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

TL;DR

This paper measures the resonance parameters of the $_{1}$ and $_{2}$ mesons through their decays to $J/\u03bc^+$, providing precise mass and width measurements that align with existing data.

Contribution

The study presents new measurements of $_{1}$ and $_{2}$ meson masses and widths using decay channels involving muons, improving precision and confirming previous results.

Findings

Mass of $_{1}$: 3510.71 MeV

Mass of $_{2}$: 3556.10 MeV

Width of $_{2}$: 2.10 MeV

Abstract

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.