Measurement of the branching ratios for the decays τ→hadron π0ν and τ→hadron π0π0ν

Abstract The Crystal Ball detector at the DORIS II storage ring at DESY has been used to measure the branching ratios for the decay modes τ ± →h ± π 0 ν and τ ± →h ± π 0 π 0 ν , where h ± is any charged hadron. The results are BR( τ ± → h ± π 0 ν ) = (22.0±0.8±1.9)%, BR( τ ± → h ± π 0 π 0 ν ) = (5.7±0.5 +1.0 −1.7 )%. The first result is in good agreement with the present world average. The decay mode h ± π 0 π 0 ν is reconstructed in τ decays for the first time. Its branching ratio, however, is somewhat lower than the corresponding world average, and therefore tends to increase the one-prong problem.