Measurement of the absolute branching fractions of J/ψ → γη and η decay modes

Authors：Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai, X. H.; Bai, Y.; Bakina, O.; Ferroli, R. Baldini; Balossino, I.; Ban, Y.; Begzsuren, K.; Berger, N.; Bertani, M.; Bettoni, D.; Bianchi, F.; Bloms, J.; Bortone, A.; Boyko, I.; Briere, R. A.; Cai, H.; Cai, X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.; Chang, W. L.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, M. L.; Chen, S. J.; Chen, X. R.; Chen, Y. B.

Source：Physical Review D, 2021, 104(9): 092004.

DOI：10.1103/PhysRevD.104.092004

Based on a data sample of (1.0087 +/- 0.0044) x 10(10) J/psi events collected by the BESIII detector at the BEPCII accelerator, the absolute branching fraction (BF) of the decay J/psi -> gamma eta is measured with high precision using events in which the radiative photon converts to e(+)e(-). Using the measured absolute BF of J/psi -> gamma eta, the absolute BFs of four dominant. decay modes are measured for the first time. The results are B(J/psi -> gamma eta) = (1.067 +/- 0.005 +/- 0.023) x 10(-3), B(eta ->gamma gamma) = (39.86 +/- 0.04 +/- 0.99)%, B(eta ->pi(0)pi(0)pi(0)) = (31.96 +/- 0.07 +/- 0.84)%, B(eta -> pi(+)pi(-)pi(0)) = (23.04 +/- 0.03 +/- 0.54)%, and B(eta -> pi(+)pi(-)gamma) = (4.38 +/- 0.02 +/- 0.10)%, where the first and second uncertainties are statistical and systematic, respectively. The results are consistent with the world average values within two standard deviations.