PaperPanorama
FAQ

Nuclear Theory·nucl-th

Wednesday·April 3, 2019

12 papers—6 primary·6 cross-listed

All12Primary6Cross-lists6
  1. 07

    [Submitted on 29 Mar 2019] (cross-list from hep-lat)

    Strange electromagnetic form factors of the nucleon with -improved Wilson fermions

    Dalibor Djukanovic🇩🇪 · Konstantin Ottnad🇩🇪 · Jonas Wilhelm🇩🇪 · Hartmut Wittig🇩🇪

    We present results for the strange contribution to the electromagnetic form factors of the nucleon computed on the CLS ensembles with flavors of -improved Wilson fermions and an -improved vector current. Several source-sink separations are investigated in order to estimate the excited-state contamination. We calculate the form factors on six ensembles with lattice spacings in the range of and pion masses in the range of , which allows for a controlled chiral and continuum extrapolation. In the computation of the quark-disconnected contributions we employ hierarchical probing as a variance reduction technique.

    Comments:
    23 pages, 9 figures; matching version accepted for publication in PRL
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1903.12566 [pdf]
    PRL(2019)·34 citations
  2. 08

    [Submitted on 2 Apr 2019] (cross-list from hep-ph)

    Quantized first-order phase transition and two sets of critical end point in droplet quark matter

    Kun Xu🇨🇳 · Mei Huang🇨🇳

    The finite-size effect on the chiral phase transition is investigated in the Nambu--Jona-Lasinio model. To take into account finite-size effects, momentum integrals are replaced by momentum summations. The ground state of quark matter at finite size is favored when applying the periodic spatial boundary condition for quarks. The zero-momentum contribution is taken into account in the periodic boundary condition, and its contribution becomes important when the system size is comparable with the pion wavelength. When the zero-mode contribution becomes dominant, the conventional first-order chiral phase transition at high baryon chemical potential splits into two first-order phase transitions in small system of quark matter, and two sets of critical end point show up in the temperature and chemical potential plane.

    Comments:
    15 pages, 8 figures, proceeding of CPOD2018
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1904.01154 [pdf]
    PoS(2019)·5 citations
  3. 09

    [Submitted on 2 Apr 2019] (cross-list from hep-lat)

    Phase structure of three flavor QCD in external magnetic fields using HISQ fermions

    Akio Tomiya🇺🇸 · Heng-Tong Ding🇨🇳 · Xiao-Dan Wang🇨🇳 · Yu Zhang🇨🇳 · Swagato Mukherjee🇺🇸 · Christian Schmidt🇩🇪

    We study the phase structure of QCD with three degenerate flavors in the external magnetic fields using highly improved staggered quarks (HISQ). The simulations are performed on lattice. In order to investigate the quark mass dependence of the chiral transition we choose the values of the bare quark masses 0.015 and 0.0009375 in the lattice unit, corresponding to MeV and 80 MeV in the continuum limit. We found no indication of a first order phase transition in the current window of quark masses and external magnetic fields. Unlike to the case with standard staggered fermions inverse magnetic catalysis is always observed at about the critical temperature. The microscopic origin of this phenomena are further discussed by looking into the Dirac eigenvalue spectrum.

    Comments:
    8 pages, 3 figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1904.01276 [pdf]
    PoS(2019)·24 citations
  4. 10

    [Submitted on 2 Apr 2019] (cross-list from astro-ph.HE)

    Equation-of-state Constraints and the QCD Phase Transition in the Era of Gravitational-Wave Astronomy

    Andreas Bauswein🇩🇪 · Niels-Uwe Friedrich Bastian🇵🇱 · David Blaschke🇵🇱 · Katerina Chatziioannou🇺🇸 · James Alexander Clark🇺🇸 · Tobias Fischer🇵🇱 · Hans-Thomas Janka🇩🇪 · Oliver Just🇯🇵 · Micaela Oertel🇫🇷 · Nikolaos Stergioulas🇬🇷

    We describe a multi-messenger interpretation of GW170817, which yields a robust lower limit on NS radii. This excludes NSs with radii smaller than about 10.7 km and thus rules out very soft nuclear matter. We stress the potential of this type of constraints when future detections become available. A very similar argumentation may yield an upper bound on the maximum mass of nonrotating NSs. We also discuss simulations of NS mergers, which undergo a first-order phase transition to quark matter. We point out a different dynamical behavior. Considering the gravitational-wave signal, we identify an unambiguous signature of the QCD phase transition in NS mergers. The occurrence of quark matter through a strong first-order phase transition during merging leads to a characteristic shift of the dominant postmerger frequency. The frequency shift is indicative for a phase transition if it is compared to the postmerger frequency which is expected for purely hadronic EoS models. A very strong deviation of several 100 Hz is observed for hybrid EoSs in an otherwise tight relation between the tidal deformability and the postmerger frequency. We address the potential impact of a first-order phase transition on the electromagnetic counterpart of NS mergers. Our simulations suggest that there would be no significant qualitative differences between a system undergoing a phase transition to quark matter and purely hadronic mergers. The quantitative differences are within the spread which is found between different hadronic EoS models. This implies on the one hand that GW170817 is compatible with a possible transition to quark matter. On the other hand these considerations show that it may not be easy to identify quantitative differences between purely hadronic mergers and events in which quark matter occurs considering solely their electromagnetic counterpart or their nucleosynthesis products. (abridged)

    Comments:
    15 pages, 11 figures, submitted to the AIP Conference Proceedings of the Xiamen-CUSTIPEN Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave Astronomy (January 3 - 7, 2019, Xiamen, China)
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1904.01306 [pdf]
    AIP Conf.Proc.(2019)·78 citations
  5. 11

    [Submitted on 2 Apr 2019] (cross-list from hep-ph)

    Wounded nucleon, quark and quark-diquark emission functions versus experimental results from RHIC

    Michał Barej🇵🇱 · Adam Bzdak🇵🇱 · Paweł Gutowski🇵🇱

    Using the wounded nucleon, quark, and quark-diquark models, we extract the wounded source emission functions from the PHOBOS data for d+Au collisions at GeV. We apply these models to compute charged particle multiplicity distributions as functions of pseudorapidity for p+p, p+Al, p+Au, d+Au, He+Au, Cu+Cu, Cu+Au, Au+Au, and U+U collisions at the same energy and compare them with experimental data from the PHOBOS and PHENIX collaborations. In symmetric collisions of heavy nuclei, the obtained distributions differ among the tested models. On the other hand, in asymmetric collisions, all three models give essentially the same distributions. The wounded quark-diquark and quark models are in reasonable agreement with data for all the investigated systems.

    Comments:
    14 pages, 11 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1904.01435 [pdf]
    PRC(2019)·9 citations
  6. 12

    [Submitted on 2 Apr 2019] (cross-list from astro-ph.HE)

    Merger of compact stars in the two-families scenario

    Roberto De Pietri🇮🇹 · Alessandro Drago🇮🇹 · Alessandra Feo🇮🇹 · Giuseppe Pagliara🇮🇹 · Michele Pasquali🇮🇹 · Silvia Traversi🇮🇹 · Grzegorz Wiktorowicz🇨🇳

    We analyse the phenomenological implications of the two-families scenario on the merger of compact stars. That scenario is based on the coexistence of both hadronic stars and strange quark stars. After discussing the classification of the possible mergers, we turn to detailed numerical simulations of the merger of two hadronic stars, i.e., "first family" stars in which delta resonances and hyperons are present, and we show results for the threshold mass of such binaries, for the mass dynamically ejected and the mass of the disk surrounding the post-merger object. We compare these results with those obtained within the one-family scenario and we conclude that relevant signatures of the two-families scenario can be suggested, in particular: the possibility of a rapid collapse to a black hole for masses even smaller than the ones associated to GW170817; during the first milliseconds, oscillations of the postmerger remnant at frequencies higher than the ones obtained in the one-family scenario; a large value of the mass dynamically ejected and a small mass of the disk, for binaries of low total mass. Finally, based on a population synthesis analysis, we present estimates of the number of mergers for: two hadronic stars; hadronic star - strange quark star; two strange quark stars. We show that for unequal mass systems and intermediate values of the total mass, the merger of a hadronic star and a strange quark star is very likely (GW170817 has a possible interpretation into this category of mergers). On the other hand, mergers of two strange quark stars are strongly suppressed.

    Comments:
    18 pages, 16 figures
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1904.01545 [pdf]
    ApJ(2019)·71 citations

Affiliations

first authorsco-authorsvia INSPIRE