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Articles de revues sur le sujet « Quark spin »

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Publié le 11 mars 2023

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1

STROBEL, GEORGE L. « BARYON MAGNETIC MOMENTS AND SPIN DEPENDENT QUARK FORCES ». International Journal of Modern Physics E 11, no 01 (février 2002) : 71–81. http://dx.doi.org/10.1142/s0218301302000697.

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The J=3/2 Δ, J=1/2 nucleon mass difference shows that quark energies can be spin dependent. It is natural to expect that quark wave functions also depend on spin. In the octet, such spin dependent forces lead to different wave functions for quarks with spin parallel or antiparallel to the nucleon spin. A two component Dirac equation wave function is used for the quarks assuming small current quark masses for the u and d quarks. Then, the neutron/proton magnetic moment ratio, the nucleon axial charge, and the spin content of the nucleon can all be simultaneously fit assuming isospin invariance between the u and d quarks, but allowing for spin dependent forces. The breakdown of the Coleman–Glashow sum rule for octet magnetic moments follows naturally in this Dirac approach as the bound quark energy also effects the magnetic moment. Empirically the bound quark energy increases with the number of strange quarks in the system. Allowing the strange quark wave function similar spin dependence predicts the magnetic moments of the octet, in close agreement with experiment. Differences between the octet and decuplet magnetic moments are also explained immediately with spin dependent wave functions.
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2

Kaur, Satvir, et Harleen Dahiya. « Study of Spin–Spin Correlations between Quark and a Spin-1/2 Composite System ». Advances in High Energy Physics 2020 (27 janvier 2020) : 1–13. http://dx.doi.org/10.1155/2020/9429631.

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We study the correlation between the fermion composite system and quark spins by using the light-cone quark–diquark model. We do the calculations for u-quark and d-quark in the fermion system by considering different polarization configurations of both. The contribution from scalar and axial-vector diquarks is taken into account. The overlap representation of light-front wavefunctions is used for the calculations. The spin–spin correlations for u and d quarks are presented in transverse impact-parameter plane and transverse momentum plane as well.
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3

FRITZSCH, H., et G. ELDAHOUMI. « CONSTITUENT QUARKS AND THE SPIN OF THE PROTON ». Modern Physics Letters A 24, no 27 (7 septembre 2009) : 2167–74. http://dx.doi.org/10.1142/s0217732309031788.

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The constituent quarks are interpreted as bound states, which have an internal structure. The quark distributions of the proton are related to those of the constituent quarks. The experiments support this hypothesis. Likewise the spin structure of the proton is related to the spin structure of the constituent quarks. We find that about 30% of the spin of a constituent quark is given by the valence quark, and 70% are provided by the gluons.
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4

SONG, XIAOTONG. « QUARK ORBITAL ANGULAR MOMENTUM IN THE BARYON ». International Journal of Modern Physics A 16, no 22 (10 septembre 2001) : 3673–97. http://dx.doi.org/10.1142/s0217751x01005018.

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Analytical and numerical results, for the orbital and spin content carried by different quark flavors in the baryons, are given in the chiral quark model with symmetry breaking. The reduction of the quark spin, due to the spin dilution in the chiral splitting processes, is transferred into the orbital motion of quarks and antiquarks. The orbital angular momentum for each quark flavor in the proton as a function of the partition factor κ and the chiral splitting probability a is shown. The cancellation between the spin and orbital contributions in the spin sum rule and in the baryon magnetic moments is discussed.
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5

Borka Jovanović, V., D. Borka, P. Jovanović, J. Milošević et S. R. Ignjatović. « Masses of constituent quarks confined in open bottom hadrons ». Modern Physics Letters A 29, no 38 (9 décembre 2014) : 1450202. http://dx.doi.org/10.1142/s0217732314502022.

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We apply color-spin and flavor-spin quark–quark interactions to the meson and baryon constituent quarks, and calculate constituent quark masses, as well as the coupling constants of these interactions. The main goal of this paper was to determine constituent quark masses from light and open bottom hadron masses, using the fitting method we have developed and clustering of hadron groups. We use color-spin Fermi–Breit (FB) and flavor-spin Glozman–Riska (GR) hyperfine interaction (HFI) to determine constituent quark masses (especially b quark mass). Another aim was to discern between the FB and GR HFI because our previous findings had indicated that both interactions were satisfactory. Our improved fitting procedure of constituent quark masses showed that on average color-spin (FB) HFI yields better fits. The method also shows the way how the constituent quark masses and the strength of the interaction constants appear in different hadron environments.
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6

BATRA, M., et A. UPADHYAY. « DETAILED BALANCE AND SPIN CONTENT OF Λ USING STATISTICAL MODEL ». International Journal of Modern Physics A 28, no 15 (16 juin 2013) : 1350062. http://dx.doi.org/10.1142/s0217751x13500620.

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The spin structure of lambda has its special importance in analyzing the spin content of other hadrons. Assuming hadrons as a cluster of quarks and gluons (generally referred as valence and sea), statistical approach has been applied to study spin distribution of lambda among quarks. We apply the principle of detailed balance to calculate the probability of various quark–gluon Fock states and check the impact of SU(3) breaking on these probabilities particularly in sea for the Fock states containing strange quark. The flavor probability when multiplied by spin and color multiplicities of these quark–gluon Fock states results in estimating the individual contributions from valence and sea. We conclude that breaking in symmetry significantly affects the polarization of quarks inside the hyperons.
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7

PASQUINI, B., S. BOFFI et P. SCHWEITZER. « THE SPIN STRUCTURE OF THE NUCLEON IN LIGHT-CONE QUARK MODELS ». Modern Physics Letters A 24, no 35n37 (7 décembre 2009) : 2903–12. http://dx.doi.org/10.1142/s021773230900111x.

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The quark spin densities related to generalized parton distributions in impact-parameter space and to transverse-momentum dependent parton distributions are reviewed within a light-cone quark model, with focus on the role of the different spin-spin and spin-orbit correlations of quarks. Results for azimuthal spin asymmetries in semi-inclusive deep inelastic scattering due to T -even transverse-momentum dependent parton distributions are also discussed.
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8

Lorcé, Cédric. « Quark Spin-Orbit Correlations ». International Journal of Modern Physics : Conference Series 37 (janvier 2015) : 1560036. http://dx.doi.org/10.1142/s2010194515600368.

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The proton spin puzzle issue focused the attention on the parton spin and orbital angular momentum contributions to the proton spin. However, a complete characterization of the proton spin structure requires also the knowledge of the parton spin-orbit correlation. We showed that this quantity can be expressed in terms of moments of measurable parton distributions. Using the available phenomenological information about the valence quarks, we concluded that this correlation is negative, meaning that the valence quark spin and kinetic orbital angular momentum are, in average, opposite. The quark spin-orbit correlation can also be expressed more intuitively in terms of relativistic phase-space distributions, which can be seen as the mother distributions of the standard generalized and transverse-momentum dependent parton distributions. We present here for the first time some examples of the general multipole decomposition of these phase-space distributions.
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9

Morimoto, Masatoshi, Yasuhiko Tsue, João da Providência, Constança Providência et Masatoshi Yamamura. « Spontaneous magnetization under a pseudovector interaction between quarks in high density quark matter ». International Journal of Modern Physics E 27, no 04 (avril 2018) : 1850028. http://dx.doi.org/10.1142/s0218301318500283.

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Spontaneous magnetization and magnetic susceptibility originated from the pseudovector-type four-point interaction between quarks are calculated in quark matter with zero temperature and finite quark chemical potential by using the two-flavor Nambu–Jona-Lasinio model. It is shown that both the chiral condensate and spin polarized condensate coexist in a narrow region of the quark chemical potential. And then, it is also shown that, in this narrow region, the spontaneous magnetization appears. Also, the magnetic susceptibility due to quarks with the positive energy is evaluated in the spin polarized phase.
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10

ŞAHIN, B., et İ. ŞAHIN. « TOP QUARK SPIN POLARIZATION IN eγ COLLISION ». Modern Physics Letters A 23, no 07 (7 mars 2008) : 519–25. http://dx.doi.org/10.1142/s021773230802433x.

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We investigate the degree of spin polarization of single top quarks in the eγ collision via the process [Formula: see text] with center-of-mass energies [Formula: see text], 1 and 1.5 TeV of the parental linear e+e- collider. Dominant spin fractions and spin asymmetries for the various top quark spin bases are investigated. We show that e+-beam direction is the favorite top quark spin decomposition axis. It is found to be comparable with the ones in pp and ep collisions.
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11

Giordano, F. « Proton Quark Helicity Structure via W-Boson Production in PP Collision @ Phenix ». International Journal of Modern Physics : Conference Series 40 (janvier 2016) : 1660018. http://dx.doi.org/10.1142/s2010194516600181.

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The spin structure of the proton has been long studied in the past decades, but, while the contributions to the proton spin from valence quarks is by now precisely known, large uncertainties are still affecting our knowledge of the sea quark contributions. The measurement of single-spin asymmetries of the parity violating W production in pp collision allows a (quasi-)model independent access to the flavor-dependent light sea quark contributions. Being maximally parity violating, the [Formula: see text] charge can be directly realted to the quark and antiquark flavor, and in addition, moving from forward to backward rapidities with respect to the polarized proton beam direction it is possible to change the relative contributions of u, d, anti-u, anti-d quarks, thus accessing each light-quark spin alignment with respect to the proton spin. At PHENIX, the W boson produced in pp collision at center of mass energies of about 500 GeV is accessed via its decays into electron (muon) at central (forward) rapidities. Here the status of the analysis and the most updated results is reported.
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12

WEBER, H. J. « PROTON STRUCTURE FUNCTIONS FROM CHIRAL DYNAMICS AND QCD CONSTRAINTS ». International Journal of Modern Physics A 14, no 19 (30 juillet 1999) : 3005–27. http://dx.doi.org/10.1142/s0217751x99001469.

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The spin fractions and deep inelastic lepton structure functions of the proton are analyzed using chiral field theory involving Goldstone bosons. A detailed comparison with recent chiral models sheds light on their successful description of the spin fractions of the proton as being due to neglecting helicity nonflip chiral transitions. This approximation is valid for zero mass but not for constituent quarks. Since the chiral spin fraction models with the pure spin-flip approximation reproduce the measured spin fractions of the proton, axialvector constituent-quark-Goldstone boson couplings are found to be inconsistent with the proton spin data. Initial quark valence distributions are then constructed using quark counting constraints at Bjorken x→1 and Regge behavior at x→0. Sea quark distributions predicted by chiral field theory on this basis have the correct order of magnitude and shape. The spin fractions also agree with the data.
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13

ANTUNES, A. C. B., et L. J. ANTUNES. « ANGULAR MOMENTUM AND SPIN EFFECTS ON THE DIQUARK FORMATION ». International Journal of Modern Physics A 26, no 07n08 (30 mars 2011) : 1295–304. http://dx.doi.org/10.1142/s0217751x11052803.

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Quark interactions inside baryons depend on the spin states of the quarks. We investigated the contribution of the spin–spin interactions of quarks in comparison with other factors necessary for diquark formation in baryons, concluding that the effects of spin–spin interactions are correlated with the state of angular momentum excitation.
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14

METZ, ANDREAS, DANIEL PITONYAK, ANDREAS SCHÄFER, MARC SCHLEGEL, WERNER VOGELSANG et JIAN ZHOU. « SINGLE SPIN ASYMMETRIES IN INCLUSIVE DIS AND MULTI-PARTON CORRELATIONS IN THE NUCLEON ». International Journal of Modern Physics : Conference Series 20 (janvier 2012) : 137–44. http://dx.doi.org/10.1142/s2010194512009178.

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Transverse single spin asymmetries in inclusive deep-inelastic lepton-nucleon scattering can be generated through multi-photon exchange between the leptonic and the hadronic part of the process. Here we consider two-photon exchange, and mainly focus on the transverse target spin asymmetry. In particular, we investigate the case where two photons couple to different quarks. Such a contribution involves a quark-photon-quark correlator in the nucleon, which has a (model-dependent) relation to the Efremov-Teryaev-Qiu-Sterman quark-gluon-quark correlator TF. Using different parameterizations for TF we compute the transverse target spin asymmetry for both a proton and a neutron target, and compare the results to recent experimental data. Potential implications on our general understanding of single spin asymmetries in hard scattering processes are discussed as well.
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15

STERN, JACQUELINE, et GÉRARD CLEMENT. « QUARK CONTRIBUTION TO THE PROTON SPIN IN THE CHIRAL QUARK-MESON MODEL ». Modern Physics Letters A 03, no 17 (décembre 1988) : 1657–61. http://dx.doi.org/10.1142/s0217732388001987.

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It has been argued that, to leading order in the 1/Nc expansion, very little of the spin of the proton is carried by the helicities of its constituent quarks, in accordance with the results of a recent EMC experiment. We investigate this question by a direct computation in the chiral quark-meson model, where the proton spin is generated by cranking a mean field hedgehog baryon. For not too small values of the quark-meson coupling constant, our results are consistent with the EMC data.
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16

BASS, STEVEN D. « THE PROTON SPIN PUZZLE : WHERE ARE WE TODAY ? » Modern Physics Letters A 24, no 14 (10 mai 2009) : 1087–101. http://dx.doi.org/10.1142/s0217732309031041.

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The proton spin puzzle has challenged our understanding of QCD for the last 20 years. New measurements of polarized glue, valence and sea quark polarization, including strange quark polarization, are available. What is new and exciting in the data, and what might this tell us about the structure of the proton? The proton spin puzzle seems to be telling us about the interplay of valence quarks with the complex vacuum structure of QCD.
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17

Akatsu, Yasunari, et Osamu Terazawa. « V and A Structures of $t\bar{t}Z$ Vertex and Top Quark Polarization : QCD Corrections ». International Journal of Modern Physics A 12, no 14 (10 juin 1997) : 2613–22. http://dx.doi.org/10.1142/s0217751x97001468.

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We calculate the energy distributions of leptons in semileptonic decay of t quarks in the process [Formula: see text], by taking into account the polarizations and spin–spin correlations of t and [Formula: see text] quarks with QCD corrections to the [Formula: see text] and [Formula: see text] vertices up to the order αs. The corrections are large to the t quark production cross-section but do not alter the energy distributions of final leptons of the parton model practically. The distributions will provide useful information about the V and A structures of t quark.
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18

Tsue, Yasuhiko, João da Providência, Constança Providência, Masatoshi Yamamura et Henrik Bohr. « Spin polarization in high density quark matter under a strong external magnetic field ». International Journal of Modern Physics E 25, no 12 (décembre 2016) : 1650106. http://dx.doi.org/10.1142/s0218301316501068.

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In high density quark matter under a strong external magnetic field, possible phases are investigated by using the two-flavor Nambu–Jona–Lasinio (NJL) model with tensor-type four-point interaction between quarks, as well as the axial-vector-type four-point interaction. In the tensor-type interaction under the strong external magnetic field, it is shown that a quark spin polarized phase is realized in all regions of the quark chemical potential under consideration within the lowest Landau level approximation. In the axial-vector-type interaction, it is also shown that the quark spin polarized phase appears in the wide range of the quark chemical potential. In both the interactions, the quark mass in zero and small chemical potential regions increases which indicates that the chiral symmetry breaking is enhanced, namely the magnetic catalysis occurs.
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19

YANG, XIN-HUA, CHUN WA WONG et KEH-CHENG CHU. « DRESSED QUARKS AND PROTON’S SPIN ». Modern Physics Letters A 06, no 13 (30 avril 1991) : 1155–61. http://dx.doi.org/10.1142/s0217732391001202.

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The effect on the proton spin of mixing gluon and sea quark configurations is studied in a perturbative treatment based on the MIT bag model. As little as 29% of the proton spin is found to remain as the intrinsic spin of quarks when they are “dressed” by gluons.
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20

Klein, Andi. « Measuring the Sea Quark Sivers Asymmetry : The E1039 Experiment at Fermilab ». International Journal of Modern Physics : Conference Series 37 (janvier 2015) : 1560064. http://dx.doi.org/10.1142/s2010194515600642.

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One of the continuing puzzles in QCD is the origin of the nucleon spin. All of the existing experimental data suggest that the contributions from the quark and gluon spins account only for about 50% of the nucleon spin. In order to account for the remaining 50%, one has to include the orbital angular momentum of the quarks and gluons. One way to establish if quarks carry significant angular momentum, is to perform a measurement of the Sivers function, which describes the correlation of the spin direction of the nucleon with the transverse momentum of the quark. We will describe the E1039 experiment at Fermilab, which will measure the Sivers asymmetry of the sea quarks via the Drell-Yan process, using a 120 GeV unpolarized proton beam on a transversely polarized NH 3 target.
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21

Liang, Zuo-Tang, et R. Rittel. « Orbiting Valence Quarks and their Influence on the Structure Functions of the Nucleon ». Modern Physics Letters A 12, no 12 (20 avril 1997) : 827–36. http://dx.doi.org/10.1142/s0217732397000856.

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It is shown that intrinsic orbital motion of the valence quarks has large influences on the spin-dependent as well as the spin-averaged nucleon structure functions. Its connection with the observed "very small contribution of quark spin to nucleon spin" and the observed violation of Gottfried sum rule is discussed.
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22

GERASYUTA, S. M., et V. I. KOCHKIN. « NEGATIVE PARITY TETRAQUARKS WITH THE OPEN CHARM ». International Journal of Modern Physics E 20, no 10 (octobre 2011) : 2153–66. http://dx.doi.org/10.1142/s0218301311020204.

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The relativistic four-quark equations are found in the framework of coupled-channel formalism. The dynamical mixing of the meson–meson states with the four-quark states is considered. The four-quark amplitudes of the negative parity tetraquarks including the quarks of three flavors (u, d, s) and the charmed quark are constructed. The poles of these amplitudes determine the masses of tetraquarks. The mass values of low-lying tetraquarks with the spin-parity JP = 0-, 1-, 2-, 3- are calculated.
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23

Pasquini, B., et C. Lorcé. « Spin/Orbital Structure of the Nucleon from Wigner Distributions ». International Journal of Modern Physics : Conference Series 40 (janvier 2016) : 1660013. http://dx.doi.org/10.1142/s2010194516600132.

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We present results for the Wigner distributions of the nucleon, which provide multidimensional images of the quark distributions in the phase space and can be seen as the mother distributions of the standard generalized and transverse-momentum dependent parton distributions. We discuss the general features of these distributions within a light-front constituent quark model, emphasizing the new information that can be deduced about the spin-orbit correlations of the quarks in the nucleon.
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24

HASSANABADI, H., A. A. RAJABI et S. ZARRINKAMAR. « SPECTRUM OF BARYONS AND SPIN–ISOSPIN DEPENDENCE ». Modern Physics Letters A 23, no 07 (7 mars 2008) : 527–37. http://dx.doi.org/10.1142/s0217732308024237.

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The constituent quark model (CQM) has recently been widely used for the description of the internal structure of baryons. The baryon spectrum is usually well described, although various models are quite different. However, the study of baryon spectroscopy is not sufficient to distinguish among the various forms of quark dynamics. It would be interesting to consider the effect of an extra residual interaction among the quarks, which contains a dependence on isospin (or flavor). In the chiral constituent quark model the non-confining part of the potential is provided by the interaction with the Goldstone bosons, giving rise to a spin- and isospin-dependent part which is crucial for the description of the spectrum for energies lower than 1.7 GeV. In this work we have introduced an improved form of the hyperfine interaction and isospin dependent quark potential. The resulting description of the baryon spectrum was found to be satisfactory and we not only have included confinement potential at large separations, but also color charge and non-confining hyperfine interaction potentials. This combination of potentials yields spectra which are very close to the ones obtained in experiments.
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25

SHIBATA, T. A. « MEASUREMENTS WITH POLARIZED HADRONS ». International Journal of Modern Physics A 19, no 07 (20 mars 2004) : 1089–98. http://dx.doi.org/10.1142/s0217751x04018993.

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Recent progress in physics with polarized hadrons is described with the emphasis on the spin structure of the nucleon. The nucleon spin problem, which was discovered by EMC in 1988, is now being studied in various experiments. Flavor separation of the quark helicity distributions has been made. Recent observations of asymmetries in deeply virtual Compton scattering (DVCS) and exclusive meson productions provide possibilities to access the total angluar momentum carried by quarks in the framework of generalized parton distributions. Single spin azimuthal asymmetries observed in semi-inclusive measurements provide a new handle to determine the transverse quark distributions which are basic but have never been measured so far.
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26

Zhang, Renqiang, Wei Sun, Feiyu Chen, Ying Chen, Ming Gong, Xiangyu Jiang et Zhaofeng Liu. « Annihilation diagram contribution to charmonium masses * ». Chinese Physics C 46, no 4 (1 avril 2022) : 043102. http://dx.doi.org/10.1088/1674-1137/ac3d8c.

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Abstract In this work, we generate gauge configurations with dynamical charm quarks on anisotropic lattices. The mass shift of and charmonia due to the charm quark annihilation effect can be investigated directly in a manner of unitary theory. The distillation method is adopted to treat the charm quark annihilation diagrams at a very precise level. For charmonia, the charm quark annihilation effect barely changes the mass, but lifts the mass by approximately 3–4 MeV. For charmonia, this effect results in positive mass shifts of approximately 1 MeV for and , but decreases the mass by approximately 3 MeV. We did not obtain a reliable result for the mass shift of . In addition, we observed that the spin averaged mass of the spin-triplet charmonia is in good agreement with , as expected by the non-relativistic quark model and measured by experiments.
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27

RHO, MANNQUE. « MASSIVE-QUARK BARYONS AS SKYRMIONS ». Modern Physics Letters A 06, no 23 (30 juillet 1991) : 2087–100. http://dx.doi.org/10.1142/s0217732391002268.

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Massive-quark baryons containing one or more charm (c) or bottom (b) quarks are described as massive scalar doublet fields "wrapped" by the soliton of the light (up and down) flavors. The spin-isospin transmutation that takes place to make the trapped scalar behave like heavy-flavored quarks is analogous to what happens to a scalar doublet in the presence of a 't Hooft–Polyakov monopole. The Wess–Zumino term plays a pivotal role here. This model predicts spectra that resemble closely those of quark models. This feature is interpreted in terms of an induced gauge (or Berry) structure associated with "fast" and "slow" degrees of freedom corresponding, respectively, to the massive- and light-flavor quarks involved in the baryon structure.
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28

Dado, Tomas. « Top-quark properties and mass measurements with the ATLAS detector ». EPJ Web of Conferences 182 (2018) : 02033. http://dx.doi.org/10.1051/epjconf/201818202033.

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The top quark is unique among the known quarks in that it decays before it has an opportunity to form hadronic bound states. This makes measurements of its properties particularly interesting as one can access directly the properties of a bare quark. The latest measurements of these properties with the ATLAS detector at the LHC [1] are presented. Measurements of top-quark spin observables in top-antitop events, each sensitive to a different coefficient of the spin density matrix, are presented and compared to the Standard Model predictions. The helicity of the W boson from the top decays and the production angles of the top quark are further discussed. Limits on the rate of flavour changing neutral currents in the production or decay of the top quark are reported. The production of top-quark pairs in association with W and Z bosons is also presented. The measurement probes the coupling between the top quark and the Z boson. The cross-section measurement of photons produced in association with top-quark pairs is also discussed. These process are all compared to the best available theoretical calculations. The latest ATLAS measurements of the top-quark mass in lepton+jets, dilepton, and all-hadronic final states are also reported. In addition, measurements aiming to measure the mass in a well-defined scheme are presented.
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29

Novoa-Brunet, Martín. « Implications of Heavy Quark Spin Symmetry and NRQCD on Bc → J/ψ, ηc form factors ». EPJ Web of Conferences 270 (2022) : 00016. http://dx.doi.org/10.1051/epjconf/202227000016.

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We discuss the analysis of Bc → J/ψ, ηc form factors, based on the heavy quark spin symmetry and nonrelativistic QCD (NRQCD) performed in Ref. [1]. We perform an expansion on the inverse of the heavy quarks’ masses using power counting rules of NRQCD up to the next-to-leading order. This allows us to classify the heavy quark spin symmetry-breaking terms and express the form factors in terms of universal functions in a selected kinematical range. Using as input the lattice QCD results for the Bc → J/ψ matrix element of the SM operator, we obtain information on other form factors.
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30

Morimoto, Masatoshi, Yasuhiko Tsue, João da Providência, Constança Providência et Masatoshi Yamamura. « Spin polarizations under a pseudovector interaction between quarks with the Kobayashi–Maskawa–’t Hooft term in high density quark matter ». International Journal of Modern Physics E 29, no 01 (janvier 2020) : 2050003. http://dx.doi.org/10.1142/s0218301320500032.

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A possibility of a quark spin polarization originating from a pseudovector condensate is investigated in the three-flavor Nambu–Jona–Lasinio model with the Kobayashi–Maskawa–’t Hooft interaction which leads to flavor mixing. It is shown that a pseudovector condensate related to the strange quark easily occurs compared with pseudovector condensate related to light quarks. Further, it is shown that the pseudovector condensate related to the strange quark appears at a slightly small chemical potential by the effect of the flavor mixing due to the Kobayashi–Maskawa–’t Hooft interaction.
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31

Kostenko, Boris. « Quark-Parton Model and Relativistic Quantum Mechanics ». EPJ Web of Conferences 173 (2018) : 02012. http://dx.doi.org/10.1051/epjconf/201817302012.

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An attempt to treat the asymptotic freedom and the quark confinement as a self-consistent problem in the framework of relativistic quantum mechanics is realized. It is shown that the confinement of quarks induces a change of their helicities together with a simultaneous alteration of orbital momenta, so that the total angular momentum of each quark is conserved. This observation may cast light on the so-called proton spin puzzle after some additional numerical estimations.
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32

CELENZA, L. S., A. PANTZIRIS, C. M. SHAKIN et HUI-WEN WANG. « ROLE OF GLUONS IN THE DYNAMICAL ORIGIN OF THE PROTON SPIN ». International Journal of Modern Physics A 04, no 16 (10 octobre 1989) : 4279–94. http://dx.doi.org/10.1142/s0217751x89001783.

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We consider the relation of dressed (or constituent) quarks to bare quarks within a specific model. In this model the bare quark obtains a dynamical mass and is nonpropagating because of its interaction with a gluon condensate. Using this model, we show that a significant part of the spin of the nucleon may be carried by the gluon field. This result may aid in explaining the recent EMC (European Muon Collaboration) data which suggests that the bare quarks carry only a fraction of the proton spin.
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33

Weber, H. J., et K. Bodoor. « Baryon Spin and Magnetic Moments in Relativistic Chiral Quark Models ». International Journal of Modern Physics E 06, no 04 (décembre 1997) : 693–709. http://dx.doi.org/10.1142/s0218301397000330.

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The spin and flavor fractions of constituent quarks in the baryon octet are obtained from their lowest order chiral fluctuations involving Goldstone bosons. SU(3) breaking suggested by the mass difference between the strange and up, down quarks is included, as are relativistic effects by means of a light-cone quark model for the proton, and the gluon contribution from the axial anomaly in the singlet channel. Magnetic moments from the Karl-Sehgal formulas are analyzed in this framework as well.
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34

KIRYLUK, JOANNA. « SPIN PHYSICS WITH STAR ». International Journal of Modern Physics A 18, no 08 (30 mars 2003) : 1335–42. http://dx.doi.org/10.1142/s0217751x0301468x.

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The STAR collaboration aims to study polarized proton-proton collisions at RHIC. The emphasis of the spin run this year is on transverse single spin asymmetries. Beyond 2001, we aim to determine directly and precisely the gluon polarization, as well as the polarizations of the u, [Formula: see text], d and [Formula: see text] quarks in the proton by measuring in addition longitudinal and double spin asymmetries. Furthermore, we aim to measure for the first time the quark transversity distributions. These measurements will improve substantially the knowledge and understanding of the spin structure of the nucleon.
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35

EBERT, D., R. N. FAUSTOV et V. O. GALKIN. « MASSES OF LIGHT MESONS IN THE RELATIVISTIC QUARK MODEL ». Modern Physics Letters A 20, no 25 (20 août 2005) : 1887–93. http://dx.doi.org/10.1142/s021773230501813x.

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The masses of the S-wave mesons consisting of the light (u, d, s) quarks are calculated within the constituent quark model. The relativistic Schrödinger-like equation with a confining potential is numerically solved for the complete relativistic [Formula: see text] potential including both spin-independent and spin-dependent terms. The obtained masses of the ground state π, ρ, K, K* and ϕ mesons and their first radial excitations are in a reasonably good overall agreement with experimental data.
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36

BAUR, U., I. HINCHLIFFE et D. ZEPPENFELD. « EXCITED QUARK PRODUCTION AT HADRON COLLIDERS ». International Journal of Modern Physics A 02, no 04 (août 1987) : 1285–97. http://dx.doi.org/10.1142/s0217751x87000661.

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Composite models generally predict the existence of excited quark and lepton states. We consider the production and experimental signatures of excited quarks Q* of spin and isospin 1/2 at hadron colliders and estimate the background for those channels which are most promising for Q* identification. Multi-TeVpp-colliders will give access to such particles with masses up to several TeV.
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37

SALEHI, NASRIN, et ALI AKBAR RAJABI. « PROTON STATIC PROPERTIES BY USING HYPERCENTRAL CONSTITUENT QUARK MODEL AND ISOSPIN ». Modern Physics Letters A 24, no 32 (20 octobre 2009) : 2631–37. http://dx.doi.org/10.1142/s0217732309031016.

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The static properties of protons are useful for understanding the quark structure of the proton. In his work we have introduced the hypercentral constituent quark model and isospin dependent potentials. Here constituent quarks interact with each other via a potential in which we have taken into account the three-body force effect and the standard two-body potential contributions. According to our model the static properties of protons containing u and d quarks are better than the other models and closer to experimental results. The two key ingredients of this improvement are the effective quark–gluon hypercentral potentials, and hyperfine interaction and isospin dependence potential. Recently, Schrödinger equation has been solved by Giannini but we have solved the Dirac equation exact analytically and we have shown that a considerable improvement in the description of the static properties of proton is obtained with an isospin dependent potential and the complete interaction including spin and isospin terms reproduces the position of the quark.
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38

Wolf, C. « SU2 × SU2 Spin Flavor Subquark Model of Family Structure ». Zeitschrift für Naturforschung A 41, no 6 (1 juin 1986) : 791–95. http://dx.doi.org/10.1515/zna-1986-0605.

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A simple spin-flavor model for the substructure o f the 6 known quarks is proposed which is able to predict the correct Dirac magnetic moments if we interpret the quark masses as constituent masses. The addition of other degrees of freedom is proposed to facilitate the prediction of the correct mixing angles.
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39

Yin, He, Wang Fan et Chun Wa Wong. « Baryon-nucleon spin-orbit forces from symmetric quark-quark spin-orbit interactions ». Nuclear Physics A 451, no 4 (avril 1986) : 653–65. http://dx.doi.org/10.1016/0375-9474(86)90297-6.

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40

GOLOSKOKOV, S. V. « IS THE ANOMALOUS BEHAVIOR OF THE POMERON SPIN-FLIP PART POSSIBLE IN PERTURBATIVE QCD ? » Modern Physics Letters A 08, no 34 (10 novembre 1993) : 3255–61. http://dx.doi.org/10.1142/s021773239300218x.

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The pomeron spin-flip properties at small quark masses and momenta transfer in the [Formula: see text] order of perturbative QCD are analyzed. It is shown that the mass and the momentum-transfer singularities exist in the axial and mass terms of the gluon-ladder diagrams for quarks on the mass shell and they are absent in the total spin-flip amplitudes of qq and γq scattering.
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41

Liu, Keh-Fei. « Quark and Glue Components of the Proton Spin from Lattice Calculation ». International Journal of Modern Physics : Conference Series 40 (janvier 2016) : 1660005. http://dx.doi.org/10.1142/s2010194516600053.

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The status of lattice calculations of the quark spin, the quark orbital angular momentum, the glue angular momentum and glue spin in the nucleon is summarized. The quark spin calculation is recently carried out from the anomalous Ward identity with chiral fermions and is found to be small mainly due to the large negative anomaly term which is believed to be the source of the ‘proton spin crisis’. We also present the first calculation of the glue spin at finite nucleon momenta.
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42

Tsue, Yasuhiko, João da Providência, Constança Providência et Masatoshi Yamamura. « Quark spin polarization in high density quark matter ». EPJ Web of Conferences 66 (2014) : 04029. http://dx.doi.org/10.1051/epjconf/20146604029.

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43

MATSUMOTO, SEIJI, KENJI TOMINAGA, OSAMU TERAZAWA et MINORU BIYAJIMA. « HEAVY QUARK POLARIZATION AND ENERGY SPECTRA OF DECAY PRODUCTS IN SEMILEPTONIC DECAYS ». International Journal of Modern Physics A 08, no 06 (10 mars 1993) : 1153–79. http://dx.doi.org/10.1142/s0217751x93000473.

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We calculate in the free quark model energy distributions of final lepton and quark pairs from c and b quark semileptonic decays in e−e+ colliders. Polarizations and spin-spin correlations of heavy quark pair are discussed, which will test the vector and axial vector couplings of the Weinberg-Salam model especially near the Z peak.
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44

NODA, HUJIO, TSUTOMU TASHIRO et SHIN-ICHI NAKARIKI. « ANTI-HYPERON POLARIZATION IN pA AND Σ-A COLLISIONS AND INTRINSIC ANTIDIQUARK STATE IN INCIDENT BARYON ». International Journal of Modern Physics E 21, no 01 (janvier 2012) : 1250001. http://dx.doi.org/10.1142/s0218301312500012.

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We discuss the relation between the polarization of inclusively produced (anti)hyperons and the incident baryon states in the framework of the constituent quark–diquark cascade model. We assume that there is an intrinsic diquark–antidiquark state in the incident baryon, in which the intrinsic diquark immediately fragments into a non-leading baryon and the antidiquark behaves as a valence constituent. It is also assumed that the valence (anti)diquark in the incident nucleon tends to combine selectively with a spin-down sea quark and, on the other hand, the spin-up valence quark in the projectile is chosen by a sea (anti)diquark in preference to the spin-down valence quark. It is found that the incident spin-1/2 baryon is mainly composed of a spin-0 valence diquark and a valence quark, and contains an intrinsic diquark–antidiquark state with a probability of about 7%.
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45

RAJPOOT, S., et MARK A. SAMUEL. « FOUR PREON COMPOSITE QUARKS AND LEPTONS ». International Journal of Modern Physics A 02, no 04 (août 1987) : 1339–49. http://dx.doi.org/10.1142/s0217751x87000715.

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A model is presented in which quarks and leptons are composites of three spin-½ preons and a scalar preon. The model is an extension of the rishon model and consists of two spin-½ preons T, V and a scalar preon S as the fundamental building blocks of matter. Assuming distinguishability of states due to the order assigned to the preons in forming the quark and lepton states, the concepts of flavour, colour and generation number acquire meaning only at the level of compositeness. The model predicts four generations of conventional quarks and leptons.
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46

GERASYUTA, S. M., et E. E. MATSKEVICH. « DIBARYONS WITH TWO HEAVY QUARKS ». International Journal of Modern Physics E 21, no 06 (juin 2012) : 1250058. http://dx.doi.org/10.1142/s0218301312500589.

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The relativistic six-quark equations are constructed in the framework of the dispersion relation technique. The relativistic six-quark amplitudes of dibaryons including the light u, d and heavy c, b quarks are calculated. The approximate solutions of these equations using the method based on the extraction of leading singularities of the heavy hexaquark amplitudes are obtained. The poles of these amplitudes determine the masses of charmed and bottom dibaryons with the isospins I = 0, 1, 2 and the spin-parities JP = 0+, 1+, 2+.
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47

TASHIRO, TSUTOMU, HUJIO NODA, SHIN-ICHI NAKARIKI et KAZUMI FUKUMA. « HYPERON POLARIZATION IN QUARK-DIQUARK CASCADE MODEL ». International Journal of Modern Physics E 16, no 07n08 (août 2007) : 2344–49. http://dx.doi.org/10.1142/s021830130700791x.

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We relate the hyperon polarizations in proton-proton and proton-nucleus collisions to the leading particle effect and use the constituent quark-diquark cascade model with SU(6) wave function. We assume that the quantization axis is characterized by the production normal of the leading baryon of the most massive cascade chain and the incident valence diquark tends to pick up a spin down sea quark or conversely a sea diquark preferentially combines with the spin up incident valence quark to form a leading baryon as compared with the spin down valence quark.
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48

Xu, Qinghua. « Measurement of Longitudinal Single-Spin Asymmetry for W± Production in Polarized Proton+Proton Collisions at STAR ». Journal of Physics : Conference Series 1643, no 1 (1 décembre 2020) : 012197. http://dx.doi.org/10.1088/1742-6596/1643/1/012197.

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Abstract The contribution from the sea quark polarization to the nucleon spin is an important piece for the complete understanding of the nucleon spin structure. The production of W ± bosons in longitudinally polarized p+p collisions at the RHIC collider at Brookhaven National Laboratory provides a unique probe of the sea quark polarization, through the parity-violating single-spin asymmetry, AL . At the STAR experiment, the W bosons that decay through the W → ev channel at mid-rapidity (|η <1.3) can be effectively determined with the Electromagnetic Calorimeters and Time Projection Chamber. The STAR measurements of AL for W boson from datasets taken in 2011 and 2012 at s =510 GeV have been included in the global analysis of polarized parton distribution functions, and provided significant constraints on the helicity distribution functions of u ¯ and d ¯ quarks. The final AL results from 2013 STAR data sample are reported, which is about three times larger than the total integrated luminosity of previous years. The combined results of AL for 2011-2013 data are also given. A flavor asymmetry of light sea quark helicity distribution, Δ u ¯ ( x ) − Δ d ¯ ( x ) > 0 , is confirmed from a re-weighting of global analysis NNPDFpol1.1 after including the new AL results. In addition, results on the double-spin asymmetries ALL for W ±, and AL for Z/γ* production are also reported.
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49

FAESSLER, AMAND, A. BUCHMANN et Y. YAMAUCHI. « THE QUARK MODEL, DEUTERON FORM FACTORS AND NUCLEAR MAGNETIC MOMENTS ». International Journal of Modern Physics E 02, no 01 (mars 1993) : 39–185. http://dx.doi.org/10.1142/s0218301393000030.

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The study of the deuteron electromagnetic form factors based on the quark cluster model is reviewed. The deuteron wave function is derived from a microscopic quark Hamiltonian with the help of the Resonating Group Method. One-pion and one-gluon exchange potentials are included in addition to a quadratic confinement potential. The photon is coupled directly to the quarks. Aside from the one-body impulse current, pion and gluon exchange currents are included on the quark level. Due to the Pauli principle on the quark level, new electromagnetic currents arise which are not present on the nucleon level. These currents, called quark exchange currents, describe processes in which a photon couples to a quark or a pair of quarks interacting via gluon or pion exchange and which are accompanied by a simultaneous quark interchange between the two threequark clusters (nucleons). They are small for low momentum transfers but appreciably influence the electromagnetic structure of the deuteron beyond a momentum transfer of q=5 fm−1. The discussion is extended to the magnetic moments of 15N, 17O and 39K by introducing the quark exchange currents as effective operators on the nucleon level. The quark exchange currents written in terms of nonlocal and spin-isospin dependent nuclear operators are effective only at short distances. They are evaluated with shell-model (harmonic oscillator) wave functions including the (short-range) Brueckner correlations. The Bethe-Goldstone equation is solved with our effective NN potential, which is derived from a microscopic quark Hamiltonian. The quark exchange currents shift the isovector magnetic moment of 39K by −20% from its Schmidt value.
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Weigel, H., et J. P. Blanckenberg. « Heavy baryons with strangeness in soliton models ». International Journal of Modern Physics : Conference Series 39 (janvier 2015) : 1560088. http://dx.doi.org/10.1142/s2010194515600885.

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We present some recent results from soliton model calculations for the spectrum of baryons with a single heavy quark. The model comprises chiral symmetry for light flavors and (approximate) heavy spin–flavor symmetry for the heavy quarks. We focus on flavor symmetry breaking for strangeness degrees of freedom.
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