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Zeitschriftenartikel zum Thema „Quarks orbital angular momentum“

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Autor: Grafiati

Veröffentlicht am 5. Oktober 2024

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1

Momeni-Feili, Maryam, Firooz Arash, Fatemeh Taghavi-Shahri und Abolfazl Shahveh. „Contribution of orbital angular momentum to the nucleon spin“. International Journal of Modern Physics A 32, Nr. 06n07 (08.03.2017): 1750036. http://dx.doi.org/10.1142/s0217751x17500361.

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We have calculated the orbital angular momentum of quarks and gluons in the nucleon. The calculations are carried out in the next to leading order utilizing the so-called valon model. It is found that the average quark orbital angular momentum is positive, but small, and the average gluon orbital angular momentum is negative and large. We also report on some regularities about the total angular momentum of the quarks and the gluon, as well as on the orbital angular momentum of the separate partons. We have also provided partonic angular momentum, [Formula: see text] as a function of [Formula: see text].

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2

Mukherjee, Asmita, Sreeraj Nair und Vikash Kumar Ojha. „Wigner Distributions and Orbital Angular Momentum of Quarks“. International Journal of Modern Physics: Conference Series 37 (Januar 2015): 1560040. http://dx.doi.org/10.1142/s201019451560040x.

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We present a recent model calculation of the Wigner distributions for the quarks and the orbital angular momentum carried by the quarks. These Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs).

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3

SONG, XIAOTONG. „QUARK ORBITAL ANGULAR MOMENTUM IN THE BARYON“. International Journal of Modern Physics A 16, Nr. 22 (10.09.2001): 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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4

LORCÉ, CÉDRIC, und BARBARA PASQUINI. „WIGNER DISTRIBUTIONS AND QUARK ORBITAL ANGULAR MOMENTUM“. International Journal of Modern Physics: Conference Series 20 (Januar 2012): 84–91. http://dx.doi.org/10.1142/s2010194512009129.

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We discuss the quark phase-space or Wigner distributions of the nucleon which combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-front constituent quark model. We show how the quark orbital angular momentum can be extracted from the Wigner distributions and compare it with alternative definitions.

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5

BURKARDT, MATTHIAS. „GPDs AND TMDs“. International Journal of Modern Physics: Conference Series 20 (Januar 2012): 75–83. http://dx.doi.org/10.1142/s2010194512009117.

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For transversely polarized nucleons the distribution of quarks in the transverse plane is transversely shifted and that shift can be described in terms of Generalized Parton Distributions (GPDs). This observation provides a 'partonic' derivation of the Ji-relation for the quark angular momentum in terms of GPDs. Wigner distributions are used to show that the difference between the Jaffe-Manohar definiton of quark orbital angular momentum and that of Ji is equal to the change of orbital angular momentum due to the final state interactions as the struck quark leaves the target in a DIS experiment.

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6

Klein, Andi. „Measuring the Sea Quark Sivers Asymmetry: The E1039 Experiment at Fermilab“. International Journal of Modern Physics: Conference Series 37 (Januar 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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7

Mukherjee, Asmita, Sreeraj Nair und Vikash Kumar Ojha. „Wigner Distributions of Quark“. International Journal of Modern Physics: Conference Series 40 (Januar 2016): 1660055. http://dx.doi.org/10.1142/s2010194516600557.

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Wigner distribution functions are the quantum analogue of the classical phase space distribution and being quantum implies that they are not genuine phase space distribution and thus lack any probabilistic interpretation. Nevertheless, Wigner distributions are still interesting since they can be related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs) under some limit. We study the Wigner distribution of quarks and also the orbital angular momentum (OAM) of quarks in the dressed quark model.

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8

Liuti, Simonetta, Aurore Courtoy, Gary R. Goldstein, J. Osvaldo Gonzalez Hernandez und Abha Rajan. „Observables for Quarks and Gluons Orbital Angular Momentum Distributions“. International Journal of Modern Physics: Conference Series 37 (Januar 2015): 1560039. http://dx.doi.org/10.1142/s2010194515600393.

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We discuss the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term – Ji decomposition – or a canonical term – Jaffe-Manohar decomposition. Orbital angular momentum has been connected in each decomposition to a different observable, a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and a twist three Generalized Parton Distribution (GPD) for the kinetic term. While the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.

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9

DIEHL, M. „ON THE DISTRIBUTION OF PARTONS IN THE TRANSVERSE PLANE“. International Journal of Modern Physics A 21, Nr. 04 (10.02.2006): 938–41. http://dx.doi.org/10.1142/s0217751x06032368.

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Elastic nucleon form factors constrain the spatial distribution of quarks in the impact parameter plane. A recent analysis found that the average impact parameter of quarks strongly depends on their longitudinal momentum, and obtained an estimate of the orbital angular momentum carried by valence quarks in the proton.

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10

THOMAS, ANTHONY W. „SPIN AND ORBITAL ANGULAR MOMENTUM IN THE PROTON“. International Journal of Modern Physics E 18, Nr. 05n06 (Juni 2009): 1116–34. http://dx.doi.org/10.1142/s0218301309013403.

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Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of the problem, showing that not only have strong upper limits have been placed on the amount of polarized glue in the proton but that the experimental determination of the spin content has become much more precise. It is now clear that the origin of the discrepancy between experiment and the naive expectation of the fraction of spin carried by the quarks and anti-quarks in the proton lies in the non-perturbative structure of the proton. We explain how the features expected in a modern, relativistic and chirally symmetric description of nucleon structure naturally explain the current data. The consequences of this explanation for the presence of orbital angular momentum on quarks and gluons is reviewed and comparison made with recent results from lattice QCD and experimental data.

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11

Lorcé, Cédric. „Quark Spin-Orbit Correlations“. International Journal of Modern Physics: Conference Series 37 (Januar 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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12

Burkardt, Matthias. „Quark Orbital Angular Momentum“. EPJ Web of Conferences 85 (2015): 02009. http://dx.doi.org/10.1051/epjconf/20158502009.

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13

Burkardt, Matthias. „Quark Orbital Angular Momentum“. Few-Body Systems 57, Nr. 6 (10.03.2016): 385–89. http://dx.doi.org/10.1007/s00601-016-1064-6.

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14

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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15

Weng, Zi-Hua. „Spin angular momentum of proton spin puzzle in complex octonion spaces“. International Journal of Geometric Methods in Modern Physics 14, Nr. 07 (16.03.2017): 1750102. http://dx.doi.org/10.1142/s021988781750102x.

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The paper focuses on considering some special precessional motions as the spin motions, separating the octonion angular momentum of a proton into six components, elucidating the proton angular momentum in the proton spin puzzle, especially the proton spin, decomposition, quarks and gluons, and polarization and so forth. Maxwell was the first to use the quaternions to study the electromagnetic fields. Subsequently the complex octonions are utilized to depict the electromagnetic field, gravitational field, and quantum mechanics and so forth. In the complex octonion space, the precessional equilibrium equation infers the angular velocity of precession. The external electromagnetic strength may induce a new precessional motion, generating a new term of angular momentum, even if the orbital angular momentum is zero. This new term of angular momentum can be regarded as the spin angular momentum, and its angular velocity of precession is different from the angular velocity of revolution. The study reveals that the angular momentum of the proton must be separated into more components than ever before. In the proton spin puzzle, the orbital angular momentum and magnetic dipole moment are independent of each other, and they should be measured and calculated respectively.

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16

SINGLETON, D. „GLUEBALL SPIN“. Modern Physics Letters A 16, Nr. 01 (10.01.2001): 41–51. http://dx.doi.org/10.1142/s0217732301002845.

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The spin of a glueball is usually taken as coming from the spin (and possibly the orbital angular momentum) of its constituent gluons. In light of the difficulties in accounting for the spin of the proton from its constituent quarks, the spin of glueballs is re-examined. The starting point is the fundamental QCD field angular momentum operator written in terms of the chromoelectric and chromomagnetic fields. First, we look at the possible restrictions placed on the structure of glueballs from the requirement that the QCD field angular momentum operator should satisfy the standard commutation relationships. This analysis can be compared to the electromagnetic charge/monopole system, where the requirement that the total field angular momentum obey the angular momentum commutation relationships places restrictions (i.e. the Dirac condition) on the system. Second, we look at the expectation value of the field angular momentum operator under some simplifying assumptions.

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17

Wakamatsu, Masashi. „Is gauge-invariant complete decomposition of the nucleon spin possible?“ International Journal of Modern Physics A 29, Nr. 09 (08.04.2014): 1430012. http://dx.doi.org/10.1142/s0217751x14300129.

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Is gauge-invariant complete decomposition of the nucleon spin possible? Although it is a difficult theoretical question which has not reached a complete consensus yet, a general agreement now is that there are at least two physically inequivalent gauge-invariant decompositions (I) and (II) of the nucleon. In these two decompositions, the intrinsic spin parts of quarks and gluons are just common. What discriminate these two decompositions are the orbital angular momentum parts. The orbital angular momenta of quarks and gluons appearing in the decomposition (I) are the so-called "mechanical" orbital angular momenta, while those appearing in the decomposition (II) are the generalized (gauge-invariant) "canonical" ones. By this reason, these decompositions are also called the "mechanical" and "canonical" decompositions of the nucleon spin, respectively. A crucially important question is which decomposition is more favorable from the observational viewpoint. The main objective of this concise review is to try to answer this question with careful consideration of recent intensive researches on this problem.

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18

BURKARDT, MATTHIAS. „QUARK ORBITAL ANGULAR MOMENTUM AND FINAL STATE INTERACTIONS“. International Journal of Modern Physics: Conference Series 25 (Januar 2014): 1460029. http://dx.doi.org/10.1142/s2010194514600295.

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Definitions of orbital angular momentum based on Wigner distributions are used to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. The difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.

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19

Burkardt, Matthias. „Quark Orbital Angular Momentum and Final State Interactions“. International Journal of Modern Physics: Conference Series 37 (Januar 2015): 1560035. http://dx.doi.org/10.1142/s2010194515600356.

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Definitions of orbital angular momentum based on Wigner distributions are used to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. The difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.

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20

Hatta, Yoshitaka. „Notes on the orbital angular momentum of quarks in the nucleon“. Physics Letters B 708, Nr. 1-2 (Februar 2012): 186–90. http://dx.doi.org/10.1016/j.physletb.2012.01.024.

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21

Liuti, S., A. Courtoy, G. R. Goldstein, J. O. Gonzalez Hernandez und A. Rajan. „Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions“. Few-Body Systems 56, Nr. 6-9 (21.05.2015): 325–30. http://dx.doi.org/10.1007/s00601-015-0950-7.

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22

Mukherjee, Asmita, Sreeraj Nair und Vikash Kumar Ojha. „Wigner Functions and Quark Orbital Angular Momentum“. EPJ Web of Conferences 85 (2015): 02011. http://dx.doi.org/10.1051/epjconf/20158502011.

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23

BENITEZ, J. „CHARM SPECTROSCOPY FROM B FACTORIES“. International Journal of Modern Physics: Conference Series 02 (Januar 2011): 158–62. http://dx.doi.org/10.1142/s2010194511000730.

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A brief review of the excited Ds and D mesons is presented. A precision measurement of the Ds1(2536) mass and width parameters is reported by BABAR. Finally, a recent BABAR study of the Dπ and D*π final states shows first observations of the radial excitations of the D0, D*0, and D*+, as well as the L = 2 excited states of the D0 and D+, where L is the orbital angular momentum of the quarks.

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24

JI, XIANGDONG. „QUARK ORBITAL ANGULAR MOMENTUM AND GENERALIZED PARTON DISTRIBUTIONS“. International Journal of Modern Physics A 18, Nr. 08 (30.03.2003): 1303–9. http://dx.doi.org/10.1142/s0217751x03014642.

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25

Hobart, Adam. „Deeply Virtual Compton Scattering with CLAS12 at Jefferson Lab“. EPJ Web of Conferences 290 (2023): 06001. http://dx.doi.org/10.1051/epjconf/202329006001.

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A key step toward a better understanding of the nucleon structure is the study of Generalized Parton Distributions (GPDs). GPDs are the object of an intense effort of research since they convey an image of the nucleon structure where the longitudinal momentum and the transverse spatial position of the partons inside the nucleon are correlated. Moreover, GPDs give access, via Ji’s sum rule, to the contribution of the orbital angular momentum of the quarks to the nucleon spin, which is important to the understanding of the origins of the nucleon spin. Deeply Virtual Compton scattering (DVCS), the electroproduction of a real photon off the nucleon at the quark level, is the golden process directly interpretable in terms of GPDs of the nucleon. The GPDs are accessed in DVCS mainly through the measurements of single- or double- spin asymmetries. Combining measurements of asymmetries from DVCS experiments on both the neutron and the proton will allow us to perform the flavor separation of the u and d quarks GPDs via linear combinations of proton and neutron GPDs. This paper introduces recent DVCS measurements from the CLAS12 experiment at Jefferson Lab with the upgraded 11 GeV polarized electron beam. Details on the data analysis along with results on Beam Spin Asymmetries are presented.

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26

Scopetta, Sergio, und Vicente Vento. „A quark model analysis of orbital angular momentum“. Physics Letters B 460, Nr. 1-2 (August 1999): 8–16. http://dx.doi.org/10.1016/s0370-2693(99)00768-6.

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27

Lorcé, C., und B. Pasquini. „The pretzelosity TMD and quark orbital angular momentum“. Physics Letters B 710, Nr. 3 (April 2012): 486–88. http://dx.doi.org/10.1016/j.physletb.2012.03.025.

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28

Liu, Keh-Fei. „Quark and Glue Components of the Proton Spin from Lattice Calculation“. International Journal of Modern Physics: Conference Series 40 (Januar 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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29

LIUTI, SIMONETTA, ABHA RAJAN, AURORE COURTOY, GARY R. GOLDSTEIN und J. OSVALDO GONZALEZ HERNANDEZ. „PARTONIC PICTURE OF GTMDS“. International Journal of Modern Physics: Conference Series 25 (Januar 2014): 1460009. http://dx.doi.org/10.1142/s201019451460009x.

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We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions — the generalized transverse momentum distributions — that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon, can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that twist three contributions to deeply virtual Compton scattering provide observables related to orbital angular momentum.

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30

Hägler, Ph, A. Mukherjee und A. Schäfer. „Quark orbital angular momentum in the Wandzura–Wilczek approximation“. Physics Letters B 582, Nr. 1-2 (Februar 2004): 55–63. http://dx.doi.org/10.1016/j.physletb.2003.11.076.

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31

Lorcé, Cédric, und Keh-Fei Liu. „Quark and Gluon Orbital Angular Momentum: Where Are We?“ Few-Body Systems 57, Nr. 6 (08.02.2016): 379–84. http://dx.doi.org/10.1007/s00601-016-1043-y.

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32

Hatta, Yoshitaka, und Xiaojun Yao. „QCD evolution of the orbital angular momentum of quarks and gluons: Genuine twist-three part“. Physics Letters B 798 (November 2019): 134941. http://dx.doi.org/10.1016/j.physletb.2019.134941.

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33

Courtoy, Aurore, Gary R. Goldstein, J. Osvaldo Gonzalez Hernandez, Simonetta Liuti und Abha Rajan. „On the observability of the quark orbital angular momentum distribution“. Physics Letters B 731 (April 2014): 141–47. http://dx.doi.org/10.1016/j.physletb.2014.02.017.

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34

Bashinsky, S. V., und R. L. Jaffe. „Quark and gluon orbital angular momentum and spin in hard processes“. Nuclear Physics B 536, Nr. 1-2 (Dezember 1998): 303–17. http://dx.doi.org/10.1016/s0550-3213(98)00559-8.

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35

Pisano, Silvia. „Precise Measurements of DVCS at JLab and Quark Orbital Angular Momentum“. Few-Body Systems 57, Nr. 8 (06.06.2016): 633–38. http://dx.doi.org/10.1007/s00601-016-1120-2.

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36

Jain, Pankaj, und John P. Ralston. „The proton electromagnetic form factorF 2 and quark orbital angular momentum“. Pramana 61, Nr. 5 (November 2003): 987–92. http://dx.doi.org/10.1007/bf02704468.

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37

Zavada, Petr. „On the role of quark orbital angular momentum in the proton spin“. EPJ Web of Conferences 85 (2015): 02031. http://dx.doi.org/10.1051/epjconf/20158502031.

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38

Wang, Fan, W. M. Sun, X. S. Chen und P. M. Zhang. „Gauge invariance, canonical quantization and Poincaré covariance in nucleon structure“. International Journal of Modern Physics: Conference Series 29 (Januar 2014): 1460249. http://dx.doi.org/10.1142/s201019451460249x.

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There are different quark and gluon momentum, spin and orbital angular momentum operators used in the study of nucleon structure. We analyze the physical contents of these operators and propose a new set of operators based on gauge invariance principle, canonical quantization rule and Poincaré covariance. Atomic structure is a simpler testing ground of these operators and has been analyzed together. These new operators are the gauge invariant version of the gauge non-invariant canonical version used in physics since the establishment of quantum mechanics and reduce to the familiar canonical ones in Coulomb gauge.

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39

Fries, Rainer J., Jacob Purcell, Michael Kordell und Che-Ming Ko. „Excited hadron channels in hadronization“. EPJ Web of Conferences 296 (2024): 13006. http://dx.doi.org/10.1051/epjconf/202429613006.

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The proper treatment of hadronic resonances plays an important role for many aspects of heavy ion collisions. We expect this to be the case also for hadronization, due to the large degeneracies of excited states, and the abundant production of hadrons from their decays. We show how a comprehensive treatment of excited meson states can be incorporated into quark recombination, and in extension, into Hybrid Hadronization. We discuss in detail the quantum mechanics of forming excited states, utilizing the Wigner distribution functions of angular momentum eigenstates of isotropic 3-D harmonic oscillators. We describe how resonance decays can be handled, based on a set of minimal assumptions, by creating an extension of hadron decays in PYTHIA 8. Finally, we present a study of hadron production by jets using PYTHIA and Hybrid Hadronization with excited mesons up to orbital angular momentum L = 4. We find that states up to L = 2 are produced profusely by quark recombination.

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40

AVILA, M. A. „SOLUTIONS OF A DIRAC HYDROGENLIKE MESON AND SCALAR CONFINEMENT AT LOW ORBITAL ANGULAR MOMENTUM STATES“. International Journal of Modern Physics A 14, Nr. 11 (30.04.1999): 1703–10. http://dx.doi.org/10.1142/s0217751x99000853.

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Wave functions of a heavy-light quark [Formula: see text] system described by a covariant Dirac Hamiltonian are analyzed. By assuming that the confinement potential is a Lorentz scalar (S), the slope of the Isgur–Wise function is calculated at zero recoil point. The result obtained is ξ′(1)= -0.93± 0.05. This means that the solutions are perfectly consistent. If relativistic corrections in the light quark wave functions are included the result is ξ′(1)=-1.01± 0.04. From heavy-light data this suggests that if relativistic effects are considered, scalar confinement is reliable in low orbital angular momentum states.

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41

Liu, Keh-Fei. „Baryons and chiral symmetry“. International Journal of Modern Physics E 26, Nr. 01n02 (Januar 2017): 1740016. http://dx.doi.org/10.1142/s021830131740016x.

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The relevance of chiral symmetry in baryons is highlighted in three examples in the nucleon spectroscopy and structure. The first one is the importance of chiral dynamics in understanding the Roper resonance. The second one is the role of chiral symmetry in the lattice calculation of [Formula: see text] term and strangeness. The third one is the role of chiral [Formula: see text] anomaly in the anomalous Ward identity in evaluating the quark spin and the quark orbital angular momentum. Finally, the chiral effective theory for baryons is discussed.

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42

MIRJALILI, ABOLFAZL, KIANOOSH KESHAVARZIAN und MOHAMMAD MEHDI YAZDANPANAH. „FLAVOR AND SPIN DEPENDENT STRUCTURE OF THE NUCLEON AND MESON“. International Journal of Modern Physics A 27, Nr. 01 (10.01.2012): 1250003. http://dx.doi.org/10.1142/s0217751x12500030.

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We employ the polarized chiral constituent quarks to extract the polarized structure function of the nucleon. The polarized valon model is used to calculate the spin dependence of parton distribution functions of meson. The connection between the polarized structure of the proton and the Goldstone bosons, using the chiral quark model (χQM) is analyzed and the spin dependence of the parton distribution functions for pion and kaon, is obtained thoroughly. These functions are evolved to high Q2 values, using the singlet, nonsinglet and quark–gluon moments (ΔMS, ΔMNS, ΔMgq) which are convoluted with the polarized valon distributions. The polarized valon distributions for meson are computed, based on a phenomenological method and a comparison between polarized and unpolarized parton distribution functions for pion and kaon are performed. As a consequence of the χQM, the SU (3)f symmetry breaking for the spin dependent of the nucleon sea distributions is achieved. The required polarized parton distributions of the proton will be obtained from the parton distribution functions of the polarized meson via the related convolution integral which are existed in the χQM. Following that the analytical result for the proton's spin structure function, [Formula: see text], is obtained and compared with experimental data. Finally, the parton orbital angular momentum of meson are introduced and the total spin of the meson, based on this quantity and the first moment of distributions for gluon and singlet sectors, are obtained.

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Jia, Duojie, Cheng-Qun Pang und Atsushi Hosaka. „Mass formula for light nonstrange mesons and Regge trajectories in quark model“. International Journal of Modern Physics A 32, Nr. 25 (10.09.2017): 1750153. http://dx.doi.org/10.1142/s0217751x17501536.

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We study the Regge-like spectra of light mesons in a relativized quark model. An analytical mass formula is presented for the light unflavored mesons with the help of auxiliary field method, by which a quasi-linear Regge–Chew–Frautschi plot is predicted for the orbitally excited states. We show that the trajectory slope is proportional to the inverse of the confining parameter [Formula: see text] when the orbital angular momentum [Formula: see text] is large. The result is tested against the experimental data of the spectra of the meson families [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] in the [Formula: see text] planes, with the fitted parameters consistent with that in the literatures.

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Stumpf, H. „Electroweak Bosons, Leptons and Han-Nambu Quarks in a Unified Spinor-Isospinor Preon Field Model“. Zeitschrift für Naturforschung A 41, Nr. 12 (01.12.1986): 1399–411. http://dx.doi.org/10.1515/zna-1986-1208.

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The model is defined by a selfregularizing nonlinear spinor-isospinor preon field equation and all observable (elementary and non-elementary) particles are assumed to be bound states o f the quantized preon field. In a series o f preceding papers this model was extensively studied. In particular for com posite electroweak bosons the Yang-Mills dynamics was derived as the effective dynamics o f these bosons. In this paper the first generation o f com posite leptons and com posite Han-Nam bu quarks is introduced and together with electroweak bosons, these particles are interpreted as “shell model” states o f the underlying preon field. The choice o f the shell model states is justified by deriving the effective fermion-boson coupling and demonstrating its equivalence with the phenom enological electroweak coupling terms o f the Weinberg-Salam model. The investigation is restricted to the left-handed parts o f the composite fermions. Color is revealed to be a hidden orbital angular momentum in the shell model and hypercharge follows from the effective coupling. The techniques o f deriving effective interactions is a “weak mapping” procedure and the calculations are done in the “low” energy limit.

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JAFFE, ROBERT L. „OPEN QUESTIONS IN HIGH ENERGY SPIN PHYSICS“. International Journal of Modern Physics A 18, Nr. 08 (30.03.2003): 1141–52. http://dx.doi.org/10.1142/s0217751x03014459.

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I describe a few of the most exciting open questions in high energy spin physics. After a brief look at (g - 2)μ and the muon electric dipole moment, I concentrate on QCD spin physics. Pressing questions include the interpretation of new asymmetries seen in semi-inclusive DIS, measuring the polarized gluon and quark transversity distributions in the nucleon, testing the DHGHY Sum Rule, measuring the orbital angular momentum in the nucleon, and many others which go beyond the space and time allotted for this talk.

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Zhu, Wei, und Jianhong Ruan. „Nucleon spin structure“. International Journal of Modern Physics E 24, Nr. 10 (Oktober 2015): 1550077. http://dx.doi.org/10.1142/s0218301315500779.

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This paper contains three parts relating to the nucleon spin structure in a simple picture of the nucleon: (i) The polarized gluon distribution in the proton is dynamically predicted starting from a low scale by using a nonlinear quantum chromodynamics (QCD) evolution equation — the Dokshitzer–Gribov–Lipatov–Altarelli–Paris (DGLAP) equation with the parton recombination corrections, where the nucleon is almost consisted only of valence quarks. We find that the contribution of the gluon polarization to the nucleon spin structure is much larger than the predictions of most other theories. This result suggests that a significant orbital angular momentum of the gluons is required to balance the gluon spin momentum. (ii) The spin structure function [Formula: see text] of the proton is studied, where the perturbative evolution of parton distributions and nonperturbative vector meson dominance (VMD) model are used. We predict [Formula: see text] asymptotic behavior at small x from lower Q2to higher Q2. The results are compatible with the data including the early HERA estimations and COMPASS new results. (iii) The generalized Gerasimov–Drell–Hearn (GDH) sum rule is understood based on the polarized parton distributions of the proton with the higher twist contributions. A simple parameterized formula is proposed to clearly present the contributions of different components in the proton to [Formula: see text]. The results suggest a possible extended objects with size 0.2–0.3 fm inside the proton.

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MIRJALILI, A., S. ATASHBAR TEHRANI und ALI N. KHORRAMIAN. „THE ROLE OF POLARIZED VALONS IN THE FLAVOR SYMMETRY BREAKING OF NUCLEON SEA“. International Journal of Modern Physics A 21, Nr. 22 (10.09.2006): 4599–615. http://dx.doi.org/10.1142/s0217751x06031107.

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Next-to-leading order approximation of the quark helicity distributions are used in the framework of polarized valon model. The flavor-asymmetry in the light-quark sea of the nucleon can be obtained from the contributions of unbroken sea quark distributions. We employ the polarized valon model and extract the flavor-broken light sea distributions which are modeled with the help of a Pauli-blocking ansatz. Using this ansatz, we can obtain broken polarized valon distributions. From there and by employing convolution integral, broken sea quark distributions are obtainable in this framework. Our results for δu, δd, [Formula: see text] and [Formula: see text] are in good agreement with recent experimental data for polarized parton distribution from HERMES experimental group and also with GRSV model. Some information on orbital angular momentum as a main ingredient of total nucleon spin are given. The Q2 evolution of this quantity, using the polarized valon model is investigated.

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AVILA, M. A. „ORBITAL RADIUS OF A HYDROGEN-LIKE MESON IN S-, P- AND D-STATES“. Modern Physics Letters A 14, Nr. 30 (28.09.1999): 2059–72. http://dx.doi.org/10.1142/s0217732399002121.

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Radial probability density function of a heavy quark–light quark [Formula: see text] system in the states S, P and D, is studied numerically. It is found that the maximum of this function at r=a0 and the light quark energy (Eq) are related through [Formula: see text], where l is the orbital angular momentum, Z=0.446/ξ, and ξ is the strength of the color Coulomb potential. Phenomenology predicts that to difference of the hydrogen atom of QED, the "color atomic number" is such that Z≤1. This can be thought of as due to an anti-screening effect from the gluons. The respective expectation value for the radial coordinate in these states is found to be [Formula: see text] These results are valid for ξ in the range 0.446<ξ<0.646 and a light quark mass in the range 0<m<300 MeV. The above relations coincide with the maximum value of the slope of the Isgur–Wise at zero recoil point in the following way [Formula: see text] The relations found in the present work imply that [Formula: see text], from which we argue that the value of ξ′(1) is very sensitive to the color Coulomb-like interaction U=-ξ/r.

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Scopetta, Sergio, und Vicente Vento. „Erratum to: “A quark model analysis of orbital angular momentum” [Phys. Lett. B 460 (1999) 8–16]“. Physics Letters B 474, Nr. 1-2 (Februar 2000): 235–36. http://dx.doi.org/10.1016/s0370-2693(00)00020-4.

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50

THOMAS, ANTHONY W., ANDREW CASEY und HRAYR H. MATEVOSYAN. „WHAT WE KNOW AND DON'T KNOW ABOUT THE ORIGIN OF THE SPIN OF THE PROTON“. International Journal of Modern Physics A 25, Nr. 22 (10.09.2010): 4149–62. http://dx.doi.org/10.1142/s0217751x10050470.

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The origin of the spin of the proton is one of the most fundamental questions in modern hadron physics. Although tremendous progress has been made since the discovery of the "spin crisis" brought the issue to the fore, much remains to be understood. We carefully review what is known and, especially in the case of lattice QCD, what is not known. We also explain the importance of QCD inspired models in providing a physical picture of proton structure and the connection between those models and what is measured experimentally and on the lattice. We specifically apply these ideas to the issue of quark orbital angular momentum in the proton. We show that the Myhrer–Thomas resolution of the proton spin crisis is remarkably consistent with modern information from lattice QCD.

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