Particle Physics and High Energy Physics
- [Maryland State - Forbes]
- Overview
Particle physics or high energy physics is the study of the fundamental particles and forces that make up matter and radiation. The fundamental particles in the universe are divided into fermions (matter particles) and bosons (force-carrying particles) in the Standard Model. There are three generations of fermions, but ordinary matter consists of only the first generation of fermions. The first generation consisted of up and down quarks forming protons and neutrons, electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, weak interactions, and strong interactions.
Quarks cannot exist alone, but form hadrons. Hadrons that contain an odd number of quarks are called baryons, and those that contain an even number are called mesons. Two baryons, protons and neutrons, make up most of the mass of ordinary matter. Mesons are unstable, with the longest lifetime being 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 rays. Muons are also produced in cyclotrons or other particle accelerators.
Particles have corresponding antiparticles that have the same mass but opposite charges. For example, the antiparticle of an electron is a positron (also called an antielectron). Electrons are negatively charged and positrons are positively charged. These antiparticles could theoretically form a corresponding form of matter, called antimatter. Some particles, such as photons, are their own antiparticles.
These elementary particles are the exciters of quantum fields and also govern their interactions. The dominant theory that explains these fundamental particles and fields and their dynamics is called the Standard Model. The reconciliation of gravity with current particle physics theories is not solved; many theories have solved the problem, such as loop quantum gravity, string theory, and supersymmetry theories.
Practical particle physics is the study of radioactive processes and these particles 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 theory. The two are closely related: the Higgs boson was hypothesized by theoretical particle physicists, and its existence was confirmed by actual experiments.
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