Nuclear Theory·nucl-th

Thursday·October 13, 2022

7 papers—5 primary·2 cross-listed

01
Constraining Neutrinoless Double-Beta Decay Matrix Elements from Ab Initio Nuclear Theory
A. Belley🇨🇦 · T. Miyagi🇩🇪 · S. R. Stroberg🇺🇸 · J. D. Holt🇨🇦
As experimental searches for neutrinoless double-beta ( $0 ν β β$ ) decay are entering a new generation, with hopes to completely probe the inverted mass hierarchy, the need for reliable nuclear matrix elements, which govern the rate of this decay, is stronger than ever. Since a large discrepancy in results is typically found with nuclear modela, a large unknown still exists on the sensitivity of these experiments to the effective neutrino mass. We consider this problem from a first-principles perspective, using the ab initio valence-space in medium similarity renormalization group. In particular, we study correlations of the $0 ν β β$ -decay matrix elements in $^{76}$ Ge with other observables, such as the double Gamow-Teller giant resonance, from 34 input chiral interactions in an attempt to constrain our uncertainties and investigate the interaction dependence of the nuclear matrix element.
nucl-thhep-phnucl-exAIP Conf.Proc.(2025)·10 citations
02
A Problem in the Statistical Description of Beta-Delayed Neutron Emission
Oliver Gorton · Calvin Johnson · Jutta Escher
Reaction measurements on fission products are being planned at both Argonne National Lab and at the Facility for Rare Isotope Beams. These indirect experiments produce specific short-lived nuclei via beta decay, and the subsequent neutron and gamma emission are studied. Some initial experiments found a surprising overabundance of gamma emission, which theory has yet to explain. To remedy this, we are developing an integrated nuclear data workflow that connects advanced nuclear shell model codes for describing the beta decay with a contemporary nuclear reaction model code.
nucl-thnucl-exEPJ Web Conf.(2023)·2 citations
03
A local-density-approximation description of high-momentum tails in isospin asymmetric nuclei
Xiao-Hua Fan · Zu-Xing Yang · Peng Yin · Peng-Hui Chen · Jian-Min Dong · Zhi-Pan Li · Haozhao Liang
We adapt the local density approximation to add the high-momentum tails (HMTs) to finite nuclei's Slater-determinant momentum distributions. The HMTs are extracted by the extended Brueckner-Hartree-Fock (EBHF) method or by the lowest order cluster approximation. With a correction factor being added to EBHF, it is sufficiently in agreement with the experimental benchmark, i.e., the high-momentum $N / Z$ ratios approximately equal to $1$ , and the low-momentum $N / Z$ ratios approximately equal to $N / Z$ of the systems. It is also found that the tensor force makes the nucleon-nucleon correlations appear more easily on the nuclear surface region and the percentage of high-momentum ( $p > 300$ MeV/c) nucleons, around $17%$ -- $18%$ , independent of isospin asymmetry.
nucl-thPLB(2022)·6 citations
04
Nucleon-nucleon correlations inside atomic nuclei: synergies, observations and theoretical models
Ranjeet Dalal🇮🇳 · I.J. Douglas MacGregor🇬🇧
While the main features of atomic nuclei are well described by nuclear mean-field models, there is a large and growing body of evidence which indicates an important additional role played by spatially-correlated nucleon-nucleon structures. The role of nucleonic structures was first suggested by Heidmann in 1950 to explain pick-up reactions of energetic nucleons. Since then a steady flux of new experimental evidence has confirmed the presence of similar structures inside atomic nuclei, dominated by correlations between pairs of nucleons. The role of these internal nucleon-nucleon correlations has been established using various energetic probes like photons, pions, leptons and hadrons. These correlated structures are essential for understanding the interaction of particles with nuclei and their presence provides an explanation of many specific nuclear phenomena including backscattered protons, copious deuteron production, sub-threshold particle production, neutrino interactions with nuclei and the EMC effect. On the theoretical side, these measurements have stimulated a large number of phenomenological models specifically devised to address these enigmatic observations. While reviews exist for specific interactions, there is currently no published commentary which systematically encompasses the wide range of experimental signatures and theoretical frameworks developed thus far. The present review draws together the synergies between a wide range of different experimental and theoretical studies, summarises progress in this area and highlights outstanding issues for further study.
nucl-thnucl-exRept.Prog.Phys.(2024)·10 citations
05
Lorentz-covariant nonlocal collision term for spin-1/2 particles
David Wagner🇩🇪 · Nora Weickgenannt🇩🇪 · Dirk H. Rischke🇩🇪
We revisit the derivation of the nonlocal collision term in the Boltzmann equation for spin-1/2 particles, using both the Wigner-function approach by de Groot, van Leeuwen, and van Weert, and the Kadanoff-Baym equation in $T$ -matrix approximation. Contrary to previous calculations, our results maintain full Lorentz covariance of the nonlocal collision term.
nucl-thPRD(2022)·35 citations
06
Nucleon transverse quark spin densities
Constantia Alexandrou🇨🇾 · Simone Bacchio🇨🇾 · Martha Constantinou🇺🇸 · Petros Dimopoulos🇮🇹 · Jacob Finkenrath🇨🇾 · Roberto Frezzotti🇮🇹 · Kyriakos Hadjiyiannakou🇨🇾 · Karl Jansen🇩🇪 · Bartosz Kostrzewa🇩🇪 · Giannis Koutsou🇨🇾 · Gregoris Spanoudes🇨🇾 · Carsten Urbach🇩🇪
We present a calculation of the Mellin moments of the nucleon transverse quark spin densities extracted from the unpolarized and transversity generalized form factors. We use three $N_{F} = 2 + 1 + 1$ ensembles of twisted mass fermions with quark masses tuned to their physical values and lattice spacings $a \sim 0.08$ ~fm, $a \sim 0.07$ ~fm and $a \sim 0.06$ ~fm and extrapolate the form factors to the continuum limit. Besides isovector densities we also include results for the tensor charge for each quark flavor using the ensemble with $a \sim 0.08$ ~fm for which we include the disconnected contributions.
↳ hep-lathep-phnucl-thPoS(2023)·2 citations
07
Machine learning-based jet and event classification at the Electron-Ion Collider with applications to hadron structure and spin physics
Kyle Lee🇺🇸 · James Mulligan🇺🇸 · Mateusz Płoskoń🇺🇸 · Felix Ringer🇺🇸 · Feng Yuan🇺🇸
We explore machine learning-based jet and event identification at the future Electron-Ion Collider (EIC). We study the effectiveness of machine learning-based classifiers at relatively low EIC energies, focusing on (i) identifying the flavor of the jet and (ii) identifying the underlying hard process of the event. We propose applications of our machine learning-based jet identification in the key research areas at the future EIC and current Relativistic Heavy Ion Collider program, including enhancing constraints on (transverse momentum dependent) parton distribution functions, improving experimental access to transverse spin asymmetries, studying photon structure, and quantifying the modification of hadrons and jets in the cold nuclear matter environment in electron-nucleus collisions. We establish first benchmarks and contrast the estimated performance of flavor tagging at the EIC with that at the Large Hadron Collider. We perform studies relevant to aspects of detector design including particle identification, charge information, and minimum transverse momentum capabilities. Additionally, we study the impact of using full event information instead of using only information associated with the identified jet. These methods can be deployed either on suitably accurate Monte Carlo event generators, or, for several applications, directly on experimental data. We provide an outlook for ultimately connecting these machine learning-based methods with first principles calculations in quantum chromodynamics.
↳ hep-phnucl-exnucl-thJHEP(2023)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE

Constraining Neutrinoless Double-Beta Decay Matrix Elements from Ab Initio Nuclear Theory

A Problem in the Statistical Description of Beta-Delayed Neutron Emission

A local-density-approximation description of high-momentum tails in isospin asymmetric nuclei

Nucleon-nucleon correlations inside atomic nuclei: synergies, observations and theoretical models

Lorentz-covariant nonlocal collision term for spin-1/2 particles

Nucleon transverse quark spin densities

Machine learning-based jet and event classification at the Electron-Ion Collider with applications to hadron structure and spin physics

Affiliations