@article{8291136c01bf41c0a856d4d664bf5fa4,
title = "Study of the Dalitz decay J /ψ →e+e-η",
abstract = "We study the electromagnetic Dalitz decay J/ψ→e+e-η and search for dielectron decays of a dark gauge boson (γ′) in J/ψ→γ′η with the two η decay modes η→γγ and η→π+π-π0 using (1310.6±7.0)×106 J/ψ events collected with the BESIII detector. The branching fraction of J/ψ→e+e-η is measured to be (1.43±0.04(stat)±0.06(syst))×10-5, with a precision that is improved by a factor of 1.5 over the previous BESIII measurement. The corresponding dielectron invariant mass dependent modulus square of the transition form factor is explored for the first time, and the pole mass is determined to be Λ=2.84±0.11(stat)±0.08(syst) GeV/c2. We find no evidence of γ′ production and set 90% confidence level upper limits on the product branching fraction B(J/ψ→γ′η)×B(γ′→e+e-) as well as the kinetic mixing strength between the standard model photon and γ′ in the mass range of 0.01≤mγ′≤2.4 GeV/c2.",
keywords = "DARK PHOTON, ETA-E(+)E(-), EMISSION, SEARCH, MESON, OMEGA, PAIR, PHI, ETA",
author = "{The BELLE collaboration} and M. Ablikim and Achasov, {M. N.} and S. Ahmed and M. Albrecht and M. Alekseev and A. Amoroso and An, {F. F.} and Q. An and Y. Bai and O. Bakina and {Baldini Ferroli}, R. and Y. Ban and K. Begzsuren and Bennett, {D. W.} and Bennett, {J. V.} and N. Berger and M. Bertani and D. Bettoni and F. Bianchi and E. Boger and I. Boyko and Briere, {R. A.} and H. Cai and X. Cai and O. Cakir and A. Calcaterra and Cao, {G. F.} and Cetin, {S. A.} and J. Chai and Chang, {J. F.} and Chang, {W. L.} and G. Chelkov and G. Chen and Chen, {H. S.} and Chen, {J. C.} and Chen, {M. L.} and Chen, {P. L.} and Chen, {S. J.} and Chen, {X. R.} and Chen, {Y. B.} and Chu, {X. K.} and G. Cibinetto and F. Cossio and Dai, {H. L.} and Dai, {J. P.} and A. Dbeyssi and D. Dedovich and Deng, {Z. Y.} and A. Denig and Muchnoi, {N. Yu}",
note = "Publisher Copyright: {\textcopyright} 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP . ",
year = "2019",
month = jan,
day = "9",
doi = "10.1103/PhysRevD.99.012006",
language = "English",
volume = "99",
journal = "Physical Review D",
issn = "2470-0010",
publisher = "AMER PHYSICAL SOC",
number = "1",
}