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Nuclear Theory·nucl-th

Wednesday·September 2, 2020

17 papers—11 primary·6 cross-listed

All17Primary11Cross-lists6
  1. 12

    [Submitted on 31 Aug 2020] (cross-list from hep-ph)

    The Strangest Proton?

    Ferran Faura🇳🇱 · Shayan Iranipour🇬🇧 · Emanuele R. Nocera🇳🇱 · Juan Rojo🇳🇱 · Maria Ubiali🇬🇧

    We present an improved determination of the strange quark and anti-quark parton distribution functions of the proton by means of a global QCD analysis that takes into account a comprehensive set of strangeness-sensitive measurements: charm-tagged cross sections for fixed-target neutrino-nucleus deep-inelastic scattering, and cross sections for inclusive gauge-boson production and -boson production in association with light jets or charm quarks at hadron colliders. Our analysis is accurate to next-to-next-to leading order in perturbative QCD where available, and specifically includes charm-quark mass corrections to neutrino-nucleus structure functions. We find that a good overall description of the input dataset can be achieved and that a strangeness moderately suppressed in comparison to the rest of the light sea quarks is strongly favored by the global analysis.

    Comments:
    Version accepted for publication in EPJC. PDF sets available from http://nnpdf.mi.infn.it/nnpdf3-1strangeness/. v3: fixed typos
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2009.00014 [pdf]
    EPJC(2020)·90 citations
  2. 13

    [Submitted on 31 Aug 2020] (cross-list from hep-ph)

    Open charm and dileptons from relativistic heavy-ion collisions

    Elena Bratkovskaya🇩🇪 · Taesoo Song🇩🇪 · Pierre Moreau🇺🇸 · Carsten Greiner🇩🇪

    We study the dynamics of open charm production and the dilepton radiation of the semi-leptonic decays of correlated pairs versus the quark-gluon plasma (QGP) radiation and hadronic sources in relativistic heavy-ion collisions. Our study is based on the Parton-Hadron-String Dynamics (PHSD) transport approach employing a non-perturbative QCD description of the strongly interacting quark-gluon plasma (sQGP) in terms of dynamical quasiparticles and the EoS based on lattice QCD. We compare the PHSD results for charm observables with the calculations from BAMPS (Boltzmann Approach to Multi-Parton Scatterings) which is based on perturbative QCD with massless partons and interaction cross sections calculated in leading order of the QCD coupling. We compare the dependence of the ratio of -mesons in over collisions scaled by the number of binary collisions as well as the elliptic flow of -mesons calculated within the PHSD and BAMPS at LHC energies. In other study, based on the PHSD calculations we find that the dileptons from correlated meson semi-leptonic decays dominate the 'thermal' radiation from the QGP in central Pb+Pb collisions at the intermediate masses ( GeV) for higher invariant energies However, for invariant energies GeV the QGP radiation overshines the contribution from decays such that one should observe a rather clear signal from the partonic dilepton radiation. This finding provides promising perspectives to measure the QGP radiation in the dilepton experiments at RHIC BES and the future FAIR/NICA facilities.

    Comments:
    5 pages, 3 figures, Contribution to the "Hard Probe-2020" Proceedings
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    2009.00040 [pdf]
    1 citation
  3. 14

    [Submitted on 1 Sept 2020] (cross-list from astro-ph.SR)

    Enhancement of Lithium in Red Clump Stars by the Additional Energy Loss Induced by New Physics

    Kanji Mori🇯🇵 · Motohiko Kusakabe🇨🇳 · A. Baha Balantekin🇺🇸 · Toshitaka Kajino🇯🇵 · Michael A. Famiano🇺🇸

    Since 7Li is easily destroyed in low temperatures, the surface lithium abundance decreases as stars evolve. This is supported by the lithium depletion observed in the atmosphere of most red giants. However, recent studies show that almost all of red clump stars have high lithium abundances A(Li)>-0.9, which are not predicted by the standard theory of the low-mass stellar evolution. In order to reconcile the discrepancy between the observations and the model, we consider additional energy loss channels which may come from physics beyond the Standard Model. A(Li) slightly increases near the tip of the red giant branch even in the standard model with thermohaline mixing because of the 7Be production by the Cameron-Fowler mechanism, but the resultant 7Li abundance is much lower than the observed values. We find that the production of 7Be becomes more active if there are additional energy loss channels, because themohaline mixing becomes more efficient and a heavier helium core is formed.

    Comments:
    8 pages, 11 figures, accepted by MNRAS
    Subjects:
    Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2009.00293 [pdf]
    MNRAS(2021)·10 citations
  4. 15

    [Submitted on 1 Sept 2020] (cross-list from hep-lat)

    New method for calculating electromagnetic effects in semileptonic beta-decays of mesons

    Chien-Yeah Seng🇩🇪 · Xu Feng🇨🇳 · Mikhail Gorchtein🇩🇪 · Lu-Chang Jin🇺🇸 · Ulf-G. Meißner🇩🇪

    We construct several classes of hadronic matrix elements and relate them to the low-energy constants in Chiral Perturbation Theory that describe the electromagnetic effects in the semileptonic beta decay of the pion and the kaon. We propose to calculate them using lattice QCD, and argue that such a calculation will make an immediate impact to a number of interesting topics at the precision frontier, including the outstanding anomalies in and the top-row Cabibbo-Kobayashi-Maskawa matrix unitarity.

    Comments:
    Version to appear in JHEP
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2009.00459 [pdf]
    JHEP(2020)·38 citations
  5. 16

    [Submitted on 30 Aug 2020] (cross-list from hep-ph)

    Heavy Quark Radiation in the Quark-Gluon Plasma in the Moliere Theory: Angular Distribution of the Radiation

    B. Blok (Technion)🇮🇱

    We study the effects of adding the Coulomb interactions to the harmonic oscillator (HO) approximation of the heavy parton propagating through the quark-gluon plasma (the extension to QCD of the Molliere theory). We explicitly find the expression for the transverse momentum distribution of the gluon radiation of the heavy quark propagating in the quark gluon plasma in the framework of the Moliere theory, taking into account the BDMPSZ radiation in the harmonic oscillator (HO) approximation, and the Coulomb logarithms described by the additional logarithmic terms in the effective potential. We show that these Coulomb logarithms significantly influence the HO distribution, derived in the BDMPSZ works, especially for the small transverse momenta, filling the dead cone, and reducing the dead cone suppression of the heavy quark radiation (dead cone effect). In addition we study the effect of the phase space constraints on the heavy quark energy loss, and argue that taking into account of both the phase space constraints and of the Coulomb gluons reduces the dependence of the heavy quark energy loss on its mas in the HO approximation.

    Comments:
    26 pages, 7 figures 2 tables. arXiv admin note: text overlap with arXiv:2002.11233, references added,a mistake in the numerical code for angular distributions leading to unphysical oscillations corrected
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2009.00465 [pdf]
    EPJC(2021)·8 citations
  6. 17

    [Submitted on 1 Sept 2020] (cross-list from physics.data-an)

    Conception and software implementation of a nuclear data evaluation pipeline

    Georg Schnabel · Henrik Sjöstrand · Joachim Hansson · Dimitri Rochman · Arjan Koning · Roberto Capote

    We discuss the design and software implementation of a nuclear data evaluation pipeline applied for a fully reproducible evaluation of neutron-induced cross sections of Fe above the resolved resonance region using the nuclear model code TALYS combined with relevant experimental data. The emphasis is on the mathematical and technical aspects of the pipeline and not on the evaluation of Fe, which is tentative. The mathematical building blocks combined and employed in the pipeline are discussed in detail. A unified representation of experimental data, systematic and statistical errors, model parameters and defects enables the application of the Generalized Least Squares (GLS) and its natural extension, the Levenberg-Marquardt (LM) algorithm, on a large collection of experimental data. The LM algorithm tailored to nuclear data evaluation accounts for the exact non-linear physics model to determine best estimates of nuclear quantities. Associated uncertainty information is derived from a Taylor expansion at the maximum of the posterior distribution. We also discuss the pipeline in terms of its IT (=information technology) building blocks, such as those to efficiently manage and retrieve experimental data of the EXFOR library and to distribute computations on a scientific cluster. Relying on the mathematical and IT building blocks, we elaborate on the sequence of steps in the pipeline to perform the evaluation, such as the retrieval of experimental data, the correction of experimental uncertainties using marginal likelihood optimization (MLO) and after a screening of thousand TALYS parameters -- including Gaussian process priors on energy dependent parameters -- the fitting of about 150 parameters using the LM algorithm. The code of the pipeline including a manual and a Dockerfile for a simplified installation is available at www.nucleardata.com.

    Comments:
    45 pages
    Subjects:
    Data Analysis, Statistics and Probability (physics.data-an); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
    arXiv:
    2009.00521 [pdf]
    Nucl.Data Sheets(2021)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE