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Nuclear Theory·nucl-th

Monday·September 30, 2019

5 papers—1 primary·4 cross-listed

All5Primary1Cross-lists4
  1. 02

    [Submitted on 27 Sept 2019] (cross-list from hep-ph)

    Evolution of magnetic fields in a transversely expanding highly conductive fluid

    M. Shokri🇮🇷 · N. Sadooghi🇮🇷

    Due to the absence of a transverse expansion with respect to the beam direction, the Bjorken flow is unable to describe certain observables in heavy ion collisions. This caveat has motivated the introduction of analytical relativistic hydrodynamics (RH) solutions with transverse expansion, in particular, the 3+1 self-similar (SSF) and Gubser flows. Inspired by recent generalizations of the Bjorken flow to the relativistic magnetohydrodynamics (RMHD), we present a procedure for a generalization of RH solutions to RMHD. Our method is mainly based on symmetry arguments. Using this method, we find the relation between RH degrees of freedom and the magnetic field evolution in the ideal limit for an infinitely conductive fluid, and determine the proper time dependence of the magnetic field in aforementioned flows. In the case of SSF, a family of solutions are found that are related through a certain differential equation. To find the magnetic field evolution in the Gubser flow, we solve RMHD equations for a stationary fluid in a conformally flat spacetime. The result is then Weyl transformed back into the Minkowski spacetime. In this case, the temporal evolution of the magnetic field exhibits a transmission between to near the center of the collision. The longitudinal component of the magnetic field is found to be sensitive to the transverse size of the fluid. We also find the radial evolution of the magnetic field for both flows. The radial domain of validity in the case of SSF is highly restricted, in contrast to the Gubser flow. A comparison of the results suggests that the Gubser RMHD may give a more appropriate qualitative picture of the magnetic field decay in the quark-gluon plasma (QGP).

    Comments:
    8 pages, 1 figures, XIII Quark Confinement and the Hadron Spectrum - Confinement2018, 31 July - 6 August 2018, Maynooth University, Ireland
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1909.12569 [pdf]
    PoS(2019)·1 citation
  2. 03

    [Submitted on 27 Sept 2019] (cross-list from hep-ph)

    On large mass and -meson photoproduction

    L. Szymanowski🇵🇱 · B. Pire🇫🇷 · S. Wallon🇫🇷

    Enlarging the set of hard exclusive reactions to be studied in the framework of QCD collinear factorization opens new possibilities to access generalized parton distributions (GPDs). We studied the photoproduction of a large invariant mass photon-photon or photon-meson pair in the generalized Bjorken regime which may be accessible both at JLab and at the EIC.

    Comments:
    4 pages, proccedings of the INT program 18-3 : Probing Nucleons and Nuclei in High Energy Collisions, to be published by World Scientific
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1909.12591 [pdf]
    0 citations
  3. 04

    [Submitted on 26 Sept 2019] (cross-list from hep-ph)

    -wave effects in diffractive electroproduction of heavy quarkonia from the photon-like transition

    Michal Krelina🇨🇱 · Jan Nemchik🇨🇿 · Roman Pasechnik🇸🇪

    We analyze the validity of a commonly used identification between structures of the virtual photon and vector meson transitions. In the existing studies of -wave vector-meson photoproduction in the literature, such an identification is typically performed in the light-front (LF) frame while the radial component of the meson wave function is rather postulated than computed from the first principles. The massive photon-like vertex, besides the -wave component, also contains an extra -wave admixture in the rest frame. However, the relative weight of these contributions cannot be justified by any reasonable nonrelativistic potential model. In this work, we investigate the relative role of the -wave contribution starting from the photon-like quarkonium transition in both frames: in the rest frame (with subsequent Melosh spin transform to the LF frame) and in the LF frame (without Melosh transform). We show that the photon-like transition imposed in the rest frame leads to significant discrepancies with the experimental data. In the second case we find that the corresponding total photoproduction cross sections are very close to those obtained with the "-wave only" transition, both leading to a good description of the data. However, we find that the "-wave only" transition leads to a better description of photoproduction data for excited heavy quarkonium states, which represent a more effective tool for study of -wave effects. Consequently, the predictions for production of excited states based on the photon-like structure of transition should be treated with a great care due to a much stronger sensitivity of the -wave contribution to the nodal structure of quarkonium wave functions.

    Comments:
    18 pages of Latex including 6 figures. The modified version which has been accepted for publication by European Physical Journal C
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1909.12770 [pdf]
    EPJC(2020)·18 citations
  4. 05

    [Submitted on 27 Sept 2019] (cross-list from hep-ph)

    Baryon modes in string breaking from gauge/string duality

    Oleg Andreev🇷🇺

    We consider the string breaking phenomenon within effective string models which purport to mimic QCD with two light flavors, with a special attention to baryon modes. We make some estimates of the string breaking distances at zero and non-zero baryon chemical potentials. Our estimates point towards the enhancement of baryon production in strong decays of heavy mesons in dense baryonic matter. We also suggest that the enhanced production of baryons in PbPb collisions is mainly due to larger values of chemical potential.

    Comments:
    6 pages, 3 figures; v2: typos corrected; v3: modification in title, comments and references added, journal version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1909.12771 [pdf]
    PLB(2020)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE