HIGH STATISTICS SEARCH FOR NU(MU)((NU)OVER-BAR(MU))-]NU(E)((NU)OVER-BAR(E)) OSCILLATIONS IN THE SMALL MIXING ANGLE REGIME

Limits on nu(mu)(<(nu)over bar>(mu)) <----> nu(e)(<(nu)over bar>(e)) o scillations based on a statistical separation of nu(e)N charged curren t interactions in the CCFR detector al Fermilab are presented. Neutrin o energies range from 30 to 600 GeV with a mean of 140 GeV, and nu(mu) , flight lengths vary from 0.9 to 1.4 km. The result excludes oscillat ions in the region with sin(2) 2 alpha > 1.8 x 10(-3) for large Delta m(2) (>1000 eV(2)) and Delta m(2) > 1.6 eV(2) for sin(2) 2 alpha = 1. This result is the most stringent limit to date for Delta m(2) > 25 eV (2) and it excludes the high Delta m(2) oscillation region favored by the LSND experiment. The nu(mu)-to-nu(e) cross-section ratio was measu red as a test of nu(mu)(<(nu)over bar>(mu) <----> nu(e) (<(nu)over bar >(e)) universality to be 1.026 +/- 0.025(stat) +/- 0.049(syst).