It&#x27;s short enough that it doesn&#x27;t even touch the detector. The evidence is that the energy from the four neutrons all shows up at once, instead of being split among four individual neutrons. <a href="http:&#x2F;&#x2F;arstechnica.com&#x2F;science&#x2F;2016&#x2F;02&#x2F;no-protons-needed-possible-discovery-of-a-four-neutron-particle&#x2F;" rel="nofollow">http:&#x2F;&#x2F;arstechnica.com&#x2F;science&#x2F;2016&#x2F;02&#x2F;no-protons-needed-pos...</a>