CHARGE-EXCHANGE REACTIONS AND THE EFFICIENCY OF SOLAR-NEUTRINO DETECTORS

The efficiencies of solar neutrino detectors are often based in part o n weak interaction strengths determined by (p, n) and other charge exc hange reactions. Although the (p, n) determinations are surprisingly g ood, it is shown that they may be inaccurate for important Gamow-Telle r transitions whose strengths are a small fraction of the sum rule lim it. This emphasizes the importance of direct calibration with nu sourc es for detectors such as I-127 and In-115 In where direct beta-decay i nformation cannot be obtained. It may also bear on recent attempts to compare charge exchange and beta decay in the mass-37 system.