Thu·Oct 13, 2022Thursday·October 13, 2022

1. 01*

   Quasi-free (p,2p) reactions in inverse kinematics for studying the fission yield dependence on temperature

   A. Graña-González · J. L. Rodríguez-Sánchez · J. Benlliure · G. García-Jiménez · H. Alvarez-Pol · D. Cortina-Gil · L. Atar · L. Audouin · G. Authelet · A. Besteiro · G. Blanchon · K. Boretzky and 50 other authors

   Despite the recent experimental and theoretical progress in the investigation of the nuclear fission process, a complete description still represents a challenge in nuclear physics because it is a very complex dynamical process, whose description involves the coupling between intrinsic and collective degrees of freedom, as well as different quantum-mechanical phenomena. To improve on the existing data on nuclear fission, we produce fission reactions of heavy nuclei in inverse kinematics by using quasi-free (p,2p) scattering, which induce fission through particle-hole excitations that can range from few to ten's of MeV. The measurement of the four-momenta of the two outgoing protons allows to reconstruct the excitation energy of the fissioning compound nucleus and therefore to study the evolution of the fission yields with temperature. The realization of this kind of experiment requires a complex experimental setup, providing full isotopic identification of both fission fragments and an accurate measurement of the momenta of the two outgoing protons. This was realized recently at the GSI/FAIR facility and here some preliminary results are presented.

   nucl-exPoS(2023)·2 citations
2. 02*

   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 ($0\nu \beta \beta$) 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 $0\nu \beta \beta$-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
3. 03*

   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
4. 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
5. 05*

   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

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.