Nuclear Theory·nucl-th

Tuesday·March 22, 2022

10 papers—5 primary·5 cross-listed

01
[Submitted on 20 Mar 2022]
A Statistical Analysis for the Neutrinoless Double-Beta Decay Matrix element of 48Ca
M. Horoi🇺🇸 · A. Neacsu🇷🇴 · S. Stoica🇷🇴
Neutrinoless double beta decay ( $0 ν β β$ ) 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 $^{48}$ Ca $0 ν β β$ 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 $0 ν β β$ NME, which has a range of (0.45 - 0.95) at 90\% confidence level of, and a mean value of 0.68.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2203.10577 [pdf]
PRC(2022)·34 citations
02
[Submitted on 20 Mar 2022]
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 $\sim$ 20\% of the Atomic Mass Evaluation (AME) and predict the remaining $\sim$ 80\%. The success of our methodology is exhibited by the unprecedented $σ_{RMS} \sim 186$ keV match to data for the training set and $σ_{RMS} \sim 316$ keV for the entire AME with $Z \geq 20$ . We show that our general methodology can be interpreted using feature importance.
Comments:
5 pages, 3 figures, comments welcome
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2203.10594 [pdf]
PRC(2022)·67 citations
03
[Submitted on 21 Mar 2022]
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 $η$ , 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 $μ^{2}$ H and $μ^{3}$ H atoms and in $μ^{3}$ He $^{+}$ and $μ^{4}$ He $^{+}$ ions at various orders in the $η$ -expansion. Our analysis supports the claim that $η ≪ 1$ in these systems and finds truncation uncertainties that are similar to the previous estimate, the only exception being the truncation uncertainties in the $μ^{3}$ He $^{+}$ ion, which are found to be larger.
Comments:
Published in JPG
Subjects:
Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2203.10792 [pdf]
J.Phys.G(2022)·12 citations
04
[Submitted on 21 Mar 2022]
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 176 $\leq$ A $\leq$ 266 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 $α$ -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 $^{208}$ Pb and nearby isotopes in probable cluster emission.
Comments:
12 pages, 2 figures, Accepted in Physica scripta, 2022
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2203.11061 [pdf]
Phys.Scripta(2022)·4 citations
05
[Submitted on 9 Mar 2022]
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.
Comments:
27 pages, 31 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); physics.app-ph (physics.app-ph)
arXiv:
2203.11073 [pdf]
0 citations
06
[Submitted on 18 Mar 2022] (cross-list from hep-ph)
Explaining the hints for lepton flavour universality violation with three $S_{2}$ 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 $S U (2)_{L}$ doublet of scalar leptoquarks $S_{2}$ is capable of providing an explanation for the tensions between the measurements and the Standard Model predictions in $(g - 2)_{μ}$ , $b \to s ℓ^{+} ℓ^{-}$ and $b \to c τ ν$ 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 $S_{2}$ , 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 $Δ F = 2$ 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 $O_{9}^{U}$ operator via off-shell photon penguin diagrams, which, together with the muoquark contribution, further improves the global fit to $b \to s ℓ^{+} ℓ^{-}$ 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
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
08
[Submitted on 18 Mar 2022] (cross-list from nucl-ex)
Mapping the $N = 40$ 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 $600000$ for the first time, enabled the measurement of $^{63 - 70}$ Fe, including first-time high-precision direct measurements ( $δ m / m \sim 1 0^{- 7}$ ) of $^{68 - 70}$ Fe, as well as the discovery of a long-lived isomeric state in $^{69}$ 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 $^{69}$ 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 $N = 40$ 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
09
[Submitted on 21 Mar 2022] (cross-list from hep-ph)
Particle production at large $p_{T}$ 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 $π^{0}$ , $η$ , and $ϕ$ in the most central (0%-5%) Xe+Xe collisions at $s_{N N}$ = 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 $π^{0}$ , $η$ , and $ϕ$ as functions of the transverse momentum $p_{T}$ are made with the jet transport parameter $q^_{0}$ , which is extracted from the available experimental data of charged hadrons provided by ALICE and CMS. The particle ratios $η / π^{0}, ϕ / π^{0}$ as functions of $p_{T}$ in Xe+Xe collisions at $s_{N N}$ = 5.44 TeV as well as in 0%-5% Pb+Pb collisions at $s_{N N}$ = 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 $π^{0}$ , $η$ , and $ϕ$ 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
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 $q$ -exponential function and, in the context of high energy collisions, explains the origin of the Tsallis non-extensive statistics distributions. The parameter $q$ 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