The tetraneutron revisited

The present search for tetraneutrons (4n) in (3He +Te) interactions yields negative results. The formation probability (F) of a tetraneutron per 4 neutrons is determined to be smaller than 1.5 × 10−7 if the 4n half-life (t 1 2 ) is assumed to be longer than 10−9 s. If t 1 2 −9 s, quantities t 1 2 and F depend upon each other according to the relation Ft 1 2 −16 s . The upper limits for the average (3He, 4n) cross section are 28 and 19 μb at 44 and 130 MeV bombarding energies, respectively. These limits are two orders of magnitude lower than a recently reported positive value.