  The decays $\chi_{c1} \rightarrow J/\psi \mu^+ \mu^-$ and $\chi_{c2}
\rightarrow J/\psi \mu^+ \mu^-$ are observed and used to study the resonance
parameters of the $\chi_{c1}$ and $\chi_{c2}$ mesons. The masses of these
states are measured to be m(\chi_{c1}) = 3510.71 \pm 0.04(stat) \pm
0.09(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 the
systematic uncertainty. The momentum-scale uncertainties largely cancel in the
mass difference m(\chi_{c2}) - m(\chi_{c1}) = 45.39 \pm 0.07(stat) \pm
0.03(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 results
are in good agreement with and have comparable precision to the current world
averages.
