TY - JOUR
T1 - Study of η →π+π-l+l-
AU - Ablikim, M.
AU - Achasov, M. N.
AU - Adlarson, P.
AU - Afedulidis, O.
AU - Kabana, S.
AU - The BESIII collaboration
N1 - Publisher Copyright:
© 2025 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 SCOAP3.
PY - 2025/4/1
Y1 - 2025/4/1
N2 - Using a sample of (10087±44)×106 J/ψ events accumulated with the BESIII detector, we analyze the decays η→π+π-l+l-(l=e or μ) via the process J/ψ→γη. The branching fraction of η→π+π-e+e-is measured to be B(η→π+π-e+e-)=(3.07±0.12stat±0.19syst)×10-4. No signal events are observed for the η→π+π-μ+μ-decay, leading to an upper limit on the branching fraction of B(η→π+π-μ+μ-)<4.0×10-7 at the 90% confidence level. Furthermore, the CP-violation asymmetry parameter is found to be ACP(η→π+π-e+e-)=(-4.04±4.69stat±0.14syst)%, showing no evidence of CP-violation with current statistics. Additionally, we extract the transition form factor from the decay amplitude of η→π+π-e+e-. Finally, axionlike particles are searched for via the decay η→π+π-A,a→e+e-, and upper limits on this branching fraction relative to that of η→π+π-e+e-are presented as a function of the axionlike particle mass in the range 5-200 MeV/c2.
AB - Using a sample of (10087±44)×106 J/ψ events accumulated with the BESIII detector, we analyze the decays η→π+π-l+l-(l=e or μ) via the process J/ψ→γη. The branching fraction of η→π+π-e+e-is measured to be B(η→π+π-e+e-)=(3.07±0.12stat±0.19syst)×10-4. No signal events are observed for the η→π+π-μ+μ-decay, leading to an upper limit on the branching fraction of B(η→π+π-μ+μ-)<4.0×10-7 at the 90% confidence level. Furthermore, the CP-violation asymmetry parameter is found to be ACP(η→π+π-e+e-)=(-4.04±4.69stat±0.14syst)%, showing no evidence of CP-violation with current statistics. Additionally, we extract the transition form factor from the decay amplitude of η→π+π-e+e-. Finally, axionlike particles are searched for via the decay η→π+π-A,a→e+e-, and upper limits on this branching fraction relative to that of η→π+π-e+e-are presented as a function of the axionlike particle mass in the range 5-200 MeV/c2.
UR - https://www.scopus.com/pages/publications/105002756976
U2 - 10.1103/PhysRevD.111.072008
DO - 10.1103/PhysRevD.111.072008
M3 - Article
AN - SCOPUS:105002756976
SN - 2470-0010
VL - 111
JO - Physical Review D
JF - Physical Review D
IS - 7
M1 - 072008
ER -