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Nuclear Theory·nucl-th

Thursday·January 14, 2016

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    [Submitted on 13 Jan 2016]

    A systematic approach to sketch Bethe-Salpeter equation

    Si-xue Qin🇺🇸

    To study meson properties, one needs to solve the gap equation for the quark propagator and the Bethe-Salpeter (BS) equation for the meson wavefunction, self-consistently. The gluon propagator, the quark-gluon vertex, and the quark--anti-quark scattering kernel are key pieces to solve those equations. Predicted by lattice-QCD and Dyson-Schwinger analyses of QCD's gauge sector, gluons are non-perturbatively massive. In the matter sector, the modeled gluon propagator which can produce a veracious description of meson properties needs to possess a mass scale, accordingly. Solving the well-known longitudinal Ward-Green-Takahashi identities (WGTIs) and the less-known transverse counterparts together, one obtains a nontrivial solution which can shed light on the structure of the quark-gluon vertex. It is highlighted that the phenomenologically proposed anomalous chromomagnetic moment (ACM) vertex originates from the QCD Lagrangian symmetries and its strength is proportional to the magnitude of dynamical chiral symmetry breaking (DCSB). The color-singlet vector and axial-vector WGTIs can relate the BS kernel and the dressed quark-gluon vertex to each other. Using the relation, one can truncate the gap equation and the BS equation, systematically, without violating crucial symmetries, e.g., gauge symmetry and chiral symmetry.

    Comments:
    4 pages, 21st International Conference on Few-Body Problems in Physics
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1601.03134 [pdf]
    EPJ Web Conf.(2016)·11 citations
  2. 02

    [Submitted on 13 Jan 2016]

    Description of electromagnetic and favored -transitions in heavy odd-mass nuclei

    A. Dumitrescu · D. S. Delion

    We describe electromagnetic and favored \alpha-transitions to rotational bands in odd-mass nuclei built upon a single particle state with angular momentum projection in the region . We use the particle coupled to an even-even core approach described by the Coherent State Model (CSM) and the coupled channels method to estimate partial -decay widths. We reproduce the energy levels of the rotational band where favored -transitions occur for 26 nuclei and predict B (E2) values for electromagnetic transitions to the bandhead using a deformation parameter and a Hamiltonian strength parameter for each nucleus, together with an effective collective charge depending linearly on the deformation parameter. Where experimental data is available, the contribution of the single particle effective charge to the total B (E2) value is calculated. The Hamiltonian describing the - nucleus interaction contains two terms, a spherically symmetric potential given by the double-folding of the M3Y nucleon-nucleon interaction plus a repulsive core simulating the Pauli principle and a quadrupole-quadrupole (QQ) interaction. The -decaying state is identified as a narrow outgoing resonance in this potential. The intensity of the transition to the first excited state is reproduced by the QQ coupling strength. It depends linearly both on the nuclear deformation and the square of the reduced width for the decay to the bandhead, respectively. Predicted intensities for transitions to higher excited states are in a reasonable agreement with experimental data. This formalism offers a unified description of energy levels, electromagnetic and favored -transitions for known heavy odd-mass -emitters.

    Comments:
    13 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1601.03160 [pdf]
    PRC(2016)·5 citations
  3. 03

    [Submitted on 11 Jan 2016]

    Cluster Decay Half-Lives of 5d Transition Metal Nuclei Using the Coulomb and Proximity Potential Model

    K. E. Abd El Mageed🇪🇬 · L. I. Abou Salem🇪🇬 · K. A. Gado · Asmaa G. Shalaby

    We have applied the Coulomb and proximity potential model,CPPM to calculate the half lives for various clusters decay of the selected even-even isotopes of the chosen nuclei. These nuclei are Hf, W, Os, Pt, and Hg in the 5d transition metal region in the periodic table with atomic number 72 greater or equal Z less than or equal 80. Furthermore, the half-lives are calculated using the universal formula for cluster decay. The calculated half-lives of alpha decay for the chosen isotopes are in good agreement with the experimental data, especially with the CPPM results. The alpha and cluster decays are more probable from the parents in the heavier mass number A equal 168,180 than from the parents in the lighter mass number A equal 156, 166.

    Comments:
    Chinese Journal of Physics vol. 53, no. 7 December 2015
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1601.03263 [pdf]
    Chin.J.Phys.(2015)·2 citations
  4. 04

    [Submitted on 12 Jan 2016] (cross-list from hep-ph)

    Direct photon production and jet energy-loss in small systems

    Chun Shen🇨🇦 · Chanwook Park🇨🇦 · Jean-François Paquet🇨🇦 · Gabriel S. Denicol🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

    Two types of penetrating probes, direct photon and QCD jets, are investigated in the background of a small and rapidly expanding droplet of quark-gluon plasma. The additional thermal electromagnetic radiation results in a 50\% enhancement of the direct photons. In high multiplicity p+Pb collisions, jets can lose a sizeable fraction of their initial energy, leading to a charged hadron of 0.8 at a transverse momentum around 10\,GeV. Those two proposed measurements can help understand the apparent collective behaviour observed in small collision systems.

    Comments:
    4 pages. Contribution to the Proceedings of Quark Matter 2015, Kobe, Japan
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1601.03070 [pdf]
    NPA(2016)·16 citations
  5. 05

    [Submitted on 12 Jan 2016] (cross-list from hep-ph)

    Rapidity regulators in the semi-inclusive deep inelastic scattering and Drell-Yan processes

    Sean Fleming🇺🇸 · Ou Z. Labun🇺🇸

    We study the semi-inclusive limit of the deep inelastic scattering and Drell-Yan (DY) processes in soft collinear effective theory. In this regime so-called threshold logarithms must be resummed to render perturbation theory well behaved. Part of this resummation occurs via the Dokshitzer, Gribov, Lipatov, Altarelli, Parisi (DGLAP) equation, which at threshold contains a large logarithm that calls into question the convergence of the anomalous dimension. We demonstrate here that the problematic logarithm is related to rapidity divergences, and by introducing a rapidity regulator can be tamed. We show that resumming the rapidity logarithms allows us to reproduce the standard DGLAP running at threshold as long as a set of potentially large non-perturbative logarithms are absorbed into the definition of the parton distribution function (PDF). These terms could, in turn, explain the steep fall-off of the PDF in the endpoint. We then go on to show that the resummation of rapidity divergences does not change the standard threshold resummation in DY, nor do our results depend on the rapidity regulator we choose to use.

    Comments:
    47 pages, 7 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1601.03093 [pdf]
    PRD(2017)·3 citations
  7. 07

    [Submitted on 13 Jan 2016] (cross-list from hep-ph)

    Short-distance RG-analysis of radiative decays

    D. A. S. Molnar🇧🇷 · R. F. Luiz🇧🇷 · R. Higa🇧🇷

    We present a renormalization-group analysis of the radiative decays into and . We assume a molecule for the long-distance structure and parametrize its short-distance physics as contact interactions. Using effective field theory techniques and power-divergence subtraction scheme, we find that short- and long-distance physics are equally important in these decays. Our calculations set a lower limit to the corresponding decay widths, which can in principle be tested experimentally. Our results may be used as guide to build models for the short-distance.

    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1601.03366 [pdf]
    6 citations

Affiliations

first authorsco-authorsvia INSPIRE