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

Abstract

The measurement of the Cabibbo-favored semileptonic decay ${\Lambda }_c^{+}\to \Lambda e^{+}{\nu }_e$ is reported using a $4.5{\mathrm{fb}}^{-1}$ 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 $\mathcal{B}({\Lambda }_c^{+}\to \Lambda e^{+}{\nu }_e)=(3.56\pm 0.11_{stat.}\pm 0.07_{syst.})\%$, 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 $|V_{cs}|=0.936\pm 0.017_{\mathcal{B}}\pm 0.024_{\mathrm{LQCD}}\pm 0.007_{{\tau }_{{\Lambda }_c}}$.

8 pages, 4 figures

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