Study of τ Decays to Six Pions and a Neutrino

The τ decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are $B({{τ}}^{{-}}{→}2{{π}}^{{-}}{{π}}⁺3{{π}}⁰{{ν}}_{{τ}}){{0ex}{0ex}}={{0ex}{0ex}}(2.2±{}0.3±{}0.4)×{}1{0}^{{-}4}$ and $B({{τ}}^{{-}}{→}3{{π}}^{{-}}2{{π}}⁺{{π}}⁰{{ν}}_{{τ}}){{0ex}{0ex}}={{0ex}{0ex}}(1.7±{}0.2±{}0.2)×{}1{0}^{{-}4}$. A search for substructure in these decays shows that they are saturated by intermediate states with ${η}$ or ${ω}$ mesons. We present the first observation of the decay ${{τ}}^{{-}}{→}2{{π}}^{{-}}{{π}}⁺{ω}{{ν}}_{{τ}}$ and the branching fraction is measured to be $(1.2±{}0.2±{}0.1)×{}{10}^{{-}4}$. The measured branching fractions are in good agreement with the isospin expectations but somewhat below the conserved-vector-current predictions.