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Nuclear Theory·nucl-th

Monday·June 17, 2019

5 papers—2 primary·3 cross-listed

All5Primary2Cross-lists3
  1. 01

    [Submitted on 14 Jun 2019]

    Viscosity calculations from Hadron Resonance Gas model: Finite size effect

    Snigdha Ghosh🇮🇳 · Subhasis Samanta🇮🇳 · Sabyasachi Ghosh🇮🇳 · Hiranmaya Mishra🇮🇳

    We have attempted to review on microscopic calculation of transport coefficients like shear and bulk viscosities in the framework of hadron resonance gas model, where a special attention is explored on the effect of finite system size. The standard expressions of transport coefficients, obtained from relaxation time approximation of kinetic theory or diagrammatic Kubo-type formalism, carry mainly two temperature dependent components -- thermodynamical phase space and relaxation time of medium constituent. Owing to quantum effect of finite system size, thermodynamical phase space can be reduced as its momentum distribution will be started from some finite lower momentum cut-off instead of zero momentum. On the other hand, relaxation time of hadrons can also face finite size effect by considering only those relaxation scales, which are lower than the system size. Owing to these phenomenological issues, we have proposed a system size dependent upper bound of transport coefficients for ideal HRG model, whose qualitative technique may also be applicable in other models. This finite size prescription may guide to shorten the broad numerical band, within which earlier estimated values of transport coefficients for hadronic matter are located. It is also suspected that the hadronic matter may not be far from the (nearly) perfect fluid nature like the quark gluon plasma.

    Comments:
    Going through a quick review of viscosity calculation in HRG models, present article highlighted finite size effect on viscosity (similar to quantum lower bound, a phenomenological upper bound can also be expected because of finite size of hadronic matter)
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1906.06029 [pdf]
    IJMPE(2019)·8 citations
  2. 02

    [Submitted on 14 Jun 2019]

    FRIGA, A New Approach To Identify Isotopes and Hyper-nuclei In N-Body Transport Models

    A. Le Fèvre🇩🇪 · J. Aichelin🇫🇷 · C. Hartnack🇫🇷 · Y. Leifels🇩🇪

    We present a new approach to identify fragments in computer simulations of relativistic heavy ion collisions. It is based on the simulated annealing technique and can be applied to n-body transport models like the Quantum Molecular Dynamics. This new approach is able to predict isotope yields as well as hyper-nucleus production. In order to illustrate its predicting power, we confront this new method with experimental data and show the sensitivity on the parameters which govern the cluster formation.

    Comments:
    14 pages, 14 figures, submitted to Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1906.06162 [pdf]
    PRC(2019)·35 citations
  3. 03

    [Submitted on 14 Jun 2019] (cross-list from hep-lat)

    Deuteron-like heavy dibaryons from Lattice QCD

    Parikshit Junnarkar🇮🇳 · Nilmani Mathur🇮🇳

    We report the first lattice quantum chromodynamics (QCD) study of deuteron()-like dibaryons with heavy quark flavours. These include particles with following dibaryon structures and valence quark contents: , , , and , and with spin ()-parity (), . Using a state-of-the art lattice QCD calculation, after controlling relevant systematic errors, we unambiguously find that the ground state masses of dibaryons , and are below their respective two-baryon thresholds, suggesting the presence of bound states which are stable under strong and electromagnetic interactions. We also predict their masses precisely. For dibaryons , and , we could not reach to a definitive conclusion about the presence of any bound state due to large systematics associated with these states. We also find that the binding of these dibaryons becomes stronger as they become heavier in mass. This study also opens up the possibility of the existence of many other exotic nuclei, which can be formed through the fusion of heavy baryons, similar to the formation of nuclei of elements in the Periodic Table.

    Comments:
    version accepted for publication in Phys. Rev. Lett
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1906.06054 [pdf]
    PRL(2019)·73 citations
  4. 04

    [Submitted on 14 Jun 2019] (cross-list from nucl-ex)

    Constraining the Neutron Star Compactness: Extraction of the Al() Reaction Rate for the -Process

    C. Wolf · C. Langer · F. Montes · J. Pereira · W.-J. Ong · T. Poxon-Pearson · S. Ahn · S. Ayoub · T. Baumann · D. Bazin · P.C. Bender · B.A. Brown and 24 other authors

    The Al()Si reaction is among the most important reactions driving the energy generation in Type-I X-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The Al() reaction was used to populate the astrophysically important states in Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. For the first time, a predicted close-lying doublet of a 2 and (4,0) state in Si was disentangled, finally resolving conflicting results from two previous measurements. Moreover, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.

    Subjects:
    Nuclear Experiment (nucl-ex); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1906.06091 [pdf]
    PRL(2019)·21 citations
  5. 05

    [Submitted on 14 Jun 2019] (cross-list from nucl-ex)

    Calculation of resonance energies from Q-values

    Christian Iliadis

    Resonance energies are frequently derived from precisely measured excitation energies and reaction Q-values. The latter quantities are usually calculated from atomic instead of nuclear mass differences. This procedure disregards the energy shift caused by the difference in the total electron binding energies before and after the interaction. Assuming that the interacting nuclei in a stellar plasma are fully ionized, this energy shift can have a significant effect, considering that the resonance energy enters exponentially into the expression for the narrow-resonance thermonuclear reaction rates. As an example, the rate of the Ar(p,)K reaction is discussed, which, at temperatures below 1 GK, depends only on the contributions of a single resonance and direct capture. In this case, disregarding the energy shift caused by the total electron binding energy difference erroneously enhances the rate by 40\% near temperatures of 70 MK.

    Comments:
    3 pages, 2 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Astrophysics of Galaxies (astro-ph.GA); Nuclear Theory (nucl-th)
    arXiv:
    1906.06282 [pdf]
    PRC(2019)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE