Measurement of ${}^{75}\mathrm{As}(\mathrm{n},\gamma ){}^{76}\mathrm{As}$ reaction relevant to 0$\nu \beta \beta$ decay searches of ${}^{76}\mathrm{Ge}$ and astrophysical $s$-process temperatures

Abstract

The cross sections and resonance structures of ${}^{75}\mathrm{As}$(n,$\gamma$)${}^{76}\mathrm{As}$ reaction are critical to the neutrinoless double-$\beta$ (0$\nu \beta \beta$) decay searches of ${}^{76}\mathrm{Ge}$, the $s$-process nucleosynthesis of nuclear astrophysics, and Neutron Resonance Capture Analysis for determining the elemental and isotopic composition of archaeological and cultural heritage. We report a high-precision measurement of the ${}^{75}\mathrm{As}$ neutron capture cross sections from 1~eV to 1~MeV, performed at the Back-n facility of the China Spallation Neutron Source using the Time-of-Flight method. In the resolved resonance region, nineteen resonance structures of ${}^{75}\mathrm{As}$(n,$\gamma$)${}^{76}\mathrm{As}$ reaction have been discovered for the first time, and inconsistencies between evaluated libraries has been resolved. Resonance parameters for the newly observed structures were extracted with the $R$-matrix code SAMMY. These findings will help refine the theoretical predictions of half-lives and decay constants for the double-$\beta$ decay searches of ${}^{76}\mathrm{Ge}$. Astrophysical Maxwellian-averaged cross sections were calculated based on the averaged cross sections in the unresolved resonance region. And the ${}^{75}\mathrm{As}$(n,$\gamma$)${}^{76}\mathrm{As}$ reaction rates were derived over the astrophysically relevant temperature range in both the main and weak $s$-processes nucleosynthesis. The present reaction rates deviate significantly from the recent theoretical predictions, and the uncertainties are significantly reduced.