CP violation in multibody decays of beauty baryons

TL;DR

This paper investigates CP violation in multibody decays of beauty baryons, analyzing angular distributions and asymmetries to identify potential CP-odd effects, with implications for LHCb measurements.

Contribution

It introduces a formalism for analyzing CP violation in multibody beauty baryon decays using angular distributions and identifies which asymmetries are sensitive to CP-odd phases.

Findings

Certain CP-odd angular asymmetries are predicted to vanish in specific decay modes.

The analysis clarifies which asymmetries are relevant for detecting CP violation.

Understanding of resonant intermediate states informs the interpretation of asymmetries.

Abstract

Beauty baryons are being observed in large numbers in the LHCb detector. The rich kinematic distributions of their multibody decays are therefore becoming accessible and provide us with new opportunities to search for CP violation. We analyse the angular distributions of some three- and four-body decays of spin-$1/2$ baryons using the Jacob-Wick helicity formalism. The asymmetries that provide access to small differences of CP-odd phases between decay amplitudes of identical CP-even phases are notably discussed. The understanding gained on processes featuring specific resonant intermediate states allows us to establish which asymmetries are relevant for what purpose. It is for instance shown that some CP-odd angular asymmetries measured by the LHCb collaboration in the $\Lambda_b \to \Lambda\,\varphi \to p\,\pi\, K^+ K^-$ decay are expected to vanish identically.