Search for the decay ${\tau }^{-}\to 4{\pi }^{-}3{\pi }^{+}\left({\pi }^0\right){\nu }_{\tau }$

We have searched for the decay of the $\tau$ lepton into seven charged particles and zero or one ${\pi }^0$. The data used in the search were collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR) and correspond to an integrated luminosity of 4.61 ${\mathrm{fb}}^{-1}$. No evidence for a signal is found. Assuming all the charged particles are pions, we set an upper limit on the branching fraction $B({\tau }^{-}\to 4{\pi }^{-}3{\pi }^{+}({\pi }^0\left){\nu }_{\tau }\right)<2.4\mathrm{}\times {10}^{-6}$ at the 90% confidence level. This limit represents a significant improvement over the previous limit.