Study of three-body charmless B decays at Belle

Using a data sample of 21.3 fb$^{-1}$ collected by the Belle detector, three body charmless decays $B^+\to K^+ h^+ h^-$ have been studied. With no assumptions on the intermediate mechanisms, the following branching fractions have been measured for the first time ${\cal{B}}(B^+\to K^+ \pi^- \pi^+) = (58.5\pm 7.1\pm 8.8)\times 10^{-6}$ and ${\cal{B}}(B^+\to K^+ K^- K^+) = (37.0\pm 3.9\pm 4.4)\times 10^{-6}$. We also present the first observations of the decay mode $B^+\to K^{*0}(892)\pi^+$ with a branching fraction of ${\cal{B}}(B^+\to K^{*0}(892) \pi^+) = (16.7^{+3.7+2.1+3.0}_{-3.4-2.1-5.9})\times 10^{-6}$ and the decay mode $B^+\to f_0(980)K^+$ with a product branching fraction of ${\cal{B}}(B^+\to f_0(980) K^+)\times{\cal{B}}(f_0(980)\to \pi^+\pi^-) = (11.7^{+2.5+1.5+4.1}_{-2.7-1.5-1.0})\times 10^{-6}$.