View source for Physics:Quantum Quark–gluon plasma

{{Short description|Deconfined state of quarks and gluons in high-energy quantum chromodynamics}}
{{Quantum matter backlink|Plasma and fusion physics}}


'''Quark–gluon plasma''' ('''QGP''' or '''quark soup'''<ref>{{Cite journal |last=Heinz |first=Ulrich |date=January 20, 2015 |title=Quark–gluon soup — The perfectly liquid phase of QCD |url=[https://www.worldscientific.com/doi/abs/10.1142/S0217751X15300112](https://www.worldscientific.com/doi/abs/10.1142/S0217751X15300112) |journal=International Journal of Modern Physics A |volume=30 |issue=02 |pages=1530011 |doi=10.1142/S0217751X15300112 |issn=0217-751X}}</ref>) is a hot, dense state of [[Physics:Quantum matter/matter|matter]] in which [[Physics:Quantum quark|quarks]] and [[Physics:Quantum gluon|gluons]] are no longer confined inside [[Physics:Quantum hadron|hadrons]]. In ordinary nuclear matter, quarks are bound inside protons and neutrons by [[Physics:Quantum chromodynamics|quantum chromodynamics]] (QCD); in quark–gluon plasma they are [[Physics:Quantum deconfinement|deconfined]] and move collectively in a strongly interacting medium.

Quark–gluon plasma occurs at [[Energy density|energy densities]] high enough to melt the [[Physics:Quantum proton|protons]] and [[Physics:Quantum neutron|neutrons]] that make up atomic nuclei. It is a very low-[[viscosity]] liquid composed of elementary quarks and gluons, a state of matter new to physics when it was discovered.<ref name="Rafelski-2015" /><ref>{{Cite journal |last1=Braun-Munzinger |first1=Peter |last2=Stachel |first2=Johanna |date=July 2007 |title=The quest for the quark–gluon plasma |url=[https://www.nature.com/articles/nature06080](https://www.nature.com/articles/nature06080) |journal=Nature |language=en |volume=448 |issue=7151 |pages=302–309 |doi=10.1038/nature06080 |pmid=17637661 |issn=0028-0836|url-access=subscription }}</ref>

Quark–gluon plasma is studied to understand the characteristics of the Universe at about 20 μs after the [[Big Bang]]. Experimental groups use [[ultrarelativistic]] beams of ions colliding with other ions or protons to create this plasma in [[particle accelerator]]s.<ref>{{Cite journal |last1=Busza |first1=Wit |last2=Rajagopal |first2=Krishna |last3=Schee |first3=Wilke van der |date=October 19, 2018 |title=Heavy Ion Collisions: The Big Picture and the Big Questions |url=[https://www.annualreviews.org/content/journals/10.1146/annurev-nucl-101917-020852](https://www.annualreviews.org/content/journals/10.1146/annurev-nucl-101917-020852) |journal=Annual Review of Nuclear and Particle Science |language=en |volume=68 |pages=339–376 |doi=10.1146/annurev-nucl-101917-020852 |arxiv=1802.04801 |issn=0163-8998}}</ref>
[[File:Quark-Gluon.png|400px|right]]

[[File:PhasDiagQGP.png|thumb|QCD phase diagram. Adapted from original made by R. S. Bhalerao.<ref>{{cite encyclopedia |last=Bhalerao |first=Rajeev S. |editor-last1=Mulders|editor-first1=M. |editor-last2=Kawagoe |editor-first2=K.|encyclopedia=1st Asia-Europe-Pacific School of High-Energy Physics |title=Relativistic heavy-ion collisions|year=2014 |publisher=CERN |series=CERN Yellow Reports: School Proceedings |volume=CERN-2014-001; KEK-Proceedings-2013–8 |location=Geneva|isbn=978-92-9083-399-4 |oclc=801745660 |doi=10.5170/CERN-2014-001 |pages=219–239|s2cid=119256218 }}</ref>]]

== History ==
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](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> The discovery of [[Physics:Quantum confinement|color confinement]] and [[Physics:Quantum asymptotic freedom|asymptotic freedom]] in QCD led to the realization that quark matter would undergo a phase transition at high temperature or density.<ref name="Gross-2023"/> Using an analogy with electromagnetic plasma, E. V. Shuryak used the term "hadronic plasma" in 1978 for matter much denser than atomic nuclei, in which hadrons merge and quarks act collectively.<ref>Shuryak, E V. "Theory of hadron plasma." Sov. Phys. - JETP (Engl. Transl.); (United States), vol. 47:2, Jan. 1978.</ref> In his next paper he used "quark-gluon plasma", the name that became standard.<ref name="Gross-2023">{{Cite journal |last1=Gross |first1=Franz |last2=Klempt |first2=Eberhard |last3=Brodsky |first3=Stanley J. |last4=Buras |first4=Andrzej J. |last5=Burkert |first5=Volker D. |last6=Heinrich |first6=Gudrun |last7=Jakobs |first7=Karl |last8=Meyer |first8=Curtis A. |last9=Orginos |first9=Kostas |last10=Strickland |first10=Michael |last11=Stachel |first11=Johanna |last12=Zanderighi |first12=Giulia |last13=Brambilla |first13=Nora |last14=Braun-Munzinger |first14=Peter |last15=Britzger |first15=Daniel |date=December 12, 2023 |title=50 Years of quantum chromodynamics |journal=The European Physical Journal C |language=en |volume=83 |issue=12 |page=1125 |doi=10.1140/epjc/s10052-023-11949-2 |doi-access=free|issn=1434-6052}}</ref>{{rp|1125}}<ref>{{Cite journal |last=Shuryak |first=E. V. |date=September 11, 1978 |title=Quark-gluon plasma and hadronic production of leptons, photons and psions |journal=Physics Letters B |volume=78 |issue=1 |pages=150–153 |doi=10.1016/0370-2693(78)90370-2 |issn=0370-2693}}</ref>

In 2000, [[CERN]] issued a press release<ref>{{Cite web|url=[https://home.cern/news/press-release/cern/new-state-matter-created-cern|title=New](https://home.cern/news/press-release/cern/new-state-matter-created-cern|title=New) State of Matter created at CERN|date=10 February 2000|website=CERN|language=en|access-date=2020-03-25}}</ref> reporting evidence for a new state of matter based on Pb-Pb heavy-ion collision studies.<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}}](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> The evidence was consistent with many characteristics of the theoretically predicted quark-gluon plasma.<ref name="Rafelski-2015">{{Cite journal|last=Rafelski|first=Johann|year=2015|title=Melting hadrons, boiling quarks|journal=The European Physical Journal A|language=en|volume=51|issue=9|article-number=114|doi=10.1140/epja/i2015-15114-0|arxiv=1508.03260|s2cid=119191818|issn=1434-6001}}</ref>

A competing team at the [[Relativistic Heavy Ion Collider]] (RHIC) characterized the CERN results as circumstantial<ref>{{Citation |last1=Collaboration |first1=STAR |title=Experimental and theoretical challenges in the search for the quark–gluon plasma: The STAR Collaboration's critical assessment of the evidence from RHIC collisions |date=2005-04-26 |last2=Adams |first2=J. |journal=Nuclear Physics A |volume=757 |issue=1–2 |pages=102–183 |doi=10.1016/j.nuclphysa.2005.03.085 |arxiv=nucl-ex/0501009 }}</ref> and suggested that the experiments yielded little information about the properties of the new state.<ref>{{Cite journal |last=Stachel |first=Johanna |date=April 10, 2006 |title=Has the quark-gluon plasma been seen? |url=[https://www.worldscientific.com/doi/abs/10.1142/S0217751X06032733](https://www.worldscientific.com/doi/abs/10.1142/S0217751X06032733) |journal=International Journal of Modern Physics A |volume=21 |issue=08n09 |pages=1750–1763 |doi=10.1142/S0217751X06032733 |issn=0217-751X}}</ref> A series of Au-Au collision studies from RHIC published in 2005 showed that the collisions produce something more like a liquid than the weakly interacting gas expected in early theoretical models.<ref>{{Cite web |title=RHIC Scientists Serve Up 'Perfect' Liquid |url=[https://www.bnl.gov/newsroom/news.php?a=110303](https://www.bnl.gov/newsroom/news.php?a=110303) |access-date=2025-11-18 |website=Brookhaven National Laboratory |language=en}}</ref>

== Role in the Standard Model ==
QCD is one part of the modern theory of [[particle physics]] called the [[Standard Model]]. Other parts of this theory describe [[electroweak interaction]]s and [[neutrino]]s. The theory of electrodynamics has been tested and found correct to a few parts in a billion. The theory of weak interactions has been tested and found correct to a few parts in a thousand. Perturbative forms of QCD have been tested to a few percent.<ref>{{Cite journal|last1=Tanabashi|first1=M.|last2=Hagiwara|first2=K.|last3=Hikasa|first3=K.|last4=Nakamura|first4=K.|last5=Sumino|first5=Y.|last6=Takahashi|first6=F.|last7=Tanaka|first7=J.|last8=Agashe|first8=K.|last9=Aielli|first9=G.|last10=Amsler|first10=C.|last11=Antonelli|first11=M.|year=2018|title=Review of Particle Physics|url=[https://pdg.lbl.gov/2019/reviews/rpp2019-rev-qcd.pdf|journal=Physical](https://pdg.lbl.gov/2019/reviews/rpp2019-rev-qcd.pdf|journal=Physical) Review D|language=en|volume=98|issue=3|pages=1–708|doi=10.1103/PhysRevD.98.030001|pmid=10020536|hdl=11384/78286 |issn=2470-0010}}</ref> Perturbative models assume relatively small changes from the ground state, simplifying calculations at the cost of generality. In contrast, non-perturbative QCD is much harder to test directly. The study of QGP, which has both high temperature and high density, is part of the effort to understand QCD beyond perturbation theory.

The study of QGP is also a testing ground for [[Thermal quantum field theory|finite-temperature field theory]], a branch of theoretical physics that studies particle physics under high-temperature conditions. Such studies are important for understanding the early evolution of the Universe, especially the first hundred microseconds after the Big Bang. They are also relevant to [[grand unification theory|grand unification theories]], which seek to unify the fundamental forces of nature except gravity.

=== Occurrence ===
The generally accepted model of the formation of the Universe states that it happened as the result of the Big Bang. In this model, in the time interval of 10<sup>−10</sup>–10<sup>−6</sup> s after the Big Bang, matter existed in the form of a quark–gluon plasma. It is possible to reproduce the density and temperature of matter from that early time in laboratory conditions. The main method is the collision of two heavy atomic nuclei accelerated to energies of more than a hundred GeV. A head-on collision creates a small fireball with a volume approximately equal to that of an atomic nucleus, allowing physicists to model the density and temperature of the early Universe.

=== Relation to electromagnetic plasma ===
A [[Physics:Quantum matter/plasma|plasma]] is matter in which charges are screened by the presence of other mobile charges. For example, Coulomb's law can be modified by screening to yield a distance-dependent charge, <math>Q \rightarrow Q e^{-r/\alpha}</math>, where the charge is reduced exponentially with distance divided by a screening length α. In QGP, the color charge of quarks and gluons is screened. QGP has analogies with an ordinary plasma, but also important differences: color charge is non-abelian, whereas electric charge is abelian. Outside a finite volume of QGP the color-electric field is not screened, so a volume of QGP must still be color-neutral and have integer electric charge.

Because of the extremely high energies involved, quark-antiquark pairs are produced by pair production. A QGP is therefore a roughly equal mixture of quarks and antiquarks of various flavors, with only a slight excess of quarks. This is not a general feature of conventional plasmas, which are often too cool for pair production.

=== Theory ===
One consequence of the non-abelian color charge is that the interaction is too strong for perturbative computations in many QGP conditions. The main theoretical tools for exploring QGP include [[lattice gauge theory]].<ref>{{Cite journal|last=Karsch|first=F.|year=1995|title=The phase transition to the quark gluon plasma: Recent results from lattice calculations|journal=Nuclear Physics A|language=en|volume=590|issue=1–2|pages=367–381|doi=10.1016/0375-9474(95)00248-Y|arxiv=hep-lat/9503010|s2cid=118967199}}</ref><ref>{{Cite journal |title=The Quark–Gluon Plasma |journal=Nuclear Physics A |volume=862–863 |issue=12 |pages=4–12 |doi=10.1016/j.nuclphysa.2011.05.014|year=2011 |arxiv=1101.3937 |last1=Satz |first1=Helmut |bibcode=2011NuPhA.862....4S |s2cid=118369368 }}</ref> The transition temperature, approximately {{val|175|ul=MeV}} in older estimates, was first predicted by lattice gauge theory. Since then, lattice gauge theory has been used to predict many other properties of this kind of matter. The [[AdS/CFT correspondence]] may also provide insights into QGP, and the fluid/gravity correspondence has been used as a theoretical framework for understanding strongly coupled fluids. QGP is believed to be a phase of QCD that can become locally thermalized and therefore suitable for an effective fluid-dynamic description.

=== Production ===
Production of QGP in the laboratory is achieved by colliding heavy atomic nuclei, or heavy ions, at relativistic energy. Matter is heated well above the Hagedorn temperature ''T''<sub>H</sub> = 150 MeV per particle, corresponding to a temperature exceeding 1.66 trillion K. Lead and gold nuclei have been used in such collisions at the CERN [[Super Proton Synchrotron]] and at the Brookhaven [[Relativistic Heavy Ion Collider]], respectively. The nuclei are accelerated to ultrarelativistic speeds, directed toward each other, and create a hot fireball in the rare event of a collision. Hydrodynamic simulations predict that this fireball expands under its own pressure and cools while expanding. Measurements of spherical and elliptic flow test these models.

=== Diagnostic tools ===
Quark–gluon plasma is produced in relativistic heavy-ion collisions.<ref>{{Cite journal|last1=Busza|first1=Wit|last2=Rajagopal|first2=Krishna|last3=van der Schee|first3=Wilke|year=2018|title=Heavy ion collisions: The big picture and the big questions|journal=[[Annual Review of Nuclear and Particle Science]]|language=en|volume=68|issue=1|pages=339–376|doi=10.1146/annurev-nucl-101917-020852|doi-access=free|arxiv=1802.04801|s2cid=119264938|issn=0163-8998}}</ref><ref name="ALICE Collaboration-2017">{{Cite journal|last=ALICE Collaboration|year=2017|title=Enhanced production of multi-strange hadrons in high-multiplicity proton–proton collisions|url=[http://www.nature.com/articles/nphys4111|journal=Nature](http://www.nature.com/articles/nphys4111|journal=Nature) Physics|language=en|volume=13|issue=6|pages=535–539|doi=10.1038/nphys4111|arxiv=1606.07424|s2cid=221304738 |issn=1745-2473}}</ref><ref>{{Cite journal|last1=Koch|first1=Peter|last2=Müller|first2=Berndt|last3=Rafelski|first3=Johann|year=2017|title=From strangeness enhancement to quark–gluon plasma discovery|journal=International Journal of Modern Physics A|language=en|volume=32|issue=31|pages=1730024–272|doi=10.1142/S0217751X17300241|arxiv=1708.08115|s2cid=119421190|issn=0217-751X}}</ref><ref name="The WA97 Collaboration-2000">{{Cite journal|last=The WA97 Collaboration|year=2000|title=Transverse mass spectra of strange and multi–strange particles in Pb–Pb collisions at 158 A GeV/c|journal=The European Physical Journal C|language=en|volume=14|issue=4|pages=633–641|doi=10.1007/s100520000386|s2cid=195312472|issn=1434-6044|url=[https://cds.cern.ch/record/429846}}](https://cds.cern.ch/record/429846}})</ref>

Important classes of experimental observations include:

* Thermal [[photon]]s and thermal [[dilepton]]s
* [[Strangeness production]]
* [[Elliptic flow]]
* [[Jet quenching]]
* [[J/ψ#J/ψ melting|J/ψ melting]]
* [[Hanbury Brown and Twiss effect]] and [[Bose–Einstein correlations]]
* [[single particle spectrum|Single-particle spectra]]

== Expected properties ==

=== Thermodynamics ===
The cross-over temperature from the normal hadronic phase to the QGP phase is about {{val|156|u=MeV}}.<ref>A. Bazavov, H.-T. Ding, P. Hegde, O. Kaczmarek, F. Karsch, N. Karthik, E. Laermann, Anirban Lahiri, R. Larsen, S.-T. Li, Swagato Mukherjee, H. Ohno, P. Petreczky, H. Sandmeyer, C. Schmidt, S. Sharma, P. Steinbrecher, Chiral crossover in QCD at zero and non-zero chemical potentials, Physics Letters B, Volume 795, 2019, Pages 15–21, ISSN 0370-2693, [https://doi.org/10.1016/j.physletb.2019.05.013](https://doi.org/10.1016/j.physletb.2019.05.013).</ref> The phenomena involved correspond to an energy density of a little less than {{val|1|u=[[Electronvolt|GeV]]/fm<sup>3</sup>}}. For relativistic matter, pressure and temperature are not independent variables, so the equation of state is a relation between energy density and pressure. This has been found through lattice computations and compared with perturbation theory and string-theory-inspired models. Response functions such as the specific heat and quark-number susceptibilities are active topics of calculation.

=== Flow ===
The discovery of QGP as an almost perfect liquid was a turning point in high-energy nuclear physics. Experiments at RHIC revealed a substance with extremely low resistance to flow.<ref>{{Cite web|url=[https://www.bnl.gov/newsroom/news.php?a=25756|title=Celebrating](https://www.bnl.gov/newsroom/news.php?a=25756|title=Celebrating) a Decade of Brewing Perfection|date=26 June 2015|website=Brookhaven National Laboratory|url-status=live|archive-url=[https://web.archive.org/web/20170628150247/https://www.bnl.gov/newsroom/news.php?a=25756|archive-date=28](https://web.archive.org/web/20170628150247/https://www.bnl.gov/newsroom/news.php?a=25756|archive-date=28) June 2017|access-date=2020-04-15|quote=Berndt Müller, Brookhaven Lab's Associate Laboratory Director for Nuclear and Particle Physics.}}</ref> Nuclear matter at low temperature is known to behave like a superfluid. When heated, the nuclear fluid evaporates into a dilute gas of nucleons and, on further heating, a gas of baryons and mesons. At the critical temperature, hadrons melt and the gas turns back into a liquid. RHIC experiments showed that this liquid has less resistance to flow than any other substance observed in laboratory experiments at any scale. Detailed measurements indicate that it is a quark–gluon plasma in which quarks, antiquarks and gluons flow collectively.<ref>Letter from Berndt Müller to Johann Rafelski, reproduced in "Discovery of Quark–Gluon Plasma: Strangeness Diaries". The European Physical Journal Special Topics. 229 (1): pp.40–41 [[doi:10.1140/epjst/e2019-900263-x]]. ISSN 1951-6401.</ref>

[[File:Schematic representation of the interaction region formed.png|thumb|upright=1.5|Schematic representation of the interaction region formed in the first moments after the collision of high-energy heavy ions.<ref name="Ollitrault-1992" />]]

In short, QGP flows like a splat of liquid and, because it is not transparent to quarks, it can attenuate jets emitted in collisions. Once formed, a ball of QGP transfers heat internally by radiation. However, unlike ordinary hot objects, there is enough energy available for gluons to collide and produce an excess of strange quarks. If QGP did not exist and the collision produced only a non-equilibrium mixture, the same energy would instead create different distributions of heavier quarks such as charm or bottom quarks.<ref name="Ollitrault-1992">{{Cite journal|last=Ollitrault|first=Jean-Yves|year=1992|title=Anisotropy as a signature of transverse collective flow|journal=Physical Review D|language=en|volume=46|issue=1|pages=229–245|doi=10.1103/PhysRevD.46.229|pmid=10014754|issn=0556-2821}}</ref><ref>{{Cite journal|last1=Borghini|first1=Nicolas|last2=Dinh|first2=Phuong Mai|last3=Ollitrault|first3=Jean-Yves|year=2001|title=Flow analysis from multiparticle azimuthal correlations|journal=Physical Review C|language=en|volume=64|issue=5|article-number=054901|doi=10.1103/PhysRevC.64.054901|arxiv=nucl-th/0105040|s2cid=119069389|issn=0556-2813}}</ref>

The equation of state is an important input into flow equations. The speed of sound, meaning the speed of QGP-density oscillations, is studied in lattice computations.<ref>{{Cite journal|last1=Borsányi|first1=Szabolcs|last2=Endrődi|first2=Gergely|last3=Fodor|first3=Zoltán|last4=Jakovác|first4=Antal|last5=Katz|first5=Sándor D.|last6=Krieg|first6=Stefan|last7=Ratti|first7=Claudia|last8=Szabó|first8=Kálmán K.|year=2010|title=The QCD equation of state with dynamical quarks|journal=Journal of High Energy Physics|language=en|volume=2010|issue=11|page=77|doi=10.1007/JHEP11(2010)077|arxiv=1007.2580|s2cid=55793321|issn=1029-8479}}</ref><ref>{{Cite journal|last1=Bazavov|first1=A.|last2=Bhattacharya|first2=Tanmoy|last3=DeTar|first3=C.|last4=Ding|first4=H.-T.|last5=Gottlieb|first5=Steven|last6=Gupta|first6=Rajan|last7=Hegde|first7=P.|last8=Heller|first8=U. M.|last9=Karsch|first9=F.|last10=Laermann|first10=E.|last11=Levkova|first11=L.|year=2014|title=Equation of state in ( 2 + 1 )-flavor QCD|journal=Physical Review D|language=en|volume=90|issue=9|article-number=094503|doi=10.1103/PhysRevD.90.094503|arxiv=1407.6387|s2cid=116984453|issn=1550-7998}}</ref><ref>{{Cite journal|last1=Borsanyi|first1=S.|last2=Fodor|first2=Z.|last3=Guenther|first3=J.|last4=Kampert|first4=K.-H.|last5=Katz|first5=S. D.|last6=Kawanai|first6=T.|last7=Kovacs|first7=T. G.|last8=Mages|first8=S. W.|last9=Pasztor|first9=A.|last10=Pittler|first10=F.|last11=Redondo|first11=J.|year=2016|title=Calculation of the axion mass based on high-temperature lattice quantum chromodynamics|url=[https://www.nature.com/articles/nature20115|journal=Nature|language=en|volume=539|issue=7627|pages=69–71|doi=10.1038/nature20115|pmid=27808190|s2cid=2943966|issn=0028-0836}}](https://www.nature.com/articles/nature20115|journal=Nature|language=en|volume=539|issue=7627|pages=69–71|doi=10.1038/nature20115|pmid=27808190|s2cid=2943966|issn=0028-0836}})</ref> The mean free path of quarks and gluons has been computed using perturbation theory as well as string-theory methods. Lattice computations of transport coefficients indicate that the mean free time of quarks and gluons in QGP may be comparable to the average interparticle spacing, supporting the interpretation of QGP as a liquid.<ref>{{Cite journal|last1=Hirano|first1=Tetsufumi|last2=Gyulassy|first2=Miklos|year=2006|title=Perfect fluidity of the quark–gluon plasma core as seen through its dissipative hadronic corona|journal=Nuclear Physics A|language=en|volume=769|pages=71–94|doi=10.1016/j.nuclphysa.2006.02.005|arxiv=nucl-th/0506049|s2cid=13047563}}</ref><ref>{{Cite journal|last1=Kharzeev|first1=Dmitri|last2=Tuchin|first2=Kirill|year=2008|title=Bulk viscosity of QCD matter near the critical temperature|url=[http://stacks.iop.org/1126-6708/2008/i=09/a=093?key=crossref.d27fef0b80f0d0c8edb66dee6bba9889|journal=Journal](http://stacks.iop.org/1126-6708/2008/i=09/a=093?key=crossref.d27fef0b80f0d0c8edb66dee6bba9889|journal=Journal) of High Energy Physics|volume=2008|issue=9|page=093|doi=10.1088/1126-6708/2008/09/093|arxiv=0705.4280|s2cid=20224239|issn=1029-8479}}</ref> The incorporation of dissipative phenomena into hydrodynamics is another active research area.<ref>{{Cite journal|last1=Blaizot|first1=J. P.|last2=Ollitrault|first2=J. Y.|year=1987|title=Structure of hydrodynamic flows in expanding quark–gluon plasmas|journal=Physical Review D|language=en|volume=36|issue=3|pages=916–927|doi=10.1103/PhysRevD.36.916|pmid=9958246|issn=0556-2821}}</ref><ref>{{Cite journal|last1=Gardim|first1=Fernando G.|last2=Grassi|first2=Frédérique|last3=Luzum|first3=Matthew|last4=Ollitrault|first4=Jean-Yves|year=2012|title=Mapping the hydrodynamic response to the initial geometry in heavy-ion collisions|journal=Physical Review C|language=en|volume=85|issue=2|article-number=024908|doi=10.1103/PhysRevC.85.024908|arxiv=1111.6538|s2cid=119187493|issn=0556-2813}}</ref><ref>{{Cite journal|last1=Gale|first1=Charles|last2=Jeon|first2=Sangyong|last3=Schenke|first3=Björn|year=2013|title=Hydrodynamic modeling of heavy-ion collisions|journal=International Journal of Modern Physics A|language=en|volume=28|issue=11|page=1340011|doi=10.1142/S0217751X13400113|arxiv=1301.5893|s2cid=118414603|issn=0217-751X}}</ref>

=== Jet quenching effect ===
Detailed predictions for the production of jets were made in the late 1970s for the CERN [[Super Proton–Antiproton Synchrotron]].<ref>{{Cite journal|last1=Jacob|first1=M.|last2=Landshoff|first2=P.V.|year=1978|title=Large transverse momentum and jet studies|journal=Physics Reports|language=en|volume=48|issue=4|pages=285–350|doi=10.1016/0370-1573(78)90177-1|url=[https://cds.cern.ch/record/262302}}](https://cds.cern.ch/record/262302}})</ref><ref>{{Cite journal|last=Jacob|first=M|year=1979|title=Jets in high energy collisions|journal=Physica Scripta|volume=19|issue=2|pages=69–78|doi=10.1088/0031-8949/19/2/001|s2cid=250809871|issn=0031-8949}}</ref><ref>{{Cite journal|last1=Horgan|first1=R.|last2=Jacob|first2=M.|year=1981|title=Jet production at collider energy|journal=Nuclear Physics B|language=en|volume=179|issue=3|pages=441–460|doi=10.1016/0550-3213(81)90013-4|url=[https://cds.cern.ch/record/134265}}](https://cds.cern.ch/record/134265}})</ref><ref>{{Cite journal|last1=Jacob|first1=M.|last2=Landshoff|first2=P.V.|year=1986|title=Minijets: origin and usefulness|journal=Modern Physics Letters A|language=en|volume=01|issue=12|pages=657–663|doi=10.1142/S021773238600083X|issn=0217-7323|url=[https://cds.cern.ch/record/172538|url-access=subscription}}](https://cds.cern.ch/record/172538|url-access=subscription}})</ref> The UA2 experiment observed the first evidence for jet production in hadron collisions in 1981,<ref>{{Cite journal|last1=Banner|first1=M.|last2=Bloch|first2=Ph.|last3=Bonaudi|first3=F.|last4=Borer|first4=K.|last5=Borghini|first5=M.|last6=Chollet|first6=J.-C.|last7=Clark|first7=A.G.|last8=Conta|first8=C.|last9=Darriulat|first9=P.|last10=Di Lella|first10=L.|last11=Dines-Hansen|first11=J.|year=1982|title=Observation of very large transverse momentum jets at the CERN p collider|journal=Physics Letters B|language=en|volume=118|issue=1–3|pages=203–210|doi=10.1016/0370-2693(82)90629-3|url=[https://cds.cern.ch/record/904153}}](https://cds.cern.ch/record/904153}})</ref> shortly after confirmed by UA1.<ref>{{Cite journal|last1=Arnison|first1=G.|last2=Astbury|first2=A.|last3=Aubert|first3=B.|last4=Bacci|first4=C.|last5=Bernabei|first5=R.|last6=Bézaguet|first6=A.|last7=Böck|first7=R. |last8=Bowcock|first8=T.J.V.|last9=Calvetti|first9=M.|last10=Carroll|first10=T.|last11=Catz|first11=P.|year=1983|title=Observation of jets in high transverse energy events at the CERN proton antiproton collider|journal=Physics Letters B|language=en|volume=123|issue=1–2|pages=115–122|doi=10.1016/0370-2693(83)90970-X|url=[https://cds.cern.ch/record/141936}}](https://cds.cern.ch/record/141936}})</ref>

The subject was later revived at RHIC. One of the most striking physical effects observed at RHIC energies is jet quenching.<ref>{{Cite journal|last1=Adcox|first1=K.|last2=Adler|first2=S.S.|last3=Afanasiev|first3=S.|last4=Aidala|first4=C.|last5=Ajitanand|first5=N.N.|last6=Akiba|first6=Y.|last7=Al-Jamel|first7=A.|last8=Alexander|first8=J.|last9=Amirikas|first9=R.|last10=Aoki|first10=K.|last11=Aphecetche|first11=L.|year=2005|title=Formation of dense partonic matter in relativistic nucleus–nucleus collisions at RHIC: Experimental evaluation by the PHENIX Collaboration|journal=Nuclear Physics A|language=en|volume=757|issue=1–2|pages=184–283|doi=10.1016/j.nuclphysa.2005.03.086|arxiv=nucl-ex/0410003|s2cid=119511423}}</ref><ref>{{Cite journal|last1=Adams|first1=J.|last2=Aggarwal|first2=M.M.|last3=Ahammed|first3=Z.|last4=Amonett|first4=J.|last5=Anderson|first5=B.D.|last6=Arkhipkin|first6=D.|last7=Averichev|first7=G.S. |last8=Badyal|first8=S.K.|last9=Bai|first9=Y.|last10=Balewski|first10=J.|last11=Barannikova|first11=O.|year=2005|title=Experimental and theoretical challenges in the search for the quark–gluon plasma: The STAR Collaboration's critical assessment of the evidence from RHIC collisions|journal=Nuclear Physics A|language=en|volume=757|issue=1–2|pages=102–183|doi=10.1016/j.nuclphysa.2005.03.085|arxiv=nucl-ex/0501009|s2cid=119062864}}</ref><ref>{{Cite journal|last1=Back|first1=B.B.|last2=Baker|first2=M.D.|last3=Ballintijn|first3=M.|last4=Barton|first4=D.S.|last5=Becker|first5=B.|last6=Betts|first6=R.R.|last7=Bickley|first7=A.A. |last8=Bindel|first8=R.|last9=Budzanowski|first9=A.|last10=Busza|first10=W.|last11=Carroll|first11=A.|year=2005|title=The PHOBOS perspective on discoveries at RHIC|journal=Nuclear Physics A|language=en|volume=757|issue=1–2|pages=28–101|doi=10.1016/j.nuclphysa.2005.03.084|arxiv=nucl-ex/0410022}}</ref> At the first stage of interaction between colliding relativistic nuclei, partons of the colliding nuclei give rise to secondary partons with large transverse momentum. Passing through hot, compressed plasma, these partons lose energy. The magnitude of energy loss depends on QGP properties such as temperature and density. Colored quarks and gluons are the elementary objects of the plasma, so parton energy loss in QGP differs from energy loss in a medium made of colorless hadrons. Under RHIC conditions, parton energy losses are estimated as {{tmath|\frac{dE}{dx} {{=}} 1~\text{GeV/fm} }}. This conclusion is supported by comparing high-transverse-momentum hadron yields in nucleon-nucleon and nucleus-nucleus collisions at the same energy. The reduced yield in nucleus-nucleus collisions suggests that nuclear collisions cannot be regarded as a simple superposition of nucleon-nucleon collisions. For a short time and small volume, quarks and gluons form an almost ideal liquid whose collective properties affect the motion and energy loss of partons.<ref>{{Cite book|last=Schukraft|first=Jürgen|url=[https://indico.cern.ch/event/114939/contributions/62599/attachments/48842/70225/CERN_HI_Dec_2010.pdf|title=ALICE—'Little](https://indico.cern.ch/event/114939/contributions/62599/attachments/48842/70225/CERN_HI_Dec_2010.pdf|title=ALICE—'Little) Bang': The first 3 weeks ...|year=2010}}</ref>

In November 2010, CERN announced the first direct observation of jet quenching based on heavy-ion collisions.<ref>{{cite press release |title=LHC experiments bring new insight into primordial universe |url=[https://press.web.cern.ch/press-releases/2010/11/lhc-experiments-bring-new-insight-primordial-universe|publisher=[[CERN](https://press.web.cern.ch/press-releases/2010/11/lhc-experiments-bring-new-insight-primordial-universe|publisher=[[CERN)]] |date=November 26, 2010 |access-date=December 2, 2010}}</ref><ref>{{cite journal |last=Aad |first=G. |display-authors=etal |collaboration=ATLAS Collaboration |title=Observation of a Centrality-Dependent Dijet Asymmetry in Lead-Lead Collisions at {{sqrt|s<sub>NN</sub>}} = 2.76 TeV with the ATLAS Detector at the LHC |journal=Physical Review Letters |volume=105 |issue=25 |date=13 December 2010 |doi=10.1103/physrevlett.105.252303 |doi-access=free |article-number=252303 |pmid=21231581 |arxiv=1011.6182 |bibcode=2010PhRvL.105y2303A }}</ref><ref>{{cite journal |last=Chatrchyan |first=S. |display-authors=etal |collaboration=CMS Collaboration |title=Observation and studies of jet quenching in Pb-Pb collisions at {{sqrt|s<sub>NN</sub>}} = 2.76 TeV |journal=Physical Review C |volume=84 |issue=2 |date=12 August 2011 |doi=10.1103/physrevc.84.024906 |doi-access=free |article-number=024906 |arxiv=1102.1957 |bibcode=2011PhRvC..84b4906C }}</ref><ref>{{cite web|url=[http://home.web.cern.ch/about/physics/heavy-ions-and-quark-gluon-plasma|archive-url=https://web.archive.org/web/20121203180310/http://home.web.cern.ch/about/physics/heavy-ions-and-quark-gluon-plasma|url-status=live|archive-date=December](http://home.web.cern.ch/about/physics/heavy-ions-and-quark-gluon-plasma|archive-url=https://web.archive.org/web/20121203180310/http://home.web.cern.ch/about/physics/heavy-ions-and-quark-gluon-plasma|url-status=live|archive-date=December) 3, 2012|title=Heavy ions and quark–gluon plasma|author=CERN|date=18 July 2012}}</ref>

=== Direct photons and dileptons ===
Thermal photons and dileptons are important electromagnetic probes of the QGP formed in relativistic heavy-ion collisions. Unlike hadrons, which predominantly reflect the final stages of the collision, electromagnetic probes are emitted throughout the space–time evolution of the fireball, from the early deconfined phase through the hadronic stage up to kinetic freeze-out, when strong interactions cease. Because photons and leptons interact only electromagnetically, their mean free path is much larger than the size of the collision volume. They can therefore escape the medium with minimal final-state interactions and provide direct information about the temperature and dynamics of the matter created in the collision. Dilepton invariant mass helps separate partonic and hadronic effects, making it useful for studying the average temperature of the plasma and its equilibration time.<ref>{{Cite journal |last=Bailhache |first=R. |last2=Appelshäuser |first2=H. |date=September 22, 2025 |title=Dileptons at Colliders as Probes of the Quark–Gluon Plasma |url=[https://www.annualreviews.org/content/journals/10.1146/annurev-nucl-121423-100858](https://www.annualreviews.org/content/journals/10.1146/annurev-nucl-121423-100858) |journal=Annual Review of Nuclear and Particle Science |language=en |volume=75 |pages=463–486 |doi=10.1146/annurev-nucl-121423-100858 |issn=0163-8998}}</ref>

=== Glasma hypothesis ===
Since 2008, physicists have discussed a hypothetical precursor state of QGP called the [[color glass condensate|glasma]], in which dressed particles are condensed into a glassy or amorphous state below the genuine transition between the confined state and the plasma liquid.<ref>{{Cite journal |title=From Glasma to Quark Gluon Plasma in heavy ion collisions |year=2008 |arxiv=0806.1356 |bibcode=2008JPhG...35j4003V |doi=10.1088/0954-3899/35/10/104003 |volume=35 |issue=10 |journal=Journal of Physics G: Nuclear and Particle Physics |article-number=104003|last1=Venugopalan |first1=Raju |s2cid=15121756 }}</ref> This would be analogous to the formation of metallic glasses, or amorphous alloys, below the onset of the liquid metallic state.

Although the high temperatures and densities predicted to produce QGP have been realized in the laboratory, the resulting matter does not behave as a quasi-ideal state of free quarks and gluons. Instead, it behaves as an almost perfect dense fluid.<ref name="Zajc">{{Cite journal|first=WA|last=Zajc|year=2008|title=The fluid nature of quark–gluon plasma|journal=Nuclear Physics A|volume=805|issue=1–4|pages=283c–294c|arxiv=0802.3552|doi=10.1016/j.nuclphysa.2008.02.285|s2cid=119273920}}</ref> The possibility that QGP would not yet be free at accelerator temperatures was predicted in 1984 as a consequence of remnant effects of confinement.<ref>{{Cite journal|last1=Plümer|first1=M.|last2=Raha|first2=S.|last3=Weiner|first3=R. M.|name-list-style=amp|year=1984|title=How free is the quark–gluon plasma|journal=Nucl. Phys. A|volume=418|pages=549–557|doi=10.1016/0375-9474(84)90575-X}}</ref><ref>{{Cite journal|last1=Plümer|first1=M.|last2=Raha|first2=S.|last3=Weiner|first3=R. M.|name-list-style=amp|year=1984|title=Effect of confinement on the sound velocity in a quark–gluon plasma|journal=Phys. Lett. B|volume=139|issue=3|pages=198–202|doi=10.1016/0370-2693(84)91244-9}}</ref>

=== Neutron stars ===
It has been hypothesized that the core of some massive [[neutron star]]s may contain deconfined quark matter related to quark–gluon plasma.<ref>{{Cite journal |last1=Annala |first1=Eemeli |last2=Gorda |first2=Tyler |last3=Hirvonen |first3=Joonas |last4=Komoltsev |first4=Oleg |last5=Kurkela |first5=Aleksi |last6=Nättilä |first6=Joonas |last7=Vuorinen |first7=Aleksi |date=2023-12-19 |title=Strongly interacting matter exhibits deconfined behavior in massive neutron stars |journal=Nature Communications |language=en |volume=14 |issue=1 |page=8451 |doi=10.1038/s41467-023-44051-y |pmid=38114461 |issn=2041-1723|pmc=10730725 |arxiv=2303.11356 }}</ref>

== Onset of deconfinement ==
The central issue in the formation of quark–gluon plasma is the search for the [[Physics:Quantum deconfinement|onset of deconfinement]]. From the beginning of QGP research, the question was whether sufficient energy density could be achieved in nucleus-nucleus collisions. This depends on how much energy each nucleon loses. An influential reaction picture was the scaling solution presented by [[James Bjorken|Bjorken]].<ref>{{Cite journal|last=Bjorken|first=J. D.|year=1983|title=Highly relativistic nucleus-nucleus collisions: The central rapidity region|journal=Physical Review D|language=en|volume=27|issue=1|pages=140–151|doi=10.1103/PhysRevD.27.140|issn=0556-2821}}</ref> This model applies to ultra-high-energy collisions. In experiments at CERN SPS and BNL RHIC, the situation is usually divided into three stages:<ref name="Letessier-2002">{{Cite book|last1=Letessier|first1=Jean|url=[https://books.google.com/books?id=SAlbKkdor1gC|title=Hadrons](https://books.google.com/books?id=SAlbKkdor1gC|title=Hadrons) and Quark–Gluon Plasma|last2=Rafelski|first2=Johann|author2-link=Johann Rafelski|date=2002-05-30|publisher=Cambridge University Press|isbn=978-1-139-43303-7|language=en|ref=7}}</ref>

* Primary parton collisions and baryon stopping at the time of complete overlap of the colliding nuclei.
* Redistribution of particle energy and creation of new particles in the QGP fireball.
* Equilibration and expansion of QGP matter before hadronization.

More experimental evidence points to the strength of QGP formation mechanisms, possibly operating even in LHC-energy proton-proton collisions.<ref name="ALICE Collaboration-2017" />

=See also=
{{#invoke:PhysicsQC|tocHeadingAndList|Physics:Quantum basics/See also/Matter}}
{{div col |colwidth=27em}}
* [[Physics:Quantum chromodynamics|Quantum chromodynamics]]
* [[Physics:Quantum confinement|Color confinement]]
* [[Color-glass condensate]]
* [[Physics:Quantum hadron|Hadrons]]
* [[Hadronization]]
* [[Hagedorn temperature]]
* [[Neutron star]]
* [[Physics:Quantum matter/plasma|Plasma physics]]
* [[QCD matter]]
* [[Physics:Quantum electrodynamics|Quantum electrodynamics]]
* [[Quantum hydrodynamics]]
* [[Relativistic plasma]]
* [[Relativistic nuclear collision]]
* [[Strangeness production]]
* [[Strange matter]]
* [[List of unsolved problems in physics]]
  {{div col end}}

== Further reading ==

=== Books ===

* {{Cite book|title=Quark-Gluon Plasma, Heavy Ion Collisions and Hadrons|publisher=World Scientific|year=2024|isbn=978-981-128234-8|author-last=Shuryak|author-first=Edward|series=World Scientific Lecture Notes in Physics |volume=85 |location=Singapore|language=en|doi=10.1142/13570}}
* {{Cite book |title=Melting Hadrons, Boiling Quarks – From Hagedorn Temperature to Ultra-Relativistic Heavy-Ion Collisions at CERN |publisher=Springer International Publishing |year=2016 |isbn=978-3-319-17544-7 |editor-last=Rafelski |editor-first=Johann |editor-link=Johann Rafelski |location=Cham |language=en |doi=10.1007/978-3-319-17545-4 |doi-access=free }}
* {{Cite book|last=E|first=Fortov Vladimr|url=[https://books.google.com/books?id=AwvyCwAAQBAJ|title=Thermodynamics](https://books.google.com/books?id=AwvyCwAAQBAJ|title=Thermodynamics) And Equations Of State For Matter: From Ideal Gas To Quark–gluon Plasma|publisher=World Scientific|year=2016|isbn=978-981-4749-21-3|language=en|location=Singapore}}
* {{Cite book|last1=Yagi|first1=Kohsuke|url=[https://books.google.com/books?id=C2bpxwUXJngC|title=Quark–Gluon](https://books.google.com/books?id=C2bpxwUXJngC|title=Quark–Gluon) Plasma: From Big Bang to Little Bang|last2=Hatsuda|first2=Tetsuo|last3=Miake|first3=Yasuo|publisher=Cambridge University Press|year=2005|isbn=978-0-521-56108-2|series=Cambridge monographs on particle physics, nuclear physics, and cosmology|location=Cambridge}}
* {{Cite book|last=Florkowski|first=Wojciech|url=[https://books.google.com/books?id=GhY8DQAAQBAJ|title=Phenomenology](https://books.google.com/books?id=GhY8DQAAQBAJ|title=Phenomenology) of ultra-relativistic heavy-ion collisions|publisher=World Scientific|year=2010|isbn=978-981-4280-66-2|location=Singapore}}
* {{Cite book|date=2010|isbn=978-3-642-02285-2|editor1-last=Sarkar|editor1-first=Sourav|volume=785|location=Berlin; Heidelberg|language=en|doi=10.1007/978-3-642-02286-9|arxiv=0810.3553|editor-last2=Satz|editor-first2=Helmut|editor-last3=Sinha|editor-first3=Bikash|last1=Banerjee|first1=Debasish|last2=Nayak|first2=Jajati K.|last3=Venugopalan|first3=Raju|title=The Physics of the Quark-Gluon Plasma |series=Lecture Notes in Physics|pages=105–137}}
* {{Cite book|last1=Herrera Corral |first1=G. |url=[https://materials.springer.com/bp/docs/978-3-642-01539-7|title=Relativistic](https://materials.springer.com/bp/docs/978-3-642-01539-7|title=Relativistic) Heavy Ion Physics|publisher=Springer: Berlin; Heidelberg|year=2010|isbn=978-3-642-01538-0|editor-last=Stock|editor-first=R.|series=Landolt-Börnstein – Group I Elementary Particles, Nuclei and Atoms|volume=23|location=Berlin; Heidelberg|doi=10.1007/978-3-642-01539-7|arxiv=1010.3164 |citeseerx=10.1.1.314.4982}}
* {{Cite book|last1=Sahu|first1=P. K.|url=[https://books.google.com/books?id=dk5bPgAACAAJ|title=Quark](https://books.google.com/books?id=dk5bPgAACAAJ|title=Quark) Gluon Plasma and Hadron Physics|last2=Phatak|first2=S. C.|last3=Viyogi|first3=Yogendra Pathak|author3-link=Y. P. Viyogi|publisher=Narosa|year=2009|isbn=978-81-7319-957-8|language=en}}
* {{Cite book|title=The Physics of the Quark-Gluon Plasma|date=1985|publisher=Springer Berlin; Heidelberg|isbn=978-3-540-15211-8|series=Lecture Notes in Physics|volume=225|location=Berlin; Heidelberg|language=en|doi=10.1007/bfb0114317|arxiv=hep-ph/9509334 |last1=Müller |first1=Berndt |author-link=Berndt Müller }}
* {{cite book |last1=Damjanovic |first1=Sanja |last2=Metag |first2=Volker |last3=Schukraft |first3=Jürgen |editor-last=Damjanovic |editor-first=Sanja |editor2-last=Metag |editor2-first=Volker |editor3-last=Schukraft |editor3-first=Jürgen |chapter=Research at the CERN accelerators from 1983 onwards – ultra-relativistic heavy-ion physics: searching for the quark–gluon plasma |title=Hans Joachim Specht – Scientist and Visionary |series=Springer Biographies |publisher=Springer Nature |location=Cham |year=2024 |pages=58–93 |isbn=978-3-031-92352-4 |doi=10.1007/978-3-031-92353-1 |url=[https://link.springer.com/book/10.1007/978-3-031-92353-1](https://link.springer.com/book/10.1007/978-3-031-92353-1) }}

=== Review articles with a historical perspective ===

* {{Cite journal|last1=Jacob|first1=M.|last2=Tran Thanh Van|first2=J.|year=1982|title=Quark matter formation and heavy ion collisions|journal=Physics Reports|language=en|volume=88|issue=5|pages=321–413|doi=10.1016/0370-1573(82)90083-7}}
* {{Cite book|url=[https://books.google.com/books?id=8AD3GDoVaMkC|title=Quark–gluon](https://books.google.com/books?id=8AD3GDoVaMkC|title=Quark–gluon) plasma: theoretical foundations|publisher=North-Holland|year=2003|isbn=978-0-444-51110-2|editor-last=Kapusta|editor-first=J. I.|location=Amsterdam|editor-last2=Müller|editor-first2=B.|editor2-link=Berndt Müller|editor-last3=Rafelski|editor-first3=Johann|editor3-link=Johann Rafelski|ref=0}} A collection of reprints of theory articles up to 1992.
* {{cite journal |last1=Kajantie |first1=K. |last2=Miettinen |first2=H. I. |title=Temperature measurement of quark-gluon plasma formed in high-energy nucleus-nucleus collisions |journal=Zeitschrift für Physik C: Particles and Fields |volume=9 |year=1981 |issue=4 |pages=341–348 |doi=10.1007/BF01548770 |publisher=Springer}}
* {{cite journal |last=Specht |first=Hans J. |title=Nucleus-Nucleus Collisions: Observations and Expectations |journal=Nuclear Physics A |volume=400 |year=1983 |pages=43c–63c |publisher=Elsevier |doi=10.1016/0375-9474(83)90427-X}}
* {{cite journal|last1=Gazdzicki|first1=Marek|last2=Gorenstein|first2=Mark|last3=Seyboth|first3=Peter|year=2020|title=Brief history of the search for critical structures in heavy-ion collisions|journal=Acta Physica Polonica B|volume=51|issue=5|page=1033|doi=10.5506/APhysPolB.51.1033|arxiv=2004.02255|s2cid=214802159}}
* {{Cite journal|last=Rafelski|first=Johann|year=2020|title=Discovery of Quark–Gluon Plasma: Strangeness Diaries|journal=The European Physical Journal Special Topics|language=en|volume=229|issue=1|pages=1–140|doi=10.1140/epjst/e2019-900263-x|arxiv=1911.00831|s2cid=207869782|issn=1951-6401}}
* {{Cite journal|last1=Pasechnik|first1=Roman|last2=Šumbera|first2=Michal|year=2017|title=Phenomenological Review on Quark–Gluon Plasma: Concepts vs. Observations|journal=Universe|language=en|volume=3|issue=1|page=7|doi=10.3390/universe3010007|arxiv=1611.01533|s2cid=17657668|issn=2218-1997|doi-access=free}}
* {{Cite journal|last1=Satz|first1=Helmut|last2=Stock|first2=Reinhard|year=2016|title=Quark Matter: The Beginning|journal=Nuclear Physics A|language=en|volume=956|pages=898–901|doi=10.1016/j.nuclphysa.2016.06.002}}
* {{Cite journal|last=Gazdzicki|first=M.|year=2012|title=On the history of multi-particle production in high energy collisions|url=[https://www.actaphys.uj.edu.pl/vol43/abs/v43p0791|journal=Acta](https://www.actaphys.uj.edu.pl/vol43/abs/v43p0791|journal=Acta) Physica Polonica B|language=en|volume=43|issue=4|page=791|doi=10.5506/APhysPolB.43.791|arxiv=1201.0485|s2cid=118418649|issn=0587-4254}}
* {{Cite journal|last=Müller|first=B.|year=2012|title=Strangeness and the quark–gluon plasma: thirty years of discovery|url=[https://www.actaphys.uj.edu.pl/vol43/abs/v43p0761|journal=Acta](https://www.actaphys.uj.edu.pl/vol43/abs/v43p0761|journal=Acta) Physica Polonica B|language=en|volume=43|issue=4|page=761|doi=10.5506/APhysPolB.43.761|arxiv=1112.5382|s2cid=119280137|issn=0587-4254}}
* {{Cite journal|last=Heinz|first=Ulrich|year=2008|title=From SPS to RHIC: Maurice and the CERN heavy-ion programme|url=[http://stacks.iop.org/1402-4896/78/i=2/a=028005?key=crossref.8671cc766b779ec166b546c05ebbf3dc|journal=Physica](http://stacks.iop.org/1402-4896/78/i=2/a=028005?key=crossref.8671cc766b779ec166b546c05ebbf3dc|journal=Physica) Scripta|volume=78|issue=2|article-number=028005|doi=10.1088/0031-8949/78/02/028005|arxiv=0805.4572|s2cid=13833990|issn=0031-8949}}
* {{Cite journal|last=Baym|first=G.|year=2002|title=RHIC: From dreams to beams in two decades|journal=Nuclear Physics A|language=en|volume=698|issue=1–4|pages=xxiii–xxxii|doi=10.1016/S0375-9474(01)01342-2|arxiv=hep-ph/0104138|s2cid=12028950}}
* {{Cite report|last1=Ludlam|first1=T.|last2=Aronson|first2=S.|year=2005|title=Hunting the quark gluon plasma|url=[https://www.bnl.gov/isd/documents/29263.pdf|docket=BNL-73847-2005|publisher=Brookhaven](https://www.bnl.gov/isd/documents/29263.pdf|docket=BNL-73847-2005|publisher=Brookhaven) National Laboratory|doi=10.2172/15015225 |osti=15015225}} The so-called RHIC White papers.

== External links ==

* {{Commons category-inline}}
* [[http://www.bnl.gov/rhic/](http://www.bnl.gov/rhic/) The Relativistic Heavy Ion Collider] at [[http://www.bnl.gov/](http://www.bnl.gov/) Brookhaven National Laboratory]
* [[http://aliceinfo.cern.ch/](http://aliceinfo.cern.ch/) The Alice Experiment] {{Webarchive|url=[https://web.archive.org/web/20110602001439/http://aliceinfo.cern.ch/](https://web.archive.org/web/20110602001439/http://aliceinfo.cern.ch/) |date=2011-06-02 }} at [[https://www.cern.ch/](https://www.cern.ch/) CERN]
* [[http://theory.tifr.res.in/~sgupta/ilgti](http://theory.tifr.res.in/~sgupta/ilgti) The Indian Lattice Gauge Theory Initiative]
* Quark matter reviews: [[https://arxiv.org/abs/hep-ph/0402251](https://arxiv.org/abs/hep-ph/0402251) 2004 theory], [[https://arxiv.org/abs/nucl-ex/0405007](https://arxiv.org/abs/nucl-ex/0405007) 2004 experiment]
* Quark–Gluon Plasma reviews: [[https://arxiv.org/abs/1101.3937](https://arxiv.org/abs/1101.3937) 2011 theory]
* Lattice reviews: [[https://arxiv.org/abs/hep-ph/0303042](https://arxiv.org/abs/hep-ph/0303042) 2003], [[https://arxiv.org/abs/hep-ph/0505073](https://arxiv.org/abs/hep-ph/0505073) 2005]
* [[https://news.bbc.co.uk/2/hi/science/nature/4462209.stm](https://news.bbc.co.uk/2/hi/science/nature/4462209.stm) BBC article mentioning Brookhaven results (2005)]
* [[https://web.archive.org/web/20050423224100/http://www.aip.org/pnu/2005/split/728-1.html](https://web.archive.org/web/20050423224100/http://www.aip.org/pnu/2005/split/728-1.html) Physics News Update article on the quark–gluon liquid, with links to preprints]
* "Hadrons and Quark–Gluon Plasma" by Jean Letessier and [[Johann Rafelski]], Cambridge University Press (2002) {{ISBN|0-521-38536-9}}, Cambridge, UK.

{{Stellar core collapse}}
{{physics-footer}}
{{Phase of matter}}
{{Authority control}}

=References=
{{reflist|3}}

{{Author|Harold Foppele}}

{{Sourceattribution|Quark–gluon plasma|1}}
{{DEFAULTSORT:Quark-gluon plasma}}
[[Category:Quantum chromodynamics]]
[[Category:Quark matter]]
[[Category:Phases of matter]]
[[Category:Exotic matter]]
[[Category:Gluons]]