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Nuclear Theory·nucl-th

Wednesday·July 1, 2015

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 05

    [Submitted on 29 Jun 2015] (cross-list from hep-ph)

    Orbital Angular Momentum and Generalized Transverse Momentum Distribution

    Yong Zhao🇺🇸 · Keh-Fei Liu🇺🇸 · Yibo Yang🇺🇸

    We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of X. S. Chen et al. are the same as those derived from generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally, and discuss the strategies of calculating them in lattice QCD.

    Comments:
    8 pages
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1506.08832 [pdf]
    PRD(2016)·20 citations
  2. 06

    [Submitted on 30 Jun 2015] (cross-list from hep-ph)

    Multihadron production dynamics exploring the energy balance in hadronic and nuclear collisions

    Edward K.G. Sarkisyan🇨🇭 · Aditya Nath Mishra🇮🇳 · Raghunath Sahoo🇮🇳 · Alexander S. Sakharov🇨🇭

    The multihadron production in nucleus-nucleus collisions and its interrelation with that in (anti)proton-proton interactions are studied by exploring the charged particle mean multiplicity collision-energy and centrality dependencies in the measurements to date. The study is performed in the framework of the recently proposed effective-energy approach which, under the proper scaling of the collision energy, combines the constituent quark picture with Landau relativistic hydrodynamics counting for the centrality-defined effective energy of participants and relating different types of collisions. Within this approach, the multiplicity energy dependence and the pseudorapidity spectra from the most central nuclear collisions are well reproduced. The study of the multiplicity centrality dependence reveals a new scaling between the measured pseudorapidity spectra and the calculations. By means of this scaling, called the energy balanced limiting fragmentation scaling, one reproduces the pseudorapidity spectra for all centralities. The scaling elucidates some differences in the multiplicity and midrapidity density centrality dependence obtained at RHIC and LHC. These findings reveal an inherent similarity in the multiplicity energy dependence from the most central collisions and centrality data. A new regime in heavy-ion collisions to occur at about a TeV energy is indicated, similar to that observed in the earlier studies of the midrapidity densities. Predictions are made for the mean multiplicities to be measured in proton-proton and heavy-ion collisions at the LHC.

    Comments:
    14 pages, 9 figures, Version similar to the published version in Phys. Rev. D, Fig. 1 caption has gone through minor changes
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1506.09080 [pdf]
    PRD(2016)·71 citations
  3. 07

    [Submitted on 30 Jun 2015] (cross-list from hep-ph)

    Thermal photon emission from the pi-rho-omega system

    Nathan P. M. Holt🇺🇸 · Paul M. Hohler🇺🇸 · Ralf Rapp🇺🇸

    We investigate thermal photon emission rates in hot hadronic matter from a system consisting of pi, rho, and omega mesons. The rates are calculated using both relativistic kinetic theory with Born diagrams as well as thermal field theory at the two-loop level. This enables us to cross-check our calculations and to manage a pole contribution that arises in the Born approximation corresponding to the omega -> pi^0 gamma radiative decay. After implementing hadronic form factors to account for finite-size corrections, we find that the resulting photo-emission rates are comparable to existing results from pi rho -> pi gamma processes in the energy regime of 1-3 GeV. We expect that our new sources will provide a non-negligible contribution to the total hadronic rates, thereby enhancing calculated thermal photon spectra from heavy-ion collisions, which could improve the description of current direct-photon data from experiment.

    Comments:
    14 pages, 16 figures, published in Nuclear Physics A
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1506.09205 [pdf]
    NPA(2016)·42 citations

Affiliations

first authorsco-authorsvia INSPIRE