The tetraneutron revisited

Detection of neutron clusters

“…4,7. In addition, it is not kinematically consistent with the breakup of 14 Be into 10 Be+ 3,4 n, as a low energy multineutron (11)(12)(13)(14)(15)(16)(17)(18) MeV/N) should be associated with a high energy 10 Be. In the following the discussion is therefore limited to the 6 remaining events.…”

“…There have been essentially two categories of experiments that have searched for A n systems. The first consists of the production of A n in reactions such as neutron-induced fission of U [10,11] or proton and light-ion fragmentation of a heavy target [12,13]. Any recoiling A n are then, in principle, signaled by the radiochemical separation of decay products from ( A n,xn) reactions in a secondary target.…”

“…As such only upper limits for the A n production cross-section, assuming cross-sections for the ( A n,xn) reactions, could be determined. The only positive claim [12] was later explained as arising from an underestimation of the production of very energetic tritons [13].…”

“…We have subsequently considered the analysis of the energies assuming that 10 Be+ 4 n breakup took place. As the tetraneutron energy has been restricted to [11][12][13][14][15][16][17][18] MeV/N and the 14 Be beam energy is around 30 MeV/N, 10 Be fragments in coincidence with 4 n should have energies per nucleon higher than the beam. The resulting total kinetic energy ( Fig.…”

“…[9]) therefore does not exclude the possible existence of a very weakly bound 4 n. Experimentally, no limit has yet been placed on the binding energy of 4 n (or any other A n). Rather only limits on the production cross-sections could be estimated from twostep [10,11,12,13] or direct reactions [14,15,16,17,18,19,20]. In this paper, a new technique to produce and detect neutron clusters is presented.…”