arXiv · 2505.18598
Measurement of $\Lambda$ Polarization in the $\pi^{-}p \to K^{0} \Lambda$ Reaction at $p_{\pi^{-}}=1.33$ GeV/$c$ toward a New $\Lambda p$ Scattering Experiment
Abstract
This paper presents high-precision experimental data of the polarization of the $\Lambda$ hyperon in the $\pi^{-}p \to K^{0} \Lambda$ reaction, measured in the angular range $0.6<\cos \theta ^{CM}_{K0}<1.0$ with a fine bin width of $d\cos \theta ^{CM}_{K0}=0.05$. 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 $\Lambda$ in the range $0.60<\cos \theta ^{CM}_{K0}<0.85$ was $0.932 \pm 0.058 \,(\text{stat}) \pm 0.028 \,(\text{syst})$, 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 $\pi N$ and $\gamma N$ interactions. Besides, it indicates the feasibility of a strongly polarized $\Lambda$ beam suitable for future $\Lambda p$ scattering experiments (e.g., J-PARC E86).
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PARC E40 Collaboration, T. Sakao, K. Miwa, J. K. Ahn, Y. Akazawa, T. Aramaki, S. Ashikaga, S. Callier, N. Chiga, S. W. Choi, H. Ekawa, P. Evtoukhovitch, N. Fujioka, M. Fujita, T. Gogami, T. Harada, S. Hasegawa, S. H. Hayakawa, R. Honda, S. Hoshino, K. Hosomi, M. Ichikawa, Y. Ichikawa, M. Ieiri, M. Ikeda, K. Imai, Y. Ishikawa, S. Ishimoto, W. S. Jung, S. Kajikawa, H. Kanauchi, H. Kanda, T. Kitaoka, B. M. Kang, H. Kawai, S. H. Kim, K. Kobayashi, T. Koike, K. Matsuda, Y. Matsumoto, S. Nagao, R. Nagatomi, Y. Nakada, M. Nakagawa, I. Nakamura, T. Nanamura, M. Naruki, S. Ozawa, L. Raux, T. G. Rogers, A. Sakaguchi, H. Sako, S. Sato, T. Shiozaki, K. Shirotori, K. N. Suzuki, S. Suzuki, M. Tabata, C. d. L. Taille, H. Takahashi, T. Takahashi, T. N. Takahashi, H. Tamura, M. Tanaka, K. Tanida, Z. Tsamalaidze, M. Ukai, H. Umetsu, S. Wada, T. O. Yamamoto, J. Yoshida, K. Yoshimura. 2025-05-24. Measurement of $\Lambda$ Polarization in the $\pi^{-}p \to K^{0} \Lambda$ Reaction at $p_{\pi^{-}}=1.33$ GeV/$c$ toward a New $\Lambda p$ Scattering Experiment. https://arxiv.org/abs/2505.18598
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