Evidence for Heavy Hyperhydrogen 6LH

Evidence for the neutron-rich hypernucleus 6LH is presented from the FINUDA experiment at DAFNE, Frascati, studying (pi_, pi-) pairs in coincidence from the K- stop + 6Li --> 6LH + pi+ production reaction followed by 6LH --> 6He + pi- weak decay. The production rate of 6LH undergoing this two-body pi- decay is determined to be (2.9+/-2.0) 10-6/K-stop. Its binding energy, evaluated jointly from production and decay, is B=(4.0+/-1.1) MeV with respect to 5H+Lambda. A systematic difference of (0:98+/-0.74) MeV between B values derived separately from decay and from production is tentatively assigned to the 6LH 0+g.s. excitation.