At first this beta decay appeared to violate energy conservation, leading to the proposal of the neutrino.  
It has a mass of 940 MeV per c squared and when in a free state this particle decays in about 900 seconds.  At first this beta decay appeared to violate energy conservation, leading to the proposal of the neutrino.  Consisting of two down and one up quark, the decay products are an antineutrino, an electron, and a proton.  For ten points, name this uncharged nucleon.
It has a mass of 940 MeV per c squared and when in a free state this particle decays in about 900 seconds.  
neutron