Measurement of the absolute branching fraction of the inclusive decay ${\bar{\mathrm{\Lambda }}}_c^{-}\to \bar{n}+X$

Based on $e^{+}{e}^{-}$ collision data corresponding to an integrated luminosity of 4.5 $f{b}^{-1}$ collected at the center-of-mass energies between 4.600 and 4.699 GeV with the BESIII detector at BEPCII, the absolute branching fraction of the inclusive decay ${\mathrm{\Lambda }}_c^{+}\to n+X$, where $X$ refers to any possible final state particles, is measured. The absolute branching fraction is determined to be $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to n+X)=(32.4\pm 0.7\pm 1.5)\mathrm{\%}$, where the first uncertainty is statistical and the second systematic. Assuming $CP$ symmetry, the measurement indicates that about one-fourth of ${\mathrm{\Lambda }}_c^{+}$ (${\bar{\mathrm{\Lambda }}}_c^{-}$) decay modes with a neutron (an anti-neutron) in the final state have not been observed.