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Nuclear Theory·nucl-th

Monday·July 20, 2015

10 papers—4 primary·6 cross-listed

All10Primary4Cross-lists6
  1. 01

    [Submitted on 17 Jul 2015]

    Fluctuations in slope parameter in event-by-event hydrodynamics and momentum anisotropy in heavy ion collisions

    A. K. Chaudhuri🇮🇳

    In event by event hydrodynamic model, we have simulated 30-40\% Au+Au collisions at RHIC and computed the slope parameter from the invariant pion distribution. In each event, the slope parameter fluctuates azimuthally. Fourier expansion coefficients for the slope parameter and the Fourier expansion coefficients for the azimuthal distribution are found to be strongly correlated. Strong correlation between the two expansion coefficients suggests that in addition to azimuthal distribution, fluctuations in the slope parameter of the invariant distribution can as well be used to study the final state momentum anisotropy in relativistic energy heavy ion collisions. If measured experimentally, they can serve as additional constraint for hydrodynamical modeling.

    Comments:
    6 pages, 4 figures. arXiv admin note: text overlap with arXiv:1210.2249
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1507.04898 [pdf]
    1 citation
  2. 02

    [Submitted on 17 Jul 2015]

    Probing the properties of event-by-event distributions in Hanbury-Brown--Twiss radii

    Christopher Plumberg · Ulrich Heinz

    Hanbury-Brown--Twiss interferometry is a technique which yields effective widths (i.e., "HBT radii") of homogeneity regions in the fireballs produced in heavy ion collisions. Because the initial conditions of these collisions are stochastically fluctuating, the measured HBT radii also exhibit variation on an event-by-event basis. However, HBT measurements have, to date, been performed only on an ensemble-averaged basis, due to inherent limitations of finite particle statistics. In this paper, we show that experimental measurements to date are best characterized theoretically as weighted averages of the event-by-event HBT radii, and we propose a new method for extracting experimentally both the arithmetic mean and the variance of the event-by-event distribution of HBT radii. We demonstrate the extraction of the mean and variance of this distribution for a particular ensemble of numerically generated events, and offer some ideas to extend and generalize the method to enable measurement of higher moments of the HBT distribution as well.

    Comments:
    V1 - 18 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1507.04968 [pdf]
    PRC(2015)·13 citations
  3. 03

    [Submitted on 17 Jul 2015]

    Time evolution of the anisotropies of the hydrodynamically expanding sQGP

    Attila Bagoly🇭🇺 · Mate Csanad🇭🇺

    In high energy heavy ion collisions of RHIC and LHC, a strongly interacting quark gluon plasma (sQGP) is created. This medium undergoes a hydrodynamic evolution, before it freezes out to form a hadronic matter. The initial state of the sQGP is determined by the initial distribution of the participating nucleons and their interactions. Due to the finite number of nucleons, the initial distribution fluctuates on an event-by-event basis. The transverse plane anisotropy of the initial state can be translated into a series of anisotropy coefficients or eccentricities: second, third, fourth-order anisotropy etc. These anisotropies then evolve in time, and result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we investigate the time evolution of the anisotropies. With a numerical hydrodynamic code, we analyze how the speed of sound and viscosity influence this evolution.

    Comments:
    10 pages, 6 figures. To appear in the Gribov-85 Memorial Workshop's proceedings volume. Supported by OTKA NK 101438
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1507.05005 [pdf]
    Int.J.Mod.Phys.A(2016)·2 citations
  4. 04

    [Submitted on 17 Jul 2015]

    Analytical mass formula and nuclear surface properties in the ETF approximation

    F. Aymard🇫🇷 · F. Gulminelli🇫🇷 · J. Margueron🇫🇷

    The problem of the determination of the nuclear surface and surface symmetry energy is addressed in the framework of the Extended Thomas Fermi (ETF) approximation using Skyrme functionals. We propose an analytical model for the density profiles with variationally determined diffuseness parameters. For the case of symmetric nuclei, the resulting ETF functional can be exactly integrated, leading to an analytical formula expressing the surface energy as a function of the couplings of the energy functional. The importance of non-local terms is stressed, which cannot be simply deduced from the local part of the functional. In the case of asymmetric nuclei, we propose an approximate expression for the diffuseness and the surface energy. These quantities are analytically related to the parameters of the energy functional. In particular, the influence of the different equation of state parameters can be explicitly quantified. Detailed analyses of the different energy components (local/non-local, isoscalar/isovector, surface/curvature and higher order) are also performed. Our analytical solution of the ETF integral improves over previous models and leads to a precision better than 200 keV per nucleon in the determination of the nuclear binding energy for dripline nuclei.

    Comments:
    27 pages, 18 figures, submitted to PRC
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1507.05064 [pdf]
    J.Phys.G(2016)·7 citations

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first authorsco-authorsvia INSPIRE