The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. Each baryon has a corresponding antiparticle (antibaryon) where their corresponding antiquarks replace quarks. Each fermion has a corresponding antiparticle. The antineutrino discovered by Cowan and Reines is the antiparticle of the electron neutrino. C-parity is only defined for mesons that are their own antiparticle (i.e. neutral mesons). The undergoes quasi-elastic scattering with nucleons, whereas its antiparticle can create hyperons. Wheeler suggested that these backwards sections appeared as the antiparticle to the electron, the positron. According to certain theories, neutrinos may be their own antiparticle. The charge of an antiparticle equals that of the corresponding particle, but with opposite sign. Some particles, such as the photon, are their own antiparticle. One way to denote an antiparticle is by adding a bar over the particle's symbol. The lowest-energy superposition of these is the , which is its own antiparticle. This was the first interpretation and prediction of a particle and "corresponding antiparticle". The antineutron is the antiparticle of the neutron with symbol . This becomes possible because a quasiparticle in a superconductor is its own antiparticle.