Decoding Weak Phase Amplitudes in Charmed Baryon Decays

Abstract

In this Letter, we present a strategy to decode decay amplitudes with different weak phases in two-body charmed baryon decays, addressing a long-standing challenge to understanding CP violation in this sector. Using SU(3) flavor symmetry, we disentangle the amplitudes defined through $M={\lambda }_s{A}_s+{\lambda }_b{A}_b$ (${\lambda }_i=V_{ui}{V}_{ci}^{\ast }$), enabling a data-driven determination of their relative hierarchy across Cabibbo-favored, singly, and doubly Cabibbo-suppressed modes. Applying this framework to current data, we find that the ratio $A_b/A_s$ is approximately 100 times larger than expectation of $\mathcal{O}(1)$ at $2.1\sigma$ level. This unexpected pattern may be accommodated by SU(3) breaking effects, but it can also point to new physics. We further show that the Lee-Yang parameters provide an independent and complementary probe. To resolve this ambiguity in the origin of the enhancement, we propose a decisive discriminator using decay modes insensitive to large SU(3) breaking, in particular ${\Xi }_c^0\to p{K}^{-}$ and ${\Xi }_c^0\to {\Sigma }^{+}{\pi }^{-}$ as golden channels. Measurements of these modes will distinguish between symmetry breaking effects and new physics, establishing a clean pathway to probe CP violation in the charm baryon sector.

arXiv comment6 pages 1 tables, accepted by PRD