New extraction of CP violation in b-baryon decays

Abstract

We study CP violation in b-baryon decays of ${\Xi }_b^{-}\to {\Xi }^{-}D$ with $D=D^0,{\bar{D}}^0$ and $D_i(i=1,2)$. We find that these baryonic decay processes provide an ideal opportunity to measure the weak phase due to the absence of the relative strong phase. Explicitly, we relate $\bar{\rho }$ and $\bar{\eta }$ the CKM elements with the decay rate ratios of $R_i=\Gamma ({\Xi }_b^{-}\to {\Xi }^{-}{D}_i)/\Gamma ({\Xi }_b^{-}\to {\Xi }^{-}{D}^0)$ without the charge conjugate states. As a complementary, we also examine the decay distributions of ${\Lambda }_b\to \Lambda (\to p{\pi }^{-})D$. There are in total 32 decay observables, which can be parameterized by 9 real parameters, allowing the experiments to extract the angle $\gamma \equiv \arg (-V_{ud}{V}_{ub}^{\ast }/V_{cd}{V}_{cb}^{\ast })$ in the CKM unitarity triangle. In addition, the feasibilities of the experimental measurements are discussed. We find that $\bar{\rho }$ and $\bar{\eta }$ can be extracted at LHCb Run3 from ${\Xi }_b^{-}\to {\Xi }^{-}D$, and a full analysis of ${\Lambda }_b\to \Lambda (\to p{\pi }^{-})D$ is available at LHCb Run4.

Comments: Accepted by PLB