Thu·Apr 21, 2022Thursday·April 21, 2022

1. 01*

   Measurement of cosmogenic ${}^9$Li and ${}^8$He production rates at RENO

   H. G. Lee🇰🇷 · J. H. Choi🇰🇷 · H. I. Jang🇰🇷 · J. S. Jang🇰🇷 · S. H. Jeon🇰🇷 · K. K. Joo🇰🇷 · D. E. Jung🇰🇷 · J. G. Kim🇰🇷 · J. H. Kim🇰🇷 · J. Y. Kim🇰🇷 · S. B. Kim🇰🇷 · S. Y. Kim🇰🇷 and 17 other authors

   We report the measured production rates of unstable isotopes ${}^9$Li and ${}^8$He produced by cosmic muon spallation on ${}^{12}$C using two identical detectors of the RENO experiment. Their beta-decays accompanied by a neutron make a significant contribution to backgrounds of reactor antineutrino events in precise determination of the smallest neutrino mixing angle. The mean muon energy of its near (far) detector with an overburden of 120 (450) m.w.e. is estimated as 33.1 +- 2.3 (73.6 +- 4.4) GeV. Based on roughly 3100 days of data, the cosmogenic production rate of ${}^9$Li (${}^8$He) isotope is measured to be 44.2 +- 3.1 (10.6 +- 7.4) per day at near detector and 10.0 +- 1.1 (2.1 +- 1.5) per day at far detector. This corresponds to yields of ${}^9$Li (${}^8$He), 4.80 +- 0.36 (1.15 +- 0.81) and 9.9 +- 1.1 (2.1 +- 1.5) at near and far detectors, respectively, in a unit of 10${}^{-8}$ ${\mu }^{-1}$ g${}^{-}1$ cm${}^2$. Combining the measured ${}^9$Li yields with other available underground measurements, an excellent power-law relationship of the yield with respect to the mean muon energy is found to have an exponent of $\alpha$ = 0.75 +- 0.05.

   nucl-exhep-exPRD(2022)·7 citations
2. 02*

   Summit of the N=40 Island of Inversion: precision mass measurements and ab initio calculations of neutron-rich chromium isotopes

   R. Silwal🇨🇦 · C. Andreoiu🇨🇦 · B. Ashrafkhani🇨🇦 · J. Bergmann🇩🇪 · T. Brunner🇨🇦 · J. Cardona🇨🇦 · K. Dietrich🇨🇦 · E. Dunling🇨🇦 · G. Gwinner🇨🇦 · Z. Hockenbery🇨🇦 · J. D. Holt🇨🇦 · C. Izzo🇨🇦 and 15 other authors

   Mass measurements continue to provide invaluable information for elucidating nuclear structure and scenarios of astrophysical interest. The transition region between the $Z=20$ and $28$ proton shell closures is particularly interesting due to the onset and evolution of nuclear deformation as nuclei become more neutron rich. This provides a critical testing ground for emerging ab-initio nuclear structure models. Here, we present high-precision mass measurements of neutron-rich chromium isotopes using the sensitive electrostatic Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) facility. Our high-precision mass measurements of ${}^{59,61-63}$Cr confirm previous results, and the improved precision in measurements of ${}^{64-65}$Cr refine the mass surface beyond N=40. With the ab initio in-medium similarity renormalization group, we examine the trends in collectivity in chromium isotopes and give a complete picture of the N=40 island of inversion from calcium to nickel.

   nucl-exnucl-thPLB(2022)·22 citations
3. 03*

   Pion-nucleon sigma term ${\sigma }_{\pi N}$ and deeply bound pionic atoms

   Natsumi Ikeno🇯🇵 · Takahiro Nishi🇯🇵 · Kenta Itahashi🇯🇵 · Naoko Nose-Togawa🇯🇵 · Akari Tani🇯🇵 · Satoru Hirenzaki🇯🇵

   We investigate the possibility to determine the value of the pion-nucleon sigma term ${\sigma }_{\pi N}$ precisely by the experimental observables of the deeply bound pionic atoms. We discuss the sensitivity of the observables to ${\sigma }_{\pi N}$ and take into account the typical errors of the up-to-date experiments of the deeply bound pionic atoms. We find that the gap of the binding energies and the width of the deeply bound pionic states are good observables for the ${\sigma }_{\pi N}$ value determination by the experimental data. We also discuss the expected difficulties for the accurate determination of the value of ${\sigma }_{\pi N}$ due to the correlation between the $\sigma$ term and the potential parameter in the pion-nucleus optical potential.

   ↳ nucl-thnucl-exPTEP(2023)·7 citations
4. 04*

   Majorana neutrino mass constraints in the landscape of nuclear matrix elements

   Eligio Lisi🇮🇹 · Antonio Marrone🇮🇹

   We discuss up-to-date constraints on the Majorana neutrino mass $m_{\beta \beta }$ from neutrinoless double beta decay ($0\nu \beta \beta$) searches in experiments using different isotopes: KamLAND-Zen and EXO (${}^{136}$Xe), GERDA and MAJORANA (${}^{76}$Ge) and CUORE (${}^{130}$Te). Best fits and upper bounds on $m_{\beta \beta }$ are explored in the general landscape of nuclear matrix elements (NME), as well as for specific NME values obtained in representative nuclear models. By approximating the likelihood of $0\nu \beta \beta$ signals through quadratic forms, the analysis of separate and combined isotope data becomes exceedingly simple, and allows to clarify various aspects of multi-isotope data combinations. In particular, we analyze the relative impact of different data in setting upper bounds on $m_{\beta \beta }$, as well as the conditions leading to nonzero $m_{\beta \beta }$ at best fit, for variable values of the NMEs. Detailed results on $m_{\beta \beta }$ from various combinations of data are reported in graphical and numerical form. Implications for future $0\nu \beta \beta$ data analyses and NME calculations are briefly discussed.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2022)·13 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.