Observation of an ηc Candidate State with Mass 2978 +/- 9 MeV

An η_c candidate state has been observed with a mass M=2978+/-9 MeV and a natural line width Γ<20 MeV (90% confidence level) using the Crystal Ball NaI(T1) detector at SPEAR. Radiative transitions to this state are observed from ψ' (3684) and Jψ (3095) in the inclusive photon spectra. The branching fraction to this state from the ψ' is (0.43+/-0.08+/-0.18)%, where the errors are statistical and systematic, respectively. In addition, evidence is presented for the decay of this new state into ηπ⁺π^- and an upper limit is presented on the decay into π⁰K⁺K^-.