An alternative analysis of the LSND neutrino oscillation search data on nu -bar micro--> nu -bare.

Abstract

This analysis of data from the Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos Meson Physics Facility (LAMPF) sets bounds on neutrino oscillations in the appearance channel ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{e}$ by searching for the signature of the reaction ${\overline{\ensuremath{\nu}}}_{e}p\ensuremath{\rightarrow}{e}^{+}n$: an ${e}^{+}$ followed by a 2.2 MeV $\ensuremath{\gamma}$ ray from neutron capture. Five ${e}^{\ifmmode\pm\else\textpm\fi{}}$- $\ensuremath{\gamma}$ coincidences are observed in time with the LAMPF beam, with an estimated background of 6.2 events. The 90% confidence limits obtained in this analysis are $\ensuremath{\Delta}{m}^{2}<0.07{\mathrm{eV}}^{2}$ for ${sin}^{2}2\ensuremath{\theta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$, and ${sin}^{2}2\ensuremath{\theta}<6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ for $\ensuremath{\Delta}{m}^{2}\ensuremath{\gtrsim}20{\mathrm{eV}}^{2}$. The possible signal at the edge of the detector's sensitivity is mentioned.