Measurements of h_c(^1P_1) in psi' Decays

Abstract

We present measurements of the charmonium state $h_c{(}^1{P}_1)$ made with 106M ${\psi }^{\prime }$ events collected by BESIII at BEPCII. Clear signals are observed for ${\psi }^{\prime }\to {\pi }^0{h}_c$ with and without the subsequent radiative decay $h_c\to \gamma {\eta }_c$. First measurements of the absolute branching ratios $\mathcal{B}({\psi }^{\prime }\to {\pi }^0{h}_c)=(8.4\pm 1.3\pm 1.0)\times 10^{-4}$ and $\mathcal{B}(h_c\to \gamma {\eta }_c)=(54.3\pm 6.7\pm 5.2)$ are presented. A statistics-limited determination of the previously unmeasured $h_c$ width leads to an upper limit $\Gamma (h_c)<1.44$MeV (90% confidence). Measurements of $M(h_c)=3525.40\pm 0.13\pm 0.18$MeV/$c^2$ and $\mathcal{B}({\psi }^{\prime }\to {\pi }^0{h}_c)\times \mathcal{B}(h_c\to \gamma {\eta }_c)=(4.58\pm 0.40\pm 0.50)\times 10^{-4}$ are consistent with previous results.

5 pages, 1 figure, accepted for publication in Physical Review Letters