Measurement of Λ Polarization in the π^-p → K⁰ Λ Reaction at p_π^-=1.33 GeV/c toward a New Λp Scattering Experiment

2025/05/24 by PARC E40 Collaboration, Sakao, T., Miwa, K. +69
#FOS: Physical sciences #Nuclear Experiment (nucl-ex)

paper · doi:10.48550/arxiv.2505.18598

Abstract

This paper presents high-precision experimental data of the polarization of the Λ hyperon in the π^-p → K⁰ Λ reaction, measured in the angular range 0.6<cos θ^CM_K0<1.0 with a fine bin width of dcos θ^CM_K0=0.05. The data were obtained from the J-PARC E40 experiment at the K1.8 beamline in the J-PARC Hadron Experimental Facility. The observed average polarization of Λ in the range 0.60<cos θ^CM_K0<0.85 was 0.932 ± 0.058 (stat) ± 0.028 (syst), demonstrating the successful extraction of precise polarization observables. This result provides essential experimental input for partial wave analysis (PWA) of dynamical coupled-channel (DCC) models, which aim to uncover the underlying mechanisms of N^* resonances that emerge in intermediate states of πN and γN interactions. Besides, it indicates the feasibility of a strongly polarized Λ beam suitable for future Λp scattering experiments (e.g., J-PARC E86).

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