New extraction of CP violation in b-baryon decays

TL;DR

This paper proposes a novel method to measure CP violation and CKM parameters using b-baryon decays, particularly $ ext{Xi}_b^-$ and $ ext{Lambda}_b$, with potential for experimental implementation at LHCb.

Contribution

It introduces a new approach to extract the CKM angle gamma and CP violation parameters from baryonic decay processes without the need for strong phase differences.

Findings

Decay rate ratios relate CKM elements without strong phases.

32 decay observables enable extraction of CKM angle gamma.

Feasibility of measurements at LHCb discussed.

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 $\gamma\equiv \arg(-V_{ud}V_{ub}^*/V_{cd}V_{cb}^*)$ 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.