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Nuclear Theory·nucl-th

Thursday·September 28, 2017

3 papers—1 primary·2 cross-listed

All3Primary1Cross-lists2
  1. 01

    [Submitted on 27 Sept 2017]

    Validating neural-network refinements of nuclear mass models

    R. Utama · J. Piekarewicz

    Nuclear astrophysics centers on the role of nuclear physics in the cosmos. In particular, nuclear masses at the limits of stability are critical in the development of stellar structure and the origin of the elements. In this contribution we test and validate the predictions of recently refined nuclear mass models against the newly published AME2016 compilation. The basic paradigm underlining the recently refined nuclear mass models is based on existing state-of-the-art models that are subsequently refined through the training of an artificial neural network. We observe a significant improvement in the Bayesian Neural Network (BNN) predictions relative to the corresponding "bare" models when compared to the nearly 50 new masses reported in the AME2016 compilation. Further, AME2016 estimates for the handful of impactful isotopes in the determination of r-process abundances are found to be in fairly good agreement with our theoretical predictions. Indeed, the BNN-improved Duflo-Zuker model predicts a root-mean-square deviation relative to experiment of about 400 keV. Given the excellent performance of the BNN refinement in confronting the recently published AME2016 compilation, we are confident of its critical role in our quest for mass models of the highest quality. Moreover, as uncertainty quantification is at the core of the BNN approach, the improved mass models are in a unique position to identify those nuclei that will have the strongest impact in resolving some of the outstanding questions in nuclear astrophysics.

    Comments:
    7 pages, 3 figures, and 2 tables
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1709.09502 [pdf]
    PRC(2018)·57 citations
  2. 02

    [Submitted on 26 Sept 2017] (cross-list from hep-ph)

    Fermionic Glauber Operators and Quark Reggeization

    Ian Moult🇺🇸 · Mikhail P. Solon🇺🇸 · Iain W. Stewart🇺🇸 · Gherardo Vita🇺🇸

    We derive, in the framework of soft-collinear effective field theory (SCET), a Lagrangian describing the -channel exchange of Glauber quarks in the Regge limit. The Glauber quarks are not dynamical, but are incorporated through non-local fermionic potential operators. These operators are power suppressed in relative to those describing Glauber gluon exchange, but give the first non-vanishing contributions in the Regge limit to processes such as and . They therefore represent an interesting subset of power corrections to study. The structure of the operators, which describe certain soft and collinear emissions to all orders through Wilson lines, is derived from the symmetries of the effective theory combined with constraints from power and mass dimension counting, as well as through explicit matching calculations. Lightcone singularities in the fermionic potentials are regulated using a rapidity regulator, whose corresponding renormalization group evolution gives rise to the Reggeization of the quark at the amplitude level and the BFKL equation at the cross section level. We verify this at one-loop, deriving the Regge trajectory of the quark in the color channel, as well as the leading logarithmic BFKL equation. Results in the and color channels are obtained by the simultaneous exchange of a Glauber quark and a Glauber gluon. SCET with quark and gluon Glauber operators therefore provides a framework to systematically study the structure of QCD amplitudes in the Regge limit, and derive constraints on higher order amplitudes.

    Comments:
    31 pages, many figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1709.09174 [pdf]
    JHEP(2018)·39 citations
  3. 03

    [Submitted on 26 Sept 2017] (cross-list from hep-ph)

    Lepton Number Violation, Lepton Flavour Violation and Baryogenesis in Left-Right Symmetric Model

    Happy Borgohain🇮🇳 · Mrinal Kumar Das🇮🇳

    We did a model independent phenomenological study of baryogenesis via leptogenesis, neutrinoless double beta decay (NDBD) and charged lepton flavour violation (CLFV) in a generic left-right symmetric model (LRSM) where neutrino mass originates from the type I + type II seesaw mechanism. We studied the new physics contributions to NDBD coming from the left-right gauge boson mixing and the heavy neutrino contribution within the framework of LRSM. We have considered the mass of the RH gauge boson to be specifically 5 TeV, 10 TeV and 18 TeV and studied the effects of the new physics contributions on the effective mass and baryogenesis and compared with the current experimental limit. We tried to correlate the cosmological BAU from resonant leptogenesis with the low energy observables, notably, NDBD and LFV with a view to finding a common parameter space where they coexists.

    Comments:
    34 pages, 12 figures, version accepted for publication in Phys. Rev. D. arXiv admin note: text overlap with arXiv:1705.00922
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
    arXiv:
    1709.09542 [pdf]
    PRD(2017)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE