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Large $C P$ violation in $Λ_{b}^{0} \to p K^{-} π^{+} π^{-}$ and its $U$ -spin partner decays

Xiao-Gang He^*, Chia-Wei Liu ^†, and Jusak Tandean ^‡

State Key Laboratory of Dark Matter Physics, Tsung-Dao Lee Institute and School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 201210, China and Key Laboratory for Particle Astrophysics and Cosmology (MOE) and Shanghai Key Laboratory for Particle Physics and Cosmology, Tsung-Dao Lee Institute and School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 201210, China

^*Contact author: hexg@sjtu.edu.cn
^†Contact author: chiaweiliu@sjtu.edu.cn
^‡Contact author: jtandean@yahoo.com

Phys. Rev. D 112, L111302 – Published 4 December, 2025

DOI: https://doi.org/10.1103/vf9p-5hzx

Abstract

The LHCb Collaboration has recently found a large $C P$ -violating rate asymmetry in the $b$ -baryon decay $Λ_{b}^{0} \to p K^{-} π^{+} π^{-}$ . This is the first observation of $C P$ violation in baryon processes, opening a new window to test its standard model (SM) origin. Many more baryon decays are expected to exhibit observable signals of $C P$ violation. We show that there also exists large $C P$ violation in the U-spin partner decay mode, $Ξ_{b}^{0} \to Σ^{+} π^{-} K^{+} K^{-}$ , with rate asymmetry $A_{C P} (Ξ_{b}^{0} \to Σ^{+} π^{-} K^{+} K^{-}) = - A_{C P} (Λ_{b}^{0} \to p K^{-} π^{+} π^{-}) \frac{Br (Λ_{b}^{0} \to p K^{-} π^{+} π^{-})}{Br (Ξ_{b}^{0} \to Σ^{+} π^{-} K^{+} K^{-})} \frac{τ^{Ξ_{b}}}{τ^{Λ_{b}}}$ in the U-spin symmetry limit. By neglecting a subleading contribution in the amplitudes, $A_{C P} (Λ_{b}^{0} \to p π^{+} π^{-} π^{-}) = - (12 \pm 6) %$ . These predictions can be tested in the near future.

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References (14)

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Phys. Rev. D 112, L111302– Published 4 December, 2025

Vol. 112, Iss. 11 — 1 December 2025

Received 2 June 2025
Accepted 14 November 2025

DOI: https://doi.org/10.1103/vf9p-5hzx

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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Large $C P$ violation in $Λ_{b}^{0} \to p K^{-} π^{+} π^{-}$ and its $U$ -spin partner decays

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Large CP violation in Λb0→pK−π+π− and its U-spin partner decays

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Large $C P$ violation in $Λ_{b}^{0} \to p K^{-} π^{+} π^{-}$ and its $U$ -spin partner decays