Improved measurements of the Dalitz decays η/η′ →γe+e-

Journal
Physical Review D
ISSN
24700010
Date Issued
2024-04-01
Author(s)
Ablikim, M.
Achasov, M. N.
Adlarson, P.
Afedulidis, O.
Ai, X. C.
Aliberti, R.
Amoroso, A.
An, Q.
Bai, Y.
Bakina, O.
Balossino, I.
Ban, Y.
Bao, H. R.
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, W. L.
Che, G. R.
Chelkov, G.
Chen, C.
Chen, C. H.
Chen, Chao
Chen, G.
Chen, H. S.
Chen, M. L.
Chen, S. J.
Chen, S. L.
Chen, S. M.
Chen, T.
Chen, X. R.
Chen, X. T.
Chen, Y. B.
Chen, Y. Q.
Chen, Z. J.
Chen, Z. Y.
Choi, S. K.
Chu, X.
Cibinetto, G.
Cossio, F.
Cui, J. J.
Dai, H. L.
Dai, J. P.
Dbeyssi, A.
De Boer, R. E.
Dedovich, D.
Deng, C. Q.
Deng, Z. Y.
Denig, A.
Denysenko, I.
Destefanis, M.
De Mori, F.
Ding, B.
Ding, X. X.
Ding, Y.
Ding, Y.
Dong, J.
Dong, L. Y.
Dong, M. Y.
Dong, X.
Du, M. C.
Du, S. X.
Duan, Z. H.
Egorov, P.
Fan, Y. H.
Fang, J.
Fang, J.
Fang, S. S.
Fang, W. X.
Fang, Y.
Fang, Y. Q.
Farinelli, R.
Fava, L.
Feldbauer, F.
Felici, G.
Feng, C. Q.
Feng, J. H.
Feng, Y. T.
Fischer, K.
Fritsch, M.
Fu, C. D.
Fu, J. L.
Fu, Y. W.
Gao, H.
Gao, Y. N.
DOI
Abstract
Based on a data sample of 10 billion J/ψ events collected with the BESIII detector, improved measurements of the Dalitz decays η/η′→γe+e- are performed, where the η and η′ are produced through the radiative decays J/ψ→γη/η′. The branching fractions of η→γe+e- and η′→γe+e- are measured to be (7.07±0.05±0.23)×10-3 and (4.83±0.07±0.14)×10-4, respectively. Within the single-pole model, the parameter of electromagnetic transition form factor for η→γe+e- is determined to be Λη=(0.749±0.027±0.007) GeV/c2. Within the multipole model, we extract the electromagnetic transition form factors for η′→γe+e- to be Λη′=(0.802±0.007±0.008) GeV/c2 and γη′=(0.113±0.010±0.002) GeV/c2. The results are consistent with both theoretical predictions and previous measurements. The characteristic sizes of the interaction regions for the η and η′ are calculated to be (0.645±0.023±0.007) fm and (0.596±0.005±0.006) fm, respectively. In addition, we search for the dark photon in η/η′→γe+e-, and the upper limits of the branching fractions as a function of the dark photon are given at 90% confidence level.
Volume
109