PaperPanorama
FAQ

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
  5. 05

    Nonchiral enhancement of scalar glueball decay in the Witten-Sakai-Sugimoto model

    Frederic Brünner🇦🇹 · Anton Rebhan🇦🇹

    We estimate the consequences of finite masses of pseudoscalar mesons on the decay rates of scalar glueballs in the Witten-Sakai-Sugimoto model, a top-down holographic model of low-energy QCD, by extrapolating from the calculable vertex of glueball fields and the eta' meson which follows from the Witten-Veneziano mechanism for giving mass to the latter. Evaluating the effect on the recently calculated decay rates of glueballs in the Witten-Sakai-Sugimoto model, we find a strong enhancement of the decay of scalar glueballs into kaons and eta mesons, in fairly close agreement with experimental data on the glueball candidate f0(1710).

    ↳ hep-phhep-thnucl-thPRL(2015)·68 citations
  6. 06

    Second Order Transport Coefficient from Chiral Anomaly at Weak Coupling: Diagrammatic Resummation

    Amadeo Jimenez-Alba🇪🇸 · Ho-Ung Yee🇺🇸

    We compute one of the second order transport coefficients arising from the chiral anomaly in a high temperature weakly coupled regime of quark-gluon plasma. This transport coefficient is responsible for the CP-odd current that is proportional to the time derivative of the magnetic field, and can be considered as a first correction to the chiral magnetic conductivity at finite, small frequency. We observe that this transport coefficient has a non-analytic dependence on the coupling as at weak coupling regime, which necessitates a re-summation of infinite ladder diagrams with leading pinch singularities to get a correct leading log result: a feature quite similar to that one finds in the computation of electric conductivity. We formulate and solve the relevant CP-odd Schwinger-Dyson equation in real-time perturbation theory that reduces to a coupled set of second order differential equations at leading log order. Our result for this second order transport coefficient indicates that chiral magnetic current has some resistance to the time change of magnetic field, which may be called "chiral induction effect". We also discuss the case of color current induced by color magnetic field.

    ↳ hep-phhep-thnucl-thPRD(2015)·20 citations
  7. 07

    The role of the g9/2 orbital in the development of collectivity in the A = 60 region: The case of 61Co

    A. D. Ayangeakaa · S. Zhu · R. V. F. Janssens · M. P. Carpenter · M. Albers · M. Alcorta · T. Baugher · P. F. Bertone · C. J. Chiara · P. Chowdhury · H. M. David · A. N. Deacon and 11 other authors

    An extensive study of the level structure of 61Co has been performed following the complex 26Mg(48Ca, 2a4npg)61Co reaction at beam energies of 275, 290 and 320 MeV using Gammasphere and the Fragment Mass Analyzer (FMA). The low-spin structure is discussed within the framework of shell-model calculations using the GXPF1A effective interaction. Two quasi-rotational bands consisting of stretched-E2 transitions have been established up to spins I = 41/2 and (43/2), and excitation energies of 17 and 20 MeV, respectively. These are interpreted as signature partners built on a neutron {\nu}(g9/2)2 configuration coupled to a proton {\pi}p3/2 state, based on Cranked Shell Model (CSM) calculations and comparisons with observations in neighboring nuclei. In addition, four I = 1 bands were populated to high spin, with the yrast dipole band interpreted as a possible candidate for the shears mechanism, a process seldom observed thus far in this mass region.

    ↳ nucl-exnucl-thPRC(2015)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE