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Nuclear Theory·nucl-th

Friday·May 1, 2015

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 01

    [Submitted on 29 Apr 2015]

    Thermal photon radiation in high multiplicity p+Pb collisions at the Large Hadron Collider

    C. Shen🇨🇦 · J.-F. Paquet🇨🇦 · G. S. Denicol🇨🇦 · S. Jeon🇨🇦 · C. Gale🇨🇦

    The collective behaviour of hadronic particles has been observed in high multiplicity proton-lead collisions at the Large Hadron Collider (LHC), as well as in deuteron-gold collisions at the Relativistic Heavy-Ion Collider (RHIC). In this work we present the first calculation, in the hydrodynamic framework, of thermal photon radiation from such small collision systems. Owing to their compact size, these systems can reach temperatures comparable to those in central nucleus-nucleus collisions. The thermal photons can thus shine over the prompt background, and increase the low direct photon spectrum by a factor of 2-3 in 0-1% p+Pb collisions at 5.02 TeV. This thermal photon enhancement can therefore serve as a clean signature of the existence of a hot quark-gluon plasma during the evolution of these small collision systems, as well as validate hydrodynamic behavior in small systems.

    Comments:
    6 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1504.07989 [pdf]
    PRL(2016)·42 citations
  2. 02

    [Submitted on 30 Apr 2015]

    Rho meson form factors in a confining Nambu--Jona-Lasinio model

    Manuel E. Carrillo-Serrano🇦🇺 · Wolfgang Bentz🇯🇵 · Ian C. Cloët🇺🇸 · Anthony W. Thomas🇦🇺

    Elastic electromagnetic form factors for the meson are calculated in a Nambu--Jona-Lasinio model which incorporates quark confinement through the use of the proper-time regularization scheme. A comparison is made with recent lattice QCD results and previous quark model calculations for static quantities and the Sachs form factors. The results are qualitatively in good agreement with the lattice QCD calculations, with the exception of the quadrupole moment and corresponding form factor, which may be related to a lack of spherical symmetry on the lattice.

    Comments:
    8 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1504.08119 [pdf]
    PRC(2015)·36 citations
  3. 03

    [Submitted on 30 Apr 2015]

    Comment on "Neutron Skin of Pb from Coherent Pion Photoproduction"

    A. Gardestig🇺🇸 · C. J. Horowitz🇺🇸 · Gerald A. Miller🇺🇸

    We argue that the reaction mechanism for the coherent pion production is not known with sufficient accuracy to determine the neutron radius of 208Pb to the claimed precision of 0.03 fm.

    Comments:
    2 pages, 0 figures, Comment on C.M. Tarbert et al Phys. Rev. Lett. 112, 242502 (2014)
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1504.08347 [pdf]
    8 citations
  4. 04

    [Submitted on 30 Apr 2015]

    Systematics of nucleon density distributions and neutron skin of nuclei

    W. M. Seif · Hesham Mansour

    Proton and neutron density profiles of 760 nuclei in the mass region of A=16-304are analyzed using the Skyrme energy density for the parameter set SLy4. Simple formulae are obtained to fit the resulting radii and diffuseness data. These formulae may be useful to estimate the values of the unmeasured radii, and especially in extrapolating charge radius values for nuclei which are far from the valley of stability or to perform analytic calculations for bound and/or scattering problems. The obtained neutron and proton root-mean-square radii and the neutron skin thicknesses are in agreement with the available experimental data.

    Comments:
    14 pages,5 figures. arXiv admin note: text overlap with arXiv:1003.5225 by other authors
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1504.08350 [pdf]
    IJMPE(2015)·59 citations
  5. 05

    [Submitted on 29 Apr 2015] (cross-list from astro-ph.HE)

    Three-Dimensional Simulations of SASI- and Convection-Dominated Core-Collapse Supernovae

    Rodrigo Fernández

    We investigate the effect of dimensionality on the transition to explosion in neutrino-driven core-collapse supernovae. Using parameterized hydrodynamic simulations of the stalled supernova shock in one-, two- (2D), and three spatial dimensions (3D), we systematically probe the extent to which hydrodynamic instabilities alone can tip the balance in favor of explosion. In particular, we focus on systems that are well into the regimes where the Standing Accretion Shock Instability (SASI) or neutrino-driven convection dominate the dynamics, and characterize the difference between them. We find that SASI-dominated models can explode with up to ~20% lower neutrino luminosity in 3D than in 2D, with the magnitude of this difference decreasing with increasing resolution. This improvement in explosion conditions is related to the ability of spiral modes to generate more non-radial kinetic energy than a single sloshing mode, increasing the size of the average shock radius, and hence generating better conditions for the formation of large-scale, high-entropy bubbles. In contrast, convection-dominated explosions show a smaller difference in their critical heating rate between 2D and 3D (<8%), in agreement with previous studies. The ability of our numerical implementation to maintain arbitrary symmetries is quantified with a set of SASI-based tests. We discuss implications for the diversity of explosion paths in a realistic supernova environment.

    Comments:
    Accepted by MNRAS. Added a convection-dominated model to decrease the critical heating rate bracket. Minor changes otherwise
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1504.07996 [pdf]
    MNRAS(2015)·82 citations
  6. 06

    [Submitted on 30 Apr 2015] (cross-list from hep-ex)

    Neutrino Interactions and Long Baseline Physics

    Ulrich Mosel🇩🇪

    This is a very short review of neutrino-nucleus interactions and their influence on the analysis of long-baseline experiments.

    Comments:
    To appear in the proceedings of the Prospects in Neutrino Physics Conference, 15 -- 17 December, 2014, held at Queen Mary University of London, UK
    Subjects:
    High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1504.08204 [pdf]
    4 citations
  7. 07

    [Submitted on 30 Apr 2015] (cross-list from hep-lat)

    Critical point in the QCD phase diagram for extremely strong background magnetic fields

    Gergely Endrodi🇩🇪

    Lattice simulations have demonstrated that a background (electro)magnetic field reduces the chiral/deconfinement transition temperature of quantum chromodynamics for eB < 1 GeV^2. On the level of observables, this reduction manifests itself in an enhancement of the Polyakov loop and in a suppression of the light quark condensates (inverse magnetic catalysis) in the transition region. In this paper, we report on lattice simulations of 1+1+1-flavor QCD at an unprecedentedly high value of the magnetic field eB = 3.25 GeV^2. Based on the behavior of various observables, it is shown that even at this extremely strong field, inverse magnetic catalysis prevails and the transition, albeit becoming sharper, remains an analytic crossover. In addition, we develop an algorithm to directly simulate the asymptotically strong magnetic field limit of QCD. We find strong evidence for a first-order deconfinement phase transition in this limiting theory, implying the presence of a critical point in the QCD phase diagram. Based on the available lattice data, we estimate the location of the critical point.

    Comments:
    22 pages, 20 figures. v2: small changes in title and text; version accepted for publication in JHEP
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1504.08280 [pdf]
    JHEP(2015)·196 citations
  8. 08

    [Submitted on 30 Apr 2015] (cross-list from physics.comp-ph)

    Fast and accurate evaluation of Wigner 3j, 6j, and 9j symbols using prime factorisation and multi-word integer arithmetic

    H. T. Johansson🇸🇪 · C. Forssén🇸🇪

    We present an efficient implementation for the evaluation of Wigner 3j, 6j, and 9j symbols. These represent numerical transformation coefficients that are used in the quantum theory of angular momentum. They can be expressed as sums and square roots of ratios of integers. The integers can be very large due to factorials. We avoid numerical precision loss due to cancellation through the use of multi-word integer arithmetic for exact accumulation of all sums. A fixed relative accuracy is maintained as the limited number of floating-point operations in the final step only incur rounding errors in the least significant bits. Time spent to evaluate large multi-word integers is in turn reduced by using explicit prime factorisation of the ingoing factorials, thereby improving execution speed. Comparison with existing routines shows the efficiency of our approach and we therefore provide a computer code based on this work.

    Comments:
    7 pages, 2 figures. Accepted for publication in SIAM Journal on Scientific Computing (SISC)
    Subjects:
    Computational Physics (physics.comp-ph); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
    arXiv:
    1504.08329 [pdf]
    SIAM J.Sci.Comput.(2016)·57 citations

Affiliations

first authorsco-authorsvia INSPIRE