Search for High-Energy Tau-Neutrino Interactions

Kinematic selection criteria are developed for separating tau-neutrino charged-current interactions from a large background of muon- and electron-neutrino interactions. The criteria are designed to detect the three-prong decay mode of the $\ensuremath{\tau}$ lepton and rely on the three-particle combination's transverse momentum being anticorrelated with the tr\'ansverse momentum of the other visible particles and being correlated with the missing transverse momentum. The criteria are applied to a sample of events from an exposure of the Fermilab 15-ft bubble chamber to the quadrupole triplet neutrino beam. The average event energies for this beam are 90 GeV for neutrino and 60 GeV for antineutrino events. The $14 \ensuremath{\tau}$ candidates selected agree with the calculated background of 14.3\ifmmode\pm\else\textpm\fi{}1.2. An upper limit on the probability of muon neutrinos oscillating into tau neutrinos of 0.053 is obtained.