Precision Studies and Searches for CP Asymmetries in the Inclusive Decay $\hat{I}{›}_c^{+}\to \hat{I}›X$

Abstract

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 $\hat{I}›$ hyperons produced in the inclusive decay $\hat{I}{›}_c^{+}\to \hat{I}›X$, where $X$ denotes any allowed final state. The polarizations are determined to be ${\mathcal{P}}_{\hat{I}}›=-0.393\pm 0.055_{sta.}\pm 0.020_{sys.}$ and ${\mathcal{P}}_{\bar{\hat{I}}›}=0.288\pm 0.056_{sta.}\pm 0.017_{sys.}$. We then search for CP violation using an asymmetry constructed from the $\hat{I}›$ polarization and the $\hat{I}›\to p\ddot{I}{€}^{-}$ decay asymmetry parameters, and obtain ${\mathcal{A}}_{\mathrm{CP}}^{\mathrm{pol}}=0.15\pm 0.12_{sta.}\pm 0.04_{sys.}$. We also perform an updated measurement of the absolute branching fraction, resulted as $\mathcal{B}(\hat{I}{›}_c^{+}\to \hat{I}›X)=(38.07\pm 0.38_{sta.}\pm 0.49_{sys.})\%$, with precision improved by a factor of four relative to the current world average. A search for direct CP violation yields ${\mathcal{A}}_{\mathrm{CP}}^{\mathrm{dir}}=(1.5\pm 1.0_{sta.}\pm 1.0_{sys.})\%$. No evidence for CP violation in inclusive charm baryon decays is observed.