Antineutron discovery team; Bruce Cork, Glenn Lambertson, William Wenzel, and Oreste Piccioni. Bevatron, 1956. The antineutron is the antiparticle of the neutron. It differs from the neutron only in that some of its properties have equal magnitude but opposite sign. It has the same mass as the neutron, and no net electric charge, but has opposite baryon number (+1 for neutron, -1 for the antineutron). This is because the antineutron is composed of antiquarks, while neutrons are composed of quarks. In particular, the antineutron consists of one up antiquark and two down antiquarks. The antineutron was discovered in proton-proton collisions at the Bevatron (Lawrence Berkeley National Laboratory) by Bruce Cork in 1956, one year after the antiproton was discovered. The team's discovery of the antineutron, together with the discovery of the antiproton, confirmed Dirac's prediction of antimatter.