Neutrino capture cross sections for 40Ar and β-decay of 40Ti

Shell-model calculations of solar neutrino absorption cross sections for Ar-40, 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 cross section for B-8 neutrinos of (11.5 +/- 0.7) x 10(-43) Cm-2 or a total expected rate of 6.7 + 2.5 SNU. We also note that the pertinent Gamow-Teller transitions in Ar-40, experimentally accessible from the P-decay of the mirror nucleus Ti-40. Predictions for the branching ratios to states in (SC)-S-40 are presented, and the theoretical halflife of 55 +/- 5 ms is found to be in good agreement with the experimental value of 56(-12)(+18) ms.