Particle physics is the study of the fundamental forces of nature as they are embodied in the interactions of elementary and composite particles at high energies and short time and distance scales. DO NOT USE THIS TAG for point particles in classical mechanics.
When to Use This Tag
particle-physics should be used for general discussions of high-energy particle physics. DO NOT USE THIS TAG for point particles in classical mechanics.
Relation to Nuclear Physics
Particle physics is distinct from nuclear-physics in that it generally involves energies higher than the binding energies of the nucleons, though there is a rich transition region (sometimes denoted "non-perturbative") investigated by physicists from both disciplines.
Experiment
The most visible experimental effort in particle physics in the early 2010s is the recently started large-hadron-collider (LHC) at CERN. However, the discipline is much larger than that encompassing:
- high energy collider work with the LHC, the Tevatron at Fermilab, and the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL)
- fixed target efforts at many sites
- neutrino studies based on beams, cosmic rays, solar neutrinos, reactor anti-neutrinos, and radioactive decay
- ultra-high energy cosmic ray shower telescopes
- direct dark matter detection
- proton decay monitoring at essentially every large, low background detector used for other purposes
- a wide variety of astrophysical instruments probing the cosmic microwave background, baryon acoustic resonances, active-galactic nuclei, and the large-scale structure of the universe
Experimental particle physics tends to require large, expensive equipment and many experimenters, and as such is mostly carried out by government-funded scientists at a few dozen major facilities worldwide.
Theory
The core theory of particle physics currently is the so-called standard-model which embodies the theories of the strong and electro-weak forces with six quarks coming in three colors ($u$, $d$, $c$, $s$, $t$, $b$), three charged leptons ($e$, $\mu$, $\tau$), three uncharged leptons called neutrinos, and four gauge bosons (the eight color states of the gluon mediating the strong force, the photon ($\gamma$) and weak gauge bosons ($W^{\pm}$ and $Z$) mediating the electro-weak interaction, and the assumed higgs-boson (likely first reported as observed in July 2012)).
The standard model is known to be wrong about the neutrino masses (assumed to be zero but experimentally shown to mix, implying non-zero mass).
Many candidates for beyond the standard model theories exist in several large classes with names like super-symmetry, string theories, and technicolor. Some of these can be shown to be equivalent to others under certain conditions.
