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Nuclear Theory·nucl-th

Monday·April 18, 2016

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    [Submitted on 15 Apr 2016]

    -meson production at forward/backward rapidity in high-energy nuclear collisions from a multiphase transport model

    Y. J. Ye🇨🇳 · J. H. Chen🇨🇳 · Y. G. Ma🇨🇳 · S. Zhang🇨🇳 · C. Zhong🇨🇳

    Within the framework of a multiphase transport model (AMPT), the -meson production is studied in d+Au collisions at \srt = {200} GeV in the forward (d-going, ) and backward (Au-going, ) direction. The AMPT model with string melting version (parton cascade turning-on) describes the experimental data well, while the pure hadronic transport scenario of the AMPT model underestimates the -meson production rate in comparison with the data. Detailed investigations including the rapidity, transverse momentum and collision system size dependencies of -meson nuclear modification factor indicate that a combination of the initial state effect and a follow-up parton cascade is required in the AMPT model to describe the data. Similar calculations are also present in p+Pb collisions at \srt = {5.02} TeV and p+p collisions at \srt = {2.76} TeV. The findings from a comparison of AMPT model study with the data are consistent with that at RHIC energy.

    Comments:
    5 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1604.04336 [pdf]
    PRC(2016)·4 citations
  2. 02

    [Submitted on 15 Apr 2016]

    On the possibility of generating a 4-neutron resonance with a {\boldmath } isospin 3-neutron force

    E. Hiyama · R. Lazauskas🇫🇷 · J. Carbonell🇫🇷 · M. Kamimura🇯🇵

    We consider the theoretical possibility to generate a narrow resonance in the four neutron system as suggested by a recent experimental result. To that end, a phenomenological three neutron force is introduced, in addition to a realistic interaction. We inquire what should be the strength of the force in order to generate such a resonance. The reliability of the three-neutron force in the channel is exmined, by analyzing its consistency with the low-lying states of H, He and Li and the scattering. The {\it ab initio} solution of the Schrödinger equation is obtained using the complex scaling method with boundary conditions appropiate to the four-body resonances. We find that in order to generate narrow resonant states a remarkably attractive force in the channel is required.

    Comments:
    11 pages, 11 figures, minor change, published version, to be published in Physical Review C
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1604.04363 [pdf]
    PRC(2016)·86 citations
  3. 03

    [Submitted on 15 Apr 2016]

    Magnetic hexadecapole gamma transitions and neutrino-nuclear responses in medium heavy nuclei

    Lotta Jokiniemi🇫🇮 · Jouni Suhonen🇫🇮 · Hiroyasu Ejiri🇯🇵

    Neutrino-nuclear responses in the form of squares of nuclear matrix elements,NMEs, are crucial for studies of neutrino-induced processes in nuclei. In this work we investigate magnetic hexadecapole (M4) NMEs in medium-heavy nuclei. The experimentally derived NMEs, (M4), deduced from observed M4 transition half-lives are compared with the single-quasiparticle (QP) NMEs, (M4), and the microscopic quasiparticle-phonon model (MQPM) NMEs (M4). The experimentally driven M4 NMEs are found to be reduced by a coefficient with respect to (M4) and by with respect to (M4). The M4 NMEs are reduced a little by the quasiparticle-phonon correlations of the MQPM wave functions but mainly by other nucleonic and non-nucleonic correlations which are not explicitly included in the MQPM. The found reduction rates are of the same order of magnitude as those for magnetic quadrupole transitions and Gamow-Teller (GT) and spin-dipole (SD) transitions. The impact of the found reduction coefficients on the magnitudes of the NMEs involved in astroneutrino interactions and neutrinoless double beta decays are discussed.

    Comments:
    14 pages, 5 figures, accepted research article in AHEP (2016) in the Special Issue on 'Neutrino Physics in the Frontiers of Intensities and Very High Sensitivities 2016, Advances in High Energy Physics (2016)
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1604.04399 [pdf]
    Adv.High Energy Phys.(2016)·9 citations
  4. 04

    [Submitted on 15 Apr 2016]

    Ultra-relativistic nuclear collisions: where the spectators flow?

    Sergei A. Voloshin🇺🇸 · Takafumi Niida🇺🇸

    In high energy heavy ion collisions, the directed flow of particles is conventionally measured with respect to that of the projectile spectators, which is defined as positive direction. But it is not known if the spectators deflect in the "outward" direction or "inward" -- toward the center line of the collision. In this Letter we discuss how the measurements of the directed flow at mid-rapidity, especially in asymmetric collision such as Cu+Au, can be used to answer this question. We show that the existing data strongly favor the case that the spectators, in the ultrarelativistic collisions, on average deflect outwards.

    Comments:
    4 pages, 4 figures, typos corrected, added grid to Fig.4
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1604.04597 [pdf]
    PRC(2016)·26 citations
  5. 05

    [Submitted on 6 Apr 2016] (cross-list from cond-mat.mes-hall)

    Quantum Wigner molecules in semiconductor quantum dots and cold-atom optical traps and their mathematical symmetries

    Constantine Yannouleas · Uzi Landman

    Strong repelling interactions between a few fermions or bosons confined in two-dimensional circular traps lead to particle localization and formation of quantum Wigner molecules (QWMs) possessing definite point-group space symmetries. These point-group symmetries are "hidden" (or emergent), namely they cannot be traced in the circular single-particle densities (SPDs) associated with the exact many-body wave functions, but they are manifested as characteristic signatures in the ro-vibrational spectra. An example, among many, are the few-body QWM states under a high magnetic field or at fast rotation, which are precursor states for the fractional quantum Hall effect. The hidden geometric symmetries can be directly revealed by using spin-resolved conditional probability distributions, which are extracted from configuration-interaction (CI), exact-diagonalization wave functions. The hidden symmetries can also be revealed in the CI SPDs by reducing the symmetry of the trap (from circular to elliptic to quasi-linear). In addition the hidden symmetries are directly connected to the explicitly broken-symmetry (BS) solutions of mean-field approaches, such as unrestricted Hartree-Fock (UHF). A companion step of restoration of the broken symmetries via projection operators applied on the BS-UHF solutions produces wave functions directly comparable to the CI ones, and sheds further light into the role played by the emergence of hidden symmetries in the exact many-body wave functions. Illustrative examples of the importance of hidden symmetries in the many-body problem of few electrons in semiconductor quantum dots and of few ultracold atoms in optical traps (where unprecedented control of the interparticle interaction has been experimentally achieved recently) will be presented.

    Comments:
    11 pages with 4 color figures. Invited extended abstract for the Proceedings of the 16th International Conference on Computational and Mathematical Methods in Science and Engineering, CMMSE 2016, Rota, Cadiz, Spain, 4-8 July, 2016
    Subjects:
    Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    1604.01749 [pdf]
    0 citations
  6. 06

    [Submitted on 14 Apr 2016] (cross-list from hep-ph)

    Cumulative production of pions by heavy baryonic resonances in proton-nucleus collisions

    A. Motornenko🇺🇦 · M. I. Gorenstein🇺🇦

    Pion production in proton-nucleus (p+A) collisions outside the kinematical boundary of proton-nucleon (p+N) reactions, the so-called cumulative effect, is studied. Restrictions from energy-momentum conservation on the energy of pions emitted in the backward direction in the target rest frame are analyzed. It is assumed that the cumulative pions are produced in p+A reactions by heavy baryonic resonances. The baryonic resonances are first created in p+N reactions. Due to successive collisions with nuclear nucleons the masses of these resonances may then increase and, simultaneously, their longitudinal velocities decrease. We also use the Ultra relativistic Quantum Molecular Dynamics model to reveal the key role of successive collisions of baryonic resonances with nuclear nucleons for cumulative pion production in p+A reactions. Further experimental studies of cumulative hadron production in p+A reactions at high collision energies are needed to search for heavy hadron-like objects and investigate their properties.

    Comments:
    21 pages, 36 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1604.04308 [pdf]
    J.Phys.G(2017)·13 citations
  7. 07

    [Submitted on 15 Apr 2016] (cross-list from hep-ph)

    Classical Electromagnetic Fields from Quantum Sources in Heavy-Ion Collisions

    Robert Holliday🇺🇸 · Ryan McCarty🇺🇸 · Balthazar Peroutka🇺🇸 · Kirill Tuchin🇺🇸

    Electromagnetic fields are generated in high energy nuclear collisions by spectator valence protons. These fields are traditionally computed by integrating the Maxwell equations with point sources. One might expect that such an approach is valid at distances much larger than the proton size and thus such a classical approach should work well for almost the entire interaction region in the case of heavy nuclei. We argue that, in fact, the contrary is true: due to the quantum diffusion of the proton wave function, the classical approximation breaks down at distances of the order of the system size. We compute the electromagnetic field created by a charged particle described initially as a Gaussian wave packet of width 1 fm and evolving in vacuum according to the Klein-Gordon equation. We completely neglect the medium effects. We show that the dynamics, magnitude and even sign of the electromagnetic field created by classical and quantum sources are different.

    Comments:
    12 pages, 4 figures. V2: a numerical error corrected, figures improved, other minor improvements
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1604.04572 [pdf]
    NPA(2017)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE