TY - JOUR

T1 - Search for a hypothetical gauge boson and dark photons in charmonium transitions

AU - BESIII Collaboration

AU - Ачасов, Михаил Николаевич

AU - Мучной, Николай Юрьевич

AU - Николаев, Иван Борисович

N1 - The BESIII Collaboration thanks the staff of BEPCII [87] and the IHEP computing center for their strong support. This work is supported in part by National Key R&D Program of China under Contracts No. 2023YFA1606000 and No. 2023YFA1606704; National Natural Science Foundation of China (NSFC) under Contracts No. 11635010, No. 11935015, No. 11935016, No. 11935018, No. 12025502, No. 12035009, No. 12035013, No. 12061131003, No. 12192260, No. 12192261, No. 12192262, No. 12192263, No. 12192264, No. 12192265, No. 12221005, No. 12225509, No. 12235017, and No. 12361141819; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; the Strategic Priority Research Program of Chinese Academy of Sciences under Contract No. XDA0480600; CAS under Contract No. YSBR-101; 100 Talents Program of CAS; The Institute of Nuclear and Particle Physics (INPAC) and Shanghai Key Laboratory for Particle Physics and Cosmology; ERC under Contract No. 758462; German Research Foundation DFG under Contract No. FOR5327; Istituto Nazionale di Fisica Nucleare, Italy; Knut and Alice Wallenberg Foundation under Contracts No. 2021.0174 and No. 2021.0299; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Research Foundation of Korea under Contract No. NRF-2022R1A2C1092335; National Science and Technology fund of Mongolia; Polish National Science Centre under Contract No. 2024/53/B/ST2/00975; STFC (United Kingdom); Swedish Research Council under Contract No. 2019.04595; and U.S. Department of Energy under Contract No. DE-FG02-05ER41374.

PY - 2026/2/17

Y1 - 2026/2/17

N2 - We report a direct search for a new gauge boson, 푋, with a mass of 17  MeV/푐2, which could explain the anomalous excess of 푒+⁢푒− pairs observed in the 8Be nuclear transitions. The search is conducted in the charmonium decays 휒푐⁢퐽 →푋⁢퐽/휓⁡(퐽 =0,1,2) via the radiative transition 휓⁡(3686) →훾⁢휒푐⁢퐽 using (2712.4±14.3) ×106  휓⁡(3686) events collected with the BESIII detector at the BEPCII collider. No significant signal is observed, and the updated upper limit on the coupling strength of charm quark and the new gauge boson, 휀푐, is set to be |휀푐| <1.2 ×10−2 at 90% confidence level. We also report new constraints on the mixing strength 휀 between the Standard Model photon and dark photon 훾′ in the mass range from 5 to 300  MeV/푐2. The upper limits at 90% confidence level vary within (2.5–17.5)×10−3 depending on the 훾′ mass.

AB - We report a direct search for a new gauge boson, 푋, with a mass of 17  MeV/푐2, which could explain the anomalous excess of 푒+⁢푒− pairs observed in the 8Be nuclear transitions. The search is conducted in the charmonium decays 휒푐⁢퐽 →푋⁢퐽/휓⁡(퐽 =0,1,2) via the radiative transition 휓⁡(3686) →훾⁢휒푐⁢퐽 using (2712.4±14.3) ×106  휓⁡(3686) events collected with the BESIII detector at the BEPCII collider. No significant signal is observed, and the updated upper limit on the coupling strength of charm quark and the new gauge boson, 휀푐, is set to be |휀푐| <1.2 ×10−2 at 90% confidence level. We also report new constraints on the mixing strength 휀 between the Standard Model photon and dark photon 훾′ in the mass range from 5 to 300  MeV/푐2. The upper limits at 90% confidence level vary within (2.5–17.5)×10−3 depending on the 훾′ mass.

KW - Extensions of gauge sector

UR - https://www.scopus.com/pages/publications/105038761687

U2 - 10.1103/76JS-7S9F

DO - 10.1103/76JS-7S9F

M3 - Article

VL - 113

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 3

M1 - 032009

ER -