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Nuclear Theory·nucl-th

Tuesday·December 22, 2020

10 papers—5 primary·5 cross-listed

All10Primary5Cross-lists5
  1. 01

    [Submitted on 21 Dec 2020]

    Generator coordinate method with a conjugate momentum: application to the particle number projection

    N. Hizawa · K. Hagino · K. Yoshida

    We discuss an extension of the generator coordinate method (GCM) by taking simultaneously a collective coordinate and its conjugate momentum as generator coordinates. To this end, we follow the idea of the dynamical GCM (DGCM) proposed by Goeke and Reinhard. We first show that the DGCM method can be regarded as an extension of the double projection method for the center of mass motion. As an application of DGCM, we then investigate the particle number projection, for which we not only carry out an integral over the gauge angle as in the usual particle number projection but also take a linear superposition of BCS states which have different mean particle numbers. We show that the ground state energy is significantly lowered by such effect, especially for magic nuclei for which the pairing gap is zero in the BCS approximation. This suggests that the present method makes a good alternative to the variation after projection (VAP) method, as the method is much simpler than the VAP.

    Comments:
    9 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); Superconductivity (cond-mat.supr-con)
    arXiv:
    2012.11123 [pdf]
    PRC(2021)·14 citations
  3. 03

    [Submitted on 21 Dec 2020]

    Polarization of in the reaction

    Ke Wang🇨🇳 · Bo-Chao Liu🇨🇳

    In this paper, we study the polarization of the in the reaction within an effective Lagrangian approach and isobar model. In our model, the is excited through the t-channel exchanges and u-channel hyperon exchange. Compared to previous studies, we also include the contribution from a contact term, which is necessary for our model to interpret the polarization of the . In addition, we also discuss the possibility to verify the proposed two-pole structure of the using the polarization data. We find that the polarization of the or the polarization of the final in this reaction is sensitive to the invariant mass . Thus the measurement of the dependence of the polarization on the can offer valuable information about the pole structure of the .

    Comments:
    8 pages, 7 figures. Version accepted by PLB
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2012.11379 [pdf]
    PLB(2021)·1 citation
  4. 04

    [Submitted on 21 Dec 2020]

    Update of the Three-fluid Hydrodynamics-based Event Simulator: light-nuclei production in heavy-ion collisions

    M. Kozhevnikova🇷🇺 · Yu. B. Ivanov🇷🇺 · Iu. Karpenko🇨🇿 · D. Blaschke🇵🇱 · O. Rogachevsky🇷🇺

    We present an update of the event generator based on the three-fluid dynamics (3FD), complemented by Ultra-relativistic Quantum Molecular Dynamics (UrQMD) for the late stage of the nuclear collision~-- the three-fluid Hydrodynamics-based Event Simulator Extended by UrQMD final State interactions (THESEUS). Two modifications are introduced. The THESEUS table of hadronic resonances is made consistent with that of the underlying 3FD model. The main modification is that the generator is extended to simulate the light-nuclei production in relativistic heavy-ion collisions, on the equal basis with hadrons. These modifications are illustrated by applications to the description of available experimental data. The first run of the updated generator revealed a good reproduction of the NA49 data on the light nuclei. The reproduction is achieved without any extra parameters, while the coalescence approach in 3FD requires special tuning of the coalescence coefficients for each light nucleus separately.

    Comments:
    8 pages, 3 figures, version published in PRC
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2012.11438 [pdf]
    PRC(2021)·15 citations
  5. 05

    [Submitted on 21 Dec 2020]

    Collective flow at SIS energies within a hadronic transport approach: Influence of light nuclei formation and equation of state

    Justin Mohs🇩🇪 · Martha Ege🇩🇪 · Hannah Elfner🇩🇪 · Markus Mayer🇩🇪

    Collective flow observables are known to be a sensitive tool to gain insights on the equation of state of nuclear matter from heavy-ion collision observations. Towards more quantitative constraints one has to carefully assess other influences on the collective behaviour. In this work a hadronic transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is applied to study the first four anisotropic flow coefficients in Au+Au collisions at GeV in the context of the recently measured data by the HADES collaboration. In particular, the formation of light nuclei is important in this energy regime. Two different approaches are contrasted to each other: A clustering algorithm inspired by coalescence as well as microscopic formation of deuterons via explicit cross-sections. The sensitivity of directed and elliptic flow observables to the strength of the Skyrme mean field is explored. In addition, it is demonstrated that the rapidity-odd coefficient is practically zero in this energy regime and the ratio of is close to the value of 0.5 expected from hydrodynamic behaviour. This study establishes the current understanding of collective behaviour within the SMASH approach and lays the ground for future more quantitative constraints on the equation of state of nuclear matter within improved mean field calculations.

    Comments:
    Tables for all plotted calculations can be found in the anc folder
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2012.11454 [pdf]
    PRC(2022)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE