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The decays $\chi_{c1} \rightarrow J/\psi \mu^+ \mu^-$ and $\chi_{c2}\rightarrow J/\psi \mu^+ \mu^-$ are observed and used to study the resonanceparameters of the $\chi_{c1}$ and $\chi_{c2}$ mesons. The masses of thesestates are measured to be m(\chi_{c1}) = 3510.71 \pm 0.04(stat) \pm0.09(syst)MeV\,, m(\chi_{c2}) = 3556.10 \pm 0.06(stat) \pm 0.11(syst)MeV\,,where the knowledge of the momentum scale for charged particles dominates thesystematic uncertainty. The momentum-scale uncertainties largely cancel in themass difference m(\chi_{c2}) - m(\chi_{c1}) = 45.39 \pm 0.07(stat) \pm0.03(syst)MeV\,. The natural width of the $\chi_{c2}$ meson is measured to be$$\Gamma(\chi_{c2}) = 2.10 \pm 0.20(stat) \pm 0.02(syst)MeV\,.$$ These resultsare in good agreement with and have comparable precision to the current worldaverages.

$\chi_{c1}$ and $\chi_{c2}$ resonance parameters with the decays $\chi_{c1,c2}\to J/\psi\mu^+\mu^-$