Observation of psi(4040) and psi(4160) decay into eta J/psi

Abstract

The cross section for e(+)e(-) -> eta J=psi between root s=3.8 GeV and 5.3 GeV is measured via initial state radiation using 980 fb(-1) of data on and around the Upsilon(nS)(n=1, 2, 3, 4, 5) resonances collected with the Belle detector at KEKB. Two resonant structures at the psi(4040) and psi(4160) are observed in the (eta)J/psi invariant mass distribution. Fitting the mass spectrum with the coherent sum of two Breit-Wigner functions, one obtains B(psi(4040) -> (eta)J/psi)(.)Gamma(psi(4040))(e+e-) = (4.8 +/- 0.9 +/- 1.5) eV and B(psi(4160) -> (eta)J/psi(.)Gamma(psi(4160))(e+e-) = 4.0 +/- 0.8 +/- 1.4) eV for one solution and B(psi(4040) -> (eta)J/psi)(.)Gamma(psi(4040))(e+e-) = (11.2 +/- 1.3 +/- 2.1) eV and B(psi(4160) -> (eta)J/psi)(.)Gamma(psi(4160))(e+e-) = 13.8 +/- 1.3 +/- 2.1 eV for the other solution, where the first errors are statistical and the second are systematic. This is the first measurement of this hadronic transition mode of these two states, and the partial widths to (eta)J/psi are found to be about 1 MeV. There is no evidence for the Y(4260), Y(4360), psi(4415), or Y(4660) in the (eta)J/psi final state, and upper limits of their production rates in e(+)e(-) annihilation are determined.