Hadron
In particle physics, a hadron is a composite particle made of quarks held togetherby the strong force (in the same way as atoms and molecules are held together by the electromagnetic force).
Hadrons are categorized into two families:
Hadrons are categorized into two families:
- baryons, such as protons and neutrons, made of three quarks
- mesons, such as pions, made of one quark and one antiquark.
Other types of hadron may exist, such as tetraquarks (or, more generally, exotic mesons) and pentaquarks (exotic baryons), but no current evidence conclusively suggests their existence.
Of the hadrons, protons and neutrons bound to atomic nuclei are stable, while others are unstable under ordinary conditions; free neutrons decay in 15 minutes. Experimentally, hadron physics is studied by colliding protons or nuclei of heavy elements such as lead, and detecting the debris in the produced particle showers.
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