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A search for the decay of the tau lepton to seven charged pions and
one or zero pizero mesons was performed using the BaBar detector at the PEP-II asymmetric-energy e+e- collider.
The analysis uses 232.2 fb-1 of data at center-of-mass energies on or
near the Y(4S) resonance. We observe 24 events with an expected
background of 21.6+-1.3 events. Without evidence for a signal, we
calculate an upper limit of BR(tau- --> 4pi- 3pi+ (pizero) nu_tau) <
3.0*10^-7 at 90 % confidence level.
This is an improvement by nearly an order of magnitude over the previously established limit.
In addition, we set upper limits for the exclusive decays tau- --> 4pi- 3pi+ nu_tau and
tau- --> 4pi- 3pi+ pizero nu_tau.
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