Standard model of physics is the fundamental scientific theory that describes the known elementary particles of matter and the physical laws governing three of the four known fundamental forces of nature: the electromagnetic force, the weak nuclear force, and the strong nuclear force. It is one of the central achievements of modern physics and represents the current experimentally verified framework for understanding the behavior and interactions of subatomic particles. The Standard Model is based on quantum field theory and combines the principles of quantum mechanics with special relativity.
The theory organizes elementary particles into two major categories: fermions and bosons. Fermions are matter particles and are divided into quarks and leptons. Quarks combine to form larger composite particles such as protons and neutrons, while leptons include electrons, muons, tau particles, and neutrinos. These particles are considered elementary because, according to present experimental evidence, they do not appear to have internal structure. Bosons are force-carrying particles that mediate interactions between matter particles. The photon carries the electromagnetic force, gluons carry the strong nuclear force, and the W and Z bosons carry the weak nuclear force.
The Standard Model is not considered a complete theory of physics. It does not incorporate gravity as described by general relativity and therefore does not provide a quantum theory of gravitation. It also does not explain several observed features of the universe, including dark matter, dark energy, the dominance of matter over antimatter, and the full properties and masses of neutrinos.
