Test of CP Symmetry in the Neutral Decays of Λ via J/ψ→ΛΛ

2025/10/28 by BESIII Collaboration, Ablikim, M., Achasov, M. N. +685
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2510.24333

Abstract

Using (10087±44)×10⁶ J/ψ events collected with the BESIII detector, a full angular distribution analysis is carried out on the process J/ψ→ΛΛ→ nπ⁰pπ⁺+c.c. The decay parameters α₀ for Λ→ nπ⁰ and α₀ for Λ→ nπ⁰ are measured to be 0.668±0.007±0.002 and -0.677±0.007±0.003, respectively, yielding the most precise test for CP symmetry of neutral decays of Λ, A_CP⁰=(α₀+α₀)/(α₀-α₀), to be -0.006±0.007±0.002. The ratios α₀/α_- and α₀/α₊ are determined to be 0.884±0.013±0.006 and 0.885±0.013±0.004, where α_- and α₊ are the decay parameters of Λ→ pπ^- and Λ→pπ⁺, respectively. The ratios, found to be smaller than unity by more than 5σ, confirm the presence of the ΔI = 3/2 transition in the Λ and Λ decays, which is expected to improve the theoretical calculations for strong and weak phases, and A_CP, in hyperon decays. In all results, the first and second uncertainties are statistical and systematic, respectively.

Related

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• Search for Λ-Λ oscillation in J/ψ→ΛΛ decay
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