Study of $\chi_{cJ}$ radiative decays into a vector meson

TL;DR

This study measures the branching fractions and polarization of $ ext{chi}_{cJ}$ radiative decays into vector mesons using BESIII data, observing the decay $ ext{chi}_{c1} o ext{gamma} ext{phi}$ for the first time.

Contribution

First observation of $ ext{chi}_{c1} o ext{gamma} ext{phi}$ decay and detailed measurements of branching fractions and polarization fractions in $ ext{chi}_{cJ}$ radiative decays.

Findings

Branching fraction for $ ext{chi}_{c1} o ext{gamma} ext{phi}$ is $(25.8 extpm 5.2 extpm 2.3) imes 10^{-6}$.

Polarization fractions vary between decay modes, e.g., 0.29 for $ ext{chi}_{c1} o ext{gamma} ext{phi}$.

Upper limits are set for $ ext{chi}_{c0}$ and $ ext{chi}_{c2}$ decays.

Abstract

The decays $\chi_{cJ}\to\gamma V$ ($V=\phi, \rho^0, \omega$) are studied with a sample of radiative $\psip\to\gamma\chi_{cJ}$ events in a sample of $(1.06\pm0.04)\times 10^{8} \psip$ events collected with the BESIII detector. The branching fractions are determined to be: ${\cal B}(\chi_{c1}\to \gamma\phi)=(25.8\pm 5.2\pm 2.3)\times 10^{-6}$, ${\cal B}(\chi_{c1}\to \gamma\rho^0)=(228\pm 13\pm 22)\times 10^{-6}$, and ${\cal B}(\chi_{c1}\to \gamma\omega)=(69.7\pm 7.2\pm 6.6)\times 10^{-6}$. The decay $\chi_{c1}\to \gamma\phi$ is observed for the first time. Upper limits at the 90% confidence level on the branching fractions for $\chi_{c0}$ and $\chict$ decays into these final states are determined. In addition, the fractions of the transverse polarization component of the vector meson in $\chi_{c1}\to \gamma V$ decays are measured to be $0.29_{-0.12-0.09}^{+0.13+0.10}$ for $\chi_{c1}\to \gamma\phi$, $0.158\pm 0.034^{+0.015}_{-0.014}$ for $\chi_{c1}\to \gamma\rho^0$, and $0.247_{-0.087-0.026}^{+0.090+0.044}$ for $\chi_{c1}\to \gamma\omega$, respectively. The first errors are statistical and the second ones are systematic.