Neutrino absorption efficiency of an Ar-40 detector from the beta decay ofTi-40

We studied beta-delayed proton and gamma emission from Ti-40 decay. We foun d t(1/2)=52.7+/-1.5 ms and observed 28 proton groups that we organized into a Ti-40 decay scheme with 21 branches. The reduced transition strengths of these decay branches were then used to compute the neutrino detection effi ciency of the ICARUS liquid argon time-projection chamber. We found Ar-40(v ,e) cross sections (for an electron energy threshold W=5 MeV) of (14.0+/-0. 3)x10(-43) cm(,)(2) (75.1+/-1.8)x10(-43) cm(2), and (3.2+/-0.1)x10(-41) cm( 2) for B-8 neutrinos, hep neutrinos, and supernova neutrinos characterized by a temperature of 4.5 MeV. [S0556-2813(98)07812-1].