Evidence for ηc(2S) in ψ(3686)→γKS0K ±π+π+π-

Abstract

We search for the M1 radiative transition ψ(3686) →γηc(2S) by reconstructing the exclusive ηc(2S)→KS0K±π+π +π- decay using 1.06×108 ψ(3686) events collected with the BESIII detector. The signal is observed with a statistical significance of greater than 4 standard deviations. The measured mass of the ηc(2S) is 3646.9±1.6(stat)±3.6(syst) MeV/c2, and the width is 9.9±4.8(stat)±2.9(syst) MeV/c2. The product branching fraction is measured to be B(ψ(3686)→γηc(2S)) ×B(ηc(2S)→KS0K±π+π +π-)=(7.03±2.10(stat)±0.70(syst)) ×10-6. This measurement complements a previous BESIII measurement of ψ(3686)→γηc(2S) with ηc(2S)→KS0K±π+ and K +K-π0. © 2013 American Physical Society.