We report a search for a dark photon using 14.9 fb –1 of e + e – annihilation data taken at center-of-mass energies from 4.13 to 4.60 GeV with the BESIII detector operated at the BEPCII storage ring. The dark photon is assumed to be produced in the radiative annihilation process of e + e – and to predominantly decay into light dark matter particles, which escape from the detector undetected. The mass range from 1.5 to 2.9 GeV is scanned for the dark photon candidate, and no significant signal is observed. The mass dependent upper limits at the 90% confidence level on the coupling strength parameter ϵ for a dark photon coupling with an ordinary photon vary between 1.6 x 10 –3 and 5.7 x 10 –3 .

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

Measurements of the branching fractions of the inclusive decays D 0 ( D + ) → π + π + π - X

Using e + ⁢e - annihilation data corresponding to an integrated luminosity of 2.93 fb -1 taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the branching fractions of the inclusive decays D 0 → π + π + π - X and D + → π + π + π - X, where pions from $K^0_S$ decays have been excluded from the → π + π + π - system and X denotes any possible particle combination. The branching fractions of D 0 ⁡(D + ) → π + π + π - X are determined to be B⁡(D 0 → π + π + π - X) = (17.60 ± 0.11 ± 0.22)% and B(D + → π + π + π - X) = (15.25 ± 0.09 ± 0.18)%, where the first uncertainties are statistical and the second systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Search for an axion-like particle in radiative $J/ψ$ decays

We search for an axion-like particle (ALP) a through the process $\psi$(3686) → π + π – J/$\psi$, J/$\psi$ → γa, a → γγ in a data sample of (2.71 ± 0.01) x 10 9 $\psi$(3686) events collected by the BESIII detector. No significant ALP signal is observed over the expected background, and the upper limits on the branching fraction of the decay J/$\psi$ → γa and the ALP-photon coupling constant g aγγ are set at 95% confidence level in the mass range of 0.165 ≤ m a ≤ 2.84 GeV/c 2 . The limits on $\mathscr{B}$(J/$\psi$ → γa) range from 8.3 x 10 –8 to 1.8 x 10 –6 over the search region, and the constraints on the ALP-photon coupling are the most stringent to date for 0.165 ≤ m a ≤ 1.468 GeV/c 2 .

79 ASTRONOMY AND ASTROPHYSICS↗