Candidate Resonant Tetraneutron State Populated by the 4He (8H3, 8Be) ) Reaction

A candidate resonant tetraneutron state is found in the missing-mass spectrum obtained in the double-charge-exchange reaction ⁴He (⁸H3, ⁸Be) at 186 MeV /u . The energy of the state is 0.83 ±0.65 (stat ) ±1.25 (syst ) MeV above the threshold of four-neutron decay with a significance level of 4.9 σ . Utilizing the large positive Q value of the (⁸He, ⁸Be) reaction, an almost recoilless condition of the four-neutron system was achieved so as to obtain a weakly interacting four-neutron system efficiently.