Study of the τ−→K−π+π−ντ decay

We present a study of τ−→K−π+π−ντ decay using ∼669 fb−1 data, collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. The data is recorded at a center-of-mass energy 10.58 GeV. The result for the branching ratio is:B=(3.25±0.02(stat.)−0.15+0.16(sys.))×10−3. We also present results of the precise measurement of the branching ratio of other 3-prong decay modes, τ−→π−π+π−ντ, τ−→K−K+π−ντ, and τ−→K−K+K−ντ.