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

Abstract

The cross section for e+e-″㈁J/⒬ between ↔s=3.8  GeV and 5.3 GeV is measured via initial state radiation using 980  fb-1 of data on and around the ⒞(nS)(n=1,2,3,4,5) resonances collected with the Belle detector at KEKB. Two resonant structures at the ⒬(4040) and ⒬(4160) are observed in the ㈁J/⒬ invariant mass distribution. Fitting the mass spectrum with the coherent sum of two Breit-Wigner functions, one obtains B(⒬(4040)″㈁J/⒬)·ʼne+e-⒬(4040)=(4.8≤0.9≤1.5)  eV and B(⒬(4160)″㈁J/⒬)·ʼne+e-⒬(4160)=(4.0≤0.8≤1.4)  eV for one solution and B(⒬(4040)″㈁J/⒬)·ʼne+e-⒬(4040)=(11.2≤1.3≤2.1)  eV and B(⒬(4160)″㈁J/⒬)·ʼne+e-⒬(4160)=(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 ㈁J/⒬ are found to be about 1 MeV. There is no evidence for the Y(4260), Y(4360), ⒬(4415), or Y(4660) in the ㈁J/⒬ final state, and upper limits of their production rates in e+e- annihilation are determined.