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

TL;DR

This paper reports the first observation of \\psp \\to \\rho \\pi and a high-mass \\rho state in \\psp decays, providing precise measurements that contribute to understanding the \\rhopi puzzle in charmonium decays.

Contribution

It presents the first observation of \\psp \\to \\rho \\pi and a high-mass \\rho state, with improved measurements of branching fractions relevant to the \\rhopi puzzle.

Findings

First observation of \\psp \\to \\rho \\pi with measured branching fraction.

Detection of a high-mass \\rho(2150) state in \\psp decays.

Improved precision in \\psp \\to \\pi \\pi \\pi0 branching fraction.

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.