Search for the K− pp bound state via the 3He(K−, n) reaction at 1 GeV/c

The J-PARC E15 experiment searches for the simplest kaonic nuclear bound state, K−pp, via the 3He(K−,n) reaction at the K1.8BR beam-line in the J-PARC hadron experimental facility. We performed the first data-taking in May, 2013, with 5 × 109 incident kaons on the 3He target. The preliminary results are reported focusing on the forward-neutron spectrum, which shows a clear peak structure composed of the quasi-elastic K−"n" → K−n and the charge-exchange K−"p" → 0n reactions as expected.