Observation of anηcCandidate State with Mass 2978 ± 9 MeV

Abstract

An ${\eta }_c$ candidate state has been observed with a mass $M=2978\mathrm{}\pm 9$ MeV and a natural line width $\Gamma <20\mathrm{}$ MeV (90% confidence level) using the Crystal Ball NaI(T1) detector at SPEAR. Radiative transitions to this state are observed from ${\psi }^{\prime }\mathrm{}\left(3684\right)\mathrm{}$ and $\frac{J}{\psi }\mathrm{}\left(3095\right)\mathrm{}$ in the inclusive photon spectra. The branching fraction to this state from the ${\psi }^{\prime }$ 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 $\eta {\pi }^{+}{\pi }^{-}$ and an upper limit is presented on the decay into ${\pi }^0{K}^{+}{K}^{-}$.