Measurements of the Mass and Width of the eta~c Meson and of an eta~c(2S) Candidate

The mass m(etac) and total width Gamma(tot)(etac) of the eta(c) meson have been measured in two-photon interactions at the SLAC e(+)e(-) asymmetric B Factory with the BABAR detector. With a sample of approximately 2500 reconstructed eta(c) --> (KSK+/-)-K-0 pi(-/+) decays in 88 fb(-1) of data, the results are m(etac) = 2982.5 +/- 1.1 (stat) +/- 0.9(syst) MeV/c(2) and Gamma(tot)(etac) = 34.3 +/- 2.3(stat) +/- 0.9(syst) MeV/c(2). Using the same decay mode, a second resonance with 112 +/- 24 events is observed with a mass of 3630.8 +/- 3.4(stat) +/- 1.0(syst) MeV/c(2) and width of 17.0 +/- 8.3(stat) +/- 2.5(syst) MeV/c(2). This observation is consistent with expectations for the eta(c)(2S) state.