Letter
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Decoding weak phase amplitudes in charmed baryon decays

Zhi-Peng Xing¹, Jin Sun ^2,*, and Xiao-Gang He ³

¹Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing, Jiangsu 210023, China
²Particle Theory and Cosmology Group, Center for Theoretical Physics of the Universe, Institute for Basic Science (IBS), Daejeon 34126, South Korea
³State Key Laboratory of Dark Matter Physics, Tsung-Dao Lee Institute and School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 201210, China

^*Contact author: sunjin0810@ibs.re.kr

Phys. Rev. D 114, L071301 – Published 13 October, 2026

DOI: https://doi.org/10.1103/kdz9-ks7n

Abstract

In this paper, 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 $C P$ violation in this sector. Using $S U (3)$ flavor symmetry, we disentangle the amplitudes defined through $M = λ_{s} A_{s} + λ_{b} A_{b}$ ( $λ_{i} = V_{u i} V_{c i}^{*}$ ), 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 $O (1)$ at $2.1 σ$ level. This unexpected pattern may be accommodated by $S U (3)$ 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 $S U (3)$ breaking, in particular $Ξ_{c}^{0} \to p K^{-}$ and $Ξ_{c}^{0} \to Σ^{+} π^{-}$ as golden channels. Measurements of these modes will distinguish between symmetry breaking effects and new physics, establishing a clean pathway to probe $C P$ violation in the charm baryon sector.

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Phys. Rev. D 114, L071301– Published 13 October, 2026

Vol. 114, Iss. 7 — 1 October 2026

Received 16 January 2026
Accepted 6 August 2026

DOI: https://doi.org/10.1103/kdz9-ks7n

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Decoding weak phase amplitudes in charmed baryon decays

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