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Nuclear Theory·nucl-th

Tuesday·January 31, 2017

12 papers—6 primary·6 cross-listed

All12Primary6Cross-lists6
  1. 07

    The ideal relativistic fluid limit for a medium with polarization

    David Montenegro🇧🇷 · Leonardo Tinti🇺🇸 · Giorgio Torrieri🇧🇷

    We use Lagrangian effective field theory techniques to construct the equations of motion for an ideal relativistic fluid whose constituent degrees of freedom have microscopic polarization. We discuss the meaning of such a system, and argue that it is the first term in the EFT appropriate for describing polarization observables in heavy ion collisions, such as final state particle polarization and chiral magnetic and vortaic effects. We show that this system will generally require non-dissipative dynamics at higher order in gradient than second order, leading to potential stability issues known with such systems. We comment on the significance of this in the light of conjectured lower limits on viscosity.

    ↳ hep-thhep-phnucl-thphysics.flu-dynPRD(2017)·162 citations
  2. 08

    Dependence of weak interaction rates on the nuclear composition during stellar core collapse

    Shun Furusawa · Hiroki Nagakura · Kohsuke Sumiyoshi · Chinami Kato · Shoichi Yamada

    We investigate the influences of the nuclear composition on the weak interaction rates of heavy nuclei during the core collapse of massive stars. The nuclear abundances in nuclear statistical equilibrium (NSE) are calculated by some equation of state (EOS) models including in-medium effects on nuclear masses. We systematically examine the sensitivities of electron capture and neutrino-nucleus scattering on heavy nuclei to the nuclear shell effects and the single nucleus approximation. We find that the washout of shell effects at high temperatures brings significant change to weak rates by smoothing the nuclear abundance distribution: the electron capture rate decreases by 20 in the early phase and increases by 40 in the late phase at most, while the cross section for neutrino-nucleus scattering is reduced by 15. This is because the open-shell nuclei become abundant instead of those with closed neutron shells as the shell effects disappear. We also find that the single-nucleus description based on the average values leads to underestimations of weak rates. Electron captures and neutrino coherent scattering on heavy nuclei are reduced by 80 in the early phase and by 5 in the late phase, respectively. These results indicate that NSE like EOS accounting for shell washout is indispensable for the reliable estimation of weak interaction rates in simulations of core-collapse supernovae.

    ↳ astro-ph.HEnucl-thPRC(2017)·36 citations
  3. 09

    - meson production at very forward rapidities: estimating the intrinsic charm contribution

    F. Carvalho🇧🇷 · A.V. Giannini🇧🇷 · V.P. Goncalves🇧🇷 · F.S. Navarra🇧🇷

    We study - meson production at forward rapidities taking into account the non - linear effects in the QCD dynamics and the intrinsic charm component of the proton wave function. The total cross section, the rapidity distributions and the Feynman - distributions are calculated for collisions at different center of mass energies. Our results show that, at the LHC, the intrinsic charm component changes the rapidity distributions in a region which is beyond the coverage of the LHCb detectors. At higher energies the IC component dominates the and distributions exactly in the range where the produced mesons decay and contribute the most to the prompt atmospheric neutrino flux measured by the ICECUBE Collaboration. We compute the - distributions and demonstrate that they are enhanced at LHC energies by approximately one order of magnitude in the range.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·20 citations
  4. 10

    Strangeon and Strangeon Star

    Xiaoyu Lai (HUE)🇨🇳 · Renxin Xu (PKU)🇨🇳

    The nature of pulsar-like compact stars is essentially a central question of the fundamental strong interaction (explained in quantum chromo-dynamics) at low energy scale, the solution of which still remains a challenge though tremendous efforts have been tried. This kind of compact objects could actually be strange quark stars if strange quark matter in bulk may constitute the true ground state of the strong-interaction matter rather than Fe^56 (the so-called Witten's conjecture). From astrophysical points of view, however, it is proposed that strange cluster matter could be absolutely stable and thus those compact stars could be strange cluster stars in fact. This proposal could be regarded as a general Witten's conjecture: strange matter in bulk could be absolutely stable, in which quarks are either free (for strange quark matter) or localized (for strange cluster matter). Strange cluster with three-light-flavor symmetry is renamed strangeon, being coined by combining "strange nucleon" for the sake of simplicity. A strangeon star can then be thought as a 3-flavored gigantic nucleus, and strangeons are its constituent as an analogy of nucleons which are the constituent of a normal (micro) nucleus. The observational consequences of strangeon stars show that different manifestations of pulsar-like compact stars could be understood in the regime of strangeon stars, and we are expecting more evidence for strangeon star by advanced facilities (e.g., FAST, SKA, and eXTP).

    ↳ astro-ph.HEnucl-thJ.Phys.Conf.Ser.(2017)·40 citations
  5. 11

    First Results with HIJING++ in High-Energy Heavy-Ion Collisions

    Gergely Gábor Barnaföldi🇭🇺 · Gábor Bíró🇭🇺 · Miklos Gyulassy🇭🇺 · Szilveszter Miklós Haranozó🇭🇺 · Péter Lévai🇭🇺 · Guoyang Ma🇨🇳 · Gábor Papp🇭🇺 · Xin-Nian Wang🇺🇸 · Ben-Wei Zhang🇨🇳

    First calculated results with the new HIJING++ are presented for identified hadron production in high-energy heavy ion collisions. The recently developed HIJING++ version is based on the latest version of PYTHIA8 and contains all the nuclear effects has been included in the HIJING2.552, which will be improved by a new version of the shadowing parametrization and jet quenching module. Here, we summarize the major changes of the new program code beside the comparison between experimental data for some specific high-energy nucleus-nucleus collisions.

    ↳ hep-phnucl-thNucl.Part.Phys.Proc.(2017)·12 citations
  6. 12

    Finite temperature gluon spectral functions from lattice QCD

    Ernst-Michael Ilgenfritz🇷🇺 · Jan M. Pawlowski🇩🇪 · Alexander Rothkopf🇩🇪 · Anton Trunin🇷🇺

    We investigate gluon spectral functions at finite temperature in Landau gauge, based on a subset of lattice QCD ensembles with dynamical twisted mass quarks flavors, generated by the tmfT collaboration. Our study uses a novel Bayesian approach for the extraction of non-positive definite spectral functions, which for each binned spatial momentum takes into account the gluon correlation functions at all available discrete imaginary frequencies. The spectral functions are extracted at three different lattice spacing, where for each of them, a scan of temperatures around the crossover transition is carried out at fixed scale. We find indications for the existence of a well defined quasi-particle peak. Due to a relatively small number of imaginary frequencies available, we focus on the momentum and temperature dependence of the position of this spectral feature. This dispersion relation reveals different in-medium masses for longitudinal and transversal gluons at high temperatures, qualitatively consistent with weak coupling expectations.

    ↳ hep-lathep-phhep-thnucl-thEPJC(2018)·32 citations

Affiliations

first authorsco-authorsvia INSPIRE