Study of the 3 ππ+- → 0ν τ decay in Aleph

Abstract

Using Aleph data until 1993, the branching fraction of the τ into three charged π s and one π 0 has been measured to be: B ( τ ± → 3 ππ 0 ) = (4.21 ± ±.14)%. The resonant structure of this channel has also been investigated. We find a clear signal for the ω meson corresponding to a branching ratio of: B ( τ ± → ωπ ) = (1.82 ±.16)%. In this sub-channel, we bound the contribution from any 2 nd -class current to less than 13% at a 95% confidence level. The non- ω part is found to be consistent with single production i.e. ρππ . An estimate of the relative rates of the various charges of the ρ is also performed but remains inaccurate because of large interference effects.