Search for the decay τ− → 3π−2π+2π0ντ

Abstract

search for the decay of the τ lepton to five charged and two neutral pions is performed using data collected by the BABAR detector at the PEP-II asymmetric-energy e + e − collider. The analysis uses 232 fb − 1 of data at center-of-mass energies on or near the Υ ( 4 S ) resonance. We observe 10 events with an expected background of 6.5 + 2.0 − 1.4 events. In the absence of a signal, we set the limit on the branching ratio B ( τ − → 3 π − 2 π + 2 π 0 ν τ ) < 3.4 × 10 − 6 at the 90% confidence level. This is a significant improvement over the previously established limit. In addition, we search for the decay mode τ − → 2 ω π − ν τ . We observe 1 event with an expected background of 0.4 + 1.0 − 0.4 events and calculate the upper limit B ( τ − → 2 ω π − ν τ ) < 5.4 × 10 − 7 at the 90% confidence level. This is the first upper limit for this mode.