Establishing CP Violation in $b$-Baryon Decays

It is a long-standing puzzle why the {\it CP} violation (CPV) in the baryon system has not yet been definitively established as in the meson one. We demonstrate that individual partial-wave CPV in the $\Lambda_b\to p\pi^-$ and $pK^-$ decays can exceed $10\%$, but the destruction between the partial waves (the suppression by the small partial-wave weight) results in a small net direct CPV in the former (the latter) as measured currently. Our finding highlights the different dynamics responsible for CPVs in baryon and meson decays. We propose to probe the CPV observables associated with the angular distributions of the $\Lambda_b\to pa_1(1260)$, $pK_1(1270)$ decay products, which are large enough for being identified experimentally.