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Nuclear Theory·nucl-th

Wednesday·July 1, 2015

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    [Submitted on 30 Jun 2015]

    Spectra and Scattering of Light Lattice Nuclei from Effective Field Theory

    Johannes Kirscher🇮🇱 · Nir Barnea🇮🇱 · Doron Gazit🇮🇱 · Francesco Pederiva🇮🇹 · Ubirajara van Kolck🇫🇷

    An effective field theory is used to describe light nuclei, calculated from quantum chromodynamics on a lattice at unphysically large pion masses. The theory is calibrated at leading order to two available data sets on two- and three-body nuclei for two pion masses. At those pion masses we predict the quartet and doublet neutron-deuteron scattering lengths, and the alpha-particle binding energy. For MeV we obtain, respectively, fm, fm, and MeV, while for MeV fm, fm, and MeV are found. Phillips- and Tjon-like correlations to the triton binding energy are established. Higher-order effects on the respective correlation bands are found insensitive to the pion mass. As a benchmark, we present results for the physical pion mass, using experimental two-body scattering lengths and the triton binding energy as input. Hints of subtle changes in the structure of the triton and alpha particle are discussed.

    Comments:
    19 pages, 8 figures, 4 tables, submitted to PRC
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
    arXiv:
    1506.09048 [pdf]
    PRC(2015)·55 citations
  2. 02

    [Submitted on 30 Jun 2015]

    Symmetry energy systematics and its high density behavior

    Lie-Wen Chen🇨🇳

    We explore the systematics of the density dependence of nuclear matter symmetry energy in the ambit of microscopic calculations with various energy density functionals, and find that the symmetry energy from subsaturation density to supra-saturation density can be well determined by three characteristic parameters of the symmetry energy at saturation density , i.e., the magnitude , the density slope and the density curvature . This finding opens a new window to constrain the supra-saturation density behavior of the symmetry energy from its (sub-)saturation density behavior. In particular, we obtain MeV and MeV as well as MeV and MeV based on the present knowledge of MeV, MeV and MeV at fm extracted from nuclear mass and the neutron skin thickness of Sn isotopes. Our results indicate that the symmetry energy cannot be stiffer than a linear density dependence.In addition, we also discuss the quark matter symmetry energy since the deconfined quarks could be the right degree of freedom in dense matter at high baryon densities.

    Comments:
    10 pages, 5 figures. Contribution to International Workshop on Multi facets of Eos and Clustering (IWM-EC 2014), May 6-9, 2014, Catania, Italy
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
    arXiv:
    1506.09057 [pdf]
    EPJ Web Conf.(2015)·32 citations
  3. 03

    [Submitted on 30 Jun 2015]

    Electromagnetic multipoles - theory issues

    M.M. Giannini🇮🇹

    Some predictions of the Hypercentral Constituent Quark Model for the helicity amplitudes are discussed and compared with data and with the recent analysis of the Mainz group; the role of the pion cloud contribution in explaining the major part of the missing strength at low is emphasized.

    Comments:
    Physics of excited nucleons (J.-P. Bocquet, V. Kuznetsov, D. Rebreyend eds.), World Scientific, Singapore 2004, 377-381 BRAG Meeting, Grenoble 23 March 2004
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1506.09188 [pdf]
    0 citations
  4. 04

    [Submitted on 30 Jun 2015]

    Nuclear Energy Density Functionals: What do we really know?

    Aurel Bulgac · Michael McNeil Forbes · Shi Jin

    We present the simplest nuclear energy density functional (NEDF) to date, determined by only 4 significant phenomenological parameters, yet capable of fitting measured nuclear masses with better accuracy than the Bethe-Weizsäcker mass formula, while also describing density structures (charge radii, neutron skins etc.) and time-dependent phenomena (induced fission, giant resonances, low energy nuclear collisions, etc.). The 4 significant parameters are necessary to describe bulk nuclear properties (binding energies and charge radii); an additional 2 to 3 parameters have little influence on the bulk nuclear properties, but allow independent control of the density dependence of the symmetry energy and isovector excitations, in particular the Thomas-Reiche-Kuhn sum rule. This Hohenberg-Kohn-style of density functional theory successfully realizes Weizsäcker's ideas and provides a computationally tractable model for a variety of static nuclear properties and dynamics, from finite nuclei to neutron stars, where it will also provide a new insight into the physics of the r-process, nucleosynthesis, and neutron star crust structure. This new NEDF clearly separates the bulk geometric properties - volume, surface, symmetry, and Coulomb energies which amount to 8MeV per nucleon or up to 2000MeV per nucleus for heavy nuclei - from finer details related to shell effects, pairing, isospin breaking, etc. which contribute at most a few MeV for the entire nucleus. Thus it provides a systematic framework for organizing various contributions to the NEDF. Measured and calculated physical observables - symmetry and saturation properties, the neutron matter equation of state, and the frequency of giant dipole resonances - lead directly to new terms not considered in current NEDF parameterizations.

    Comments:
    25 pages, 12 figures
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
    arXiv:
    1506.09195 [pdf]
    14 citations
  5. 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
  6. 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
  7. 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