Observation of eta'--> omega e+e-

Abstract

Based on a sample of eta' mesons produced in the radiative decay Jpsi-->gamma eta' in 1.31x10^9 Jpsi events collected with the BESIII detector, the decay eta'-->omega e+e- is observed for the first time, with a statistical significance of 8 sigma. The branching fraction is measured to be B(eta'-->omega e+e-)=(1.97±0.34(stat)±0.17(cyst))x10-4, which is in agreement with theoretical predictions. The branching fraction of eta'-->omega gamma is also measured to be (2.55±0.03(stat)±0.16(cyst))x10-2, which is the most precise measurement to date, and the relative branching fraction B(eta'-->omega e+e-)B(eta'-->omega gamma) is determined to be (7.71±1.34(stat)±0.54(cyst))x10-3