A Study of Pontecorvo Reactions In Antiproton Deuterium Annihilations At Rest

The results of the analysis of a new data sample of (p) over bar annihilations at rest on deuterium and hydrogen, taken at the CERN LEAR by the OBELIX spectrometer, are presented. The (p) over bar d --> pi(-)p channel has been measured with a noticeable reduction of both the statistical and the systematic errors with respect to the previous OBELIX measurement and the branching ratio turns out to be (1.29 +/- +/- 0.07(stat) +/- 0.05(syst)).10(-5), in good agreement with the previous result. The (p) over bar d --> rho(-)p --> pi(-) pi(0)p channel has been investigated for the first time and the branching ratio is evaluated to be (2.9 +/- 0.4(stat) +/- 0.5(syst)).10(-5). Finally, as a check of the spectrometer absolute calibration, the (p) over bar p --> pi(+) pi(-) channel was also studied with a measured branching ratio of (4.27 +/- 0.15(stat) +/- 0.17(syst)).10(-3), in good agreement with the ASTERIX result.