Search for the K − pp bound state via the 3 He( 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 and the charge-exchange K−p → 0n reactions as expected.