Mon·Sep 2, 2024Monday·September 2, 2024

1. 01*

   Two-neutrino double electron capture of ${}^{124}$Xe in the first LUX-ZEPLIN exposure

   J. Aalbers🇺🇸 · D. S. Akerib🇺🇸 · A. K. Al Musalhi🇬🇧 · F. Alder🇬🇧 · C. S. Amarasinghe🇺🇸 · A. Ames🇺🇸 · T. J. Anderson🇺🇸 · N. Angelides🇬🇧 · H. M. Araújo🇬🇧 · J. E. Armstrong🇺🇸 · M. Arthurs🇺🇸 · A. Baker🇬🇧 and 193 other authors

   The broad physics reach of the LUX-ZEPLIN (LZ) experiment covers rare phenomena beyond the direct detection of dark matter. We report precise measurements of the extremely rare decay of ${}^{124}$Xe through the process of two-neutrino double electron capture (2$\nu$2EC), utilizing a $1.39\mathrm{kg}\times \mathrm{yr}$ isotopic exposure from the first LZ science run. A half-life of $T_{1/2}^{2\nu 2\mathrm{EC}}=(1.09\pm 0.14_{\text{stat}}\pm 0.05_{\text{sys}})\times 10^{22}\mathrm{yr}$ is observed with a statistical significance of $8.3\sigma$, in agreement with literature. First empirical measurements of the KK capture fraction relative to other K-shell modes were conducted, and demonstrate consistency with respect to recent signal models at the $1.4\sigma$ level.

   nucl-exphysics.ins-detJ.Phys.G(2025)·23 citations
2. 02*

   The Continuous Electron Beam Accelerator Facility at 12 GeV

   P. A. Adderley🇺🇸 · S. Ahmed🇺🇸 · T. Allison🇺🇸 · R. Bachimanchi🇺🇸 · K. Baggett🇺🇸 · M. BastaniNejad🇺🇸 · B. Bevins · M. Bevins · M. Bickley🇺🇸 · R. M. Bodenstein🇺🇸 · S. A. Bogacz🇺🇸 · M. Bruker🇺🇸 and 127 other authors

   This review paper describes the energy-upgraded CEBAF accelerator. This superconducting linac has achieved 12 GeV beam energy by adding 11 new high-performance cryomodules containing eighty-eight superconducting cavities that have operated CW at an average accelerating gradient of 20 MV/m. After reviewing the attributes and performance of the previous 6 GeV CEBAF accelerator, we discuss the upgraded CEBAF accelerator system in detail with particular attention paid to the new beam acceleration systems. In addition to doubling the acceleration in each linac, the upgrade included improving the beam recirculation magnets, adding more helium cooling capacity to allow the newly installed modules to run cold, adding a new experimental hall, and improving numerous other accelerator components. We review several of the techniques deployed to operate and analyze the accelerator performance, and document system operating experience and performance. In the final portion of the document, we present much of the current planning regarding projects to improve accelerator performance and enhance operating margins, and our plans for ensuring CEBAF operates reliably into the future. For the benefit of potential users of CEBAF, the performance and quality measures for beam delivered to each of the experimental halls is summarized in the appendix.

   ↳ physics.acc-phnucl-exPhys.Rev.Accel.Beams(2024)·45 citations
3. 03*

   Activation of momentum fluctuations in wave packet molecular dynamics: Impacts on momentum distributions of projectilelike fragments

   Lei Shen · Akira Ono🇯🇵 · Yu-Gang Ma🇨🇳

   Molecular dynamics approaches use wave packets as nucleon wave functions to simulate the time evolution of nuclear reactions. It is crucial to activate the momentum fluctuation inherent in each wave packet so that it properly affects the time evolution. In the antisymmetrized molecular dynamics (AMD) model, this has traditionally been done by splitting the wave packets, i.e., by introducing a random fluctuation to the wave packet center of each particle. The present work proposes an improved approach to activate the fluctuation in both the one-body mean-field propagation and the two-nucleon collision processes, consistently based on the gradual or sudden change of the degree of isolation, which is derived from the fragment number function used for the zero-point energy subtraction. This new method is applied to the 12C + 12C and 12C + p reactions at about 100 MeV/nucleon, focusing on the momentum distribution of the 11B fragments produced by one-proton removal from the 12C projectile. The results show that, with the momentum fluctuation suitably activated, the method correctly accounts for the recoil from the removed nucleon to the residue and the 11B momentum distribution is significantly improved, while without activating the fluctuation the distribution is too narrow compared to the experimental data. Furthermore, the AMD results indicate that the momentum distribution consists of two components; one is the high $P_z$ component with a small shift from the beam velocity, resulting from the simple removal of a proton after an energetic collision with a target particle; the other is the low $P_z$ component with a larger peak shift resulting from the decay of an excited 12C nucleus in a longer time scale. The activation of momentum fluctuation mainly affects the high $P_z$ component to broaden it. The role of cluster correlations in this problem is also investigated.

   ↳ nucl-thnucl-exPRC(2024)·2 citations
4. 04*

   How do mirror charge radii constrain density dependence of the symmetry energy?

   Bai-Shan Hu🇨🇦

   It has recently been suggested that differences in the charge radii of mirror nuclei ($\Delta R_{\mathrm{ch}}^{\mathrm{mirr}}$) are strongly correlated with the neutron-skin thickness ($R_{\mathrm{skin}}$) of neutron-rich nuclei and with the slope of the symmetry energy ($L$). To test this assumption, we present ab initio calculations of $R_{\mathrm{skin}}$ in ${}^{48}$Ca and ${}^{208}$Pb, $\Delta R_{\mathrm{ch}}^{\mathrm{mirr}}$ in ${}^{36}$Ca${-}^{36}$S, ${}^{38}$Ca${-}^{38}$Ar, ${}^{41}$Sc${-}^{41}$Ca, ${}^{48}$Ni${-}^{48}$Ca, ${}^{52}$Ni${-}^{52}$Cr, and ${}^{54}$Ni${-}^{54}$Fe mirror pairs, and $L$. Employing the recently developed 34 chiral interaction samples, identified by the history matching approach, we conduct rigorous statistical analysis of correlations among $\Delta R_{\mathrm{ch}}^{\mathrm{mirr}}$, $R_{\mathrm{skin}}$ and $L$, accounting for quantified uncertainties from low-energy constants of chiral interaction, chiral effective field theory truncation and many-body method approximation. The ab initio results reveal an appreciable $\Delta R_{\mathrm{ch}}^{\mathrm{mirr}}-L$ correlation in $fp$-shell mirror pairs. However, contrary to previous studies, the present calculation finds that the studied $sd$-shell mirror pairs do not exhibit any $\Delta R_{\mathrm{ch}}^{\mathrm{mirr}}-L$ correlation.

   ↳ nucl-thnucl-exPLB(2024)·5 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.