PaperPanorama
FAQ

Nuclear Theory·nucl-th

Wednesday·September 13, 2017

10 papers—7 primary·3 cross-listed

All10Primary7Cross-lists3
  1. 08

    [Submitted on 11 Sept 2017] (cross-list from hep-ph)

    Approach to equilibrium of quarkonium in quark-gluon plasma

    Xiaojun Yao🇺🇸 · Berndt Müller🇺🇸

    We calculate the dissociation and recombination rates of in quark-gluon plasma by using potential non-relativistic QCD. We then study the dynamical in-medium evolution of the system in a periodic box via the Boltzmann equation and explore how the system reaches equilibrium. We find that interactions between the free heavy quarks and the medium are necessary for the system to reach equilibrium. We find that the angular distribution of probes the stages at which recombination occurs. Finally, we study the system under a longitudinal expansion and show that different initial conditions evolve to distinct final ratios of hidden and open flavors. We argue that experimental measurements of the ratio could address open questions in the quarkonium production in heavy ion collisions.

    Comments:
    6 pages, 5 figures, accepted version; a missing factor in Eq.(6) is added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1709.03529 [pdf]
    PRC(2018)·65 citations
  2. 09

    [Submitted on 11 Sept 2017] (cross-list from nucl-ex)

    Collective long-range particle correlations in proton-proton and proton-nucleus collisions at the LHC with the CMS detector

    Zhenyu Chen🇺🇸

    Measurements of two-particle angular correlations of inclusive charged particles as well as identified strange hadron in pp and pPb collisions are presented over a wide range in pseudorapidity and full azimuth. The data were collected using the CMS detector at the LHC, with nucleon-nucleon center-of-mass energy of 5.02 TeV for pPb collisions and 5, 7, 13 TeV for pp collisions. The results are compared to semi-peripheral PbPb collision data at center-of-mass energy of 2.76 TeV, covering similar charged-particle multiplicity ranges of the events. For high-multiplicity pp and pPb events, a clear particle species dependence of is observed for GeV/c. When divided by the number of constituent quarks and compared at the same transverse kinetic energy per quark, a universal scaling over a broad range of particle transverse kinetic energy has been observed. For high-multiplicity pp collisions at 13 TeV, the values obtained for inclusive charged particles with two-, four- and six-particle correlations are found to be comparable within uncertainties. These measurements provide strong evidence for the collective nature of the long-range correlations observed in pp collisions.

    Comments:
    Author's Ph.D. thesis (Rice University, May 2017). Adviser: Wei Li
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1709.03567 [pdf]
    1 citation
  3. 10

    [Submitted on 10 Sept 2017] (cross-list from nucl-ex)

    Effect of broken axial symmetry on the electric dipole strength and the collective enhancement of level densities in heavy nuclei

    Eckart Grosse🇩🇪 · Arnd R. Junghans🇩🇪 · Jon N. Wilson🇫🇷

    The basic parameters for calculations of radiative neutron capture , photon strength functions and nuclear level densities near the neutron separation energy are determined based on experimental data without an ad-hoc assumption about axial symmetry - at variance to previous analysis. Surprisingly few global fit parameters are needed in addition to information on nuclear deformation, taken from Hartree Fock Bogolyubov (HFB) calculations with the Gogny force, and the generator coordinator method (GCM) assures properly defined angular momentum. For a large number of nuclei the GDR shapes and the photon strength are described by the sum of three Lorentzians (TLO), extrapolated to low energies and normalized in accordance to the dipole sum rule. Level densities are influenced strongly by the significant collective enhancement based on the breaking of shape symmetry. The replacement of axial symmetry by the less stringent requirement of invariance against rotation by 180 degree leads to a novel prediction for radiative neutron capture. It compares well to recent compilations of average radiative widths and Maxwellian average cross sections for neutron capture by even target nuclei. An extension to higher spin promises a reliable prediction for various compound nuclear reactions also outside the valley of stability. Such predictions are of high importance for future nuclear energy systems and waste transmutation as well as for the understanding of the cosmic synthesis of heavy elements.

    Comments:
    Pacs. Nos.:21.10.Ma, 24.30.Cz, 24.60.Dr, 25.20.Dc, 25.40.Lw, 26.20.Kn; 25 pages, 12 figures; to appear in Physica Scripta, special issue on "Shapes and symmetries in Nuclei" (2017)
    Subjects:
    Nuclear Experiment (nucl-ex); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1709.03884 [pdf]
    Phys.Scripta(2017)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE