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Nuclear Theory·nucl-th

Thursday·June 30, 2016

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 05

    [Submitted on 28 Jun 2016] (cross-list from hep-ph)

    The LPM effect in sequential bremsstrahlung: dimensional regularization

    Peter Arnold🇺🇸 · Han-Chih Chang🇺🇸 · Shahin Iqbal🇵🇰

    The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. Of recent interest is the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD). In previous papers, we have developed methods for computing such corrections without making soft-gluon approximations. However, our methods require consistent treatment of canceling ultraviolet (UV) divergences associated with coincident emission times, even for processes with tree-level amplitudes. In this paper, we show how to use dimensional regularization to properly handle the UV contributions. We also present a simple diagnostic test that any consistent UV regularization method for this problem needs to pass.

    Comments:
    59 pages, 8 figures [main change from v1: addition of the new appendix B summarizing more about use of the i*epsilon prescription in earlier work]
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1606.08853 [pdf]
    JHEP(2016)·31 citations
  2. 06

    [Submitted on 28 Jun 2016] (cross-list from hep-ph)

    Studying the P_c(4450) resonance in J/psi photoproduction off protons

    A. N. Hiller Blin🇪🇸 · C. Fernández-Ramírez🇲🇽 · A. Jackura🇺🇸 · V. Mathieu🇺🇸 · V. I. Mokeev🇺🇸 · A. Pilloni🇺🇸 · A. P. Szczepaniak🇺🇸

    A resonance-like structure, the P_c(4450), has recently been observed in the J/psi p spectrum by the LHCb collaboration. We discuss the feasibility of detecting this structure in J/psi photoproduction in the CLAS12 experiment at JLab. We present a first estimate of the upper limit for the branching ratio of the P_c(4450) to J/psi p. Our estimates, which take into account the experimental resolution effects, predict that it will be possible to observe a sizable cross section close to the J/psi production threshold and shed light on the P_c(4450) resonance in the future photoproduction measurements.

    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1606.08912 [pdf]
    PRD(2016)·111 citations
  3. 07

    [Submitted on 29 Jun 2016] (cross-list from nucl-ex)

    First Measurement of Collectivity of Coexisting Shapes based on Type II Shell Evolution: The Case of Zr

    C. Kremer · S. Aslanidou · S. Bassauer · M. Hilcker · A. Krugmann · P. von Neumann-Cosel · T. Otsuka · N. Pietralla · V. Yu. Ponomarev · N. Shimizu · M. Singer · G. Steinhilber and 4 other authors

    Background: Type II shell evolution has recently been identified as a microscopic cause for nuclear shape coexistence. Purpose: Establish a low-lying rotational band in 96-Zr. Methods: High-resolution inelastic electron scattering and a relative analysis of transition strengths are used. Results: The B(E2; 0_1^+ -> 2_2^+) value is measured and electromagnetic decay strengths of the secdond 2^+ state are deduced. Conclusions: Shape coexistence is established for 96-Zr. Type II shell evolution provides a systematic and quantitative mechanism to understand deformation at low excitation energies.

    Comments:
    5 pages, 4 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1606.09057 [pdf]
    PRL(2016)·112 citations
  4. 08

    [Submitted on 29 Jun 2016] (cross-list from nucl-ex)

    Spectroscopy of the neutron-rich hypernucleus He from electron scattering

    T. Gogami🇯🇵 · C. Chen🇺🇸 · D. Kawama🇯🇵 · P. Achenbach🇩🇪 · A. Ahmidouch🇺🇸 · I. Albayrak🇺🇸 · D. Androic🇭🇷 · A. Asaturyan🇦🇲 · R. Asaturyan🇦🇲 · O. Ates🇺🇸 · P. Baturin🇺🇸 · R. Badui🇺🇸 and 74 other authors

    The missing mass spectroscopy of the He hypernucleus was performed, using the LiHe reaction at the Thomas Jefferson National Accelerator Facility Hall C. The binding energy of the ground state (1/2) was determined with a smaller error than that of the previous measurement, being = 5.55 0.10(stat.) 0.11(sys.) MeV. The experiment also provided new insight into charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at = 3.65 0.20(stat.) 0.11(sys.) MeV was observed and assigned as a mixture of 3/2 and 5/2 states, confirming the "gluelike" behavior of , which makes an unstable state in He stable against neutron emission.

    Comments:
    6 pages, 4 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1606.09157 [pdf]
    PRC(2016)·44 citations

Affiliations

first authorsco-authorsvia INSPIRE