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Nuclear Theory·nucl-th

Tuesday·August 2, 2016

9 papers—5 primary·4 cross-listed

All9Primary5Cross-lists4
  1. 06

    [Submitted on 1 Aug 2016] (cross-list from hep-ph)

    Charmonium spectrum and their electromagnetic transitions with higher multipole contributions

    Wei-Jun Deng🇨🇳 · Hui Liu🇨🇳 · Long-Cheng Gui🇨🇳 · Xian-Hui Zhong🇨🇳

    The charmonium spectrum is calculated with two nonrelativistic quark models, the linear potential model and the screened potential model. Using the obtained wavefunctions, we evaluate the electromagnetic transitions of charmonium states up to multiplet. The higher multipole contributions are included by a multipole expansion of the electromagnetic interactions. Our results are in reasonable agreement with the measurements. As conventional charmonium states, the radiative decay properties of the newly observed charmonium-like states, such as , , , are discussed. The as , its radiative decay properties well agree with the observations. From the radiative decay properties of , one can not exclude it as a dominant state. We also give discussions of possibly observing the missing charmonium states in radiative transitions, which might provide some useful references to look for them in forthcoming experiments. The higher multipole contributions to the electromagnetic transitions are analyzed as well. It is found that the higher contribution from the magnetic part could give notable corrections to some E1 dominant processes by interfering with the E1 amplitudes. Our predictions for the normalized magnetic quadrupole amplitudes of the processes are in good agreement with the recent CLEO measurements.

    Comments:
    20 pages, 1 figure. Large improvement was done according to the referee's suggestions. To be published in PRD. arXiv admin note: text overlap with arXiv:1510.08269
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1608.00287 [pdf]
    PRD(2017)·150 citations
  2. 07

    [Submitted on 1 Aug 2016] (cross-list from hep-ph)

    Virtual states and generalized completeness relation in the Friedrichs Model

    Zhiguang Xiao🇨🇳 · Zhi-Yong Zhou🇨🇳

    We study the well-known Friedrichs model, in which a discrete state is coupled to a continuum state. By examining the pole behaviors of the Friedrichs model in a specific form factor thoroughly, we find that, in general, when the bare discrete state is below the threshold of the continuum state, there should also be a virtual-state pole accompanying the bound-state pole originating from the bare discrete state as the coupling is turned on. There are also other second-sheet poles originating from the singularities of the form factor. We give a general argument for the existence of these two kinds of states. As the coupling is increased to a certain value, the second-sheet poles may merge and become higher-order poles. We then discuss the completeness relations incorporating bound states, virtual states, and resonant states corresponding to higher-order poles.

    Comments:
    15 pages, 8 figures; Minor modifications, imporved figures, version to appear in Phys. Rev. D
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    1608.00468 [pdf]
    PRD(2016)·27 citations
  3. 08

    [Submitted on 1 Aug 2016] (cross-list from hep-ph)

    Hot origin of the Little Bang

    S.V. Akkelin🇺🇦

    Ultrarelativistic heavy ion collisions produce a quark-gluon matter which lies in the future light cone originating from given points on the plane of the Minkowski spacetime manifold. We show that in a weak coupling regime the Minkowski vacuum of massless fields presents itself in the "Little Bang" region as a thermal state of low particles, in close analogy to the Unruh effect for uniformly accelerated observers which are causally restricted to a Rindler wedge. It can shed some light on the mechanisms of early time thermalization in ultrarelativistic heavy ion collisions.

    Comments:
    17 pages
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1608.00472 [pdf]
    EPJA(2017)·2 citations
  4. 09

    [Submitted on 1 Aug 2016] (cross-list from nucl-ex)

    Analysis of Neutron Stars Observations Using a Correlated Fermi Gas Model

    O. Hen · A.W. Steiner · E. Piasetzky · L.B. Weinstein

    Background: The nuclear symmetry energy is a fundamental ingredient in determining the equation of state (EOS) of neutron stars (NS). Recent terrestrial experiments constrain both its value and slope at nuclear saturation density, however, its value at higher densities is unknown. Assuming a Free Fermi-gas (FFG) model for the kinetic symmetry energy, the high-density extrapolation depends on a single parameter, the density dependence of the potential symmetry energy. The Correlated Fermi-gas (CFG) model improves on the FFG model by including the effects of short-range, correlated, high-momentum, nucleons in nuclear matter. Using the CFG model for the kinetic symmetry energy along with constraints from terrestrial measurements leads to a much softer density dependence for the potential symmetry energy. Purpose: Examine the ability of the FFG and CFG models to describe NS observables that are directly sensitive to the symmetry energy at high-density. Specifically, examine the ability of the CFG model, with its softer density dependence of the potential symmetry energy, to describe a two solar-mass NS. Methods: Using a Bayesian analysis of NS observables we compare the CFG and FFG models and examine the resulting parameters in the NS EOS and the density dependence of the potential symmetry energy. Results: Despite the large difference in the density dependence of the potential part of the symmetry energy, both models can describe the NS data and support a two solar-mass NS. The different density dependences has only a small effect on the NS EOS. Conclusions: While sensitive to the high-density values of the symmetry energy, NS observables alone are not enough to distinguish between the CFG and FFG models. This indicates that the NS EOS, obtain from Bayesian analysis of NS observables, is robust and is not sensitive to the exact nuclear model used for the kinetic symmetry energy.

    Comments:
    5 pages, 3 figures
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1608.00487 [pdf]
    13 citations

Affiliations

first authorsco-authorsvia INSPIRE