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Nuclear Theory·nucl-th

Thursday·April 23, 2020

6 papers—5 primary·1 cross-listed

All6Primary5Cross-lists1
  1. 01

    [Submitted on 21 Apr 2020]

    Short-range correlation effects on the neutron star cooling

    Lucas A. Souza · Rodrigo Negreiros · Mariana Dutra · Débora P. Menezes · Odilon Lourenço

    Short range correlations (SRC) have been known to be an important aspect of nuclear theory for some time. Recent works have re-ignited interest on this topic, particularly due to the fact that it has recently been demonstrated that SRC may be responsible for breaking pairing gaps in nuclear matter. In this work we revisit the concept of SRC for beta equilibrated matter in neutron stars. We construct two equivalent models, with and without SRC and proceed to investigate the thermal evolution of stars described by such models. We show that SRC play a major role in the thermal evolution of neutron stars. It will be shown that while the SRC largely leaves the macroscopic properties of the star unaltered, it significantly alters the proton fraction, thus leading to an early onset of the direct Urca (DU) process, which in turns leads to stars exhibiting much faster cooling.

    Comments:
    7 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
    arXiv:
    2004.10309 [pdf]
    10 citations
  2. 02

    [Submitted on 22 Apr 2020]

    -decay to first state with partial isospin symmetry restoration from spherical QRPA calculations

    Dong-Liang Fang🇨🇳 · Amand Faessler🇩🇪

    With partially restored isospin symmetry, we calculate the nuclear matrix element for a special decay mode of (two neutrino double beta decay) -- the decay to the first excited states. With the realistic CD-Bonn nuclear force, we analyze the dependence of the nuclear matrix elements on the iso-vector and iso-scalar parts of proton-neutron particle-particle interaction. The dependence on the different nuclear matrix element is observed and the results are explained. We also give the phase space factors with numerical electron wave functions and properly chosen excitation energies. Finally we give our results for the half-lives of this decay mode for different nuclei.

    Comments:
    9 pages, 3 figures, to be published in Chinese Physics C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2004.10374 [pdf]
    CPC(2020)·3 citations
  3. 03

    [Submitted on 21 Apr 2020]

    resonances in Ca+Ca, Ni+Ni and Au+Au reactions from 1 AGeV to 2 AGeV: Consistency between yields, mass shifts and decoupling temperatures

    Tom Reichert🇩🇪 · Paula Hillmann🇩🇪 · Marcus Bleicher🇩🇪

    The Ultra-relativistic Quantum Molecular Dynamics (UrQMD) transport approach is used to calculate (1232) yields in Ca+Ca, Ni+Ni and Au+Au collisions between 1 AGeV and 2 AGeV. We compare and validate two different methods to extract the yields of (1232) resonances in such low energy nuclear collisions: Firstly, the spectra at low are used to infer the (1232) yield in A+A collisions, a method employed by the GSI/FOPI experiment. Secondly, we employ the invariant mass method used by the HADES collaboration, which has recently reported data in the channel. We show that both methods are compatible with each other and with the theoretical calculations, indicating that the new HADES results are compatible with the previous FOPI measurements. Then we use the ratio to extract the kinetic decoupling temperatures of the (1232) resonances. We find that the extracted temperatures are consistent with the predicted mass shift of the resonance and the freeze-out parameters estimated from complementary studies (blast wave fits, coarse graining).

    Comments:
    6 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex)
    arXiv:
    2004.10539 [pdf]
    NPA(2021)·14 citations
  4. 04

    [Submitted on 22 Apr 2020]

    Light nuclei in the hadron resonance gas

    Benjamin Dönigus🇩🇪

    The description of the production of light (anti-)(hyper-)nuclei in a hadron resonance gas, or statistical-thermal model approach, has proven to be rather successful, despite the fact that the binding energies of these compound objects are small compared to the emitting fireball temperature. We summarise some recent developments and findings in this approach.

    Comments:
    19 pages, 10 figures, Invited review IJMPE
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2004.10544 [pdf]
    IJMPE(2020)·19 citations
  5. 05

    [Submitted on 22 Apr 2020]

    Centrifugal effects in N-Delta states

    J. A. Niskanen🇫🇮

    Recently it has been pointed out that in the two-baryon or system the width of the state is greatly diminished due to the relative kinetic energy of the two baryons, since the internal energy of the particles, available for pionic decay, is smaller. For nonzero orbital angular momenta this effect becomes state dependent. Also the real part of the energy can get contribution from the centrifugal barrier leading to rotational series of diffuse states. Obviously, these states may have an interpretation as isospin one dibaryons. Direct and explicit calculations for this are presented with some details of the coupled state wave functions displayed. With finite expectation values of these repulsive effects it may be possible to define state dependent effective thresholds for states and these, in turn, can show resonant like behavior.

    Comments:
    22 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2004.10699 [pdf]
    PRC(2020)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE