Pole position of Λ(1405) measured in d(K,n)πΣ reactions

J-PARC E31 Collaboration

Research output: Contribution to journalArticlepeer-review


We measured a set of π±Σ, π0Σ0, and πΣ0 invariant mass spectra below and above the K¯N mass threshold in K-induced reactions on deuteron. The measured πΣ mass spectral shape is well reproduced via the two-step mechanism, i.e., a neutron knocked out at a forward angle from a deuteron by an incident K, with the K¯ recoiled backward reacting with the residual nucleon to produce π and Σ. We deduced the S-wave K¯N→πΣ and K¯N→K¯N scattering amplitudes in the isospin 0 channel in the framework of a K¯N and πΣ coupled channel. We find that a resonance pole corresponding to Λ(1405) is located at 1417.7−7.4+6.0 (fitting errors)−1.0+1.1 (systematic errors) + [−26.1−7.9+6.0 (fitting errors)−2.0+1.7 (systematic errors)] i MeV/c2, closer to the K¯N mass threshold than the value determined by the Particle Data Group.

Original languageEnglish
Article number137637
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Publication statusPublished - 2023 Feb 10


  • Hyperon resonance
  • Kaon-nucleon interation
  • Meson-baryon bound state
  • Scattering amplitude

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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