Measurement of Branching Fractions for ${\mathrm{\Lambda }}_c^{+}\to n{K}_S^0{\pi }^{+}$ and ${\mathrm{\Lambda }}_c^{+}\to n{K}_S^0{K}^{+}$

Based on 4.5 fb${}^{-1}$ of $e^{+}{e}^{-}$ collision data accumulated at center-of-mass energies between $4.600\mathrm{G}\mathrm{e}\mathrm{V}$ and $4.699\mathrm{G}\mathrm{e}\mathrm{V}$ with the BESIII detector, we measure the absolute branching fraction of the Cabibbo-favored decay ${\mathrm{\Lambda }}_c^{+}\to n{K}_S^0{\pi }^{+}$ with the precision improved by a factor of 2.8 and report the first evidence for the singly-Cabibbo-suppressed decay ${\mathrm{\Lambda }}_c^{+}\to n{K}_S^0{K}^{+}$. The branching fractions for ${\mathrm{\Lambda }}_c^{+}\to n{K}_S^0{\pi }^{+}$ and ${\mathrm{\Lambda }}_c^{+}\to n{K}_S^0{K}^{+}$ are determined to be $(1.86\pm 0.08\pm 0.04)\times {10}^{-2}$ and $(3.9_{-1.4}^{+1.7}\pm 0.3)\times {10}^{-4}$, respectively, where the first uncertainties are statistical and the second ones are systematic.