Study of Ac plus - Ag plus ?g and test of lepton flavor universality with Ac plus - Al plus ?l decays

Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ai, X. C.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai, Y.; Bakina, O.; Balossino, I; Ban, Y.; Bao, H-R; Batozskaya, V; Begzsuren, K.; Berger, N.; Berlowski, M.; Bertani, M.; Bettoni, D.; Bianchi, F.; Bianco, E.; Bortone, A.; Boyko, I; Briere, R. A.; Brueggemann, A.; Cai, H.; Cai, X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.; Chang, T. T.; Chang, W. L.; Che, G. R.; Chelkov, G.; Chen, C.; Chen, Chao; Chen, G.; Chen, H. S.

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摘要

The study of the Cabibbo-favored semileptonic decay A thorn c -A & mu; thorn & nu;& mu; is reported using 4.5 fb-1 of e thorn e- annihilation data collected at center-of-mass energies ranging from 4.600 to 4.699 GeV. The branching fraction of the decay is measured to be BoA thorn c -A & mu; thorn & nu;& mu; thorn 1/4 o3.48 ? 0.14stat ? 0.10syst thorn %, 3 times more precise than the prior world average result. Tests of lepton flavor universality using A thorn c -Ae thorn & nu;e (e 1/4 e, & mu;) decays are reported for the first time, based on measurements of the differential decay rates and the forward-backward asymmetries in separate four-momentum transfer regions. The results are compatible with Standard Model predictions. Furthermore, we improve the determination of the form-factor parameters in A thorn c -Ae thorn & nu;e decays, which provide stringent tests and calibration for lattice quantum chromodynamics calculations.

关键词

SEMILEPTONIC DECAYS