Abstract
The absolute branching fraction of is reported for the first time based on an annihilation sample of events collected with the BESIII detector at . The branching fraction is determined to be , which is improved by about 30% in precision over the previous indirect measurements. Combining this result with the world average of , we obtain the ratio to be , which agrees with the standard model prediction assuming lepton flavor universality. The asymmetry of the branching fractions of and is also determined, and no evidence for violation is found.
- Received 15 July 2021
- Accepted 16 August 2021
DOI:https://doi.org/10.1103/PhysRevLett.127.121802
Published by the American Physical Society under the terms of the 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.
Published by the American Physical Society