In particle physics, antimatter is a material composed of the antiparticle "partners" to the corresponding particles of ordinary matter. A particle and its antiparticle have the same mass as one another, but opposite electric charge and other quantum numbers. For example, a proton has positive charge while an antiproton has negative charge. A collision between any particle and its antiparticle partner leads to their mutual annihilation, giving rise to various proportions of intense photons (gamma rays), neutrinos, and sometimes less-massive particle–antiparticle pairs. The consequence of annihilation is a release of energy available for heat or work, proportional to the total matter and antimatter mass, in accord with the mass–energy equivalence equation, .