Branching fraction of τ− → π−K0sK0s(π0)ντ decays

Abstract

We present a study of τ − → π − K 0 S K 0 S ( π 0 ) ν τ and τ − → K − K 0 S K 0 S ( π 0 ) ν τ decays using a data set of 430 million τ lepton pairs, corresponding to an integrated luminosity of 468 fb − 1 , collected with the BABAR detector at the PEP-II asymmetric energy e + e − storage rings. We measure branching fractions of ( 2.31 ± 0.04 ± 0.08 ) × 10 − 4 and ( 1.60 ± 0.20 ± 0.22 ) × 10 − 5 for the τ − → π − K 0 S K 0 S ν τ and τ − → π − K 0 S K 0 S π 0 ν τ decays, respectively. We find no evidence for τ − → K − K 0 S K 0 S ν τ and τ − → K − K 0 S K 0 S π 0 ν τ decays and place upper limits on the branching fractions of 6.3 × 10 − 7 and 4.0 × 10 − 7 at the 90% confidence level.