Hadron
A hadron is a composite particle made of two or more quarks.[1] Quarks and gluons combine to form hadrons, and the most familiar hadrons, the proton and the neutron, are the building blocks of the atomic nucleus.[2][3]
Kinds of hadron
Hadrons are divided into two groups. Baryons, such as protons and neutrons, are made of three quarks (or three antiquarks). Mesons are made of one quark and one antiquark.[4] According to CERN's glossary, atomic nuclei can also be thought of as hadrons, because they too are made of quarks at the most basic level.[5]
What holds them together
The quarks inside a hadron are held together by the strong nuclear force. The US Department of Energy explains that this force is so powerful that it is extremely difficult to separate quarks and gluons, so they stay bound inside composite particles.[6]
Hadrons in experiments
The Large Hadron Collider at CERN collides two kinds of hadron: protons, and the nuclei of lead atoms (also called lead ions).[7]
Quark–gluon plasma
According to the Department of Energy, the only way to separate quarks and gluons is to create a state of matter called quark–gluon plasma. In this plasma, the density and temperature are so high that protons and neutrons melt. Such a soup of quarks and gluons filled the whole universe until a few fractions of a second after the Big Bang.[8]
References
- ↑ "Hadron". CERN Open Data Portal glossary. CERN. Retrieved 20 October 2026.
A composite particle made of two or more quarks.
- ↑ "DOE Explains...Quarks and Gluons". US Department of Energy, Office of Science. Retrieved 20 October 2026.
the ways they combine into composite particles called hadrons
- ↑ "DOE Explains...Quarks and Gluons". US Department of Energy, Office of Science. Retrieved 20 October 2026.
Quarks and gluons are the building blocks of protons and neutrons, which in turn are the building blocks of atomic nuclei.
- ↑ "Hadron". CERN Open Data Portal glossary. CERN. Retrieved 20 October 2026.
There are two sub-categories of hadrons: "baryons", such as protons and neutrons, are made of three quarks (or three anti-quarks), while "mesons" are made of a quark and an anti-quark.
- ↑ "Hadron". CERN Open Data Portal glossary. CERN. Retrieved 20 October 2026.
Atomic nuclei can also be considered hadrons, since they are also fundamentally made of quarks.
- ↑ "DOE Explains...Quarks and Gluons". US Department of Energy, Office of Science. Retrieved 20 October 2026.
Because the strong nuclear force is so powerful, it makes it extremely difficult to separate quarks and gluons. Because of this, quarks and gluons are bound inside composite particles.
- ↑ "Hadron". CERN Open Data Portal glossary. CERN. Retrieved 20 October 2026.
The LHC collides two species of hadrons: protons and lead nuclei (also called lead ions).
- ↑ "DOE Explains...Quarks and Gluons". US Department of Energy, Office of Science. Retrieved 20 October 2026.
The only way to separate these particles is to create a state of matter known as quark-gluon plasma. In this plasma, the density and temperature are so high that protons and neutrons melt. This soup of quarks and gluons permeated the entire universe until a few fractions of a second after the Big Bang