Improved measurement of the branching fractions for J/ψ → γπ0, γη, and γη′

Authors：Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ai, X. C.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai, Y.; Bakina, O.; Balossino, I.; Ban, Y.; Batozskaya, V.; Begzsuren, K.; Berger, N.; Berlowski, M.; Bertani, M.; Bettoni, D.; Bianchi, F.; Bianco, E.; Bortone, A.; Boyko, I.; Briere, R. A.; Brueggemann, A.; Cai, H.; Cai, X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.; Chang, T. T.; Chang, W. L.; Che, G. R.; Chelkov, G.; Chen, C.; Chen, Chao; Chen, G.; Chen, H. S.

Source：Physical Review D, 2023, 108(9): 092002.

DOI：10.1103/PhysRevD.108.092002

• RADIATIVE DECAYS
• TOF

Using a data sample of (1.0087 +/- 0.0044) x 10(10) J/psi events collected with the BESIII detector, the decays of J/psi -> gamma pi(0) (eta, eta ') -> gamma gamma gamma are studied. Newly measured branching fractions are B(J/psi -> gamma pi(0)) = (3.34 +/- 0.02 +/- 0.09) x 10(-5), B(J/psi -> gamma eta) = (1.096 +/- 0.001 +/- 0.019) x 10(-3), and B(J/psi -> gamma eta ') = (5.40 +/- 0.01 +/- 0.11) x 10(-3), where the first uncertainties are statistical and the second are systematic. These results are consistent with the world average values within two standard deviations. The ratio of partial widths Gamma(J/psi -> gamma eta ')/Gamma(J/psi -> gamma eta) is measured to be 4.93 +/- 0.13. The singlet-octet pseudoscalar mixing angle theta(P) is determined to be theta(P) = -(22.11 +/- 0.26)degrees or -(19.34 +/- 0.34)degrees with two different phenomenological models.