Spectroscopic study of the Λ(1405) resonance via the d(K−, n) reaction at J-PARC

The structure of the Λ(1405) hyperon is an important and long-standing issue related to the K-nucleus interaction. The J-PARC E31 experiment has been performed to investigate the Λ(1405) spectrum shape. Because it is hard to form the Λ(1405) directly by a KN scattering in free space, E31 uses the d(K-, n) reaction with an incident kaon momentum of 1 GeV/c. We will identify three final states - ς-π+, ς+π-, ς0π0-so that the isospin structure of hyperon resonance states produced can be decomposed. The first physics run of the E31 experiment was performed in 2016. To enhance the statistics of the data set, we have performed the second physics run in the beginning of 2018. During the second run of E31, around 3.9×1010 kaons impacted on the deuteron target.