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Nuclear Theory·nucl-th

Thursday·December 24, 2015

14 papers—6 primary·8 cross-listed

All14Primary6Cross-lists8
  1. 01

    [Submitted on 23 Dec 2015]

    Anisotropic hydrodynamics for conformal Gubser flow

    Michael Strickland🇺🇸 · Mohammad Nopoush🇺🇸 · Radoslaw Ryblewski🇵🇱

    In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3)_q symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equation subject to Gubser flow. Using this as our standard, we find that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches.

    Comments:
    4 pages, 1 figure; proceedings contribution for Quark Matter 2015, Kobe, Japan
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1512.07334 [pdf]
    NPA(2016)·24 citations
  2. 02

    [Submitted on 23 Dec 2015]

    Multiplicity fluctuations of net protons on the hydrodynamic freeze-out surface

    Lijia Jiang🇨🇳 · Pengfei Li🇨🇳 · Huichao Song (Peking U.)🇨🇳

    This proceeding briefly summarizes our recent work on calculating the correlated fluctuations of net protons on the hydrodynamic freeze-out surface near the QCD critical point. For both Poisson and Binomial baselines, our calculations could roughly reproduce the energy dependent cumulant and of net protons, but always over-predict and due to the positive contributions from the static critical fluctuations.

    Comments:
    Accepted version with minor corrections and updates
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1512.07373 [pdf]
    NPA(2016)·20 citations
  3. 03

    [Submitted on 23 Dec 2015]

    Generalization of the model-independent Laurent-Pietarinen single-channel pole-extraction formalism to multiple channels

    Alfred Svarc🇭🇷 · Mirza Hadzimehmedovic🇧🇦 · Hedim Osmanovic🇧🇦 · Jugoslav Stahov🇧🇦 · Lothar Tiator🇩🇪 · Ron L. Workman🇺🇸

    A method to extract resonance pole information from single-channel partial-wave amplitudes based on a Laurent (Mittag-Leffler) expansion and conformal mapping techniques has recently been developed. This method has been applied to a number of reactions and provides a model-independent extraction procedure which is particularly useful in cases where a set of amplitudes is available only at descrete energies. This method has been generalized and applied to the case of a multi-channel fit, where several sets of amplitudes are analysed simultaneously. The importance of unitarity constraints is discussed. The final result provides a powerful, model-independent tool for analyzing partial-wave amplitudes of coupled or connected channels based entirely on the concepts of analyticity and unitarity.

    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1512.07403 [pdf]
    PLB(2016)·19 citations
  4. 04

    [Submitted on 23 Dec 2015]

    Unified description of electron-nucleus scattering within the spectral function formalism

    Noemi Rocco🇮🇹 · Alessandro Lovato🇺🇸 · Omar Benhar🇺🇸

    We developed a novel approach based on a generalization of factorization and nuclear spectral functions, allowing for a consistent treatment of the amplitudes involving one- and two-nucleon currents, whose contribution to the nuclear electromagnetic response in the transverse channel is known to be significant. We report the results of calculations of the inclusive electron-carbon cross section, showing that the inclusion of processes involving two-nucleon currents appreciably improves the agreement between theory and data in the dip region, between the quasi elastic and -production peaks. The implications for the analysis of neutrino-nucleus cross sections are discussed.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1512.07426 [pdf]
    PRL(2016)·97 citations
  5. 05

    [Submitted on 20 Dec 2015]

    Lightening-like interactions in nuclear collisions at CERN large hadron collider

    Khaled Abdel-Waged🇸🇦 · Nuha Felemban🇸🇦

    A simple basic model for describing proton-nucleus (pA) and nucleus-nucleus (AA) collisions has been the intra-nuclear cascade model, where the interactions are simulated by a sequence of binary nucleon-nucleon (NN) collisions. This model helped to establish many scientific concepts and also creates the foundation for more modern simulation codes, especially at low and intermediate energies. In this paper, we present a new Monte Carlo model for pA and AA collisions at high CERN Large Hadron collider energies. The model implements HIJING code with a collective cascade recipe, that induces striking light-like effect in a large nucleus. A single collision (lightening) event is shown to be a complex process:A primary interacting nucleon passes its energy to the surrounding nucleons in a large nucleus. This new simulation code is shown to be good to reproduce the Large Hadron collider (LHC) data, especially the charged particle pseudorapidity density in p+Pb and Pb+Pb collisions at LHC energies.

    Comments:
    The European Physical Society Conference on High Energy Physics
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1512.07583 [pdf]
    PoS(2015)·0 citations
  6. 06

    [Submitted on 23 Dec 2015]

    Isovector spin-singlet (T=1, S=0) and isoscalar spin-triplet (T=0, S=1) pairing interactions and spin-isospin response

    H. Sagawa (RIKEN, Nishina Center and University of Aizu, Japan)🇯🇵 · C.L. Bai (Sichuan University, Chengdu, China)🇨🇳 · G. Colo' (Universita' degli Studi and INFN, Milano, Italy)🇮🇹

    We review several experimental and theoretical advances that emphasise common aspects of the study of T=1 and T=0 pairing correlations in nuclei. We first discuss several empirical evidences of the special role played by the T=1 pairing interaction. In particular, we show the peculiar features of the nuclear pairing interaction in the low density regime, and possible outcomes such as the BCS-BEC crossover in nuclear matter and, in an analogous way, in loosely bound nuclei. We then move to the competition between T=1 and T=0 pairing correlations. The effect of such competition on the low-lying spectra is studied in N=Z odd-odd nuclei by using a three-body model; it is shown that the inversion of the 0+ and 1+ states near the ground state, and the strong magnetic dipole transitions between them, can be considered as a clear manifestation of strong T=0 pairing correlations in these nuclei. The effect of T=0 pairing correlations is also quite evident if one studies charge-changing transitions. The Gamow-Teller (GT) states in N=Z+2 nuclei are studied here by using self-consistent HFB+QRPA calculations in which the T=0 pairing interaction is taken into account. Strong GT states are found, near the ground state of daughter nuclei; these are compared with available experimental data from charge-exchange reactions, and such comparison can pinpoint the value of the strength of the T=0 interaction. Pair transfer reactions are eventually discussed: while two-neutron transfer has been long proposed as a tool to measure the T=1 superfluidity in the nuclear ground states, the study of deuteron transfer is still in its infancy, despite its potential interest in revealing effects coming from both T=1 and T=0 interactions.

    Comments:
    Paper submitted to Physica Scripta for inclusion in the Focus Issue entitled "Focus Issue on Nuclear Structure: Celebrating the 75 Nobel Prize" (by A. Bohr and B.R. Mottelson). arXiv admin note: text overlap with arXiv:nucl-th/0512021 by other authors
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1512.07589 [pdf]
    Phys.Scripta(2016)·51 citations

Affiliations

first authorsco-authorsvia INSPIRE