Study of Λc+ → Λμ+νμ and test of lepton flavor universality with Λc+ → Λℓ+νℓ decays

Abstract

The study of the Cabibbo-favored semileptonic decay Λc+→Λμ+νμ is reported using 4.5 fb-1 of e+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 B(Λc+→Λμ+νμ)=(3.48±0.14stat±0.10syst)%, 3 times more precise than the prior world average result. Tests of lepton flavor universality using Λc+→Λℓ+νℓ (ℓ=e, μ) 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 Λc+→Λℓ+νℓ decays, which provide stringent tests and calibration for lattice quantum chromodynamics calculations