Search for Neutrino Oscillations in the Appearance Channel Anti Muon Neutrion Going to Anti Electron Neutrino and Measurements of Neutrino-Carbon Cross Sections.

This document describes the results of a neutrino oscillation experiment in the channel | nu_{mu} to | nu_{rm e} and measurements of neutrino-carbon cross sections. This is an accelerator based experiment performed using nu_ {rm e}, |nu_ {mu} and nu_ {mu} neutrinos from the LAMPF A -6 beam stop. The |nu_{ mu} were used to look for neutrino oscillations and the mu_{rm e} were used to measure the neutrino-carbon cross sections. The main features of the detector are its large mass of liquid scintillator (180 tons of mineral oil with 0.03 g/l b-PBD added), recording of history before and after a prompt event, good particle identification and an active cosmic-ray anticoincidence shield. The detector is located 29.8 m from the neutrino source. The 1220 photomultiplier tubes on the inside of the tank provide 25% photocathode coverage with uniform spacing. If |nu _{mu} oscillates into |nu_{rm e}, the positron from the reaction |nu _{rm e}p to e^+n followed by a 2.2 MeV gamma ray is the event signature for oscillations. There is no significant |nu_{ rm e} production at the beam stop. An analysis of data taken in 1994 yields 7 events consistent with neutrino oscillations with an estimated background of 1.1 events. If we interpret these events as arising from neutrino oscillations the 90% confidence level upper limit of the oscillation probability is 10.3 times 10^{-3} and the 90% confidence level lower limit is 3.4 times 10^{-3}. In a separate analysis, 283 +/- 27 ^{12}C(nu_ {rm e},e^-)^ {12}N_{rm g.s. } events with subsequent ^{12 }N(beta^+)^{12 }C were observed. The measured total cross section is (9.0 +/- 0.8(stat.) +/- 0.8(syst.)) times 10^{-42} cm^2 . Also 138 +/- 43 events were observed for the reaction nu_sp{ rm e}{12}C to ^{12} N*e^ - and the resulting cross section is (5.0 +/- 1.6(stat.) +/- 0.5(syst.)) times 10^{-42 } cm^2. The ratio of the exclusive events to inclusive events is 0.67 +/- 0.08(stat.) +/- 0.06(syst.). These cross sections are in good agreement with theoretical calculations and other experimental measurements.