Hadron

Article By:

Mann, Alfred K. Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania.

Last reviewed:June 2020

DOI:https://doi.org/10.1036/1097-8542.304500

The generic name of a class of particles which interact strongly with one another. Examples of hadrons are protons, neutrons, the π, K, and D mesons, and their antiparticles. Protons and neutrons, which are the constituents of ordinary nuclei, are members of a hadronic subclass called baryons, as are strange and charmed baryons, for example, $\text{Λ}{}^{\text{0}}{}_s$ and $\text{Λ}{}^{\text{0}}{}_c$. Baryons have half-integral spin, obey Fermi-Dirac statistics, and are known as fermions. Mesons, the other subclass of hadrons, have zero or integral spin, obey Bose-Einstein statistics, and are known as bosons. The electric charges of baryons and mesons are either zero or ±1 times the charge on the electron. Masses of the known mesons and baryons cover a wide range, extending from the pi meson, with a mass approximately one-seventh that of the proton, to values of the order of 10 times the proton mass. The spectrum of meson and baryon masses is not understood. See also: Baryon; Bose-Einstein statistics; Fermi-Dirac statistics; Meson; Neutron; Proton

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