Hello, I was wondering if there is any evidence on how (free/not within nucleus) neutron/neutron interactions work. I know there is QCD which states they attract (but maybe only in a nucleus?), but that's theory - has this been experimentally proven at all ? I'm only interested in the free particle scenario as the rules within a nucleus may be entirely different when protons come into play. Same question applies for Neutron/Anti-neutron, Neutrino/Neutrino, Neutrino/Anti-Neutrino interactions. I only found theoretical predictions on these interactions (or nothing at all) and sometimes they were even contradictory. I think QCD definetly does not act on neutrinos/anti-neutrinos and I'm really having trouble believing that neutrino/anti-neutrino pairs would not attract each other even tho they annihilate upon collision. Something smells foul here I think ;) Maybe somebody could clarify this to me ? Thanks and cheers !