Editing Particle physics (section)

{{Short description|Study of subatomic particles and forces}}
{{Use Oxford spelling|date=September 2016}}
{{Use dmy dates|date=July 2020}}
{{Standard model of particle physics}}

'''Particle physics''' or '''high-energy physics''' is the study of [[Elementary particle|fundamental particles]] and [[fundamental interaction|forces]] that constitute [[matter]] and [[radiation]]. The field also studies combinations of elementary particles up to the scale of [[protons]] and [[neutrons]], while the study of combinations of protons and neutrons is called [[nuclear physics]].

The fundamental particles in the [[universe]] are classified in the [[Standard Model]] as [[fermion]]s (matter particles) and [[boson]]s (force-carrying particles). There are three [[Generation (particle physics)|generations]] of fermions, although ordinary matter is made only from the first fermion generation. The first generation consists of [[Up quark|up]] and [[down quark]]s which form [[proton]]s and [[neutron]]s, and [[electron]]s and [[electron neutrino]]s. The three fundamental interactions known to be mediated by bosons are [[electromagnetism]], the [[weak interaction]], and the [[strong interaction]].

[[Quark|Quarks]] cannot exist on their own but form [[hadron]]s. Hadrons that contain an odd number of quarks are called [[baryon]]s and those that contain an even number are called [[meson]]s. Two baryons, the [[proton]] and the [[neutron]], make up most of the mass of ordinary matter. Mesons are unstable and the longest-lived last for only a few hundredths of a [[microsecond]]. They occur after collisions between particles made of quarks, such as fast-moving protons and neutrons in [[cosmic ray]]s. Mesons are also produced in [[cyclotron]]s or other [[particle accelerator]]s.

Particles have corresponding [[antiparticle]]s with the same [[mass]] but with opposite [[electric charge]]s. For example, the antiparticle of the [[electron]] is the [[positron]]. The electron has a negative electric charge, the positron has a positive charge. These antiparticles can theoretically form a corresponding form of matter called [[antimatter]]. Some particles, such as the [[photon]], are their own antiparticle.

These [[elementary particle]]s are excitations of the [[Field (physics)#Quantum fields|quantum fields]] that also govern their interactions. The dominant theory explaining these fundamental particles and fields, along with their dynamics, is called the [[Standard Model]]. The [[Quantum gravity|reconciliation of gravity]] to the current particle physics theory is not solved; many theories have addressed this problem, such as [[loop quantum gravity]], [[string theory]] and [[Supersymmetry|supersymmetry theory]].

Experimental particle physics is the study of these particles in [[Radioactive decay|radioactive]] processes and in particle accelerators such as the [[Large Hadron Collider]]. Theoretical particle physics is the study of these particles in the context of [[cosmology]] and [[quantum mechanics|quantum theory]]. The two are closely interrelated: the [[Higgs boson]] was postulated theoretically before being confirmed by experiments.