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Nuclear Theory·nucl-th

Wednesday·May 24, 2017

9 papers—7 primary·2 cross-listed

All9Primary7Cross-lists2
  1. 01

    [Submitted on 22 May 2017]

    Modelling double charge exchange response function for tetraneutron system

    Rimantas Lazauskas🇫🇷 · Emiko Hiyama🇯🇵 · Jaume Carbonell🇫🇷

    This work is an attempt to model the response function of a recent RIKEN experimental study of the double charge exchange He(He,Be)n reaction in order to put in evidence an eventual enhancement mechanism of the zero energy cross section, including a near-threshold resonance. This resonance can indeed be reproduced only by adding to the standard nuclear Hamiltonian an unphysically large T=3/2 attractive 3n-force which destroys the neighboring nuclear chart. No other mechanisms like cusps or related structures were found.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1705.07927 [pdf]
    PTEP(2017)·15 citations
  2. 02

    [Submitted on 22 May 2017]

    The shear and bulk relaxation times from the general correlation functions

    Alina Czajka🇨🇦 · Sangyong Jeon🇨🇦

    In this paper we present two quantum field theoretical analyses on the shear and bulk relaxation times. First, we discuss how to find Kubo formulas for the shear and the bulk relaxation times. Next, we provide results on the shear viscosity relaxation time obtained within the diagrammatic approach for the massless theory.

    Comments:
    4 pages, 2 figures, proceedings of XXVIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions - Quark Matter 2017
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1705.07971 [pdf]
    NPA(2017)·0 citations
  3. 03

    [Submitted on 23 May 2017]

    Multiplicity Derivative: A new signature of first order phase transition in intermediate energy heavy ion collision

    S. Mallik🇮🇳 · G. Chaudhuri🇮🇳 · P. Das🇮🇳 · S Das Gupta🇨🇦

    Measurement of M, the total multiplicity, for central collision between comparable mass heavy ions can provide a signature for first order phase transition. The derivative of M with respect to E*/A where E* is the excitation energy in the centre of mass and A the total mass of the dissociating system is expected to go through maximum as a function of E*. Theoretical modelling shows that this is the energy where the specific heat Cv maximizes which typically happens at first order phase transition. The measurement of total M is probably feasible in more than one laboratory.

    Comments:
    4 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1705.08187 [pdf]
    PRC(2017)·29 citations
  4. 04

    [Submitted on 23 May 2017]

    A kinetic regime of hydrodynamic fluctuations and long time tails for a Bjorken expansion

    Yukinao Akamatsu🇯🇵 · Aleksas Mazeliauskas🇺🇸 · Derek Teaney🇺🇸

    We develop a set of kinetic equations for hydrodynamic fluctuations which are equivalent to nonlinear hydrodynamics with noise. The hydro-kinetic equations can be coupled to existing second order hydrodynamic codes to incorporate the physics of these fluctuations, which become dominant near the critical point. We use the hydro-kinetic equations to calculate the modifications of energy momentum tensor by thermal fluctuations from the earliest moments and at late times in Bjorken expansion. The solution to the kinetic equations precisely determines the coefficient of the first fractional power () in the energy momentum tensor gradient expansion. Numerically, we find that the contribution to the longitudinal pressure from hydrodynamic fluctuations is comparable to the second order hydrodynamic terms for typical medium parameters used to simulate heavy ion collisions.

    Comments:
    5 pages, no figures, Proceedings for the 26th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2017), February 5-11 2017, Chicago, Illinois, USA
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1705.08199 [pdf]
    NPA(2017)·4 citations
  5. 05

    [Submitted on 23 May 2017]

    Specific features and symmetries for magnetic and chiral bands in nuclei

    A. A. Raduta

    Magnetic and chiral bands have been a hot subject for more than twenty years. Therefore, quite large volumes of experimental data as well as theoretical descriptions have been accumulated. Although some of the formalisms are not so easy to handle, the results agree impressively well with the data. The objective of this paper is to review the actual status of both experimental and theoretical investigations. Aiming at making this material accessible to a large variety of readers, including young students and researchers, I gave some details on the schematic models which are able to unveil the main features of chirality in nuclei. Also, since most formalisms use a rigid triaxial rotor for the nuclear system's core, I devoted some space to the semi-classical description of the rigid triaxial as well as of the tilted triaxial rotor. In order to answer the question whether the chiral phenomenon is spread over the whole nuclear chart and whether it is specific only to a certain type of nuclei, odd-odd, odd-even or even-even, the current results in the mass regions of are briefly described for all kinds of odd/even-odd/even systems. The chiral geometry is a sufficient condition for a system of proton-particle, neutron-hole and a triaxial rotor to have the electromagnetic properties of chiral bands. In order to prove that such geometry is not unique for generating magnetic bands with chiral features, I presented a mechanism for a new type of chiral bands. One tries to underline the fact that this rapidly developing field is very successful in pushing forward nuclear structure studies.

    Comments:
    80 pages, 22 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1705.08220 [pdf]
    PPNP(2016)·56 citations
  6. 06

    [Submitted on 23 May 2017]

    Inhomogeneity growth in two-component fermionic systems

    P.Napolitani🇫🇷 · M.Colonna🇮🇹

    The dynamics of fermionic many-body systems is investigated in the framework of Boltzmann-Langevin (BL) stochastic one-body approaches. Within the recently introduced BLOB model, we examine the interplay between mean-field effects and two-body correlations, of stochastic nature, for nuclear matter at moderate temperature and in several density conditions, corresponding to stable or mechanically unstable situations. Numerical results are compared to analytic expectations for the fluctuation amplitude of isoscalar and isovector densities, probing the link to the properties of the employed effective interaction, namely symmetry energy (for isovector modes) and incompressibility (for isoscalar modes). For unstable systems, clusterization is observed. The associated features are compared to analytical results for the typical length and time scales characterizing the growth of unstable modes in nuclear matter and for the isotopic variance of the emerging fragments. We show that the BLOB model is generally better suited than simplified approaches previously introduced to solve the BL equation, and it is therefore more advantageous in applications to open systems, like heavy ion collisions.

    Comments:
    19 pages, 13 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1705.08268 [pdf]
    PRC(2017)·17 citations
  7. 07

    [Submitted on 23 May 2017]

    Mass differences and neutron pairing in Ca, Sn and Pb isotopes

    B.S. Ishkhanov · S.V. Sidorov · T.Yu. Tretyakova · E.V. Vladimirova

    Various estimates of the even-odd effect of the mass shell of atomic nuclei are considered. Based on the experimental mass values of the Ca, Sn, and Pb isotopes, the dependence of the energy gap on the neutrons number is traced and the relationship of this characteristic to the properties of external neutron subshells is shown. In nuclei with closed proton shells, effects directly related to neutron pairing and effects of nucleon shells are discussed.

    Comments:
    corrected typos
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1705.08329 [pdf]
    CPC(2017)·4 citations
  8. 08

    [Submitted on 23 May 2017] (cross-list from hep-ph)

    New explicit expressions for Dirac bilinears

    Cédric Lorcé (Ecole polytechnique, CPHT)🇫🇷

    We derive new explicit expressions for the Dirac bilinears based on a generic representation of the massive Dirac spinors with canonical polarization. These bilinears depend on a direction in Minkowski space which specifies the form of dynamics. We argue that such a dependence is unavoidable in a relativistic theory with spin, since it originates from Wigner rotation effects. Contrary to most of the expressions found in the literature, our ones are valid for all momenta and canonical polarizations of the spinors. As a by-product, we also obtain a generic explicit expression for the covariant spin vector.

    Comments:
    9 pages, version accepted in PRD
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1705.08370 [pdf]
    PRD(2018)·43 citations
  9. 09

    [Submitted on 23 May 2017] (cross-list from hep-ph)

    The transverse momentum distribution of hadrons within jets

    Zhong-Bo Kang🇺🇸 · Xiaohui Liu🇨🇳 · Felix Ringer🇺🇸 · Hongxi Xing🇺🇸

    We study the transverse momentum distribution of hadrons within jets, where the transverse momentum is defined with respect to the standard jet axis. We consider the case where the jet substructure measurement is performed for an inclusive jet sample . We demonstrate that this observable provides new opportunities to study transverse momentum dependent fragmentation functions (TMDFFs) which are currently poorly constrained from data, especially for gluons. The factorization of the cross section is obtained within Soft Collinear Effective Theory (SCET), and we show that the relevant TMDFFs are the same as for the more traditional processes semi-inclusive deep inelastic scattering (SIDIS) and electron-positron annihilation. Different than in SIDIS, the observable for the in-jet fragmentation does not depend on TMD parton distribution functions which allows for a cleaner and more direct probe of TMDFFs. We present numerical results and compare to available data from the LHC.

    Comments:
    28 pages, 3 figures, published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1705.08443 [pdf]
    JHEP(2017)·113 citations

Affiliations

first authorsco-authorsvia INSPIRE