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The cross section for e^+e^- to eta J/psi between sqrt{s}=3.8 GeV/c^2 and 5.3 GeV/c^2 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 BR(psi(4040)toeta J/psi)cdotGamma_{ee}^{psi(4040)} = (4.8pm0.9pm1.4) eV and BR(psi(4160)toeta J/psi)cdotGamma_{ee}^{psi(4160)} = (4.0pm0.8pm1.4) eV for one solution and BR(psi(4040)toeta J/psi)cdotGamma_{ee}^{psi(4040)} = (11.2pm1.3pm1.9) eV and BR(psi(4160)toeta J/psi)cdotGamma_{ee}^{psi(4160)} = (13.8pm1.3pm2.0) 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.
By analyzing data samples of 2.9 fb^{-1} collected at sqrt s=3.773 GeV, 482 pb^{-1} collected at sqrt s=4.009 GeV and 67 pb^{-1} collected at sqrt s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the BEPCII storage ring, we sear
We have measured several branching ratios for $psi^prime$ decay using the data collected by FNAL E835 experiment during year 2000, obtaining ${cal B}(psi^prime to e^+ e^-) = 0.0068pm0.0001pm0.0004$, ${cal B}(psi^prime to J/psi pi^+ pi^-) = 0.292pm0.0
We measure the mass of the eta meson using psi(2S) --> eta J/psi events acquired with the CLEO-c detector operating at the CESR e+e- collider. Using the four decay modes eta --> gamma gamma, 3pi0, pi+pi-pi0, and pi+pi-gamma, we find M(eta)=547.785 +-
The first observation of exotic states with a new quark content $c bar{c} u bar{s}$ decaying to the $J/psi K^+$ final state is reported with high significance from an amplitude analysis of the $B^+ to J/psi phi K^+$ decay. The analysis is carried out
We study the electromagnetic Dalitz decay $J/psi to e^+e^- eta$ and search for di-electron decays of a dark gauge boson ($gamma$) in $J/psi to gamma eta$ with the two $eta$ decay modes $eta rightarrow gamma gamma$ and $eta rightarrow pi^+pi^-pi^0$ us