PaperPanorama
FAQ

Nuclear Theory·nucl-th

Monday·March 20, 2017

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 05

    [Submitted on 16 Mar 2017] (cross-list from hep-ph)

    Small- Asymptotics of the Quark Helicity Distribution: Analytic Results

    Yuri V. Kovchegov🇺🇸 · Daniel Pitonyak🇺🇸 · Matthew D. Sievert🇺🇸

    In this Letter, we analytically solve the evolution equations for the small- asymptotic behavior of the (flavor singlet) quark helicity distribution in the large- limit. These evolution equations form a set of coupled integro-differential equations, which previously could only be solved numerically. This approximate numerical solution, however, revealed simplifying properties of the small- asymptotics, which we exploit here to obtain an analytic solution. We find that the small- power-law tail of the quark helicity distribution scales as with , in excellent agreement with the numerical estimate obtained previously. We then verify this solution by cross-checking the predicted scaling behavior of the auxiliary "neighbor dipole amplitude" against the numerics, again finding excellent agreement.

    Comments:
    5 pages, 2 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1703.05809 [pdf]
    PLB(2017)·78 citations
  2. 06

    [Submitted on 17 Mar 2017] (cross-list from hep-ph)

    Yield ratios of identified hadrons in p+p, p+Pb, Pb+Pb collisions at the Large Hadron Collider

    Feng-lan Shao🇨🇳 · Guo-jing Wang🇨🇳 · Rui-qin Wang🇨🇳 · Hai-hong Li🇨🇳 · Jun Song🇨🇳

    Yield ratios of identified hadrons observed in high multiplicity p+p and p+Pb collisions at LHC show remarkable similarity with those in Pb+Pb collisions, indicating some important and universal underlying dynamics in hadron production for different quark gluon final states. We use the quark combination model to explain the data of yield ratios in these three collision systems. The observed and can be reproduced simultaneously by quark combination, and these two ratios reflect the rate of baryon production at hadronization which is the same in light sector and strange sector and is roughly constant in p+p, p+Pb and Pb+Pb collision systems over three orders of magnitude in charged particle multiplicity.The data of , , and show a hierarchy behavior relating to the strangeness content, and are naturally explained by quark combination both in the saturate stage at high multiplicity and in the increase stage at moderate multiplicity. Our results suggest that the dynamical characteristic of quark combination is necessary in describing the production of hadrons in small systems created in p+p and p+Pb collisions.

    Comments:
    8 pages, 2 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1703.05862 [pdf]
    PRC(2017)·18 citations
  3. 07

    [Submitted on 17 Mar 2017] (cross-list from hep-lat)

    A simple model for a scalar two-point correlator in the presence of a resonance

    Peter C. Bruns🇩🇪

    We present a simple toy model for a scalar-isoscalar two-point correlator, which can serve as a testing ground for the extraction of resonance parameters from Lattice QCD calculations. We discuss in detail how the model correlator behaves when it is restricted to a finite spatial volume, and how the finite-volume data can be used to reconstruct the spectral function of the correlator in the infinite volume, which allows to extract properties of the resonance from such data.

    Subjects:
    High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1703.05940 [pdf]
    1 citation
  4. 08

    [Submitted on 17 Mar 2017] (cross-list from hep-ph)

    Baryon number fluctuations in chiral effective models and their phenomenological implications

    Gabor Almasi🇩🇪 · Bengt Friman🇩🇪 · Krzysztof Redlich🇩🇪

    We study the critical properties of net-baryon-number fluctuations at the chiral restoration transition in a medium at finite temperature and net baryon density. The chiral dynamics of quantum chromodynamics (QCD) is modeled by the Polykov-loop extended Quark-Meson Lagrangian, that includes the coupling of quarks to vector meson and temporal gauge fields. The Functional Renormalization Group is employed to properly account for the criticality at the phase boundary. We focus on the properties and systematics of ratios of the net-baryon-number cumulants , for , near the phase boundary. The results are presented in the context of the recent experimental data of the STAR Collaboration on fluctuations of the net proton number in heavy ion collisions at RHIC. We show that the model results for the energy dependence of the cumulant ratios are in good overall agreement with the data, with one exception. At center-of-mass energies below , we find that the measured fourth-order cumulant deviates considerably from the model results, which incorporate the expected and criticality. We assess the influence of model assumptions and in particular of repulsive vector-interactions, which are used to modify the location of the critical endpoint in the model, on the cumulants ratios. Finally, we discuss a possibility to test to what extent the fluctuations are affected by nonequilibrium dynamics by comparing certain ratios of cumulants.

    Comments:
    15 pages, 13 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1703.05947 [pdf]
    PRD(2017)·63 citations
  5. 09

    [Submitted on 17 Mar 2017] (cross-list from hep-lat)

    The role of the Euclidean signature in lattice calculations of quasi-distributions and other non-local matrix elements

    Raúl A. Briceño🇺🇸 · Maxwell T. Hansen🇩🇪 · Christopher J. Monahan🇺🇸

    Lattice quantum chromodynamics (QCD) provides the only known systematic, nonperturbative method for first-principles calculations of nucleon structure. However, for quantities such as lightfront parton distribution functions (PDFs) and generalized parton distributions (GPDs), the restriction to Euclidean time prevents direct calculation of the desired observable. Recently, progress has been made in relating these quantities to matrix elements of spatially nonlocal, zero-time operators, referred to as quasidistributions. Even for these time-independent matrix elements, potential subtleties have been identified in the role of the Euclidean signature. In this work, we investigate the analytic behavior of spatially non-local correlation functions and demonstrate that the matrix elements obtained from Euclidean lattice QCD are identical to those obtained using the LSZ reduction formula in Minkowski space. After arguing the equivalence on general grounds, we also show that it holds in a perturbative calculation, where special care is needed to identify the lattice prediction. Finally we present a proof of the uniqueness of the matrix elements obtained from Minkowski and Euclidean correlation functions to all order in perturbation theory.

    Comments:
    14 pages, 5 figures. Version published in Phys. Rev. D
    Subjects:
    High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1703.06072 [pdf]
    PRD(2017)·61 citations

Affiliations

first authorsco-authorsvia INSPIRE