Precise measurement of hadronic τ-decays with an η meson

We have studied hadronic τ decay modes involving an η meson using 490 fb−1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. The following branching fractions have been measured: B(τ−→K−ηντ)=(1.58±0.05±0.09)×10−4, B(τ−→K−π0ηντ)=(4.6±1.1±0.4)×10−5, B(τ−→π−π0ηντ)=(1.35±0.03±0.07)×10−3, B(τ−→π−KS0ηντ)=(4.4±0.7±0.2)×10−5, and B(τ−→K∗−ηντ)=(1.34±0.12±0.09)×10−4. These results are substantially more precise than previous measurements. The new measurements are compared with theoretical calculations based on the CVC hypothesis or the chiral perturbation theory. We also set upper limits on branching fractions for τ decays into K−KS0ηντ, π−KS0π0ηντ, K−ηηντ, π−ηηντ and non-resonant K−π0ηντ final states.