Observation and study of the decay J/psi -> phi eta eta '

Abstract

We report the observation and study of the decay J/psi -> phi eta eta' phi eta eta' using 1.3 x 10(9) J/psi events collected with the BESIII detector. Its branching fraction, including all possible intermediate states, is measured to be (2.32 +/- 0.06 +/- 0.16) x 10(-4). We also report evidence for a structure, denoted as X, in the phi eta' mass spectrum in the 2.0-2.1 GeV/c(2) region. Using two decay modes of the eta' meson (gamma pi(+)pi(-) and eta pi(+)pi(-)), a simultaneous fit to the Ore mass spectra is performed. Assuming the quantum numbers of the X to be J(P) = 1(-), its significance is found to be 4.4 sigma, with a mass and width of (2002.1 +/- 27.5 +/- 21.4) MeV/c(2) and (129 +/- 17 +/- 9) MeV, respectively, and a product branching fraction B(J/psi -> eta X) x B(X -> phi eta') = (9.8 +/- 1.2 +/- 1.7) x 10(-5). Alternatively, assuming J(P) = 1(+), the significance is 3.8 sigma, with a mass and width of (2062.8 +/- 13.1 +/- 7.2) MeV/c(2) and (177 +/- 36 +/- 35) MeV, respectively, and a product branching fraction B(J/psi -> eta X)x B(X -> phi eta') = (9.6 +/- 1.4 +/- 2.0) x 10(-5). The angular distribution of J/psi -> eta X is studied and the two J(P) assumptions of the X cannot be clearly distinguished due to the limited statistics. In all measurements the first uncertainties are statistical and the second systematic.