Precision Studies and Searches for CP Asymmetries in the Inclusive Decay Λ_{c}^{+}→ΛX

Based on e^{+}e^{-} annihilation data collected with the BESIII detector at center-of-mass energies from 4.600 to 4.699 GeV, corresponding to an integrated luminosity of 4.5  fb^{-1}, we present the first measurement of the longitudinal polarization of Λ hyperon produced in the inclusive decay Λ_{c}^{+}→ΛX, where X denotes any allowed final states. The polarizations are determined to be P_{Λ}=-0.393±0.055_{stat}±0.020_{syst} and P_{Λ[over ¯]}=0.288±0.056_{stat}±0.017_{syst}. A search for CP violation is performed using an asymmetry constructed from the Λ polarization and the Λ→pπ^{-} decay asymmetry parameter, and A_{CP}^{pol}=0.15±0.12_{stat}±0.03_{syst} was obtained. Furthermore, an updated measurement of the absolute branching fraction is reported as B(Λ_{c}^{+}→ΛX)=(38.07±0.38_{stat}±0.49_{syst})%, representing a fourfold precision improvement over the previous BESIII measurement. A search for CP violation in the decay rate yields A_{CP}^{dir}=(1.5±1.0_{stat}±1.0_{syst})%. No evidence for CP violation is observed in this inclusive charm baryon decay. The subscripts 'stat' and 'syst' denote statistical and systematic uncertainties, respectively.