Precision Measurement of the Branching Fractions of eta ' Decays

Abstract

Based on a sample of (1310.6 +/- 7.0) x 10(6)J/psi events collected with the BESIII detector, we present measurements of J=. and. 0 absolute branching fractions using the process J/psi -> gamma eta'. By analyzing events where the radiative photon converts into an e(+)e(-) pair, the branching fraction for J/psi -> gamma eta'is measured to be (5.27 +/- 0.03 +/- 0.05) x 10(-3). The absolute branching fractions of the five dominant decay channels of the. 0 are then measured for the first time and are determined to be B(eta' -> gamma pi(+)pi(-))= (29.90 +/- 0.03 +/- 0.55)%, B(eta' -> eta pi(+)pi(-)) = (41.24 +/- 0.08 +/- 1.24)%, B(eta' -> gamma gamma) = (21.36 +/- 0.10 +/- 0.92)%, B(eta' -> gamma omega) = (2.489 +/- 0.018 +/- 0.074)%, and B(eta' -> gamma gamma) = (2.331 +/- 0.012 +/- 0.035)%, where the first uncertainties are statistical and the second systematic.