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  • Open Access

Establishing CP Violation in b-Baryon Decays

Jia-Jie Han1, Ji-Xin Yu1,*, Ya Li2,†, Hsiang-nan Li3,‡, Jian-Peng Wang1,§, Zhen-Jun Xiao4,∥, and Fu-Sheng Yu1,¶

  • 1Frontiers Science Center for Rare Isotopes, and School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, People’s Republic of China
  • 2Department of Physics, College of Sciences, Nanjing Agricultural University, Nanjing 210095, People’s Republic of China
  • 3Institute of Physics, Academia Sinica, Taipei, Taiwan 115, Republic of China
  • 4Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023, People’s Republic of China

  • *Contact author: yujx18@lzu.edu.cn
  • †Contact author: liyakelly@163.com
  • ‡Contact author: hnli@phys.sinica.edu.tw
  • §Contact author: wangjp20@lzu.edu.cn
  • ∥Contact author: xiaozhenjun@njnu.edu.cn
  • Contact author: yufsh@lzu.edu.cn
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Phys. Rev. Lett. 134, 221801 – Published 4 June, 2025

DOI: https://doi.org/10.1103/ynnx-f63h

Abstract

It is a long-standing puzzle why the 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 Λb→pπ− 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 Λb→pa1(1260), pK1(1270) decay products, which are large enough for being identified experimentally.

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Phys. Rev. Lett. 134, 221801– Published 4 June, 2025
  • Received 31 December 2024
  • Revised 7 May 2025
  • Accepted 15 May 2025
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