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

TL;DR

This paper reports the first measurements of the $h_c(^1P_1)$ charmonium state in $$ decays, including branching ratios, mass, and an upper limit on its width, using a large sample of $$ events.

Contribution

It provides the first measurements of absolute branching ratios and mass of the $h_c$ state in $$ decays, improving understanding of charmonium spectroscopy.

Findings

Measured $ o ^0 h_c$ branching ratio as (8.4 d7 10^{-4})

Determined $h_c$ mass as 3525.40 MeV/$c^2$

Set an upper limit on $h_c$ width at 1.44 MeV

Abstract

We present measurements of the charmonium state $h_c(^1P_1)$ made with 106M $\psi'$ events collected by BESIII at BEPCII. Clear signals are observed for $\psi'\to\pi^0 h_c$ with and without the subsequent radiative decay $h_c\to\gamma\eta_c$. First measurements of the absolute branching ratios $\mathcal{B}(\psi' \to\pi^0 h_c) = (8.4 \pm 1.3 \pm 1.0) \times 10^{-4}$ and $\mathcal{B}(h_c \to \gamma \eta_c) = (54.3 \pm 6.7 \pm5.2)%$ 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 $\mathcal{B}(\psi'\to \pi^0 h_c) \times \mathcal{B}(h_c \to \gamma\eta_c) = (4.58 \pm 0.40 \pm 0.50) \times 10^{-4}$ are consistent with previous results.