Study of the Semileptonic Decay ${\Lambda }_{c}^{+}\to \Lambda {e}^{+}{\nu }_{e}$

The study of the Cabibbo-favored semileptonic decay ${\Lambda }_{c}^{+}\to \Lambda {e}^{+}{\nu }_{e}$ is reported using a $4.5\text{}\text{}{\mathrm{fb}}^{-1}$ data sample of ${e}^{+}{e}^{-}$ annihilations collected at center-of-mass energies ranging from 4.600 GeV to 4.699 GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be $B\left({\Lambda }_{c}^{+}\to \Lambda {e}^{+}{\nu }_{e}\right)=\left(3.56±0.1{1}_{\mathrm{stat}}±0.0{7}_{\mathrm{syst}}\right)%$, which is the most precise measurement to date. Furthermore, we perform an investigation of the internal dynamics in ${\Lambda }_{c}^{+}\to \Lambda {e}^{+}{\nu }_{e}$. We provide the first direct comparisons of the differential decay rate and form factors with those predicted from lattice quantum chromodynamics (LQCD) calculations. Combining the measured branching fraction with a ${q}^{2}$-integrated rate predicted by LQCD, we determine $|{V}_{cs}|=0.936±0.01{7}_{B}±0.02{4}_{\mathrm{LQCD}}±0.00{7}_{{\tau }_{{\Lambda }_{c}}}$.