Paper detail

Search for the Decay tau- --> 3pi- 2pi+ 2pi0 nu_tau

A search for the decay of the tau 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 Y(4S) 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(tau- --> 3pi- 2pi+ 2pi0 nu_tau) < 3.4x10^{-6} at the 90% confidence level. This is a significant improvement over the previously established limit. In addition, we search for the decay mode tau- --> 2omega pi- nu_tau. We observe 1 event with an expected background of 0.4^{+1.0}_{-0.4} events and calculate the upper limit B(tau- --> 2omega pi- nu_tau) < 5.4x10^{-7} at the 90% confidence level. This is the first upper limit for this mode.