Capture of solar and higher-energy neutrinos by 127I.

Abstract

We discuss and improve a recent treatment of the absorption of solar neutrinos by $^{127}\mathrm{I}$, in connection with a proposed solar neutrino detector. With standard-solar-model fluxes and an in-medium value of -1.0 for the axial-vector coupling constant ${\mathit{g}}_{\mathit{A}}$, we obtain a $^{8}\mathrm{neutrino}$ cross section of 3.3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}42}$, about 50% larger than in our previous work, and a $^{7}\mathrm{Be}$ cross section that is less certain but nevertheless also larger than before. We then apply the improved techniques to higher incoming energies that obtain at the LAMPF beam dump, where an experiment is underway to finalize a calibraiton of the $^{127}\mathrm{I}$ with electron neutrinos from muon decay. We find that forbidden operators, which play no role in solar-neutrino absorption, contribute nonnegligibly to the LAMPF cross section, and that the preliminary LAMPF mean value is significantly larger than our prediction.