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Nuclear Theory·nucl-th

Tuesday·March 22, 2022

10 papers—5 primary·5 cross-listed

All10Primary5Cross-lists5
  1. 01

    A Statistical Analysis for the Neutrinoless Double-Beta Decay Matrix element of 48Ca

    M. Horoi🇺🇸 · A. Neacsu🇷🇴 · S. Stoica🇷🇴

    Neutrinoless double beta decay () nuclear matrix elements (NME) are the object of many theoretical calculation methods, and are very important for analysis and guidance of a large number of experimental efforts. However, there are large discrepancies between the NME values provided by different methods. In this paper we propose a statistical analysis of the Ca NME using the interacting shell model, emphasizing the range of the NME probable values and its correlations with observables that can be obtained from the existing nuclear data. Based on this statistical analysis with three independent effective Hamiltonians we propose a common probability distribution function for the NME, which has a range of (0.45 - 0.95) at 90\% confidence level of, and a mean value of 0.68.

    nucl-thhep-phPRC(2022)·34 citations
  2. 02

    Physically Interpretable Machine Learning for nuclear masses

    M. R. Mumpower · T. M. Sprouse · A. E. Lovell · A. T. Mohan

    We present a novel approach to modeling the ground state mass of atomic nuclei based directly on a probabilistic neural network constrained by relevant physics. Our Physically Interpretable Machine Learning (PIML) approach incorporates knowledge of physics by using a physically motivated feature space in addition to a soft physics constraint that is implemented as a penalty to the loss function. We train our PIML model on a random set of 20\% of the Atomic Mass Evaluation (AME) and predict the remaining 80\%. The success of our methodology is exhibited by the unprecedented keV match to data for the training set and keV for the entire AME with . We show that our general methodology can be interpreted using feature importance.

    nucl-thastro-ph.SRPRC(2022)·67 citations
  3. 03

    Bayesian analysis of nuclear polarizability corrections to the Lamb shift of muonic H-atoms and He-ions

    Simone Salvatore Li Muli🇩🇪 · Bijaya Acharya🇩🇪 · Oscar Javier Hernandez🇩🇪 · Sonia Bacca🇩🇪

    The extraction of nuclear charge radii from spectroscopy experiments in muonic atoms is currently limited by the large uncertainties associated with the theoretical evaluation of the nuclear polarizability effects. To facilitate calculations, these polarizability corrections are conventionally expressed as an expansion in a dimensionless parameter , which has been argued in previous literature to hold an approximate value of 0.33 in light-nuclear systems. In this work, we check this claim by doing a Bayesian analysis of the nuclear-polarizability corrections to the Lamb shift in H and H atoms and in He and He ions at various orders in the -expansion. Our analysis supports the claim that in these systems and finds truncation uncertainties that are similar to the previous estimate, the only exception being the truncation uncertainties in the He ion, which are found to be larger.

    nucl-thphysics.atom-phJ.Phys.G(2022)·12 citations
  4. 04

    A comprehensive study of decay modes associated with Pb isotopes

    R. Sharma · A. Jain · P. K. Sharma · S. K. Jain · G. Saxena

    Decay modes in Pb isotopes within the range 176A266 are investigated by the calculation of half-lives using several empirical formulas. These formulas along with various theoretical treatments are first tested to reproduce experimental half-lives and known decay modes of Pb isotopes, which are in consequence applied to estimate half-lives and decay modes of unknown Pb isotopes. A comparison between -decay and weak-decay from the stable to drip-line isotopes is canvassed which leads to the excellent match with experimental data and applicability of applied empirical formulas. In addition, the full chain of Pb isotopes is probed as potential daughter candidates of cluster emission from superheavy nuclei which ensued the predominant role of Pb and nearby isotopes in probable cluster emission.

    nucl-thPhys.Scripta(2022)·4 citations
  5. 05

    Questioning the 239Pu(n,2n)238Pu cross section shape above emission threshold

    O. Bouland · V. Meot · O. Roig

    In the light of the JEF(F) European project longstanding story according to the determination of the most exact shape of the 239Pu(n, 2n)238Pu reaction cross section and a recent measurement by Meot et al., this paper aims to shed another light on this topic by bringing new theoretical feedback. To achieve this goal, the AVXSF-LNG computer program has been upgraded to model second-chance reactions using its decay-probability module and, then chained to the TALYS-ECIS06 nuclear reaction system of codes. Present diligent calculation of the (n,2n) cross section over the energy range from the threshold to the onset of third-chance fission at about 12 MeV, suggests that current evaluations under-estimate the 239Pu(n,2n) cross section below 10 MeV; under-estimation of the order of 7% relatively to the JEFF-3.1 evaluation. On this ground, we propose an upward correction to the normalization of the measurement by Meot et al. Correction factor of about 1.24 with a maximum uncertainty on present fitted model estimated to 11.6%. Latter value is extracted from a sensitivity analysis of the calculation route to the level density model that is selected for the non-equilibrated residual nucleus and to alternative choices we can make in terms of neutron fission cross section measurement references for the 238Pu and 239Pu target nuclei.

    nucl-thnucl-exphysics.app-ph0 citations

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