Study of the Semileptonic Decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e$

The measurement of the Cabibbo-favored semileptonic decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e$ is reported using a $4.5{\mathrm{f}\mathrm{b}}^{-1}$ 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 $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e)=(3.56\pm {0.11}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{.}}\pm {0.07}_{\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{.}})\mathrm{\%}$, which is the most precise measurement to date. Furthermore, we perform an investigation of the internal dynamics in ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{e}^{+}{\nu }_e$. 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 $\mathrm{\mid }{V}_{cs}\mathrm{\mid }=0.936\pm {0.017}_{\mathcal{B}}\pm {0.024}_{\mathrm{L}\mathrm{Q}\mathrm{C}\mathrm{D}}\pm {0.007}_{{\tau }_{{\mathrm{\Lambda }}_c}}$.