Shell-Model Calculation For The Ga-71(Nu,E-)Ge-71 Solar Neutrino Detector

Gamow-Teller allowed neutrino capture transitions between the ground state of /sup 71/Ga and accessible excited states in /sup 71/Ge are calculated in a model space of the 2p and 1f shells. The total (p,n) Gamow-Teller strength function is also calculated. The effects of model-space truncation are systematically investigated and detailed comparisons are made between calculated and experimental spectroscopic data for states in /sup 71/Ga and /sup 71/Ge. The calculated effect of excited-state transitions is in good agreement with a previous phenomenological estimate (based upon beta decay measurements in the vicinity of mass 71) except for the higher energy /sup 8/B neutrinos. For these rare high energy neutrinos, there is not yet sufficient experimental information to make a complete phenomenological estimate. The total cross section for /sup 8/B neutrinos is calculated to be about ten times larger than the ground-state--to--ground-state capture rate. The overall uncertainty in the capture rate for a /sup 71/Ga detector that is caused by excited state transitions is estimated to be about 5 percent for a standard solar model and about 1 percent for nonstandard models that are consistent with the /sup 37/Cl solar neutrino experiment.