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

Abstract

We present measurements of the charmonium state $h_c(^1P_1)$ made with 106M $ψ'$ events collected by BESIII at BEPCII. Clear signals are observed for $ψ'\toπ^0 h_c$ with and without the subsequent radiative decay $h_c\toγη_c$. First measurements of the absolute branching ratios $\mathcal{B}(ψ' \toπ^0 h_c) = (8.4 \pm 1.3 \pm 1.0) \times 10^{-4}$ and $\mathcal{B}(h_c \to γη_c) = (54.3 \pm 6.7 \pm5.2)%$ are presented. A statistics-limited determination of the previously unmeasured $h_c$ width leads to an upper limit $Γ(h_c)<1.44 $MeV (90% confidence). Measurements of $M(h_c) = 3525.40 \pm 0.13 \pm 0.18 $MeV/$c^2$ and $\mathcal{B}(ψ'\to π^0 h_c) \times \mathcal{B}(h_c \to γη_c) = (4.58 \pm 0.40 \pm 0.50) \times 10^{-4}$ are consistent with previous results.