The basic K nuclear cluster K- pp and its enhanced formation in the p + p -> K+ + X reaction

We have studied the structure of K- pp nuclear cluster comprehensively by solving this three-body system exactly in a variational method starting from the Ansatz that the Lambda(1405) resonance (Lambda*) is a K-p bound state. We have found that our original prediction for the presence of K-pp as a compact bound system with M = 2322$MeV/c2, B = 48 MeV and Gamma = 60 MeV remains unchanged by varying the Kba-rN and NN interactions widely as far as they reproduce Lambda(1405). The structure of K- pp reveals a molecular feature, namely, the K- in Lambda* as an "atomic center" plays a key role in producing strong covalent bonding with the other proton. We have shown that the elementary process, p + p -> K+ + Lambda* + p, which occurs in a short impact parameter and with a large momentum transfer (Q ~ 1.6$ GeV/c), leads to unusually large self-trapping of Lambda* by the participating proton, since the Lambda*-p system exists as a compact doorway state propagating to K- pp (R{Lambda*-p} ~ 1.67 fm).