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Nuclear Theory·nucl-th

Thursday·April 23, 2015

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    Hadronic and partonic sources of direct photons in relativistic heavy-ion collisions

    O. Linnyk🇩🇪 · V. Konchakovski🇩🇪 · T. Steinert🇩🇪 · W. Cassing🇩🇪 · E.L. Bratkovskaya🇩🇪

    The direct photon spectra and flow (, ) in heavy-ion collisions at SPS, RHIC and LHC energies are investigated within a relativistic transport approach incorporating both hadronic and partonic phases -- the Parton-Hadron-String Dynamics (PHSD). In the present work, four extensions are introduced compared to our previous calculations: (i) going beyond the soft-photon approximation (SPA) in the calculation of the bremsstrahlung processes , (ii) quantifying the suppression due to the Landau-Pomeranchuk-Migdal (LPM) coherence effect, (iii) adding the additional channels and and (iv) providing predictions for Pb+Pb collisions at = 2.76 TeV. The first issue extends the applicability of the bremsstrahlung calculations to higher photon energies in order to understand the relevant sources in the region GeV, while the LPM correction turns out to be important for GeV in the partonic phase. The results suggest that a large elliptic flow of the direct photons signals a significant contribution of photons produced in interactions of secondary mesons and baryons in the late (hadronic) stage of the heavy-ion collision. In order to further differentiate the origin of the direct photon azimuthal asymmetry (late hadron interactions vs electromagnetic fields in the initial stage), we provide predictions for the triangular flow of direct photons. Additionally, we illustrate the magnitude of the photon production in the partonic and hadronic phases as functions of time and local energy density. Finally, the 'cocktail' method for an estimation of the background photon elliptic flow, which is widely used in the experimental works, is supported by the calculations within the PHSD transport approach.

    nucl-thhep-phPRC(2015)·111 citations
  2. 02

    T-matrix in discrete oscillator representation

    V. S. Vasilevsky · M. D. Soloha-Klymchak

    We investigate T-matrix for bound and continuous-spectrum states in the discrete oscillator representation. The investigation is carried out for a model problem - the particle in the field of a central potential. A system of linear equations is derived to determine the coefficients of the T-matrix expansion in the oscillator functions. We selected four potentials (Gaussian, exponential, Yukawa, and square-well ones) to demonstrate peculiarities of the T-matrix and its dependence on the potential shape. We also study how the T-matrix expansion coefficients depend on the parameters of the oscillator basis such as the oscillator length and the number of basis functions involved in calculations.

    nucl-thquant-phUkr.J.Phys.(2015)·2 citations
  3. 03

    Prospective study on microscopic potential with Gogny interaction

    G. Blanchon · M. Dupuis · H. F. Arellano

    We present our current studies and our future plans on microscopic potential based on effective nucleon-nucleon interaction and many-body theory. This framework treats in an unified way nuclear structure and reaction. It offers the opportunity to link the underlying effective interaction to nucleon scattering observables. The more consistently connected to a variety of reaction and structure experimental data the framework will be, the more constrained effective interaction will be. As a proof of concept, we present some recent results for both neutron and proton scattered from spherical target nucleus, namely 40 Ca, using the Gogny D1S interaction. Possible fruitful crosstalks between microscopic potential, phenomenological potential and effective interaction are exposed. We then draw some prospective plans for the forthcoming years including scattering from spherical nuclei experiencing pairing correlations, scattering from axially deformed nuclei, and new effective interaction with reaction constraints.

    nucl-thEPJA(2015)·15 citations
  4. 04

    Entropic and enthalpic phase transitions in high energy density nuclear matter

    Igor Iosilevskiy🇷🇺

    Features of Gas-Liquid (GL) and Quark-Hadron (QH) phase transitions (PT) in dense nuclear matter are under discussion in comparison with their terrestrial counterparts, e.g. so-called "plasma" PT in shock-compressed hydrogen, nitrogen etc. Both, GLPT and QHPT, when being represented in widely accepted temperature - baryonic chemical potential plane, are often considered as similar, i.e. amenable to one-to-one mapping by simple scaling. It is argued that this impression is illusive and that GLPT and QHPT belong to different classes: GLPT is typical enthalpic PT (Van-der-Waals-like) while QHPT ("deconfinement-driven") is typical entropic PT. Subdivision of 1st-order fluid-fluid phase transitions into enthalpy- and entropy-driven subclasses was proposed previously [arXiv:1403.8053]. Properties of enthalpic and entropic PTs differ significantly. Entropic PTs are always internal parts of more general and extended thermodynamic anomalies - domains with abnormal (negative) sign for the set of (usually positive) second derivatives of thermodynamic potential. Three of them are of primary importance: Gruneizen and thermal expansion and thermal pressure coefficients. Negative sign of these derivatives lead to violation of standard behavior and relative order in P-V plane for many iso-lines, e.g. isotherms, isentropes, shock adiabats etc. Entropic PTs have more complicated topology of stable and metastable areas within its two-phase region in comparison with conventional enthalpic (VdW-like) PTs. In particular, new additional metastable region, bounded by new additional spinodal, appears in the case of entropic PT. All the features of entropic PTs and accompanying abnormal thermodynamics region have transparent geometrical interpretation - multi-layered structure of thermodynamic surfaces for temperature, entropy and internal energy as a pressure-volume functions, e.g. T(P,V), S(P,V) and U(P,V).

    nucl-thhep-thphysics.plasm-ph11 citations

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