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Artykuły w czasopismach na temat „Pion masses”

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Data publikacji: 6 września 2023

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1

LEBIEDOWICZ, PIOTR, та ANTONI SZCZUREK. "EXCLUSIVE PRODUCTION OF π+π- PAIRS IN PROTON-PROTON AND PROTON-ANTIPROTON COLLISIONS". International Journal of Modern Physics A 26, № 03n04 (2011): 748–50. http://dx.doi.org/10.1142/s0217751x11052724.

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We report on a detailed investigation of four-body pp → ppπ+π- and [Formula: see text] reactions which constitute an irreducible background to three-body processes pp → ppM, where M is a broad resonance in the π+π- channel, e.g. M = σ, ρ0, f0(980), f2(1275), f0(1500). We include double-diffractive contribution (both pomeron and reggeon exchanges) as well as the pion-pion rescattering contributions. The first process dominates at higher energies and small pion-pion invariant masses while the second becomes important at lower energies and higher pion-pion invariant masses. We compare our results with the experimental data. We make predictions for future experiments at PANDA, RHIC, Tevatron and LHC energies. The two-dimensional distribution in rapidity space of pions (yπ+, yπ-) is particularly interesting. The higher the incident energy, the higher preference for the same-hemisphere emission of pions. The processes considered constitute a sizeable contribution to the total nucleon-nucleon cross section as well as to pion inclusive cross section.

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2

Dominguez, C. A., M. Loewe, and M. Lushozi. "Scalar Form Factor of the Pion in the Kroll-Lee-Zumino Field Theory." Advances in High Energy Physics 2015 (2015): 1–4. http://dx.doi.org/10.1155/2015/803232.

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The renormalizable Kroll-Lee-Zumino field theory of pions and a neutral rho-meson is used to determine the scalar form factor of the pion in the space-like region at next-to-leading order. Perturbative calculations in this framework are parameter-free, as the masses and the rho-pion-pion coupling are known from experiment. Results compare favorably with lattice QCD calculations.

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3

Friedrich, Jan. "Chiral symmetry breaking: Current experimental status and prospects." EPJ Web of Conferences 282 (2023): 01007. http://dx.doi.org/10.1051/epjconf/202328201007.

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Chiral symmetry, linked to the smallness of the quark masses compared to the QCD bound states, and its breaking pattern are exploited in effective field theory to describe a multitude of phenomena by a few low-energy constants. Those concern light-meson dynamics and decays, their couplings to photons and meson-nucleon interactions. Special emphasis is given to the pion properties, in terms of pion-pion low-energy scattering, the pion polarizability and the chiral anomaly, which describes the coupling of three pions to a photon. These properties are studied by the COMPASS collaboration at CERN since first data taking with pion beams in the year 2004, and several following campaigns. In the framework of the upcoming AMBER collaboration, it is planned to extend the studies to the kaon sector.

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4

Bussone, Andrea, Michele Della Morte, and Tadeusz Janowski. "Electromagnetic corrections to the hadronic vacuum polarization of the photon within QEDL and QEDM." EPJ Web of Conferences 175 (2018): 06005. http://dx.doi.org/10.1051/epjconf/201817506005.

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We compute the leading QED corrections to the hadronic vacuum polarization (HVP) of the photon, relevant for the determination of leptonic anomalous magnetic moments, al. We work in the electroquenched approximation and use dynamical QCD configurations generated by the CLS initiative with two degenerate flavors of nonperturbatively O(a)-improved Wilson fermions. We consider QEDL and QEDM to deal with the finite-volume zero modes. We compare results for the Wilson loops with exact analytical determinations. In addition we make sure that the volumes and photon masses used in QEDM are such that the correct dispersion relation is reproduced by the energy levels extracted from the charged pions two-point functions. Finally we compare results for pion masses and the HVP between QEDL and QEDM. For the vacuum polarization, corrections with respect to the pure QCD case, at fixed pion masses, turn out to be at the percent level.

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5

Cahill, Reginald T., and Susan M. Gunner. "The Pion Mass Formula." Australian Journal of Physics 51, no. 3 (1998): 509. http://dx.doi.org/10.1071/p96110.

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The often used Gell-Mann–Oakes–Renner (GMOR) mass formula for Nambu-Goldstone (NG) bosons in QCD, such as the pions, involves the condensate ·q q Ò fp and the quark current masses. Within the context of the Global Colour Model (GCM) for QCD a manifestly different formula was recently found. Remarkably, Langfeld and Kettner have shown the two formulae to be equivalent. Here we note that the above recent analyses refer to the constituent pion and not the exact pion, even within the GCM. Further we generalise the Langfeld-Kettner identity to include the full response of the constituent quark correlators to the presence of a non-zero (and momentum dependent) quark current mass. Results are reported using an effective gluon correlator from meson data fitting.

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6

Sanchis-Alepuz, Hèlios, Christian S. Fischer, and Stanislav Kubrak. "Pion cloud effects on baryon masses." Physics Letters B 733 (June 2014): 151–57. http://dx.doi.org/10.1016/j.physletb.2014.04.031.

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7

Nam, Soonkeon, and Ron L. Workman. "Generalized Skyrme model with pion masses." Physical Review D 41, no. 7 (1990): 2323–26. http://dx.doi.org/10.1103/physrevd.41.2323.

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8

SAHU, SARIRA, and S. C. PHATAK. "NUCLEON PROPERTIES IN CHIRAL COLOR DIELECTRIC MODEL." Modern Physics Letters A 07, no. 08 (1992): 709–21. http://dx.doi.org/10.1142/s0217732392000689.

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The chiral extension of color dielectric model has been used to study the static properties of nucleon. In this calculation we have treated the gluon and the pion fields perturbatively. It is found that the neutron charge rms radius and the pion-nucleon coupling constant are almost insensitive to the parameters used and are in excellent agreement with the experimental values. For better fitting the proton charge rms radius, nucleon magnetic moments and axial coupling constant prefer large quark masses (~100 MeV) and small glueball masses (<1100 MeV). The strong coupling constant is found to be very sensitive to the quark and glueball masses.

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9

Pasupathy, J. "PCAC and Modifications in Hadron Properties in Nuclear Medium." Modern Physics Letters A 12, no. 26 (1997): 1943–49. http://dx.doi.org/10.1142/s0217732397001989.

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It is known that the Adler zero condition when imposed on pion amplitudes leads to several relations between hadron masses through the dual resonance formula of Lovelace, Shapiro and Veneziano. In particular the Lovelace quantization condition leads to the relation [Formula: see text] which is well satisfied experimentally. The Regge slope parameter α′ can be related to the gluon condensate. The latter is modified in the nuclear medium as compared to its value in the QCD vacuum. Combining the PCAC hypothesis with changes in gluon condensate leads to lowering of vector masses in the nuclear medium. It also leads to predictions regarding, nucleon isobar mass differences, pion decay constant in the medium, pion amplitudes and transverse momentum distribution of secondaries in heavy ion collisions.

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10

Sasaki, Chihiro, David Blaschke, Pok Man Lo, Michał Marczenko, Kenji Morita, and Krzysztof Redlich. "Parity Doubling in QCD Thermodynamics." Proceedings 13, no. 1 (2019): 7. http://dx.doi.org/10.3390/proceedings2019013007.

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Motivated by the recent lattice study by FASTSUM collaboration, effective masses of the baryon parity-doublers are shown for various pion masses. A general trend of the nucleon and delta parity-doublers is consistent with the lattice Quantum Chromodynamics (QCD) observation, whereas the hyperon masses exhibit a qualitatively different behavior, traced back to the lattice set-up with the heavy pion comparable to the kaon. As an application to hot QCD, we demonstrate the fluctuations and correlations involving baryon number in hot hadronic matter with modified masses of negative-parity baryons, in the context of the hadron resonance gas. Confronting the baryon number susceptibility, baryon–charge and baryon–strangeness correlations as well as their ratios with the lattice QCD data for the physical pion mass, we find that the strong downward mass shift in the hyperons can accidentally reproduce some correlation ratios, however it also tends to overshoot the individual fluctuations and correlations of lattice simulations. Another application of nucleon parity doubling is the physics of neutron stars. Under beta equilibrium and charge neutrality, hadronic matter with unbroken chiral symmetry can be favored in the core of the neutron stars.

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11

Daum, M., R. Frosch, and P. R. Kettle. "The charged and neutral pion masses revisited." Physics Letters B 796 (September 2019): 11–14. http://dx.doi.org/10.1016/j.physletb.2019.07.027.

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12

SIDHARTH, B. G. "THE PION MODEL." International Journal of Modern Physics E 20, no. 06 (2011): 1527–32. http://dx.doi.org/10.1142/s0218301311018514.

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We revisit the problem of a mechanism that generates the mass spectrum of elementary particles. This has vexed physicists for several decades now. In this connection, we deduce a formula that gives the masses of all known elementary particles, even though other quantum numbers are suppressed. These considerations become important in view of the Large Hadron Collider which is expected to attain 14 TeV by 2013.

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13

Boyle, Peter, Nicolas Garron, Julia Kettle, Ava Khamseh, and Justus Tobias Tsang. "BSM Kaon Mixing at the Physical Point." EPJ Web of Conferences 175 (2018): 13010. http://dx.doi.org/10.1051/epjconf/201817513010.

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We present a progress update on the RBC-UKQCD calculation of beyond the standard model (BSM) kaon mixing matrix elements at the physical point. Simulations are performed using 2+1 flavour domain wall lattice QCD with the Iwasaki gauge action at 3 lattice spacings and with pion masses ranging from 430 MeV to the physical pion mass.

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14

Kotov, A. Yu, M. P. Lombardo, and A. Trunin. "Finite temperature QCD phase transition and its scaling window from Wilson twisted mass fermions." EPJ Web of Conferences 258 (2022): 05012. http://dx.doi.org/10.1051/epjconf/202225805012.

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We study the properties of finite temperature QCD using lattice simulations with Nf = 2 + 1 + 1 Wilson twisted mass fermions for pion masses from physical up to heavy quark regime. In particular, we investigate the scaling properties of the chiral phase transition close to the chiral limit. We found compatibility with O(4) universality class for pion masses up to physical and in the temperature range [120 : 300] MeV. We also discuss other alternatives, including mean field behaviour or Z2 scaling. We provide an estimation of the critical temperature in the chiral limit, T0 = 134−4+6 MeV, which is stable against various scaling scenarios.

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15

PAULI, HANS-CHRISTIAN, and ASMITA MUKHERJEE. "ON THE SIZE OF HADRONS." International Journal of Modern Physics A 16, no. 26 (2001): 4351–64. http://dx.doi.org/10.1142/s0217751x01005407.

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The form factor and the mean-square radius of the pion are calculated analytically from a parametrized form of a [Formula: see text] wave function. The numerical wave function was obtained previously by solving numerically an eigenvalue equation for the pion in a particular model. The analytical formulas are of more general interest than just being valid for the pion and can be generalized to the case with unequal quark masses. Two different parametrizations are investigated. Because of the highly relativistic problem, noticeable deviations from a nonrelativistic formula are obtained.

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16

Jena, S. N., M. K. Muni, and H. R. Pattnaik. "( q q ¯ ) -pion mass and decay constant in a relativistic independent-quark model." Canadian Journal of Physics 87, no. 11 (2009): 1171–80. http://dx.doi.org/10.1139/p09-097.

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The mass and decay constant of the [Formula: see text]-pion together with the masses of ρ and ω mesons are calculated in a chiral symmetric potential model of independent quarks, taking into account the corrections due to the possible residual interactions, such as quark–pion coupling arising out of the requirement of chiral symmetry and quark gluon coupling arising out of one-gluon-exchange, and that due to the spurious center-of-mass motion of the meson core. The effective potential representing phenomenologically the nonperturbative gluon interactions, including gluon self coupling, is chosen with equally mixed scalar and vector parts in a logarithmic form. The result obtained for the physical mass of [Formula: see text]-pion is consistent with that of the PCAC-pion, and the pion-decay constant reasonably agrees with experiment.

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17

SUKHORUCHKIN, SERGEY, and DMITRY SUKHORUCHKIN. "CLUSTER EFFECTS IN NUCLEAR BINDING ENERGIES." International Journal of Modern Physics E 20, no. 04 (2011): 906–9. http://dx.doi.org/10.1142/s0218301311018940.

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Stable character of differences of nuclear binding energies of nuclei differing by 6 He or 4 He clusters is used to check the tuning effect in particle masses which consists in integer relation between electromagnetic mass differences of leptons and pion as well as rational relations between other particle masses.

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18

Scior, Philipp, Lorenz von Smekal, and Dominik Smith. "Spectrum of QCD at Finite Isospin Density." EPJ Web of Conferences 175 (2018): 07042. http://dx.doi.org/10.1051/epjconf/201817507042.

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We study the phase diagram of QCD at finite isospin density using two flavors of staggered quarks. We investigate the low temperature region of the phase diagram where we find a pion condensation phase at high chemical potential. We started a basic analysis of the spectrum at finite isospin density. In particular, we measured pion, rho and nucleon masses inside and outside of the pion condensation phase. In agreement with previous studies in two-color QCD at finite baryon density we find that the Polyakov loop does not depend on the density in the staggered formulation.

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19

CONTRERAS, C., та M. LOEWE. "THE LINEAR σ-MODEL AND FINITE TEMPERATURE EFFECTS". International Journal of Modern Physics A 05, № 12 (1990): 2297–312. http://dx.doi.org/10.1142/s0217751x90001069.

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We discuss the temperature effects on the masses and couplings constants in the linear σ-model including the effective pion decay constant fπ(T). We analyze in detail the region where our discussion is valid. The temperature effects on masses include an explicit discussion concerning the role of the thermal tadpoles as a mass contribution due to the vacuum.

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20

Giusti, Davide, Vittorio Lubicz, Guido Martinelli, Francesco Sanfilippo, and Silvano Simula. "HVP contributions to the muon (g−2) including QED corrections with twisted-mass fermions." EPJ Web of Conferences 175 (2018): 06006. http://dx.doi.org/10.1051/epjconf/201817506006.

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We present a lattice calculation of the Hadronic Vacuum Polarization (HVP) contribution of the strange and charm quarks to the anomalous magnetic moment of the muon including leading-order electromagnetic (e.m.) corrections. We employ the gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with Nf = 2+1 + 1 dynamical quarks at three values of the lattice spacing (a ≃ 0.062,0.082,0.089 fm) with pion masses in the range Mπ ≃ 210 - 450 MeV. The strange and charm quark masses are tuned at their physical values. Neglecting discon-nected diagrams and after the extrapolations to the physical pion mass and to the continuum limit we obtain: [see formula in PDF] and [see formula in PDF] for the strange and charm contributions, respectively.!

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21

Steele, T. G. "Hölder Inequalities and QCD Sum-Rule Bounds on the Masses of Light Quarks." International Journal of Modern Physics A 16, supp01b (2001): 582–84. http://dx.doi.org/10.1142/s0217751x01007546.

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QCD Laplace Sum-Rules must satisfy a fundamental Hölder inequality if they are to consistently represent an integrated hadronic spectral function. The Laplace sum-rules of pion currents is shown to violate this inequality unless the u and d quark masses are sufficiently large, placing a lower bound on mu+md, the SU(2)-invariant combination of the light-quark masses.

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22

Tavares, O. A. P., and E. L. Medeiros. "Nuclear radii from nuclear masses." International Journal of Modern Physics E 28, no. 04 (2019): 1950021. http://dx.doi.org/10.1142/s0218301319500216.

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Single uncharged pion production in neutron- and proton-induced reactions on complex nuclei, combined with the nuclear Fermi Gas Model, has been used to evaluate the average equivalent radius of a [Formula: see text] nucleus directly from the experimental nuclear mass-values of [Formula: see text] and its neighbors [Formula: see text] and [Formula: see text] isobars. A simple formula without adjustable parameters has been derived which gives nuclear radius-values that are in good agreement with updated, equivalent root-mean-square (rms) radius-values derived from experiments for a set of 540 nuclides comprising spherical, quasi-spherical, stable and long-term half-life nuclides. We shall call by RFNM-approach the present method of nuclear radius determination.

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23

Yang, Yi-Bo, Ying Chen, Terrence Draper, Jian Liang, and Keh-Fei Liu. "Proton mass decomposition." EPJ Web of Conferences 175 (2018): 14002. http://dx.doi.org/10.1051/epjconf/201817514002.

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We report the results on the proton mass decomposition and also on the related quark and glue momentum fractions. The results are based on overlap valence fermions on four ensembles of Nf = 2 + 1 DWF configurations with three lattice spacings and volumes, and several pion masses including the physical pion mass. With 1-loop pertur-bative calculation and proper normalization of the glue operator, we find that the u, d, and s quark masses contribute 9(2)% to the proton mass. The quark energy and glue field energy contribute 31(5)% and 37(5)% respectively in the MS scheme at µ = 2 GeV. The trace anomaly gives the remaining 23(1)% contribution. The u, d, s and glue momentum fractions in the MS scheme are consistent with the global analysis at µ = 2 GeV.

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24

YANG, SHIN NAN, GUAN-YEU CHEN, SABIT S. KAMALOV, L. TIATOR, and D. DRECHSEL. "S11 RESONANCES IN A COUPLED-CHANNEL DYNAMICAL MODEL." International Journal of Modern Physics A 20, no. 08n09 (2005): 1656–61. http://dx.doi.org/10.1142/s0217751x0502313x.

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A self-consistent analysis of pion scattering and pion photoproduction within a coupled channels dynamical model is presented. The results indicate the existence of a third and a fourth S11 resonance with the masses 1846±47 and 2113±70 MeV . In the case of pion photoproduction, we found that background contributions to the imaginary part of the S-wave multipole become large and negative in the region of the S11(1535) resonance. Due to this fact, much larger resonance contributions are required in order to explain the results of the recent multipole analysis. For the first S11(1535) resonance we obtain a value of 72±2×10-3 GeV -1/2 for the electromagnetic helicity amplitude A1/2.

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25

Monemzadeh, M., N. Tazimi, and Sh Babaghodrat. "Calculating Masses of Pentaquarks Composed of Baryons and Mesons." Advances in High Energy Physics 2016 (2016): 1–4. http://dx.doi.org/10.1155/2016/6480926.

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We consider an exotic baryon (pentaquark) as a bound state of two-body systems composed of a baryon (nucleon) and a meson. We used a baryon-meson picture to reduce a complicated five-body problem to simple two-body problems. The homogeneous Lippmann-Schwinger integral equation is solved in configuration space by using one-pion exchange potential. We calculate the masses of pentaquarksθc(uuddc¯)andθb(uuddb¯).

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26

Finkenrath, Jacob, Constantia Alexandrou, Simone Bacchio, et al. "Simulation of an ensemble of Nf = 2 + 1 + 1 twisted mass cloverimproved fermions at physical quark masses." EPJ Web of Conferences 175 (2018): 02003. http://dx.doi.org/10.1051/epjconf/201817502003.

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We present a general strategy aimed at generating Nf = 2+1+1 configurations with quarks at their physical mass using maximally twisted mass fermions to ensure automatic O(a) improvement, in the presence of a clover term tuned to reduce the charged to neutral pion mass difference. The target system, for the moment, is a lattice of size 643 × 128 with a lattice spacing a ~ 0:08 fm. We show preliminary results on the pion and kaon mass and decay constants.

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27

HECHT, M. B., C. D. ROBERTS, and S. M. SCHMIDT. "DYSON-SCHWINGER EQUATIONS – ASPECTS OF THE PION." International Journal of Modern Physics A 16, supp01c (2001): 1241–44. http://dx.doi.org/10.1142/s0217751x01009429.

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The contemporary use of Dyson-Schwinger equations in hadronic physics is exemplified via applications to the calculation of pseudoscalar meson masses, and inclusive deep inelastic scattering with a determination of the pion's valence-quark distribution function.

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28

Borasoy, B., та Ulf-G. Meißner. "Baryon masses and pion-nucleon σ-term to second order in the quark masses". Physics Letters B 365, № 1-4 (1996): 285–91. http://dx.doi.org/10.1016/0370-2693(95)01286-9.

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29

Sun, Bao-Xi, Xiao-Fu Lu, Peng-Nian Shen, and En-Guang Zhao. "Relativistic Mean-Field Approximation with Density-Dependent Screening Meson Masses in Nuclear Matter." International Journal of Modern Physics E 12, no. 04 (2003): 543–54. http://dx.doi.org/10.1142/s0218301303001363.

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The Debye screening masses of the σ, ω and neutral ρ mesons and the photon are calculated in the relativistic mean-field approximation. As the density of the nucleon increases, all the screening masses of mesons increase. A different result with Brown–Rho scaling is shown, which implies a reduction in the mass of all the mesons in the nuclear matter, except the pion. Replacing the masses of the mesons with their corresponding screening masses in the Walecka-1 model, five saturation properties of the nuclear matter are fixed reasonably, and then a density-dependent relativistic mean-field model is proposed without introducing the nonlinear self-coupling terms of mesons.

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30

Ruiz Arriola, E., J. E. Amaro, and R. Navarro Pérez. "Three pion nucleon coupling constants." Modern Physics Letters A 31, no. 28 (2016): 1630027. http://dx.doi.org/10.1142/s0217732316300275.

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There exist four pion nucleon coupling constants, [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] 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 [Formula: see text] based on a partial wave analysis of the [Formula: see text] self-consistent nucleon–nucleon Granada-2013 database comprising 6713 published data in the period 1950–2013.

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31

MAGHRBI, YASSER, and BERND KRUSCHE. "DOUBLE PION PHOTOPRODUCTION OFF 7Li." International Journal of Modern Physics A 26, no. 03n04 (2011): 708–11. http://dx.doi.org/10.1142/s0217751x11052608.

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Data for quasi-free photoproduction of π0π0 and π0π+/- pairs from 7 Li have been analyzed in view of the in-medium properties of hadrons. Data have been measured with the CB/TAPS detector setup using the Glasgow photon tagging spectrometer for incident photon energies up to 820 MeV. The double π0 invariant mass distributions show an enhancement with respect to the mixed charged channel at small invariant masses. This enhancement could be consistent with an in-medium modification of the ππ interaction in the I = J = 0 channel, however effects from final state interactions must also be considered.

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32

Kaneko, Takashi, Brian Colquhoun, Hidenori Fukaya, and Shoji Hashimoto. "D meson semileptonic form factors in Nf = 3 QCD with Möbius domain-wall quarks." EPJ Web of Conferences 175 (2018): 13007. http://dx.doi.org/10.1051/epjconf/201817513007.

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e present our calculation of D → π and D → K semileptonic form factors in Nf = 2 + 1 lattice QCD. We simulate three lattice cutoffs a-1 ≃ 2.5, 3.6 and 4.5 GeV with pion masses as low as 230 MeV. The Möbius domain-wall action is employed for both light and charm quarks. We present our results for the vector and scalar form factors and discuss their dependence on the lattice spacing, light quark masses and momentum transfer.

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33

Dominguez, C. A., and L. A. Hernandez. "Determination of the temperature dependence of the up- and down-quark masses in QCD." Modern Physics Letters A 31, no. 36 (2016): 1630042. http://dx.doi.org/10.1142/s0217732316300421.

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The temperature dependence of the sum of the QCD up- and down-quark masses, (mu[Formula: see text]+[Formula: see text]md) and the pion decay constant, f[Formula: see text], are determined from two thermal finite energy QCD sum rules for the pseudoscalar-current correlator. This quark mass remains mostly constant for temperatures well below the critical temperature for deconfinement/chiral-symmetry restoration. As this critical temperature is approached, the quark mass increases sharply with increasing temperature. This increase is far more pronounced if the temperature dependence of the pion mass (determined independently from other methods) is taken into account. The behavior of f[Formula: see text](T) is consistent with the expectation from chiral symmetry, i.e. that it should follow the thermal dependence of the quark condensate, independently of the quark mass.

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34

Golterman, Maarten, Kim Maltman, and Santiago Peris. "Pion mass dependence of the HVP contribution to muon g – 2." EPJ Web of Conferences 175 (2018): 06010. http://dx.doi.org/10.1051/epjconf/201817506010.

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One of the systematic errors in some of the current lattice computations of the HVP contribution to the muon anomalous magnetic moment g – 2 is that associated with the extrapolation to the physical pion mass. We investigate this extrapolation assuming lattice pion masses in the range of 220 to 440 MeV with the help of two-loop chiral perturbation theory, and find that such an extrapolation is unlikely to lead to control of this systematic error at the 1% level. This remains true even if various proposed tricks to improve the chiral extrapolation are taken into account.

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35

Howarth, Dean, and Joel Giedt. "The sigma meson from lattice QCD with two-pion interpolating operators." International Journal of Modern Physics C 28, no. 10 (2017): 1750124. http://dx.doi.org/10.1142/s0129183117501248.

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In this paper, we describe our studies of the sigma meson, [Formula: see text], using two-pion correlation functions. We use lattice quantum chromodynamics in the quenched approximation with so-called clover fermions. By working at unphysical pion masses we are able to identify a would-be resonance with mass less than [Formula: see text], and then extrapolate to the physical point. We include the most important annihilation diagram, which is “partially disconnected” or “single annihilation”. Because this diagram is quite expensive to compute, we introduce a somewhat novel technique for the computation of all-to-all diagrams, based on momentum sources and a truncation in momentum space. In practice, we use only [Formula: see text] modes, so the method reduces to wall sources. At the point where the mass of the pion takes its physical value, we find a resonance in the [Formula: see text] two-pion channel with a mass of approximately [Formula: see text] MeV, consistent with the expected properties of the sigma meson, given the approximations we are making.

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36

Krusch, Steffen. "Finkelstein–Rubinstein constraints for the Skyrme model with pion masses." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 462, no. 2071 (2006): 2001–16. http://dx.doi.org/10.1098/rspa.2006.1664.

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The Skyrme model is a classical field theory modelling the strong interaction between atomic nuclei. It has to be quantized in order to compare it to nuclear physics. When the Skyrme model is semi-classically quantized it is important to take the Finkelstein–Rubinstein constraints into account. Recently, a simple formula has been derived to calculate the constraints for Skyrmions which are well approximated by rational maps. However, if a pion mass term is included in the model, Skyrmions of sufficiently large baryon number are no longer well approximated by the rational map ansatz. This paper addresses the question how to calculate Finkelstein–Rubinstein constraints for Skyrme configurations which are only known numerically.

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37

Namysłowski, J. M. "Pion and rho meson masses from quark and gluon condensates." Progress in Particle and Nuclear Physics 36 (January 1996): 107–17. http://dx.doi.org/10.1016/0146-6410(96)00014-2.

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38

Belounnas, Amel. "Study of baryonic resonances and ρ meson production in the reaction pp → ppπ+π− at 3.5 GeV with HADES". EPJ Web of Conferences 199 (2019): 02012. http://dx.doi.org/10.1051/epjconf/201919902012.

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We report on measurements of baryon resonance and ρ meson production in the exclusive pp → ppπ+π− channel at a beam kinetic energy of 3.5 GeV measured with the HADES experimental setup. The differential distributions are compared to Monte Carlo simulations based on a resonance model assuming an incoherent sum of contributions of various baryonic resonances with masses below 2 GeV and using inputs from one pion production measured in the same experiment. A very good description of the two pion production is achieved allowing for an estimate of the contribution of one and double baryon-resonance excitation. Using appropriate kinematical cuts the ρ meson signal could also be extracted.

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39

Buballa, Michael, Stefano Carignano, and Lennart Kurth. "Inhomogeneous phases in the quark-meson model with explicit chiral-symmetry breaking." European Physical Journal Special Topics 229, no. 22-23 (2020): 3371–85. http://dx.doi.org/10.1140/epjst/e2020-000101-x.

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AbstractWe investigate the existence of inhomogeneous chiral phases in the quark-meson model with explicit chiral-symmetry breaking. We find that the inhomogeneous region shrinks with increasing pion masses but survives for the physical value of mπ. The instability towards inhomogeneous matter occurs in the scalar channel, while pseudoscalar modes are disfavored.

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40

Fan, Zhouyou, Rui Zhang, and Huey-Wen Lin. "Nucleon gluon distribution function from 2 + 1 + 1-flavor lattice QCD." International Journal of Modern Physics A 36, no. 13 (2021): 2150080. http://dx.doi.org/10.1142/s0217751x21500809.

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The parton distribution functions (PDFs) provide process-independent information about the quarks and gluons inside hadrons. Although the gluon PDF can be obtained from a global fit to experimental data, it is not constrained well in the large-[Formula: see text] region. Theoretical gluon-PDF studies are much fewer than those of the quark PDFs. In this work, we present the first lattice-QCD results that access the [Formula: see text]-dependence of the gluon unpolarized PDF of the nucleon. The lattice calculation is carried out with nucleon momenta up to 2.16 GeV, lattice spacing [Formula: see text] fm, and with valence pion masses of 310 and 690 MeV. We use reduced Ioffe-time distributions to cancel the renormalization and implement a one-loop perturbative pseudo-PDF gluon matching. We neglect mixing of the gluon operator with the quark singlet sector. Our matrix-element results in coordinate space are consistent with those obtained from the global PDF fits of CT18 NNLO and NNPDF3.1 NNLO. Our fitted gluon PDFs at both pion masses are consistent with global fits in the [Formula: see text] region.

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41

Mondal, Sourav, M. Padmanath, and Nilmani Mathur. "Spectroscopy of Charmed and Bottom Hadrons using Lattice QCD." EPJ Web of Conferences 175 (2018): 05021. http://dx.doi.org/10.1051/epjconf/201817505021.

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We present preliminary results on the light, charmed and bottom baryon spectra using overlap valence quarks on the background of 2+1+1 flavours HISQ gauge configurations of the MILC collaboration. These calculations are performed on three different gauge ensembles at three lattice spacings (a ∼ 0.12 fm, 0.09 fm and 0.06 fm) and for physical strange, charm and bottom quark masses. The SU(2) heavy baryon chiral perturbation theory is used to extrapolate baryon masses to the physical pion mass and the continuum limit extrapolations are also performed. Our results are consistent with the well measured charmed baryons. We predict the masses of many other states which are yet to be discovered.

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42

Helmes, Christopher, Bastian Knippschild, Bartosz Kostrzewa та ін. "The η′ meson at the physical point with Nf = 2 Wilson twisted mass fermions". EPJ Web of Conferences 175 (2018): 05025. http://dx.doi.org/10.1051/epjconf/201817505025.

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We present results for the η′ meson and the topological susceptibility in Nf = 2 flavour lattice QCD. The results are obtained using Wilson twisted mass fermions at maximal twist with pion masses ranging from 340 MeV down to the physical point. A comparison to literature values is performed giving a handle on discretisation effects.

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43

Erben, Felix, Jeremy Green, Daniel Mohler, and Hartmut Wittig. "Towards extracting the timelike pion form factor on CLS twoflavour ensembles." EPJ Web of Conferences 175 (2018): 05027. http://dx.doi.org/10.1051/epjconf/201817505027.

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Results are presented from an ongoing study of the ρ resonance. The focus is on CLS 2-flavour ensembles generated using O(a) improved Wilson fermions with pion masses ranging from 265 to 437 MeV. The energy levels are extracted by solving the GEVP of correlator matrices, created with the distillation approach involving ρ and ππ interpolators. The study is done in the centre-of-mass frame and several moving frames. One aim of this work is to extract the timelike pion form factor after applying the Lüscher formalism. We therefore plan to integrate this study with the existing Mainz programme for the calculation of the hadronic vacuum polarization contribution to the muon g – 2.

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44

Collins, Sara, Kevin Eckert, Jochen Heitger, Stefan Hofmann, and Wolfgang Söldner. "Leptonic decay constants for D-mesons from 3-flavour CLS ensembles." EPJ Web of Conferences 175 (2018): 13019. http://dx.doi.org/10.1051/epjconf/201817513019.

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e report on the status of an ongoing effort by the RQCD and ALPHA Collaborations, aimed at determining leptonic decay constants of charmed mesons. Our analysis is based on large-volume ensembles generated within the CLS effort, employing Nf = 2 + 1 non-perturbatively O(a) improved Wilson quarks, tree-level Symanzik-improved gauge action and open boundary conditions. The ensembles cover lattice spac-ings from a ≈ 0.09 fm to a ≈ 0.05 fm, with pion masses varied from 420 to 200 MeV. To extrapolate to the physical masses, we follow both the (2ml + ms) = const. and the ms = const. lines in parameter space.

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45

VIGIL, JUAN ESTRADA, and LUIS MASPERI. "DYNAMICAL COSMOLOGICAL CONSTANT AND RELATIONS AMONG PSEUDO-GOLDSTONE BOSONS." Modern Physics Letters A 13, no. 06 (1998): 423–28. http://dx.doi.org/10.1142/s0217732398000486.

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The present apparent cosmological constant is interpreted as the potential of the lightest pseudo-Goldstone boson. Some numerical relations among cosmological parameters and particle masses are shown to arise from the mixture of this very light particle, whose interaction is of the gravitational order, with other pseudo-Goldstone bosons like the pion and the axion which feel the strong interaction.

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46

Campostrini, M., K. J. M. Moriarty, J. Potvin, and C. Rebbi. "Testing pseudofermion lattice QCD with small quark masses and large volumes." Canadian Journal of Physics 67, no. 8 (1989): 792–97. http://dx.doi.org/10.1139/p89-137.

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We report on extensive tests done on the pseudofermion algorithm in a simulation of lattice QCD with dynamical quarks. These tests are carried out in a more realistic context than many of the studies previously attempted as a lattice volume of 103 × 32 sites and quark mass of about 50 to 200 MeV are used throughout the calculation. Wilson loop factors of various sizes, as well as chiral condensates and pion propagators, are shown to change by less than 5% when the pseudofermion algorithm is tuned to simulate QCD more accurately.

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47

Galeão, A. P., J. A. Castilho Alcarás, and P. Leal Ferreira. "Two-Body Dirac Equation Approach to the Deuteron." International Journal of Modern Physics E 07, no. 01 (1998): 89–106. http://dx.doi.org/10.1142/s021830139800004x.

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The two-body Dirac(Breit) equation with potentials associated to one-boson-exchanges with cutoff masses is solved for the deuteron and its observables calculated. The 16-component wave-function for the Jπ=1+ state contains four independent radial functions which satisfy a system of four coupled differential equations of first order. This system is numerically integrated, from infinity towards the origin, by fixing the value of the deuteron binding energy and imposing appropriate boundary conditions at infinity. For the exchange potential of the pion, a mixture of direct plus derivative couplings to the nucleon is considered. We varied the pion-nucleon coupling constant, and the best results of our calculations agree with the lower values recently determined for this constant.

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48

GOYAL, ASHOK, and SUKANTA DUTTA. "CONSTRAINING THE RIGHT-HANDED INTERACTIONS FROM PION CONDENSATE MATTER." International Journal of Modern Physics A 15, no. 04 (2000): 509–22. http://dx.doi.org/10.1142/s0217751x00000240.

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We consider right-handed neutrino emission from charged and neutral pion condensate matter that could have been present in the supernova core associated with SN 1987 A. This is used to constrain the strength of right-handed interactions and we get an excluded range of values for the right-handed W boson and extra neutral Z' boson masses. For vanishing WL–WR mixing we obtain (1.3–1.8) MWL ≈≤ MWR ≤≈ (370–700) MWL and (1.3–1.8) MWL ≈≤ MN' ≤≈ 158MWL.

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49

Weber, H. J., and H. T. Williams. "Non-strange baryon masses with color hyperfine and pion exchange interactions." Physics Letters B 205, no. 2-3 (1988): 118–22. http://dx.doi.org/10.1016/0370-2693(88)91632-2.

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Coppola, M., D. Gómez Dumm, and N. N. Scoccola. "Charged pion masses under strong magnetic fields in the NJL model." Physics Letters B 782 (July 2018): 155–61. http://dx.doi.org/10.1016/j.physletb.2018.04.043.

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