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Nuclear Theory·nucl-th

Tuesday·August 16, 2016

14 papers—4 primary·10 cross-listed

All14Primary4Cross-lists10
  1. 05

    [Submitted on 11 Aug 2016] (cross-list from hep-ph)

    Particle Physics Models for the 17 MeV Anomaly in Beryllium Nuclear Decays

    Jonathan L. Feng🇺🇸 · Bartosz Fornal🇺🇸 · Iftah Galon🇺🇸 · Susan Gardner🇺🇸 · Jordan Smolinsky🇺🇸 · Tim M. P. Tait🇺🇸 · Philip Tanedo🇺🇸

    The 6.8 anomaly in excited 8Be nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in 8Be decays and the characteristics of the observed anomaly. To develop its particle interpretation, we provide an effective operator analysis for excited 8Be decays to particles with a variety of spins and parities and show that these considerations exclude simple models with scalar particles. We discuss the required couplings for a gauge boson to give the observed signal, highlighting the significant dependence on the precise mass of the boson and isospin mixing and breaking effects. We present anomaly-free extensions of the Standard Model that contain protophobic gauge bosons with the desired couplings to explain the 8Be anomaly. In the first model, the new force carrier is a U(1)B gauge boson that kinetically mixes with the photon; in the second model, it is a U(1)(B-L) gauge boson with a similar kinetic mixing. In both cases, the models predict relatively large charged lepton couplings ~ 0.001 that can resolve the discrepancy in the muon anomalous magnetic moment and are amenable to many experimental probes. The models also contain vectorlike leptons at the weak scale that may be accessible to near future LHC searches.

    Comments:
    35 pages + references, 6 figures; v2: generality of vector candidates discussion clarified, references added, published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1608.03591 [pdf]
    PRD(2017)·254 citations
  2. 06

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

    In-Medium Pion Valence Distributions in a Light-Front Model

    J. P. B. C de Melo · K. Tsushima · (Laboratório de Fisica Teorica e Computacional - LFTC, Universidade Cruzeiro do Sul) · I. Ahmed · (National Center for Physics, Quaidi-i-Azam University Campus)

    Pion valence distributions in nuclear medium and vacuum are studied in a light-front constituent quark model. The in-medium input for studying the pion properties is calculated by the quark-meson coupling model. We find that the in-medium pion valence distribution, as well as the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.

    Comments:
    16 pages. 10 eps figures, typos corrected. Version to appear Physics Letters B
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1608.03858 [pdf]
    PLB(2017)·11 citations
  3. 07

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

    Search for doubly-heavy dibaryons in a quark model

    J. Vijande🇪🇸 · A. Valcarce🇪🇸 · J.-M. Richard🇫🇷 · P. Sorba🇫🇷

    We study the stability of hexaquark systems containing two heavy quarks and four light quarks within a simple quark model. No bound or metastable state is found. The reason stems on a delicate interplay between chromoelectric and chromomagnetic effects. Our calculation provides also information about anticharmed pentaquarks that are seemingly unbound in simple quark models.

    Comments:
    6 pages. To be published in Phys. Rev. D
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1608.03982 [pdf]
    PRD(2016)·31 citations
  4. 08

    [Submitted on 14 Aug 2016] (cross-list from hep-ph)

    Hadronic molecules with a meson in a medium

    T. F. Caramés🇪🇸 · C. E. Fontoura🇧🇷 · G. Krein🇧🇷 · K. Tsushima🇧🇷 · J. Vijande🇪🇸 · A. Valcarce🇪🇸

    We study the effect of a hot and dense medium on the binding energy of hadronic molecules with open-charm mesons. We focus on a recent chiral quark-model-based prediction of a molecular state in the system. We analyze how the two-body thresholds and the hadron-hadron interactions are modified when quark and meson masses and quark-meson couplings change in a function of the temperature and baryon density according to predictions of the Nambu--Jona-Lasinio model. We find that in some cases the molecular binding is enhanced in medium as compared to their free-space binding. We discuss the consequences of our findings for the search for exotic hadrons in high-energy heavy-ion collisions as well as in the forthcoming facilities FAIR or J-PARC.

    Comments:
    Corrected one author name
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1608.04040 [pdf]
    PRD(2016)·15 citations
  5. 09

    [Submitted on 14 Aug 2016] (cross-list from hep-ph)

    Impacts of B-factory measurements on determination of fragmentation functions from electron-positron annihilation data

    M. Hirai🇯🇵 · H. Kawamura🇯🇵 · S. Kumano🇯🇵 · K. Saito🇯🇵

    Fragmentation functions are determined for the pion and kaon by global analyses of charged-hadron production data in electron-positron annihilation. Accurate measurements were reported by the Belle and BaBar collaborations for the fragmentation functions at the center-of-mass energies of 10.52 GeV and 10.54 GeV, respectively, at the KEK and SLAC B factories, whereas other available measurements were mostly done at higher energies, mainly at the mass of 91.2 GeV. There is a possibility that gluon fragmentation functions, as well as quark fragmentation functions, are accurately determined by scaling violation. We report our global analysis of the fragmentation functions especially to show impacts of the B-factory measurements on the fragmentation function determination. Our results indicate that the fragmentation functions are determined more accurately not only by the scaling violation but also by high-statistical nature of the Belle and BaBar data. However, there are some tensions between the Belle and BaBar data in comparison with previous measurements. We also explain how the flavor dependence of quark fragmentation functions and the gluon function are separated by using measurements at different values. In particular, the electric and weak changes are different depending on the quark type, so that a light-quark flavor separation also became possible in principle due to the precise data at both GeV and 91.2 GeV.

    Comments:
    19 pages, 5 style files, 1 logo file, 8 eps figures, Progress of Theoretical and Experimental Physics (PTEP) in press
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1608.04067 [pdf]
    PTEP(2016)·23 citations
  6. 10

    [Submitted on 14 Aug 2016] (cross-list from hep-ph)

    Precise Determination of the U-235 Reactor Antineutrino Cross Section per Fission

    Carlo Giunti🇮🇹

    We investigate which among the reactor antineutrino fluxes from the decays of the fission products of , , , and may be responsible for the reactor antineutrino anomaly if the anomaly is due to a miscalculation of the antineutrino fluxes. We find that it is very likely that at least the calculation of the flux must be revised. From the fit of the data we obtain the precise determination of the cross section per fission, which is more precise than the calculated value and differs from it by . The cross sections per fission of the other fluxes have large uncertainties and in practice their values are undetermined by the fit.

    Comments:
    9 pages. Final version published in Physics Letters B 764 (2017) 145
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1608.04096 [pdf]
    PLB(2017)·41 citations
  7. 11

    [Submitted on 15 Aug 2016] (cross-list from hep-ph)

    Sound Attenuation in Quark Matter Due to Pairing Fluctuations

    Boris Kerbikov🇷🇺

    The sound wave in dense quark matter is subject to strong absorption due to diquark field fluctuations above T critical. The result is another facet of Mandelshtam-Leontovich slow relaxation time theory.

    Comments:
    Talk at the 19th International Seminar QUARKS 2016
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1608.04252 [pdf]
    EPJ Web Conf.(2016)·3 citations
  8. 12

    [Submitted on 15 Aug 2016] (cross-list from hep-ph)

    Finite Temperature QCD Sum Rules: a Review

    Alejandro Ayala🇲🇽 · C. A. Dominguez🇿🇦 · M. Loewe🇿🇦

    The method of QCD sum rules at finite temperature is reviewed, with emphasis on recent results. These include predictions for the survival of charmonium and bottonium states, at and beyond the critical temperature for de-confinement, as later confirmed by lattice QCD simulations. Also included are determinations in the light-quark vector and axial-vector channels, allowing to analyse the Weinberg sum rules, and predict the dimuon spectrum in heavy ion collisions in the region of the rho-meson. Also in this sector, the determination of the temperature behaviour of the up-down quark mass, together with the pion decay constant, will be described. Finally, an extension of the QCD sum rule method to incorporate finite baryon chemical potential is reviewed.

    Comments:
    Minor typos corrected. To be published in the review section of Advances in High Energy Physics
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1608.04284 [pdf]
    Adv.High Energy Phys.(2017)·38 citations
  9. 13

    [Submitted on 15 Aug 2016] (cross-list from nucl-ex)

    High-precision quadrupole moment reveals significant intruder component in 33Al20 ground state

    H. Heylen🇧🇪 · M. De Rydt🇧🇪 · G. Neyens🇧🇪 · M.L. Bissell🇧🇪 · L. Caceres🇫🇷 · R. Chevrier🇫🇷 · J.M. Daugas🇫🇷 · Y. Ichikawa🇯🇵 · Y. Ishibashi🇯🇵 · O. Kamalou🇫🇷 · T.J. Mertzimekis🇬🇷 · P. Morel🇫🇷 and 9 other authors

    The electric quadrupole moment of the 33Al20 ground state, located at the border of the island of inversion, was obtained using continuous-beam beta-detected nuclear quadrupole resonance (beta-NQR). From the measured quadrupole coupling constant Q = 2.31(4) MHz in an alpha-Al2O3 crystal, a precise value for the electric quadrupole moment is extracted: Qs= 141(3) mb. A comparison with large-scale shell model calculations shows that 33Al has at least 50% intruder configurations in the ground state wave function, favoring the excitation of two neutrons across the N = 20 shell gap. 33Al therefore clearly marks the gradual transition north of the deformed Na and Mg nuclei towards the normal Z>14 isotopes.

    Comments:
    6 pages, 4 figures. Accepted for publication in Physical Review C
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1608.04360 [pdf]
    PRC(2016)·18 citations
  10. 14

    [Submitted on 15 Aug 2016] (cross-list from hep-ph)

    Hadronic matter at the edge: A survey of some theoretical approaches to the physics of the QCD phase diagram

    Alejandro Ayala🇲🇽

    In the past few years a wealth of high quality data has made possible to test current theoretical ideas about the properties of hadrons subject to extreme conditions of density and temperature. The relativistic heavy-ion program carried out at the CERN-SPS and under development at the BNL-RHIC and CERN-LHC has provided results that probe the evolution of collisions of hadronic matter at high energies from the initially large density to the late dilute stages. In addition, QCD on the lattice has produced results complementing these findings with first principles calculations for observables in a regime where perturbative techniques cannot describe the nature of strongly coupled systems. This work aims to review some recent developments that make use of field theoretical methods to describe the physics of hadrons at finite temperature and density. I concentrate on two of the main topics that have been explored in the last few years: (1) The search for the structure of the phase diagram and (2) analytical signals linked to the chiral symmetry restoration/deconfinement.

    Comments:
    14 pages, 1 figure. More references added. arXiv admin note: text overlap with arXiv:0908.2709 by other authors
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1608.04378 [pdf]
    J.Phys.Conf.Ser.(2016)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE