Observation of the decay τ → ϱππντ

An analysis of the decay τ^- → π^-π^-π⁺π⁰ν _τ has been performed with the ARGUS detector at the DORIS II storage ring. From a study of the two pion subsystems we have found first evidence for the decays τ^- → ρ{variant}⁰π^-π⁰ν_τ , τ^- → ρ{variant} ^-π⁺π^-ν_τ, and τ^- → ρ{variant}⁺π^-π^-ν_τ with relative contributions to the decay τ^- → π^-π^-π⁺π⁰ν _τ of 0.30 ± 0.04, 0.26 ± 0.05, and 0.10 ± 0.03, respectively. The fraction of the subchannel τ^- → ωπ^-ν_τ has been determined to be 0.33 ± 0.05. The production of ρ{variant} mesons is enhanced by a factor of 1.9 ± 0.3 over that of ω mesons. We conclude that in more than 81% (95% CL) of all τ^- → π^-π^-π⁺π⁰ν _τ decays either a ρ{variant} or ω meson is produced.