Shell model calculation for the 71Ga(ν,e-)71Ge solar neutrino detector

Gamow-Teller allowed neutrino capture transitions between the ground state of 71Ga and accessible excited states in 71Ge 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 71Ga and 71Ge. 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 8B 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 8B 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 71Ga 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 37Cl solar neutrino experiment