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Nuclear Theory·nucl-th

Monday·August 31, 2015

9 papers—3 primary·6 cross-listed

All9Primary3Cross-lists6
  1. 04

    [Submitted on 27 Aug 2015] (cross-list from hep-ph)

    Electromagnetic Heavy Lepton Pair Production in Relativistic Heavy-Ion Collisions

    M. Y. Sengul🇹🇷 · M. C. Guclu🇹🇷 · O. Mercan🇹🇷 · N. G. Karakus🇹🇷

    We calculate the cross sections of electromagnetic productions of muon and tauon pair productions from the ultra-relativistic heavy ion collisions. Since the Compton wavelengths of muon and tauon are comparable to the radius of the colliding ions, nuclear form factors play important roles for calculating the cross sections. Recent measurement [1] indicates that the neutrons are differently distributed from the protons therefore this affects the cross section of the heavy lepton pair production. In order to see the effects of the neutron distributions in the nucleus, we used analytical expression of the Fourier transforms of the Wood-Saxon distribution. Cross section calculations show that Wood-Saxon distribution function is more sensitive to the parameter R compare to the parameter a.

    Comments:
    14 pages, 33 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1508.07051 [pdf]
    EPJC(2016)·18 citations
  2. 05

    [Submitted on 28 Aug 2015] (cross-list from hep-lat)

    Lattice study on QCD-like theory with exact center symmetry

    Takumi Iritani🇯🇵 · Etsuko Itou🇯🇵 · Tatsuhiro Misumi🇯🇵

    We investigate QCD-like theory with exact center symmetry, with emphasis on the finite-temperature phase transition concerning center and chiral symmetries. On the lattice, we formulate center symmetric gauge theory with three fundamental Wilson quarks by twisting quark boundary conditions in a compact direction (-QCD model). We calculate the expectation value of Polyakov loop and the chiral condensate as a function of temperature on 16^3 x 4 and 20^3 x 4 lattices along the line of constant physics realizing . We find out the first-order center phase transition, where the hysteresis of the magnitude of Polyakov loop exists depending on thermalization processes. We show that chiral condensate decreases around the critical temperature in a similar way to that of the standard three-flavor QCD, as it has the hysteresis in the same range as that of Polyakov loop. We also show that the flavor symmetry breaking due to the twisted boundary condition gets qualitatively manifest in the high-temperature phase. These results are consistent with the predictions based on the chiral effective model in the literature. Our approach could provide novel insights to the nonperturbative connection between the center and chiral properties.

    Comments:
    25 pages, 6 figures, to apper in JHEP
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1508.07132 [pdf]
    JHEP(2015)·38 citations
  3. 06

    [Submitted on 28 Aug 2015] (cross-list from hep-ph)

    The light scalar mesons as tetraquarks

    Gernot Eichmann🇩🇪 · Christian S. Fischer🇩🇪 · Walter Heupel🇩🇪

    We present a numerical solution of the four-quark Bethe-Salpeter equation for ground-state scalar tetraquarks with J^PC = 0^++. We find that the four-body equation dynamically generates pseudoscalar-meson poles in the Bethe-Salpeter amplitude. The resulting tetraquarks are genuine four-quark states that are dominated by pseudoscalar meson-meson correlations. Diquark-antidiquark contributions are subleading because of their larger mass scale. In the light quark sector, the sensitivity of the tetraquark wave function to the pion poles leads to an isoscalar tetraquark mass M_sigma ~ 350 MeV which is comparable to that of the sigma/f0(500). The masses of its multiplet partners kappa and a0/f0 follow a similar pattern. This provides support for a tetraquark interpretation of the light scalar meson nonet in terms of 'meson molecules'.

    Comments:
    7 pages, 4 figures; version accepted by PLB
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1508.07178 [pdf]
    PLB(2016)·90 citations
  4. 07

    [Submitted on 28 Aug 2015] (cross-list from hep-ph)

    Thermalization, evolution and LHC observables in an integrated hydrokinetic model of A+A collisions

    V.Yu. Naboka🇺🇦 · Iu.A. Karpenko🇺🇦 · Yu.M. Sinyukov🇺🇦

    A further development of the evolutionary picture of A+A collisions, which we call the integrated HydroKinetic Model (iHKM), is proposed. The model comprises a generator of the initial state GLISSANDO, pre-thermal dynamics of A+A collisions leading to thermalization, subsequent relativistic viscous hydrodynamic expansion of quark-gluon and hadron medium (vHLLE), its particlization, and finally hadronic cascade ultrarelativistic QMD. We calculate mid-rapidity charged-particle multiplicities, pion, kaon, and antiproton spectra, charged-particle elliptic flows, and pion interferometry radii for Pb+Pb collisions at the energies available at the CERN Large Hadron Collider, TeV, at different centralities. We find that the best description of the experimental data is reached when the initial states are attributed to the very small initial time 0.1 fm/c, the pre-thermal stage (thermalization process) lasts at least until 1 fm/c, and the shear viscosity at the hydrodynamic stage of the matter evolution has its minimal value, . At the same time it is observed that the various momentum anisotropies of the initial states, different initial and relaxation times, as well as even a treatment of the pre-thermal stage within just viscous or ideal hydrodynamic approach, leads sometimes to worse but nevertheless similar results, if the normalization of maximal initial energy density in most central events is adjusted to reproduce the final hadron multiplicity in each scenario. This can explain a good enough data description in numerous variants of hybrid models without a prethermal stage when the initial energy densities are defined up to a common factor.

    Comments:
    22 pages, 11 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1508.07204 [pdf]
    PRC(2016)·28 citations
  5. 08

    [Submitted on 27 Aug 2015] (cross-list from physics.plasm-ph)

    Direct and secondary nuclear excitation with x-ray free-electron lasers

    Jonas Gunst · Yuanbin Wu · Naveen Kumar · Christoph H. Keitel · Adriana Pálffy

    The direct and secondary nuclear excitation produced by an x-ray free electron laser when interacting with a solid-state nuclear target is investigated theoretically. When driven at the resonance energy, the x-ray free electron laser can produce direct photoexcitation. However, the dominant process in that interaction is the photoelectric effect producing a cold and very dense plasma in which also secondary processes such as nuclear excitation by electron capture may occur. We develop a realistic theoretical model to quantify the temporal dynamics of the plasma and the magnitude of the secondary excitation therein. Numerical results show that depending on the nuclear transition energy and the temperature and charge states reached in the plasma, secondary nuclear excitation by electron capture may dominate the direct photoexcitation by several orders of magnitude, as it is the case for the 4.8 keV transition from the isomeric state of Mo, or it can be negligible, as it is the case for the 14.4 keV Mössbauer transition in . These findings are most relevant for future nuclear quantum optics experiments at x-ray free electron laser facilities.

    Comments:
    17 pages, 7 figures; minor corrections made; accepted by Physics of Plasmas
    Subjects:
    Plasma Physics (physics.plasm-ph); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
    arXiv:
    1508.07264 [pdf]
    Phys.Plasmas(2015)·15 citations
  6. 09

    [Submitted on 28 Aug 2015] (cross-list from hep-ph)

    New physics effects on neutrinoless double beta decay from right-handed current

    Shao-Feng Ge🇩🇪 · Manfred Lindner🇩🇪 · Sudhanwa Patra🇩🇪

    We study the impact of new physics contributions to neutrinoless double beta decay arising from right-handed current in comparison with the standard mechanism. If the light neutrinos obtain their masses from Type-II seesaw within left-right symmetric model, where the Type-I contribution is suppressed to negligible extent, the right-handed PMNS matrix is the same as its left-handed counterpart, making it highly predictable and can be tested at next-generation experiments. It is very attractive, especially with recent cosmological constraint favoring the normal hierarchy under which the neutrinoless double beta decay is too small to be observed unless new physics appears as indicated by the recent diboson excess observed at ATLAS. The relative contributions from left- and right-handed currents can be reconstructed with the ratio between lifetimes of two different isotopes as well as the ratio of nuclear matrix elements. In this way, the theoretical uncertainties in the calculation of nuclear matrix elements can be essentially avoided. We also discuss the interplay of neutrinoless double beta decay measurements with cosmology, beta decay, and neutrino oscillation.

    Comments:
    10 pages, 5 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1508.07286 [pdf]
    JHEP(2015)·51 citations

Affiliations

first authorsco-authorsvia INSPIRE