Status of Λn interaction study via the final state interaction effect in γ+d->K⁺+Λ+n production

The study of Baryon interaction including strangeness have been mainly carried by Hypernuclear experiment, because of difficulties of the Hyperon-Nucleon (YN) scattering. The recent results of ^4_ΛH and ^4_ΛHe measurements show existing of a charge symmetry breaking  (CSB) in ΛN interaction.  It is suggested that the ΛN CSB is due to ΛΣ coupling in ΛN. On the other hand, there is lack of precise data in the Λn interaction. The measurement of Λn interaction is one of the key issues in the strangeness nuclear physics. The Λn interaction can be extracted by comparing cross-sections of  γ+d->K⁺+Λ+n and  γ+p->K⁺+Λ due to final state effect of Λn.

We have been investigating strangeness photoproduction with tagged photon beam in Research Center for Electron Photon Science (ELPH), Tohoku University. The spectrometer, NKS2, was originally designed for K⁰ Λ production.  Upgrades of NKS2 detectors for the Λn FSI experiment are in progress: high resolution TOF counter by Multi-gap Resistive Plate Chamber and Electron Veto by Aerogel Cherenkov counter.

We will present the plan of experiment with beam time estimation and requirements/achievement of detector performance.