Because particles and antiparticles have opposite conserved charges, Majorana fermions have zero charge. The process by which baryons came to outnumber their antiparticles is called baryogenesis. The antimatter weapon core would have to consist primarily of neutral antiparticles. "Antimatter" is matter that is composed of the antiparticles of those that constitute ordinary matter. The neutral B mesons, and , spontaneously transform into their own antiparticles and back. Particle accelerators use electric fields to propel electrons and their antiparticles to high energies. The laws of nature are very nearly symmetrical with respect to particles and antiparticles. QFT naturally incorporated antiparticles in its formalism. In this theory, the weak interaction acts only on left-handed particles (and right-handed antiparticles). Many different kinds of antiparticles are also produced by (and contained in) cosmic rays. Since neutral kaons carry strangeness, they cannot be their own antiparticles. In 2011, a study confirmed earlier speculation that the Van Allen belt could confine antiparticles.