Update on the search for ν-barμ→ν-bare oscillations by the KARMEN2 experiment

The neutrino experiment KARMEN sets the most stringent exclusion limits for ν-barμ→ν-bare oscillations. Analyzing the data set recorded from Feb.1997 up to March 2000 with the upgraded experimental configuration, the search of ν-bare appearance via the p(ν-bare, e+)n reaction yields no hints for neutrino oscillations. Applying a likelihood method to the measured event sample of 11 events (background expectation 12.3 events), we deduce an upper limit of sin2 (2Θ) < 1.3 · 10-3 for large Δm2 > 100 eV2 and Δm2 < 0.049 eV2 for sin2 (2Θ)=1