub {ital p}}. As a by-product, the analyzing power for elastic {pi}{sup +}{ital p} scattering at 415 MeV/{ital c} was also measured. This second result is in good agreement with phase shift calculations.
Pion and kaon correlations in high energy heavy-ion collisions
Wolf, K.L.; Wolf, K.L.
1996-12-31
Data analysis is in progress for recent experiments performed by the NA44 collaboration with the first running of 160 A GeV {sup 208}Pb-induced reactions at the CERN SPS. Identified singles spectra were taken for pions, kaons, protons, deuterons, antiprotons and antideuterons. Two-pion interferometry measurements were made for semi-central-triggered {sup 208}Pb + Pb collisions. An upgraded multi-particle spectrometer allows high statistics data sets of identified particles to be collected near mid-rapidity. A second series of experiments will be performed in the fall of 1995 with more emphasis on identical kaon interferometry and on the measurement of rare particle spectra and correlations. Modest instrumentation upgrades by TAMU are designed to increase the trigger function for better impact parameter selection and improved collection efficiency of valid events. An effort to achieve the highest degree of projectile-target stopping is outlined and it is argued that an excitation function on the SPS is needed to better understand reaction mechanisms. Analysis of experimental results is in the final stages at LBL in the EOS collaboration for two-pion interferometry in the 1.2 A GeV Au+Au reaction, taken with full event characterization. 35 refs., 15 figs., 5 tabs.
Pion correlations and calorimeter design for high energy heavy ion collisions. Progress report
Wolf, K.L.
1997-04-01
Data analysis is in progress for recent experiments performed by the NA44 collaboration with the first running of 160 A GeV {sup 208}Pb-induced reactions at the CERN SPS. Identified singles spectra were taken for pions, kaons, protons, deuterons, antiprotons and antideuterons. Two-pion interferometry measurements were made for semi-central-triggered {sup 208}Pb + Pb collisions. An updated multi-particle spectrometer allows high statistics data sets of identified particles to be collected near mid-rapidity. A second series of experiments will be performed in the fall of 1995 with more emphasis on identical kaon interferometry and on the measurement of rare particle spectra and correlations. Modest instrumentation upgrades by TAMU are designed to increase the trigger function for better impact parameter selection and improved collection efficiency of valid events. An effort to achieve the highest degree of projectile-target stopping is outlined and it is argued that an excitation function on the SPS is needed to better understand reaction mechanisms. Analysis of experimental results is in the final stages at LBL in the EOS collaboration for two-pion interferometry in the 1.2 A GeV Au + Au reaction, taken with full event characterization.
Immune reaction induced by X-rays and pions and its stimulation by schizophyllan (SPG).
Inomata, T; Goodman, G B; Fryer, C J; Chaplin, D J; Palcic, B; Lam, G K; Nishioka, A; Ogawa, Y
1996-07-01
Female C57BL/6 mice aged 6-8 weeks with transplanted Lewis lung cancer cells were used to investigate the anti-tumour effects and immune reactions in tumour tissue induced by X-ray and pion irradiation and their modification by schizophyllan (SPG). The effect of SPG on the rate of lung metastasis and the survival time of the mice was also studied using the same tumour system. These studies showed that in this tumour system the "practical' relative biological effectiveness (RBE) of pions was 1.33 in the dose ranges used (3 Gy x 4 = P3; 6 Gy x 4 = P6). SPG increased the suppression of tumour growth associated with moderate doses of radiation: X-rays (4 Gy x 4 = X4) or P3. SPG also decreased the number of lung metastases and prolonged the life span of the mice, these effects being independent of radiation. The addition of SPG to radiation increased both the macrophage infiltration and T-lymphocyte infiltration in the local tumour and the lung nodules. There did not appear to be any major differential effect of SPG on the pion-treated mice compared with those treated with X-rays.
A ROTATING INCONEL BAND TARGET FOR PION PRODUCTION AT A NEUTRINO FACTORY, USING STUDY II PARAMETERS.
KING,B.J.; SIMOS,N.P.; WEGGEL,R.V.; MOKHOV,N.V.
2001-05-04
A conceptual design is presented for a high power pion production target, based on a rotating band of inconel alloy 718, that is intended to provide a back-up targetry option for the Neutrino Factory Study II. The target band has a 2.5 m radius and has an I-beam cross section that is 6 cm high and with a 0.6 cm thick webbing. The pion capture scenario and proton beam parameters are as specified for the Study II base-line targetry option, i.e. capture into a 20 Tesla tapered solenoidal channel with proton beam fills at 2.5 Hz containing 6 short bunches, each spaced by 20 milliseconds, of 1.67 x 10{sup 13} 24 GeV protons. The target is continuously rotated at 1 m/s to Carey heat away from the production region and through a water cooling tank. The mechanical layout and cooling setup are described and results are presented from realistic MARS Monte Carlo computer simulations of the pion yield and energy deposition in the target and from ANSYS finite element calculations for the corresponding shock heating stresses.
A ROTATING METAL BAND TARGET FOR PION PRODUCTION AT MUON COLLIDERS.
KING,B.J.; SIMOS,N.; WEGGEL,R.V.; MOKHOV,N.V.
2002-01-18
A conceptual design is presented for a high power pion production target for muon colliders that is based on a rotating metal band. Three candidate materials are considered for the target band: inconel alloy 718, titanium alloy 6Al-4V grade 5 and nickel. A pulsed proton beam tangentially intercepts a chord of the target band that is inside a 20 Tesla tapered solenoidal magnetic pion capture channel similar to designs previously considered for muon colliders and neutrino factories. The target band has a radius of 2.5 meters and is continuously rotated at approximately 1 m/s to carry heat away from the production region and through a water cooling tank. The mechanical layout and cooling setup of the target are described, including the procedure for the routine replacement of the target band. A rectangular band cross section is assumed, optionally with I-beam struts to enhance stiffness and minimize mechanical vibrations. Results are presented from realistic MARS Monte Carlo computer simulations of the pion yield and energy deposition in the target and from ANSYS finite element calculations for the corresponding shock heating stresses. The target scenario is found to perform satisfactorily and with conservative safety margins for multi-MW pulsed proton beams.
Lectures on Chiral Symmetries and Soft Pion Processes
DOE R&D Accomplishments Database
Nambu, Y.
1966-08-01
At the Istanbul Summer School in 1962 I gave lectures on "Chiral Symmetries in Weak and Strong Interactions." It is only recently, however, that the basic ideas that were started several years ago have begun to bear fruit. We will cover in the present lectures more or less the same general field, but certainly there will be a lot more results to be discussed now than four years ago.
NASA Astrophysics Data System (ADS)
Csörgő, T.; Kittel, W.; Metzger, W. J.; Novák, T.
2008-05-01
A parametrization of the Bose-Einstein correlation function of pairs of identical pions produced in hadronic e+e- annihilation is proposed within the framework of a model (the τ-model) in which space-time and momentum space are very strongly correlated. Using information from the Bose-Einstein correlations as well as from single-pion spectra, it is then possible to reconstruct the space-time evolution of pion production.
Regge phenomenology of pion photoproduction off the nucleon at forward angles
Yu, Byung Geel; Choi, Tae Keun; Kim, W.
2011-02-15
We present a Regge model for pion photoproduction which is basically free of parameters within the framework of the s-channel helicity amplitude. For completeness we take into account axial mesons a{sub 1}(1260), b{sub 1}(1235) and tensor meson a{sub 2}(1320) in addition to the primary {pi}+{rho} exchanges for charged pion photoproduction, while the axial meson h{sub 1}(1170) exchange is added to the model of {omega}+{rho}{sup 0}+b{sub 1} exchanges for the neutral case. The present model deals for the first time with the a{sub 2} and h{sub 1} Regge poles in the s-channel helicity amplitude. For model independence, we use coupling constants of all exchanged mesons determined from empirical decay widths or from the SU(3) relations together with consistency check with existing estimates that are widely accepted in other reaction processes. Based on these coupling constants the simultaneous description of four photoproduction channels is given. Within the Regge regime, s>>4M{sup 2} and -t<2 GeV{sup 2}, cross sections and spin polarization asymmetries at various photon energies are analyzed and results are obtained in better agreement with experimental data without referring to any fitting procedure. The model confirms dominance of the nucleon Born term in the sharp rise of the charged pion cross section at very forward angles, while dominance of the {omega} exchange with the nonsense wrong signature zero leads to the deep dip in the neutral pion cross section. In contrast to existing models, however, our model for the charged pion case shows quite a different production mechanism due to the crucial role of the tensor meson a{sub 2} exchange in the cross section and spin polarization asymmetries. Also the axial meson b{sub 1} exchange is found to give a sizable contribution to the photon polarization asymmetry. In the neutral case, the role of the b{sub 1} is not significant, but the isoscalar h{sub 1} exchange gives an important contribution to the dip
Hyperon-Nucleon Interactions and the Composition of Dense Matter from Quantum Chromodynamics
Konstantinos Orginos, Silas Beane, Emmanuel Chang, Saul Cohen, Huey-Wen Lin, Tom Luu, Assumpta Parreno, Martin Savage, Andre Walker-Loud, William Detmold
2012-10-01
The low-energy n{Sigma}{sup -} interactions determine, in part, the role of the strange quark in dense matter, such as that found in astrophysical environments. The scattering phase-shifts for this system are determined from a numerical evaluation of the QCD path integral using the technique of Lattice QCD. Our results, performed at a pion mass of m{sub {pi}} ~ 389 MeV in two large lattice volumes, and at one lattice spacing, are extrapolated to the physical pion mass using effective field theory. The calculated interactions indicate that the strange quark plays an important role in dense matter.
Polarization and dilepton anisotropy in pion-nucleon collisions
NASA Astrophysics Data System (ADS)
Speranza, Enrico; Zétényi, Miklós; Friman, Bengt
2017-01-01
Hadronic polarization and the related anisotropy of the dilepton angular distribution are studied for the reaction πN → Ne+e-. We employ consistent effective interactions for baryon resonances up to spin-5/2, where non-physical degrees of freedom are eliminated, to compute the anisotropy coefficients for isolated intermediate baryon resonances. It is shown that the spin and parity of the intermediate baryon resonance is reflected in the angular dependence of the anisotropy coefficient. We then compute the anisotropy coefficient including the N (1520) and N (1440) resonances, which are essential at the collision energy of the recent data obtained by the HADES Collaboration on this reaction. We conclude that the anisotropy coefficient provides useful constraints for unraveling the resonance contributions to this process.
NASA Astrophysics Data System (ADS)
Lv, M.; Ma, Y. G.; Chen, J. H.; Fang, D. Q.; Zhang, G. Q.
2017-02-01
Nuclear modification factors Rcp of protons and pions are investigated by simulating Au+Au collisions from 0.8 A to 1.8 A GeV in a framework of an isospin-dependent quantum molecular dynamics (IQMD) model. The Rcp of protons rise with an increase in the transverse particle momentum pT at different beam energies owing to radial flow and the multiple-collision effect. The rate of increase of Rcp is suppressed at higher beam energies. While the Rcp of pions display weaker pT dependence. By changing the in-medium nucleon-nucleon cross section, the Rcp of protons change a lot, while the Rcp of pions do not. In addition, by deactivating the N Δ →N N and π N →Δ channels, the Rcp of protons change slightly in their increasing rates compared with the "original" case (with these two channels). However, the Rcp of pions is shifted down for the "no N Δ →N N " case and has an inverse trend for the "no π N →Δ " case. Based on these observations, we argue that the observable Rcp is a suitable tool to better distinguish in-medium effects of protons and pions.
The pion nucleon scattering lengths from pionic hydrogen and deuterium
NASA Astrophysics Data System (ADS)
Schröder, H.-Ch.; Badertscher, A.; Goudsmit, P. F. A.; Janousch, M.; Leisi, H. J.; Matsinos, E.; Sigg, D.; Zhao, Z. G.; Chatellard, D.; Egger, J.-P.; Gabathuler, K.; Hauser, P.; Simons, L. M.; Rusi El Hassani, A. J.
2001-07-01
This is the final publication of the ETH Zurich Neuchâtel PSI collaboration on the pionic hydrogen and deuterium precision X-ray experiments. We describe the recent hydrogen 3 p 1 s measurement, report on the determination of the Doppler effect correction to the transition line width, analyze the deuterium shift measurement and discuss implications of the combined hydrogen and deuterium results. From the pionic hydrogen 3 p 1 s transition experiments we obtain the strong-interaction energy level shift \\varepsilon_{1s} = -7.108±0.013 (stat.)±0.034 (syst.) eV and the total decay width Γ_{1s} = 0.868±0.040 (stat.)±0.038 (syst.) eV of the 1s state. Taking into account the electromagnetic corrections we find the hadronic π N s-wave scattering amplitude a_{π-prightarrowπ-p} = 0.0883±0.0008 m_{π}^{-1} for elastic scattering and a_{π-prightarrowπ0n} = -0.128±0.006 m_{π} ^{-1} for single charge exchange, respectively. We then combine the pionic hydrogen results with the 1 s level shift measurement on pionic deuterium and test isospin symmetry of the strong interaction: our data are still compatible with isospin symmetry. The isoscalar and isovector π N scattering lengths (within the framework of isospin symmetry) are found to be b_0 = -0.0001^{+0.0009}_{-0.0021} m_{π}^{-1} and b1 = -0.0885^{+0.0010}_{-0.0021} m_{π} ^{-1}, respectively. Using the GMO sum rule, we obtain from b_1 a new value of the π N coupling constant (g_{π N} = 13.21_{-0.05}^{+0.11}) from which follows the Goldberger Treiman discrepancy Δ_{{GT}} =0.027_{-0.008}^{+0.012}. The new values of b_0 and g_{π N} imply an increase of the nucleon sigma term by at least 9 MeV.
Process of e⁺e⁻ → ππX (3823) in the soft pion
Voloshin, M. B.
2015-06-23
The production of the resonance X(3823), identified as the charmonium ³D₂ state, in the process e⁺e⁻ → ππX(3823) has been recently reported by BESIII. Here it is pointed out that this process is fully described, up to one overall coupling constant, in the soft pion limit. An interpretation of the available and possible future data within the discussed theoretical framework may reveal new features of the charmoniumlike states. In particular, the observed relative yield for this process at different energies strongly suggests a very significant enhancement of the amplitude at the charmoniumlike peak near 4.36 GeV.
Heavy ion precompound phenomena: A glance at hard gamma and subthreshold pion production
Blann, M.; Remington, B.A.
1987-08-01
We test a relaxation model based on two body nucleon-nucleon scattering processes to interpret phenomena observed in heavy ion reactions. We use the Boltzmann master equation to accomplish this. By assuming that the projectile nucleons share the total excitation with equal a-priori probability of all configurations, we are able to reproduce several sets of neutron spectra from /sup 20/Ne and /sup 12/C induced reactions on /sup 165/Ho. With no additional free parameters our model successfully reproduces subthreshold pion production cross sections, high energy ..gamma..-ray spectra, and angular distributions of high energy ..gamma..-rays. 40 refs., 12 figs., 2 tabs.
Top-Higgs and top-pion phenomenology in the top triangle moose model
NASA Astrophysics Data System (ADS)
Chivukula, R. Sekhar; Simmons, Elizabeth H.; Coleppa, Baradhwaj; Logan, Heather E.; Martin, Adam
2011-03-01
We discuss the deconstructed version of a topcolor-assisted technicolor model wherein the mechanism of top quark mass generation is separated from the rest of electroweak symmetry breaking. The minimal deconstructed version of this scenario is a “triangle moose” model, where the top quark gets its mass from coupling to a top-Higgs field, while the gauge boson masses are generated from a Higgsless sector. The spectrum of the model includes scalar (top-Higgs) and pseudoscalar (top-pion) states. In this paper, we study the properties of these particles, discuss their production mechanisms and decay modes, and suggest how best to search for them at the LHC.
Precise photoproduction of the charged top-pions at the LHC with forward detector acceptances
NASA Astrophysics Data System (ADS)
Sun, Hao; Yue, Chong-Xing
2014-04-01
We study the photoproduction of the charged top-pion predicted by the top triangle moose (TTM) model (a deconstructed version of the topcolor-assisted technicolor TC2 model) via the processes at the 14 TeV Large Hadron Collider (LHC) including next-to-leading order (NLO) QCD corrections. Our results show that the production cross sections and distributions are sensitive to the free parameters and . A typical QCD correction value is and this does not depend much on as well as the forward detector acceptances.
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.
Top-Higgs and top-pion phenomenology in the top triangle moose model
Chivukula, R. Sekhar; Simmons, Elizabeth H.; Coleppa, Baradhwaj; Logan, Heather E.; Martin, Adam
2011-03-01
We discuss the deconstructed version of a topcolor-assisted technicolor model wherein the mechanism of top quark mass generation is separated from the rest of electroweak symmetry breaking. The minimal deconstructed version of this scenario is a ''triangle moose'' model, where the top quark gets its mass from coupling to a top-Higgs field, while the gauge boson masses are generated from a Higgsless sector. The spectrum of the model includes scalar (top-Higgs) and pseudoscalar (top-pion) states. In this paper, we study the properties of these particles, discuss their production mechanisms and decay modes, and suggest how best to search for them at the LHC.