In particle physics, a particle refers to a fundamental constituent of matter or a carrier of fundamental forces. These particles are the building blocks of the universe as we currently understand it and are described within the framework of the Standard Model of particle physics.
Particles in particle physics can be classified into two main categories:
Matter Particles (Fermions): Matter particles are the elementary particles that make up ordinary matter. They are further divided into two types:
a. Quarks: Quarks are fundamental particles that are never observed in isolation due to a property called color confinement. Quarks combine to form composite particles called hadrons, such as protons and neutrons. There are six known types or flavors of quarks: up, down, charm, strange, top, and bottom.
b. Leptons: Leptons are another type of matter particles that do not experience the strong nuclear force. Examples of leptons include electrons, muons, and neutrinos. There are six known flavors of leptons: electron, electron neutrino, muon, muon neutrino, tau, and tau neutrino.
Force-Carrying Particles (Gauge Bosons): Force-carrying particles, also known as gauge bosons, mediate the fundamental forces in the universe. The known fundamental forces are:
a. Photon: The photon is the gauge boson of the electromagnetic force, responsible for interactions between electrically charged particles.
b. W and Z Bosons: The W and Z bosons are responsible for mediating the weak nuclear force, which governs certain types of radioactive decays and interactions involving neutrinos.
c. Gluons: Gluons are the force-carrying particles of the strong nuclear force, also known as the color force. They bind quarks together inside hadrons.
d. Graviton (Theoretical): The graviton is a hypothetical particle that is postulated to be the gauge boson of the gravitational force. However, the graviton has not been experimentally observed yet, and the gravitational force is not fully incorporated into the Standard Model.
Additionally, the Higgs boson is an important particle in particle physics. It is associated with the Higgs field, which gives particles their mass and was discovered at the Large Hadron Collider (LHC) in 2012.
It's important to note that within the realm of particle physics, the term "particle" can also refer to excitations or quanta of fields, as particles and fields are closely interconnected through quantum field theory. This understanding arises from the principles of wave-particle duality and the framework of quantum mechanics.