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

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

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