Elementary particle

In particle physics, an elementary particle refers to a particle of which other, larger particles are composed. For example, atoms are made up of smaller particles known as electrons, protons, and neutrons. The proton and neutron, in turn, are composed of more elementary particles known as quarks. One of the outstanding problems of particle physics is to find the most elementary particles - or the so-called fundamental particles - which make up all the other particles found in Nature, and are not themselves made up of smaller particles.

The Standard Model of particle physics contains 12 species of elementary fermions ("matter particles") and 12 species of elementary bosons ("radiation particles"), plus their corresponding antiparticles. However, the Standard Model is widely considered to be a provisional theory rather than a truly fundamental one, and it is possible that some or all of its "elementary" particles are actually composite particles. There might also be other elementary particles not described by the Standard Model, the most prominent being the graviton, the hypothetical particle that carryies the gravitational force.

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