Measurement of the cross section for the reactionI127(νe,e−)Xebound states127with neutrinos from the decay of stopped muons

Abstract

The cross section for the reaction $^{127}\mathrm{I}({\ensuremath{\nu}}_{e},{e}^{\ensuremath{-}})^{127}{\mathrm{Xe}}_{bound states}$ has been measured for electron neutrinos from the decay of stopped muons to be $[2.84\ifmmode\pm\else\textpm\fi{}0.91(\text{stat})\ifmmode\pm\else\textpm\fi{}0.25(\text{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}\phantom{\rule{0.3em}{0ex}}{\text{cm}}^{2}$. A tank containing $1540\phantom{\rule{0.3em}{0ex}}\text{kg}$ of $^{127}\mathrm{I}$ in the form of NaI solution was placed $8.53\phantom{\rule{0.3em}{0ex}}\mathrm{m}$ from the Los Alamos Meson Physics Facility beamstop, where it received a typical flux of $5\ifmmode\times\else\texttimes\fi{}{10}^{7}{\ensuremath{\nu}}_{e}∕({\text{cm}}^{2}\phantom{\rule{0.3em}{0ex}}\mathrm{s})$. The $^{127}\mathrm{Xe}$ atoms produced by neutrino capture were extracted from the target solution, placed in miniature proportional counters, and their number was determined by counting. This is the first measurement of a neutrino capture cross section for an $\mathrm{I}$ nucleus and is in good agreement with a recent calculation.