The Production and Decay Dynamics of the Charmed Baryon Λ_c⁺ in e⁺e^- Annihilations near Threshold

2025/08/15 by BESIII Collaboration, Ablikim, M., Achasov, M. N. +700 · 1 citation
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2508.11400

Abstract

The study of the charmed baryons is crucial for investigating the strong and weak interactions in the Standard Model and for gaining insights into the internal structure of baryons. In an e⁺e^- experiment the lightest charmed baryon, Λ_c⁺, can be produced in pairs through the single photon annihilation process. This process can be described by two complex electromagnetic form factors. The presence of a non-zero relative phase between these form factors gives rise to a transverse polarization of the charmed baryon and provides additional constraints on the dynamic parameters in the decays. In this article, we present the first observation of the transverse polarization of Λ_c⁺ in the reaction e⁺e^- → Λ_c⁺Λ_c^-, based on 6.4~fb^-1 of e⁺e^- annihilation data collected at center-of-mass energies between 4600 MeV and 4951 MeV with the BESIII detector. The decay asymmetry parameters in the decays Λ_c⁺ → pK_S⁰, Λπ⁺, Σ⁰π⁺, and Σ⁺π⁰ are simultaneously extracted from the joint angular distributions. From these parameters, both the weak and strong phase shifts are extracted, and several C P observables are tested. The obtained results show that the transverse polarization of the produced baryon significantly enhances the capability of searching for C P-violating effects, opening a novel way for exploring C P violation in the charmed baryon sector.

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Cited by

• Measurements of the cross sections of e⁺e^-→ Σ_cΣ_c and Λ_c⁺Σ_c^- near kinematic thresholds

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