Observation of eta_c(1S) and eta_c(2S) decays to K+ K- pi+ pi- pi0 in two-photon interactions

TL;DR

This study observes eta_c(1S), eta_c(2S), and chi_c0(1P) resonances decaying to specific final states in two-photon interactions, measuring their properties and searching for additional resonances with high statistical significance.

Contribution

First observation of eta_c(2S) decays to K+ K- pi+ pi- pi0 in two-photon interactions, with precise measurements of its mass and width, and evidence for other charmonium states.

Findings

eta_c(1S), chi_c0(1P), eta_c(2S) observed with high significance

Measured eta_c(2S) mass as 3638.5 MeV/c^2 and width as 13.4 MeV

No significant signal for chi_c2(2P) resonance

Abstract

We study the processes gamma gamma -> K^0_S K pi and gamma gamma -> K+ K- pi+ pi- pi0 using a data sample of 519.2 fb-1 recorded by the BaBar detector at the PEP-II asymmetric-energy e+e- collider at center-of-mass energies near the Upsilon(nS) (n = 2,3,4) resonances. We observe the eta_c(1S), chi_c0(1P) and eta_c(2S) resonances produced in two-photon interactions and decaying to K+K-pi+pi-pi0, with significances of 18.1, 5.4 and 5.3 standard deviations (including systematic errors), respectively, and report 4.0sigma evidence of the chi_c2(1P) decay to this final state. We measure the eta_c(2S) mass and width in K^0_S K pi decays, and obtain the values m(eta_c(2S))= 3638.5 +/- 1.5 +/- 0.8 MeV/c^2 and Gamma(eta_c(2S)) = 13.4 +/- 4.6 +/- 3.2 MeV, where the first uncertainty is statistical and the second is systematic. We measure the two-photon width times branching fraction for the reported resonance signals, and search for the \chi_{c2}(2P) resonance, but no significant signal is observed.