Observation of $\psp$ decays to $\rho(770)\pi$ and $\rho(2150)\pi$

Abstract

\pspto \rho\pi is observed for the fisrt time in a data sample of 14M \psp decays collected by the BESII detector at BEPC. The branching fraction is measured to be \BR(pspto\rho\pi)=(5.1+-0.7+-0.8)10-5, where the first error is statistical and the second one is systematic. A high mass excited \rho state wirh mass around 2.15GeV/c2 is also observed wirh \BR(pspto \rho(2150)\pi) \ra pi+pi-pi0) =(19.4+-2.5+11.2-2.1)10-5. The branching fraction of \pspto pi+pi-pi0 is measued with improved precision, \BR(\pspto pi+pi-pi0)=(18.1+-1.8+-1.9)10-5. The results may shed light on the understanding of the longstanding "\rhopi puzzle" between \jpsi and \psp hadronic decays.