Paper detail

New results on the tetraneutron, seen in context

In a recent publication an experiment is described which searched for a resonance in the four-neutron system. In a convincing way the knockout of an $α$-particle off $^8$He nuclei by protons has been measured and the missing mass of the remaining four neutrons has been calculated from the measured four-momenta of $α$-particles and protons. The missing mass spectrum shows a bump of events corresponding to excitation of the four-neutron system to the continuum. In addition, there is a peak near zero missing mass that is convincingly interpreted as a resonance with excitation energy of the four neutrons E*= 2.37(58) MeV and a width of a Breit-Wigner distribution of $Γ$=1.75(37) MeV. Unfortunately, in the Duer et al. publication no reference has been made to our paper which had appeared six months earlier, but after the submission of their manuscript to Nature. At least, the corresponding News and Views article should have mentioned our measurement, since that was presumably written after acceptance of the Duer et al. paper. Here, I try to see both results together.