Measurement of KN scattering below the KN mass threshold

¹ Research Center for Nuclear Physics, Osaka University, Ibaraki, 567-0047, Japan
² Department of Physics, Tokyo Institute of Technology, Tokyo, 152-0551, Japan
³ Department of Physics, Osaka University, Toyonaka, 560-0043, Japan
⁴ RIKEN Cluster for Pioneering Research (CPR), RIKEN, Wako, 351-0198, Japan
⁵ Department of Physics and Astronomy, University of Victoria, Victoria BC V8W 3P6, Canada
⁶ Stefan-Meyer-Institut für subatomare Physik, A-1030 Vienna, Austria
⁷ National Institute of Physics and Nuclear Engineering (IFIN-HH), Magurele, Romania
⁸ INFN Sezione di Torino, Torino, Italy
⁹ Dipartimento di Fisica Generale, Universita'di Torino, Torino, Italy
¹⁰ Department of Physics, Seoul National University, Seoul, 151-742, South Korea
¹¹ Laboratori Nazionali di Frascati dell'INFN, I-00044 Frascati, Italy
¹² Accelerator Laboratory, High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan
¹³ Department of Physics, The University of Tokyo, Tokyo, 113-0033, Japan
¹⁴ Laboratory of Physics, Osaka Electro-Communication University, Neyagawa, 572-8530, Japan
¹⁵ RIKEN Nishina Center for Accelerator-Based Science, RIKEN, Wako, 351-0198, Japan
¹⁶ ASRC, Japan Atomic Energy Agency (JAEA), Ibaraki 319-1195, Japan
¹⁷ RIKEN SPring-8 Center, RIKEN, Hyogo, 679-5148, Japan
¹⁸ Cryogenics Science Center, High Energy Accelerator Research Organization (KEK), Tsukuba, 3050801, Japan
¹⁹ Department of Physics, Kyoto University, Kyoto, 606-8502, Japan
²⁰ Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan
²¹ Mechanical Engineering Center, High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, Japan
²² Technische Universität München, D-85748, Garching, Germany
²³ Graduate School of Arts and Sciences, The Univeristy of Tokyo, Tokyo, 153-8902, Japan
²⁴ Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai, 982-0826, Japan
²⁵ Department of Physics, Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
²⁶ Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Piazza del Viminale 1, 00184 Rome, Italy
²⁷ INFN, Laboratori Nazionali di Frascati, Via Enrico Fermi 40, 00044 Frascati, Italy
²⁸ Department of Chemical Physics, Lund University, Lund, 221 00, Sweden
²⁹ Excellence Cluster University, Technische Universität München, D-85748, Garching, Germany
³⁰ Korea Unstitute of Radiological and Medical Sciences (KIRAMS), Seoul, 139-706, South Korea

^* e-mail: noumi@rcnp.osaka-u.ac..jp
^** e-mail: kentaro@rcnp.osaka-u.ac.jp
^*** e-mail: shinngo@rcnp.osaka-u.ac.jp

Published online: 16 February 2024

Abstract

Abstract. We measured πE invariant mass spectra below and above the K¯N mass threshold in the K⁻d → NπE reaction in order to study the K¯N interaction and the Λ(1405) resonance. This reaction can be described by the two-step process: (i) K¯N₁ → K¯N followed by (ii) K¯N₂ → πΣ, where N₁ and N₂ are nucleons bound in the deuteron. We deduced the S -wave scattering amplitude of K¯N →K¯N in the framework of the K¯N πΣ coupled channel so as to reproduce the observed πΣ spectra in the I = 0 channel. We found a resonance pole at 1417.7_-7.4^+6.0 (fitting error)_-1.0^+1.1 (systematic error) - i[26.9_-7.9^+6.0 (fitting error)_-2.0^+1.7 (systematic error)]MeV/c².