Measurement of the absolute branching fraction of the inclusive decay ${\overline{\Lambda }}_{c}^{-}\to \overline{n}+X$

Based on ${e}^{+}{e}^{-}$ collision data corresponding to an integrated luminosity of $4.5\text{}\text{}{\mathrm{fb}}^{-1}$ 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 ${\overline{\Lambda }}_{c}^{-}\to \overline{n}+X$, where $X$ refers to any possible final state particles, is measured. The absolute branching fraction is determined to be $B\left({\overline{\Lambda }}_{c}^{-}\to \overline{n}+X\right)=\left(32.4±0.7±1.5\right)%$, where the first uncertainty is statistical and the second systematic. Assuming $CP$ symmetry, the measurement indicates that about one fourth of ${\Lambda }_{c}^{+}$ (${\overline{\Lambda }}_{c}^{-}$) decay modes with a neutron (an antineutron) in the final state have not been observed.