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Nuclear Theory·nucl-th

Tuesday·March 22, 2022

10 papers—5 primary·5 cross-listed

All10Primary5Cross-lists5
  1. 06

    [Submitted on 18 Mar 2022] (cross-list from hep-ph)

    Explaining the hints for lepton flavour universality violation with three leptoquark generations

    Andreas Crivellin🇨🇭 · Benjamin Fuks🇫🇷 · Luc Schnell🇩🇪

    Leptoquarks are prime candidates for explaining the intriguing hints for lepton flavour universality violation. In particular, the doublet of scalar leptoquarks is capable of providing an explanation for the tensions between the measurements and the Standard Model predictions in , and processes, as well as in non-resonant di-electron production. However, in the minimal setup with a single leptoquark generation, a common explanation for all these issues is not possible as this would lead to unacceptably large charged lepton flavour violation. We therefore propose a model with three generations of , each coupling exclusively to a single lepton flavour, \textit{i.e.}~a model extending the Standard Model particle content by an electroquark, a muoquark and a tauquark. We show that after taking into account other constraints, such as those originating from electroweak precision observables and processes, it is possible to provide a combined explanation for all these hints of lepton flavour universality violation. Moreover, we find that the presence of the tauquark can generate a dimension-six operator via off-shell photon penguin diagrams, which, together with the muoquark contribution, further improves the global fit to data.

    Comments:
    48 pages, 11 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2203.10111 [pdf]
    JHEP(2022)·42 citations
  2. 07

    [Submitted on 18 Mar 2022] (cross-list from quant-ph)

    Analysis of quantum decay law: Is quantum tunneling really exponential?

    M. S. Hosseini-Ghalehni🇮🇷 · B. Azadegan🇮🇷 · S. A. Alavi🇮🇷

    The exponential decay law is well established since its first derivation in 1928, however it is not exact but only an approximate description. In recent years some experimental and theoretical indications for non-exponential decay have been documented. First we solve analytically the time-dependent Schrödinger equation in one dimension for a potential consisting of an infinite wall plus a rectangular barrier with finite width and also a cut harmonic oscillator potential by considering it as a sequence of square potentials. Then using the staggered Leap-Frog method, we solve the time-dependent Schrödinger equation for the cut harmonic oscillator potential. In both methods, time dependence of the survival probability of the particle and the decay parameter {\lambda} are analyzed. The results exhibit non-exponential behavior for survival probability at short and intermediate times.

    Comments:
    16 pages, 16 Figures. Replaced with the version pulished in The European Physical Journal Plus
    Subjects:
    Quantum Physics (quant-ph); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2203.10134 [pdf]
    Eur.Phys.J.Plus(2022)·0 citations
  3. 08

    [Submitted on 18 Mar 2022] (cross-list from nucl-ex)

    Mapping the Island of Inversion: Precision Mass Measurements of Neutron-rich Fe Isotopes

    W. S. Porter🇨🇦 · B. Ashrafkhani🇨🇦 · J. Bergmann🇩🇪 · C. Brown🇬🇧 · T. Brunner🇨🇦 · J. D. Cardona🇨🇦 · D. Curien🇫🇷 · I. Dedes🇵🇱 · T. Dickel🇩🇪 · J. Dudek🇫🇷 · E. Dunling🇨🇦 · G. Gwinner🇨🇦 and 23 other authors

    Nuclear properties across the chart of nuclides are key to improving and validating our understanding of the strong interaction in nuclear physics. We present high-precision mass measurements of neutron-rich Fe isotopes performed at the TITAN facility. The multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS), achieving a resolving power greater than for the first time, enabled the measurement of Fe, including first-time high-precision direct measurements () of Fe, as well as the discovery of a long-lived isomeric state in Fe. These measurements are accompanied by both mean-field and ab initio calculations using the most recent realizations which enable theoretical assignment of the spin-parities of the Fe ground and isomeric states. Together with mean-field calculations of quadrupole deformation parameters for the Fe isotope chain, these results benchmark a maximum of deformation in the island of inversion in Fe, and shed light on trends in level densities indicated in the newly-refined mass surface.

    Comments:
    9 pages, 6 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2203.10141 [pdf]
    PRC(2022)·21 citations
  4. 09

    [Submitted on 21 Mar 2022] (cross-list from hep-ph)

    Particle production at large in Xe+Xe collisions with jet quenching using the higher twist approach

    Qing Zhang🇨🇳 · Wei Dai🇨🇳 · Lei Wang🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳

    The production of , , and in the most central (0%-5%) Xe+Xe collisions at = 5.44 TeV is investigated in the framework of the perturbative QCD (pQCD) improved parton model at an accuracy of next-to-leading order (NLO). The jet quenching effect is effectively incorporated by medium-modified fragmentation functions via the higher-twist approach. Predictions of the nuclear modification factors of , , and as functions of the transverse momentum are made with the jet transport parameter , which is extracted from the available experimental data of charged hadrons provided by ALICE and CMS. The particle ratios as functions of in Xe+Xe collisions at = 5.44 TeV as well as in 0%-5% Pb+Pb collisions at = 5.02 TeV are also presented. The numerical simulations of the scaled ratios of charged hadron production in the Xe+Xe 5.44 TeV system over those in the Pb+Pb 5.02 TeV system give a good description of the CMS data, and the scaled ratios of , , and production coincide with the curve of charged hadron production.

    Comments:
    8 pages, 7 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2203.10742 [pdf]
    CPC(2022)·7 citations
  5. 10

    [Submitted on 21 Mar 2022] (cross-list from hep-ph)

    Nambu--Jona-Lasinio model with a fractal inspired coupling

    E. Megias🇪🇸 · M. J. Teixeira🇧🇷 · V. S. Timóteo🇧🇷 · A. Deppman🇧🇷

    The Nambu--Jona-Lasino model is modified by the inclusion of a running-coupling that was obtained by a fractal approach to Quantum Chromodynamics. The coupling follows a -exponential function and, in the context of high energy collisions, explains the origin of the Tsallis non-extensive statistics distributions. The parameter is completely determined in terms of the number of colours and the number of quark flavours. We study several aspects of the extended model and compare our results to the standard NJL model, where a constant coupling is used in combination with a sharp cutoff to regularize the gap equation. We show that the modified coupling regularizes the model in a smooth cutoff fashion and reproduces the pion mass and decay constant, providing an almost identical Gell-Mann-Oakes-Renner relation as in the standard NJL model. In both models the relation is satisfied in similar cutoff scales. An important novelty of this work is the physical explanation, in terms of the fractal QCD vacuum, for a running coupling that renormalizes the quark condensate.

    Comments:
    15 pages, 6 figures, 1 table; v2 typos corrected, added references, figures 5 and 6 improved, abstract extended, added discussion in Secs. 1, 2.2, 2.4 and 3. It matches the version published in Physics Letters B
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2203.11080 [pdf]
    PLB(2025)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE