Muon capture on light isotopes measured with the Double Chooz detector

Le résumé fourni par la source

Using the Double Chooz detector, designed to measure the neutrino mixing angle ${\ensuremath{\theta}}_{13}$, the products of ${\ensuremath{\mu}}^{\ensuremath{-}}$ capture on $^{12}\mathrm{C},^{13}\mathrm{C},^{14}\mathrm{N}$, and $^{16}\mathrm{O}$ have been measured. Over a period of 489.5 days, $2.3\ifmmode\times\else\texttimes\fi{}{10}^{6}$ stopping cosmic ${\ensuremath{\mu}}^{\ensuremath{-}}$ have been collected, of which $1.8\ifmmode\times\else\texttimes\fi{}{10}^{5}$ captured on carbon, nitrogen, or oxygen nuclei in the inner detector scintillator or acrylic vessels. The resulting isotopes were tagged using prompt neutron emission (when applicable), the subsequent $\ensuremath{\beta}$ decays, and, in some cases, $\ensuremath{\beta}$-delayed neutrons. The most precise measurement of the rate of $^{12}\mathrm{C}({\ensuremath{\mu}}^{\ensuremath{-}},\ensuremath{\nu})^{12}\mathrm{B}$ to date is reported: $6.{57}_{\ensuremath{-}0.21}^{+0.11}\ifmmode\times\else\texttimes\fi{}{10}^{3}\phantom{\rule{0.28em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$, or $(17.{35}_{\ensuremath{-}0.59}^{+0.35})%$ of nuclear captures. By tagging excited states emitting $\ensuremath{\gamma}\mathrm{s}$, the ground state transition rate to $^{12}\mathrm{B}$ has been determined to be $5.{68}_{\ensuremath{-}0.23}^{+0.14}\ifmmode\times\else\texttimes\fi{}{10}^{3}\phantom{\rule{0.28em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. The heretofore unobserved reactions $^{12}\mathrm{C}({\ensuremath{\mu}}^{\ensuremath{-}},\ensuremath{\nu}\ensuremath{\alpha})^{8}\mathrm{Li},^{13}\mathrm{C}({\ensuremath{\mu}}^{\ensuremath{-}},\ensuremath{\nu}n\ensuremath{\alpha})^{8}\mathrm{Li}$, and $^{13}\mathrm{C}({\ensuremath{\mu}}^{\ensuremath{-}},\ensuremath{\nu}n)^{12}\mathrm{B}$ are measured. Further, a population of $\ensuremath{\beta}n$ decays following stopping muons is identified with $5.5\ensuremath{\sigma}$ significance. Statistics limit our ability to identify these decays definitively. Assuming negligible production of $^{8}\mathrm{He}$, the reaction $^{13}\mathrm{C}({\ensuremath{\mu}}^{\ensuremath{-}},\ensuremath{\nu}\ensuremath{\alpha})^{9}\mathrm{Li}$ is found to be present at the $2.7\ensuremath{\sigma}$ level. Limits are set on a variety of other processes.

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