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Nuclear Theory·nucl-th

Wednesday·September 23, 2015

11 papers—6 primary·5 cross-listed

All11Primary6Cross-lists5
  1. 07

    [Submitted on 22 Sept 2015] (cross-list from astro-ph.HE)

    Equation of state constraints for the cold dense matter inside neutron stars using the cooling tail method

    J. Nättilä · A. W. Steiner · J. J. E. Kajava · V. F. Suleimanov · J. Poutanen

    The cooling phase of thermonuclear (type-I) X-ray bursts can be used to constrain the neutron star (NS) compactness by comparing the observed cooling tracks of bursts to accurate theoretical atmosphere model calculations. By applying the so-called cooling tail method, where the information from the whole cooling track is used, we constrain the mass, radius, and distance for three different NSs in low-mass X-ray binaries 4U 1702-429, 4U 1724-307, and SAX J1810.8-260. Care is taken to only use the hard state bursts where it is thought that only the NS surface alone is emitting. We then utilize a Markov chain Monte Carlo algorithm within a Bayesian framework to obtain a parameterized equation of state (EoS) of cold dense matter from our initial mass and radius constraints. This allows us to set limits on various nuclear parameters and to constrain an empirical pressure-density relation for the dense matter. Our predicted EoS results in NS radius between 10.5-12.8 km (95% confidence limits) for a mass of 1.4 . Due to systematic errors and uncertainty in the composition these results should be interpreted as lower limits for the radius.

    Comments:
    23 pages, 12 figures, revised version, accepted for publication in A&A
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    1509.06561 [pdf]
    Astron.Astrophys.(2016)·144 citations
  2. 08

    [Submitted on 22 Sept 2015] (cross-list from hep-ph)

    Fluctuations in the Statistical Model of the Early Stage of nucleus-nucleus collisions

    R. V. Poberezhnyuk🇺🇦 · M. I. Gorenstein🇺🇦 · M. Gazdzicki🇩🇪

    Predictions on fluctuations of hadron production properties in central heavy ion collisions are presented. They are based on the Statistical Model of the Early Stage and extend previously published results by considering the strongly intensive measures of fluctuations. In several of the considered cases a significant change in collision energy dependence of calculated quantities as a result of the phase transition is predicted. This provides an opportunity to observe new signals of the onset of deconfinement in heavy ion collisions experiments.

    Comments:
    11 pages, 9 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1509.06577 [pdf]
    Acta Phys.Polon.B(2016)·4 citations
  3. 09

    [Submitted on 22 Sept 2015] (cross-list from astro-ph.SR)

    Quantum Simulations of Nuclei and Nuclear Pasta with the Multi-resolution Adaptive Numerical Environment for Scientific Simulations

    I. Sagert · G. I. Fann · F. J. Fattoyev · S. Postnikov · C. J. Horowitz

    Neutron star and supernova matter at densities just below the nuclear matter saturation density is expected to form a lattice of exotic shapes. These so-called nuclear pasta phases are caused by Coulomb frustration. Their elastic and transport properties are believed to play an important role for thermal and magnetic field evolution, rotation and oscillation of neutron stars. Furthermore, they can impact neutrino opacities in core-collapse supernovae. In this work, we present proof-of-principle 3D Skyrme Hartree-Fock (SHF) simulations of nuclear pasta with the Multi-resolution ADaptive Numerical Environment for Scientific Simulations (MADNESS). We perform benchmark studies of , and nuclear ground states and calculate binding energies via 3D SHF simulations. Results are compared with experimentally measured binding energies as well as with theoretically predicted values from an established SHF code. The nuclear pasta simulation is initialized in the so-called waffle geometry as obtained by the Indiana University Molecular Dynamics (IUMD) code. The size of the unit cell is 24\:fm with an average density of about , proton fraction of and temperature of MeV. Our calculations reproduce the binding energies and shapes of light and heavy nuclei with different geometries. For the pasta simulation, we find that the final geometry is very similar to the initial waffle state. In the present pasta calculations spin-orbit forces are not included but will be added in the future. Within the MADNESS framework, we can successfully perform calculations of inhomogeneous nuclear matter. By using pasta configurations from IUMD it is possible to explore different geometries and test the impact of self-consistent calculations on the latter.

    Comments:
    16 pages, 15 figures, 4 tables; additional section about spin-orbit impact on the shape of the pasta phase
    Subjects:
    Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Methods for Astrophysics (astro-ph.IM); Nuclear Theory (nucl-th)
    arXiv:
    1509.06671 [pdf]
    PRC(2016)·26 citations
  4. 10

    [Submitted on 22 Sept 2015] (cross-list from hep-ph)

    Strangeness production and long-range correlations in pp collisions in string fusion approach

    Vladimir Kovalenko🇷🇺 · Vladimir Vechernin (Saint Petersburg State University, Russia)🇷🇺

    The effects of string fusion on the correlations in strange particles production in proton-proton collisions at high energy are studied in the framework of a Monte Carlo string-parton model. The model is based on the strings formation in elementary dipole-dipole collisions. The hardness of the elementary interaction is defined by a transverse size of the colliding dipoles. The interaction between strings is realized in the accordance with the string fusion model prescriptions by the introduction of the lattice in the impact parameter plane and taking into account the finite rapidity length of strings. The particles species differentiation is implemented according to Schwinger mechanism. The parameters of the model are fixed with the experimental data on total inelastic cross section and charged multiplicity. In the framework of the model the long-range correlation functions with an accounting of strangeness have been studied. A new intensive event-by-event observable has been proposed, which characterizes the fraction of strange particles in the event. The predictions on the correlations between strangeness, multiplicity and mean transverse momentum are obtained for pp collisions at 7 TeV.

    Comments:
    4 pages, 2 figures, Proc. SQM2015
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1509.06696 [pdf]
    J.Phys.Conf.Ser.(2016)·6 citations
  5. 11

    [Submitted on 22 Sept 2015] (cross-list from hep-ph)

    The production of photons in relativistic heavy-ion collisions

    Jean-François Paquet🇨🇦 · Chun Shen🇨🇦 · Gabriel S. Denicol🇺🇸 · Matthew Luzum🇪🇸 · Björn Schenke🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

    In this work it is shown that the use of a hydrodynamical model of heavy ion collisions which incorporates recent developments, together with updated photon emission rates greatly improves agreement with both ALICE and PHENIX measurements of direct photons, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy. The event-by-event hydrodynamical model uses IP-Glasma initial states and includes, for the first time, both shear and bulk viscosities, along with second order couplings between the two viscosities. The effect of both shear and bulk viscosities on the photon rates is studied, and those transport coefficients are shown to have measurable consequences on the photon momentum anisotropy.

    Comments:
    17 pages, 13 figures. Augmented discussion; now also includes STAR photon data. Some typos corrected; agrees with published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1509.06738 [pdf]
    PRC(2016)·442 citations

Affiliations

first authorsco-authorsvia INSPIRE