First observation of the hyper superheavy hydrogen {^6_\Lambda H}

International audienceThree candidate events of the neutron-rich hypernucleus H-6(Lambda) were uniquely identified in the FINUDA experiment at DA Phi NE, Frascati, by observing pi(+) mesons from the (K-stop(-), pi(+)) production reaction on Li-6 targets, in coincidence with pi(-) mesons from H-6(Lambda) -> He-6 + pi(-) weak decay. Details of the experiment and the analysis of its data are reported, leading to an estimate of (2.9 +/- 2.0) . 10(-6)/K-stop(-) for the H-6(Lambda) production rate times the two-body pi(-) weak decay branching ratio. The H-6(Lambda) binding energy with respect to H-5+ Lambda was determined jointly from production and decay to be B-Lambda = (4.0 +/- 1.1) MeV, assuming that H-5 is unbound with respect to H-3 + 2n by 1.7 MeV. The binding energy determined from production is higher, in each one of the three events, than that determined from decay, with a difference of (0.98 +/- 0.74) MeV here assigned to the 0(g.s.)(+) -> I+ excitation. The consequences of this assignment to Lambda hypernuclear dynamics are briefly discussed