Fri·Jun 17, 2022Friday·June 17, 2022

1. 01*

   Re-investigation of the interplay of fission modes and non-equilibrium fission processes in heavy actinide nuclei 249Bk and 257Md

   R. Dubey🇵🇱 · G. Kaur🇫🇷 · Abhishek Yadav🇮🇳 · N. Saneesh🇮🇳 · Akhil Jhingan🇮🇳 · P. Sugathan🇮🇳 · Tathagata Banerjee🇮🇹 · K.S. Golda🇮🇳 · Hardev Singh🇮🇳 · Meenu Thakur🇮🇳 · Ruchi Mahajan🇺🇸

   Measurements of mass and angular distributions of fission fragments from actinide nuclei 249Bk and 257Md, produced in fusion reactions 11B and 19F + 238238U, are presented. Experimentally observed mass ratio distributions indicate 'multi-chance fission' through the interplay of fission modes in the fission process, and they agree well with predictions from calculations using the GEF ('GEneral description of Fission observables') model code. Furthermore, to test the signatures of events from non-compound nuclear processes in the fission of 249Bk and 257Md nuclei, Monte Carlo statistical decay model calculations using GEMINI++ were performed for the measured mass distribution at all energies. For comparison purposes, the fission fragment mass distributions of neighboring heavy actinide nuclei, previously measured in the fission of 250Cf and 254Fm nuclei produced by 12C and 16O projectiles on a 238U target, are also presented. The measured angular anisotropy data for the 19F + 238U reaction differ from the results of the Transition State Model at energies below the fusion barrier. As a result of the present study, we suggest considering the interplay between K relaxation time, dynamic dissipation, and their influence on shell correction to understand the evolution of fission dynamics in heavy-ion-induced actinide nuclei

   nucl-exnucl-thPLB(2024)·1 citation
2. 02*

   Study of dielectric breakdown in liquid xenon with the XeBrA experiment

   J. Watson🇺🇸 · I. Olcina🇺🇸 · J. Soria🇺🇸 · D. N. McKinsey🇺🇸 · S. Kravitz🇺🇸 · E. E. Deck🇺🇸 · E. P. Bernard🇺🇸 · L. Tvrznikova🇺🇸 · W. L. Waldron🇺🇸 · Q. Riffard🇺🇸 · K. O'Sullivan

   Maintaining the electric fields necessary for the current generation of noble liquid time projection chambers (TPCs), with drift lengths exceeding one meter, requires a large negative voltage applied to their cathode. Delivering such high voltage is associated with an elevated risk of electrostatic discharge and electroluminescence, which would be detrimental to the performance of the experiment. The Xenon Breakdown Apparatus (XeBrA) is a five-liter, high voltage test chamber built to investigate the contributing factors to electrical breakdown in noble liquids. In this work, we present the main findings after conducting scans over stressed electrode areas, surface finish, pressure, and high voltage ramp speed in the medium of liquid xenon. Area scaling and surface finish were observed to be the dominant factors affecting breakdown, whereas no significant changes were observed with varying pressure or ramp speed. A general rise in both anode current and photon rate was observed in the last 30 seconds leading up to a breakdown, with a marked increase in the last couple of seconds. In addition, the position of breakdowns was reconstructed with a system of high-speed cameras and a moderate correlation with the Fowler-Nordheim field emission model was found. Tentative evidence for bubble nucleation being the originating mechanism of breakdown in the liquid was also observed. We deem the results presented in this work to be of particular interest for the design of future, large TPCs, and practical recommendations are provided.

   ↳ physics.ins-dethep-exnucl-exRev.Sci.Instrum.(2023)·10 citations
3. 03*

   Influence of nuclear structure in relativistic heavy-ion collisions

   Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳

   Many probes are proposed to determine the quark-gluon plasma and explore its properties in ultra-relativistic heavy-ion collisions. Some of them are related to initial states of the collisions, such as collective flow, Hanbury-Brown-Twiss (HBT) correlation, chiral magnetic effects and so on. The initial states can come from geometry overlap of the colliding nuclei, fluctuations or nuclear structure with the intrinsic geometry asymmetry. The initial geometry asymmetry can transfer to the final momentum distribution in the aspect of hydrodynamics during the evolution of the fireball. Different from traditional methods for nuclear structure study, the ultra-relativistic heavy-ion collisions could provide a potential platform to investigate nuclear structures with the help of the final-state observables after the fireball expansion. This chapter first presents a brief introduction of the initial states in relativistic heavy-ion collisions, and then delivers a mini-review for the nuclear structure effects on experimental observables in the relativistic energy domain.

   ↳ nucl-thnucl-ex24 citations
4. 04*

   Study of exclusive photoproduction of charmonium in ultra-peripheral lead-lead collisions

   LHCb collaboration

   The cross-sections of exclusive (coherent) photoproduction $J/\psi$ and $\psi (2S)$ mesons in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of $5.02\mathrm{TeV}$ are measured using a data sample corresponding to an integrated luminosity of $228\pm 10{\mu \mathrm{b}}^{-1}$, collected by the LHCb experiment in 2018. The differential cross-sections are measured separately as a function of transverse momentum and rapidity in the nucleus-nucleus centre-of-mass frame for $J/\psi$ and $\psi (2S)$ mesons. The integrated cross-sections are measured to be \mbox{${\sigma }_{J/\psi }^{\mathrm{coh}}=5.965\pm 0.059\pm 0.232\pm 0.262\mathrm{mb}$} and \mbox{${\sigma }_{\psi (2S)}^{\mathrm{coh}}=0.923\pm 0.086\pm 0.028\pm 0.040\mathrm{mb}$}, where the first listed uncertainty is statistical, the second systematic and the third due to the luminosity determination. The cross-section ratio is measured to be \mbox{${\sigma }_{\psi (2S)}^{\mathrm{coh}}/{\sigma }_{J/\psi }^{\mathrm{coh}}=0.155\pm 0.014\pm 0.003$}, where the first uncertainty is statistical and the second is systematic. These results are compatible with theoretical predictions.

   ↳ hep-exnucl-exJHEP(2023)·100 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.