Neutrino Capture Cross Sections for Ar-40 and beta-decay of Ti-40

Abstract

Shell-model calculations of solar neutrino absorption cross sections for $^{40}$Ar, the proposed component of the ICARUS detector, are presented. It is found that low-lying Gamow-Teller transitions lead to a significant enhancement of the absorption rate over that expected from the Fermi transition between the isobaric analog states, leading to an overall absorption rate of 6.7 SNU. We also note that the pertinent Gamow-Teller transitions in $^{\sss 40}$Ar are experimentally accessible from the $\beta$-decay of the mirror nucleus $^{\sss 40}$Ti. Predictions for the branching ratios to states in $^{\sss 40}$Sc are presented, and the theoretical halflife of 53~ms is found to be in good agreement with the experimental value of $56^{+18}_{-12}$~ms.