We have searched for a deeply bound kaonic state by using the FINUDA spectrometer installed at the e+e- collider DAΦNE. Almost monochromatic K-’s produced through the decay of φ(1020) mesons are used to observe K- absorption reactions stopped on very thin nuclear targets. Taking this unique advantage, we have succeeded to detect a kaon-bound state K-pp through its two-body decay into a Λ hyperon and a proton. The binding energy and the decay width are determined from the invariant-mass distribution as 115-5+6(stat)-4+3(syst) MeV and 67-11+14(stat)-3+2(syst) MeV, respectively.
