Observation of ηc(1S) and ηc(2S) decays to K+K−π+π−π0 in two-photon interactions

Abstract

We study the processes γ γ → K 0 S K ± π ∓ and γ γ → K + K − π + π − π 0 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 Υ ( n S ) ( n = 2 , 3, 4) resonances. We observe the η c ( 1 S ) , χ c 0 ( 1 P ) and η c ( 2 S ) resonances produced in two-photon interactions and decaying to K + K − π + π − π 0 , with significances of 18.1, 5.4 and 5.3 standard deviations (including systematic errors), respectively, and report 4.0 σ evidence of the χ c 2 ( 1 P ) decay to this final state. We measure the η c ( 2 S ) mass and width in K 0 S K ± π ∓ decays, and obtain the values m ( η c ( 2 S ) ) = 3638.5 ± 1.5 ± 0.8 MeV / c 2 and Γ ( η c ( 2 S ) ) = 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 χ c 2 ( 2 P ) resonance, but no significant signal is observed.