Improved measurement of absolute branching fraction of the inclusive decay $ {\Lambda}_c^{+}\to {K}_S^0X $

By analyzing 4.5 fb −1 of e + e − collision data accumulated with the BESIII detector at center-of-mass energies ranging from 4599.53 MeV to 4698.82 MeV, we report the measurement of the absolute branching fraction (BF) of the inclusive decay ${\Lambda}_c^{+}\to {K}_S^0X$ using the double-tag technique. The result is $\mathcal{B}\left({\Lambda}_c^{+}\to {K}_S^0X\right)$ = (10.9 ± 0.2 ± 0.1)%, where the first uncertainty is statistical and the second is systematic. This result indicates that there are still undiscovered decay channels containing ${K}_S^0$ in the final state with a combined BF of (3.0 ± 0.4)%. The BF of the inclusive decay ${\Lambda}_c^{+}\to {\overline{K}}^0/{K}^0X$ is calculated to be $\mathcal{B}\left({\Lambda}_c^{+}\to {\overline{K}}^0/{K}^0X\right)$ = (21.8 ± 0.4 ± 0.2)%, The result is in agreement with the prediction of the statistical isospin model.