Physicists may have finally spotted elusive clusters of four neutrons
For six decades, researchers have hunted for clusters of four neutrons called tetraneutrons. But evidence for their existence has been shaky. Now, scientists say they have observed neutron clusters that appear to be tetraneutrons. The result strengthens the case that the fab four is more than a figment of physicists’ imaginations. But some scientists doubt that the claimed tetraneutrons are really what they seem.
Unlike an atomic nucleus, in which protons and neutrons are solidly bound together, the purported tetraneutrons seem to be quasi-bound, or resonant, states. That means that the clumps last only for fleeting instants — in this case, less than a billionth of a trillionth of a second, the researchers report in the June 23 Nature.
Tetraneutrons fascinate physicists because, if confirmed, the clusters would help scientists isolate and probe mysterious neutron-neutron forces and the inner workings of atomic nuclei. All atomic nuclei contain one or more protons, so scientists don’t have a complete understanding of the forces at play within groups composed only of neutrons.
Conclusively spotting the four-neutron assemblage would be a first. “Up to now, there was no real observation of … such a system that is composed only from neutrons,” says nuclear physicist Meytal Duer of the Technical University of Darmstadt in Germany.
