Observation of the eta_c(2S) in exclusive B-->K KsK-pi+ decays

TL;DR

This paper reports the observation of the eta_c(2S) charmonium state in B meson decays, confirming its mass and setting an upper limit on its width, consistent with theoretical models.

Contribution

First observation of eta_c(2S) in B decays with measured mass and width constraints, supporting heavy-quark potential models.

Findings

Mass measured at 3654 MeV/c^2

Width upper limit set at 55 MeV/c^2

Properties align with theoretical predictions

Abstract

We report the observation of a narrow peak in the KsK-pi+ invariant mass distribution in a sample of exclusive B-->K KsK-pi+ decays collected with the Belle detector at the KEKB asymmetric energy e+e- collider. The measured mass of the peak is M=3654+-6(stat)+-8(syst) MeV/c^2 and we place a 90% confidence level upper limit on the width of Gamma<55 MeV/c^2. The properties agree with heavy-quark potential model expectations for the eta_c(2S), the n=2 singlet S charmonium state.