Search for intermediate resonances and dark gauge bosons in J/psi -> gamma pi(0)eta '

Abstract

We report on an analysis of the decay J/psi -> gamma pi(0)eta' using a sample of o1310.6 +/- 7.0THORN x 10(6) J/psi events collected with the BESIII detector. We search for the CP-violating process eta c -> pi(0)eta' and a dark gauge boson U' in J/psi -> U'eta', U' -> gamma pi 0, pi 0 -> gamma gamma. No evidence of an.c signal is observed in the pi(0)eta' invariantmass spectrum and the upper limit of the branching fraction is determined to be 5.6 x 10(-5) at the 90% confidence level. We also find no evidence of U' production and set upper limits at the 90% confidence level on the product branching fraction B(J/psi -> U'eta') x B(U' -> pi(0)gamma) in the range between (0.8 - 6.5) x 10(-7) for 0.2 <= m(U') <= 2.1 GeV/c(2). In addition, we study the process J/psi -> omega eta' with omega -> gamma pi(0). The branching fraction of J/psi -> omega eta' is found to be (1.87 +/- 0.09 +/- 0.12) x 10(-4), where the first uncertainty is statistical and the second is systematic, with a precision that is improved by a factor of 1.4 over the previously published BESIII measurement.