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Nuclear Theory·nucl-th

Tuesday·May 2, 2017

14 papers—8 primary·6 cross-listed

All14Primary8Cross-lists6
  1. 09

    [Submitted on 28 Apr 2017] (cross-list from hep-ph)

    Fierz-complete NJL model study: fixed points and phase structure at finite temperature and density

    Jens Braun🇩🇪 · Marc Leonhardt🇩🇪 · Martin Pospiech🇩🇪

    Nambu-Jona-Lasinio-type models are frequently employed as low-energy models in various research fields. With respect to the theory of the strong interaction, this class of models is indeed often used to analyze the structure of the phase diagram at finite temperature and quark chemical potential. The predictions from such models for the phase structure at finite quark chemical potential are of particular interest as this regime is difficult to access with lattice Monte Carlo approaches. In this work, we consider a Fierz-complete version of a Nambu-Jona-Lasinio model. By studying its renormalization group flow, we analyze in detail how Fierz-incomplete approximations affect the predictive power of such model studies. In particular, we investigate the curvature of the phase boundary at small chemical potential, the critical value of the chemical potential above which no spontaneous symmetry breaking occurs, and the possible interpretation of the underlying dynamics in terms of difermion-type degrees of freedom. We find that the inclusion of four-fermion channels other than the conventional scalar-pseudoscalar channel is not only important at large chemical potential but also leaves a significant imprint on the dynamics at small chemical potential as measured by the curvature of the finite-temperature phase boundary.

    Comments:
    24 pages, 8 figures, 1 table, (version as accepted for publication in Phys. Rev. D; Editors' Suggestion)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1705.00074 [pdf]
    PRD(2017)·70 citations
  2. 10

    [Submitted on 28 Apr 2017] (cross-list from astro-ph.HE)

    Critical assessment of nuclear sensitivity metrics for the r-process

    Zachary Shand · Rachid Ouyed · Nico Koning · Iris Dillmann · Reiner Krücken · Prashanth Jaikumar

    Any simulation of the r-process is affected by uncertainties in our present knowledge of nuclear physics quantities and astrophysical conditions. It is common to quantify the impact of these uncertainties through a global sensitivity metric, which is then used to identify specific nuclides that would be most worthwhile to measure experimentally. Using descriptive statistics, we assess a set of metrics used in previous sensitivity studies, as well as a new logarithmic measure. For certain neutron-rich nuclides lying near the r-process path for the typical hot-wind scenario, we find opposing conclusions on their relative sensitivity implied by different metrics, although they all generally agree which ones are the most sensitive nuclei. The underlying reason is that sensitivity metrics which simply sum over variations in the r-process distribution depend on the scaling used in the baseline, which often varies between simulations. We show that normalization of the abundances causes changes in the reported sensitivity factors and recommend reporting a minimized F statistic in addition to a scale estimation for rough calibration to be used when comparing tables of sensitivity factors from different studies.

    Comments:
    6 pages, 2 figures, 2 tables
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    1705.00099 [pdf]
    1 citation
  3. 11

    [Submitted on 29 Apr 2017] (cross-list from hep-ph)

    Formation of hadrons at chemical freeze-out

    David Blaschke🇵🇱 · Jakub Jankowski🇵🇱 · Michal Naskret🇵🇱

    We use a kinetic condition to predict the chemical freeze-out parameters for hadronic species produced in heavy ion collisions. The resulting freeze-out lines for different hadrons lie close to one another in the temperature and baryochemical potential plane, defining a universal, narrow region. The chemical freeze-out is driven by the localization of hadrons due to the chiral symmetry breaking and confining aspects of the QCD transition.

    Comments:
    15 pages, 6 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1705.00169 [pdf]
    8 citations
  4. 12

    [Submitted on 30 Apr 2017] (cross-list from physics.atom-ph)

    Theory of the n=2 levels in muonic helium-3 ions

    Beatrice Franke (1 and 2)🇩🇪 · Julian J. Krauth (1 and 3)🇩🇪 · Aldo Antognini (4 and 5)🇨🇭 · Marc Diepold (1)🇩🇪 · Franz Kottmann (4)🇨🇭 · Randolf Pohl (3 and 1) ((1) Max-Planck-Institut für Quantenoptik, Garching, Germany, (2) Triumf, Vancouver, Canada, (3) Johannes Gutenberg-Universität Mainz, Quantum, Institut für Physik and Exzellenzcluster PRISMA, Mainz, Deutschland, (4) Institute for Particle Physics and Astrophysics, ETH Zurich, Zurich, Switzerland, (5) Paul Scherrer Institute, Villigen, Switzerland)🇩🇪

    The present knowledge of Lamb shift, fine-, and hyperfine structure of the 2S and 2P states in muonic helium-3 ions is reviewed in anticipation of the results of a first measurement of several transition frequencies in the muonic helium-3 ion, . This ion is the bound state of a single negative muon and a bare helium-3 nucleus (helion), . A term-by-term comparison of all available sources, including new, updated, and so far unpublished calculations, reveals reliable values and uncertainties of the QED and nuclear structure-dependent contributions to the Lamb shift and the hyperfine splitting. These values are essential for the determination of the helion rms charge radius and the nuclear structure effects to the hyperfine splitting in . With this review we continue our series of theory summaries in light muonic atoms; see Antognini et al., Ann. Phys. 331, 127 (2013), Krauth et al., Ann.Phys. 366, 168 (2016), and Diepold et al., ArXiv 1606.05231 (2016).

    Comments:
    27 pages, continues series of theory summaries from muonic hydrogen up to muonic helium-4, revised manuscript, updated numbers
    Subjects:
    Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th)
    arXiv:
    1705.00352 [pdf]
    Eur.Phys.J.D(2017)·29 citations
  5. 13

    [Submitted on 30 Apr 2017] (cross-list from hep-ph)

    Radiative decay of heavy neutrinos at MiniBooNE and MicroBooNE

    Luis Alvarez-Ruso🇪🇸 · Eduardo Saul-Sala🇪🇸

    The MiniBooNE experiment reported results from the analysis of and appearance searches, which showed an excess of signal-like events at low reconstructed neutrino energies with respect to the expected background. A proposed explanation for this anomaly is based on the existence of a heavy (~MeV) sterile neutrino. These would be produced by electromagnetic and neutral current interactions. A fraction of them decays radiatively inside the detector. The emitted photon is misidentified as an electron or positron in MiniBooNE. We have investigated the production by coherent and incoherent electroweak interactions at the MiniBooNE and MicroBooNE targets, CH and Ar, respectively. Studying the propagation inside the detector, we obtain the energy and angular distributions of emitted photons for a choice of model parameters. The distinctive shape and total number of photon events from this mechanism at MicroBooNE makes its experimental investigation possible.

    Comments:
    Poster presented at NuPhys2016 (London, 12-14 December 2016). 4 pages, LaTeX, 8 eps
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1705.00353 [pdf]
    14 citations
  6. 14

    [Submitted on 1 May 2017] (cross-list from hep-ph)

    Are there near-threshold Coulomb-like Baryonia?

    Li-Sheng Geng🇨🇳 · Jun-Xu Lu🇨🇳 · Manuel Pavon Valderrama🇨🇳 · Xiu-Lei Ren🇨🇳

    The system can exchange a pion near the mass-shell. Owing to the opposite intrinsic parity of the and , the pion is exchanged in S-wave. This gives rise to a Coulomb-like force that might be able to bind the system. If one takes into account that the pion is not exactly on the mass shell, there is a shallow S-wave state, which we generically call the and for the and systems respectively. For the baryon-antibaryon case this Coulomb-like force is independent of spin: the baryonia will appear either in the spin or configurations with G-parities . For the baryon-baryon case the Coulomb-like force is attractive in the spin configuration, for which a doubly charmed molecule is expected to form near the threshold. This type of spectrum might be very well realized in other molecular states composed of two opposite parity hadrons with the same spin and a mass difference close to that of a pseudo-Goldstone boson, of which a few examples include the , , , and molecules.

    Comments:
    7 pages, 3 figures, corresponds to published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1705.00516 [pdf]
    PRD(2018)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE