Proposal of an experiment about $\Lambda -n$ interaction via FSI in $\gamma +d$ reaction at ELPH, Tohoku University

The experiment of strangeness photo-production, NKS2, has been carried out at Research Center for Electron Photon Science (ELPH), Tohoku University. We had focused on the neutral channel near the threshold and reported $K^{\mathrm{0}}$ and Lambda differential cross section of $\gamma +d$ reaction in that energy region. ELPH started to provide the real photon beam from a 1.3 GeV electron synchrotron after recovering from the damage of the Great East Japan Earthquake. As the prospect of the next experiment, we are planning to measure $\Lambda -n$ interaction via $\gamma +d\to K^{+}+\Lambda +n$. Theoretical studies predict that the $K^{\mathrm{+}}$ cross section enhanced only near the threshold region due to FSI of $\Lambda +n$ in $\gamma +d$ reaction comparing to $\gamma +p$. NKS2 has an acceptance in forward angle and covers almost full kinematic region. The characteristics give us an advantage of experiment, that is, not only $K^{+}$ but also $K^{+}$ Lambda coincidence measurement. Additionally, the gamma beam provided (maximum: 1.25 GeV) is suitable for the strangeness photo production in the threshold region (0.9 GeV in lab). We will present a capability of measurement for $\Lambda +n$ interaction using the NKS2 spectrometer at ELPH.