Elementary particles, as described by the Standard Model of particle physics, can be classified into several categories based on their properties and interactions. Here are the main classifications:
Quarks: Quarks are fundamental particles that are the building blocks of hadrons, which include protons and neutrons. There are six types, or flavors, of quarks: up (u), down (d), charm (c), strange (s), top (t), and bottom (b). Quarks have fractional electric charges and interact through the strong nuclear force.
Leptons: Leptons are another category of elementary particles that do not participate in the strong nuclear force. There are three charged leptons: electron (e), muon (μ), and tau (τ), each with an associated neutrino: electron neutrino (νe), muon neutrino (νμ), and tau neutrino (ντ). Leptons have integer electric charges and interact through the electromagnetic and weak nuclear forces.
Gauge Bosons: Gauge bosons are particles that mediate the fundamental forces in the Standard Model. They include the photon (γ), which mediates the electromagnetic force, the W and Z bosons, which mediate the weak nuclear force, and the gluons (g), which mediate the strong nuclear force. The Higgs boson (H) is also a gauge boson associated with the Higgs field, responsible for giving particles mass.
Graviton (Theoretical): The graviton is a hypothetical particle predicted in theories that attempt to reconcile general relativity with quantum mechanics. It is proposed to mediate the gravitational force but has not been detected experimentally.
These classifications represent the particles in the framework of the Standard Model. However, it's important to note that there may be additional particles beyond the Standard Model that have not yet been discovered or fully understood, such as dark matter particles or particles associated with supersymmetry or other extensions of the Standard Model. Research in particle physics continues to explore these possibilities.