Results of a search for the hc(1P1) state of charmonium in the ηcγ and J/ψπ0 decay modes -: art. no. 032001

We report evidence for the h(c) state of charmonium in its eta(c)gamma decay mode and lack of evidence in the J/psi pi(0) mode. We studied these channels in (p) over barp annihilations near the center of gravity of the P-3(J) states, where the h(c) was reported in the J/psi pi(0) mode by E760, our previous experiment, at 3526.2 +/- 0.15 +/- 0.2 MeV, with Gamma(R)<= 1 MeV. We observe an event excess in the eta(c)gamma mode near 3526 MeV. Testing the null hypothesis of a linearly varying background cross section against the alternate hypothesis that includes a resonance near 3526 MeV, we reject the null hypothesis with P similar to 0.001. The resonance mass is 3525.8 +/- 0.2 +/- 0.2 MeV and the resonance width <= 1 MeV. We estimate 10.0 +/- 3.5 <Gamma((p) over barp)B(eta c)gamma < 12.0 +/- 4.5 eV, corresponding to fixed values 0.5 <Gamma(R)< 1.0 MeV. We find no event excess within the search region in the J/psi pi(0) mode.