M. AblikimM.N, AchasovP. AdlarsonS. AhmedM. AlbrechtKolcu, Onur BuğraÇetin, Serkant Ali2021-09-282021-09-282021Ablikim, M., Achasov, M. N., Adlarson, P., Ahmed, S., Albrecht, M., Aliberti, R., Amoroso, A., An, M. R., An, Q., Bai, X. H., Bai, Y., Bakina, O., Ferroli, R. B., Balossino, I., Ban, Y., Begzsuren, K., Berger, N., Bertani, M., Bettoni, D., … Collaboration, B. (2021). First Measurement of the Absolute Branching Fraction of $\Lambda \to p \mu^- \bar{\nu}_{\mu}$. https://doi.org/10.1103/PhysRevLett.127.1218020031-9007https://doi.org/10.1103/PhysRevLett.127.121802https://hdl.handle.net/20.500.12713/2106The absolute branching fraction of ??p??¯?? is reported for the first time based on an e+e? annihilation sample of 10×109??J/? events collected with the BESIII detector at ?s=3.097??GeV. The branching fraction is determined to be B(??p??¯??)=[1.48±0.21(stat)±0.08(syst)]×10?4, which is improved by about 30% in precision over the previous indirect measurements. Combining this result with the world average of B(??pe?¯?e), we obtain the ratio {[?(??p??¯??)]/[?(??pe?¯?e)]} to be 0.178±0.028, which agrees with the standard model prediction assuming lepton flavor universality. The asymmetry of the branching fractions of ??p??¯?? and ¯??¯p?+?? is also determined, and no evidence for CP violation is found.eninfo:eu-repo/semantics/openAccessAbsoluteBranchingMeasurementArticle127121834597097WOS:0007046651000042-s2.0-85115305739Q110.1103/PhysRevLett.127.121802Q1