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Study of $e^+e^-\toωχ_{cJ}$ at center-of-mass energies from 4.21 to 4.42 GeV

Based on data samples collected with the BESIII detector at the BEPCII collider at 9 center-of-mass energies from 4.21 to 4.42 GeV, we search for the production of $e^+e^-\to ωχ_{cJ}$ ($J$=0, 1, 2). The process $e^+e^-\to ωχ_{c0}$ is observed for the first time, and the Born cross sections at $\sqrt{s}$=4.23 and 4.26 GeV are measured to be $(55.4\pm 6.0\pm 5.9)$ and $(23.7\pm 5.3\pm 3.5)$ pb, respectively, where the first uncertainties are statistical and the second are systematic. The $ωχ_{c0}$ signals at the other 7 energies and $e^+e^-\to ωχ_{c1}$ and $ωχ_{c2}$ signals are not significant, and the upper limits on the cross sections are determined. By examining the $ωχ_{c0}$ cross section as a function of center-of-mass energy, we find that it is inconsistent with the line shape of the $Y(4260)$ observed in $e^+ e^-\toπ^+π^-J/ψ$. Assuming the $ωχ_{c0}$ signals come from a single resonance, we extract mass and width of the resonance to be $(4230\pm8\pm6)$ MeV/$c^2$ and $(38\pm12\pm2)$ MeV, respectively, and the statistical significance is more than $9σ$.