Ablikim, M (reprint author), Inst High Energy Phys, Beijing 100049, Peoples R China.
The process psi(3686) -> pi(0)h(c), h(c) -> gamma eta(c) has been studied with a data sample of 106 +/- 4 million Psi(3686) events collected with the BESIII detector at the BEPCII storage ring. The mass and width of the P-wave charmonium spin-singlet state h(c)(P-1(1)) are determined by simultaneously fitting distributions of the pi(0) recoil mass for 16 exclusive eta(c) decay modes. The results, M(h(c)) 3525.31 +/- 0.11(stat) +/- 0.14(syst) MeV/c(2) and Gamma(h(c)) = 0.70 +/- 0.28 +/- 0.22 MeV, are consistent with and more precise than previous measurements. We also determine the branching ratios for the 16 exclusive eta(c) decay modes, five of which have not been measured previously. New measurements of the eta(c) line- shape parameters in the E1 transition h(c) -> gamma eta(c) are made by selecting candidates in the h(c) signal sample and simultaneously fitting the hadronic mass spectra for the 16 eta(c) decay channels. The resulting eta(c) mass and width values are M(eta(c)) = 2984.49 +/- 1.16 +/- 0.52 MeV/c(2) and Gamma(eta(c)) 36.4 +/- 3.2 +/- 1.7 MeV.