Measurement of the absolute branching fraction of the inclusive decay ${\Lambda }_{c}^{+}\to {K}_{S}^{0}X$

We report the first measurement of the absolute branching fraction of the inclusive decay ${\Lambda }_{c}^{+}\to {K}_{S}^{0}X$ . The analysis is performed using an ${e}^{+}{e}^{-}$ collision data sample corresponding to an integrated luminosity of 567 ${\text{pb}}^{-1}$ taken at $\sqrt{s}$ = 4.6 GeV with the BESIII detector. Using eleven Cabibbo-favored ${\overline{\Lambda }}_{c}^{-}$ decay modes and the double-tag technique, this absolute branching fraction is measured to be $B\left({\Lambda }_{c}^{+}\to {K}_{S}^{0}X\right)=\left(9.9±0.6±0.4\right)%$ , where the first uncertainty is statistical and the second systematic. The relative deviation between the branching fractions for the inclusive decay and the observed exclusive decays is $\left(18.7±8.3\right)%$ , which indicates that there may be some unobserved decay modes with a neutron or excited baryons in the final state.