Updated measurements of the M1 transition $ψ(3686) \to γη_{c}(2S)$ with $η_{c}(2S) \to K \bar{K} π$
hep-ex
/ Authors
BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, M. R. An, Q. An
and 624 more authors
Y. Bai, O. Bakina, I. Balossino, Y. Ban, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, J. F. Chang, W. L. Chang
/ Abstract
Based on a data sample of $(27.08 \pm 0.14 ) \times 10^8~ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, the M1 transition $ψ(3686) \to γη_{c}(2S)$ with $η_{c}(2S) \to K\bar{K}π$ is studied, where $K\bar{K}π$ is $K^{+} K^{-} π^{0}$ or $K_{S}^{0}K^{\pm}π^{\mp}$. The mass and width of the $η_{c}(2S)$ are measured to be $(3637.8 \pm 0.8 (\rm {stat}) \pm 0.2 (\rm {syst}))$ MeV/$c^{2}$ and $(10.5 \pm 1.7 (\rm {stat}) \pm 3.5 (\rm {syst}))$ MeV, respectively. The product branching fraction $\mathcal{B}\left(ψ(3686) \rightarrow γη_{c}(2 S)\right) \times \mathcal{B}(η_{c}(2 S) \rightarrow K \bar{K} π)$ is determined to be $(0.97 \pm 0.06 (\rm {stat}) \pm 0.09 (\rm {syst})) \times 10^{-5}$. Using $\mathcal{BR}(η_{c}(2S)\to K\bar{K}π)=(1.86^{+0.68}_{-0.49})\%$, we obtain the branching fraction of the radiative transition to be $\mathcal{BR}(ψ(3686) \to γη_{c}(2S)) = (5.2 \pm 0.3 (\rm {stat}) \pm 0.5 (\rm {syst}) ^{+1.9}_{-1.4} (extr)) \times 10^{-4}$, where the third uncertainty is due to the quoted $\mathcal{BR}(η_{c}(2S) \to K\bar{K}π)$.