Editing State of matter (section)

===Quark matter===
{{Main|QCD matter}}

In regular cold matter, [[quark]]s, fundamental particles of nuclear matter, are confined by the [[strong force]] into [[hadron]]s that consist of 2–4 quarks, such as protons and neutrons. Quark matter or quantum chromodynamical (QCD) matter is a group of phases where the strong force is overcome and quarks are deconfined and free to move. Quark matter phases occur at extremely high densities or temperatures, and there are no known ways to produce them in equilibrium in the laboratory; in ordinary conditions, any quark matter formed immediately undergoes radioactive decay.

[[Strange matter]] is a type of [[quark matter]] that is suspected to exist inside some neutron stars close to the [[Tolman–Oppenheimer–Volkoff limit]] (approximately 2–3 [[solar mass]]es), although there is no direct evidence of its existence. In strange matter, part of the energy available manifests as [[strange quark]]s, a heavier analogue of the common [[down quark]]. It may be stable at lower energy states once formed, although this is not known.

[[Quark–gluon plasma]] is a very high-temperature phase in which [[quark]]s become free and able to move independently, rather than being perpetually bound into particles, in a sea of [[gluon]]s, subatomic particles that transmit the [[strong interaction|strong force]] that binds quarks together. This is analogous to the liberation of electrons from atoms in a plasma. This state is briefly attainable in extremely high-energy heavy ion collisions in [[particle accelerator]]s, and allows scientists to observe the properties of individual quarks. Theories predicting the existence of quark–gluon plasma were developed in the late 1970s and early 1980s,<ref>{{Cite book|last=Satz|first=H.|url=https://books.google.com/books?id=OY8uAAAAIAAJ|title=Statistical Mechanics of Quarks and Hadrons: Proceedings of an International Symposium Held at the University of Bielefeld, F.R.G., August 24–31, 1980|date=1981|publisher=North-Holland|isbn=978-0-444-86227-3|language=en}}</ref> and it was detected for the first time in the laboratory at CERN in the year 2000.<ref>{{cite arXiv|last1=Heinz|first1=Ulrich|last2=Jacob|first2=Maurice|date=2000-02-16|title=Evidence for a New State of Matter: An Assessment of the Results from the CERN Lead Beam Programme|eprint=nucl-th/0002042}}</ref><ref>{{Cite news|last=Glanz|first=James|date=2000-02-10|title=Particle Physicists Getting Closer To the Bang That Started It All|language=en-US|work=The New York Times|url=https://www.nytimes.com/2000/02/10/world/particle-physicists-getting-closer-to-the-bang-that-started-it-all.html|access-date=2020-05-10|issn=0362-4331}}</ref> Unlike plasma, which flows like a gas, interactions within QGP are strong and it flows like a liquid.

At high densities but relatively low temperatures, quarks are theorized to form a quark liquid whose nature is presently unknown. It forms a distinct [[Color–flavor locking|color-flavor locked]] (CFL) phase at even higher densities. This phase is [[superconductive]] for color charge. These phases may occur in [[neutron star]]s but they are presently theoretical.