The investigation of Λ(1405) state in the stopped K⁻ reaction on deuterium

¹ Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan
² RIKEN Nishina Center, RIKEN, Saitama 351-0198, Japan
³ Department of Physics, Isfahan University of Technology, Isfahan 84156-83111, Iran
⁴ College of Science and Technology, Nihon University, Chiba 274-8501, Japan

^a e-mail: tsuzuki@phys.s.u-tokyo.ac.jp

Abstract

Nowadays, extensive studies of the problem of the deeply bound nuclei stimulate the reconsid eration of Λ(1405) state as the theoretical basis of the binding of nuclei, and the old question of the nature of Λ(1405) becomes a modern subject by the new interest. In contrast to one of conventional interpretations of Λ(1405) as the N quasi-bound state at 1405 MeV/c² , a two-pole hypothesis, by which Λ(1405) consists of two poles at 1420 and 1390 MeV/c² couple mainly with N and Σπ channels, respectively, was proposed recently. On the other hand, a very recent theoretical analysis has clarified that the (Σπ)⁰ invariant mass spectra after K⁻ absorption in d reflect strikingly resonant formation of Λ(1405) (or Λ(1420)) and thus are capable of distinguishing different Ansatz’s. We have proposed a new experiment by means of the stopped K⁻ reaction on liquid deuterium at J-PARC K1.8BR beamline with E15/E17 experimental devices, so as to give a new precision- and high-statistics-data of (Σπ)⁰ mass spectra to examine the issue, Λ(1405) or Λ(1420), in the most reliable way, and thus to answer the most fundamental questions of N interaction and nuclei.