Quark gluon plasma is a phase of Quantum Chromodynamics (QCD) which exists at extremely high temperature and density. It is believed to have existed during the first 20 or 30 microseconds after the big bang brought the universe into existence. Experiments at CERN's Super Proton Synchrotron first tried to create the QGP in the 1980s and 1990s, and may have been partially successful. Currently, experiments at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) are continuing this effort [1] (http://www.bnl.gov/rhic/). CERN's new experiment, Alice [2] (http://pcaliweb02.cern.ch/NewAlicePortal/en/index.html), will start soon at the Large Hadron Collider (LHC). Quantum chromodynamics (QCD) is the physical theory describing one of the fundamental forces, the strong interaction. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... According to the Big Bang theory, the universe originated in an extremely dense and hot state (bottom). ... The deepest visible-light image of the cosmos. ... CERN logo CERN is the European Organization for Nuclear Research, the worlds largest particle physics laboratory, situated on the border between France and Switzerland, just west of Geneva. ... The Super Proton Synchrotron (SPS) is a particle accelerator at CERN. Originally specified as a 300 GeV machine, the SPS was actually built to be capable of 400GeV, an operating voltage it achieved on the official commisioning date of 17 June 1976. ... Events and trends The 1980s marked an abrupt shift towards more conservative lifestyles after the momentous cultural revolutions which took place in the 1960s and 1970s and the definition of the AIDS virus in 1981. ... Events and trends The 1990s are generally classified as having moved slightly away from the more conservative 1980s, but keeping the same mind-set. ... Aerial view of Brookhaven National Laboratory. ... The Relativistic Heavy Ion Collider (RHIC) is a heavy-ion collider located at and operated by the Brookhaven National Laboratory in Upton, New York. ... CERN logo CERN is the European Organization for Nuclear Research, the worlds largest particle physics laboratory, situated on the border between France and Switzerland, just west of Geneva. ... CMS detector for LHC at CERN The Large Hadron Collider (short LHC) is a particle accelerator and collider located at CERN. It is currently under construction and scheduled to start operation in 2007. ...

General Introduction

The QGP contains quarks and gluons, just as normal (hadronic) matter does. The difference between these two phases of QCD is the following. In normal matter each quark either pairs up with an anti-quark to form a meson or joins with two other quarks to form a baryon (such as the proton and the neutron). In the QGP, by contrast, these mesons and baryons lose their identities and make a much larger mass of quarks and gluons [3] (http://theory.tifr.res.in/~sgupta/ilgti/infocenter/). In normal matter quarks are confined; in the QGP quarks are deconfined. 1974 discovery photograph of a possible charmed baryon, now identified as the Σc++ In particle physics, the quarks are subatomic particles thought to be elemental and indivisible. ... In particle physics, gluons mediate strong interactions of quarks in quantum chromodynamics. ... In particle physics, a hadron is a subatomic particle which experiences the strong nuclear force. ... The acronym QCD can mean: Quantum chromodynamics Quintessential Player This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... 1974 discovery photograph of a possible charmed baryon, now identified as the Σc++ In particle physics, the quarks are subatomic particles thought to be elemental and indivisible. ... In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... In particle physics, the baryons are a family of subatomic particles including the proton and the neutron (collectively called nucleons), as well as a number of unstable, heavier particles (called hyperons). ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... This article refers to a particle physics phenomenon. ...

Why is this a plasma?

A plasma is matter in which charges are screened due to the presence of other mobile charges; in other words, Coulomb's Law is modified to yield a distance-dependent charge. In a QGP, the colour charge of the quarks and gluons are screened. The QGP has other analogies with a normal plasma. There are also dissimilarities due to the fact that the colour charge is non-Abelian, whereas the electric charge is Abelian. This article is about plasma in the sense of an ionized gas. ... Charge is a word with many different meanings. ... The Debye length is the scale over which mobile charge carriers screen out electric fields in plasmas and other conductors. ... In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrical force that one stationary, electrically charged substance of small volume (ideally, a point source) exerts on another. ... In quantum chromodynamics (QCD), color or color charge refers to a certain property of the subatomic particles called quarks. ... 1974 discovery photograph of a possible charmed baryon, now identified as the Σc++ In particle physics, the quarks are subatomic particles thought to be elemental and indivisible. ... In particle physics, gluons mediate strong interactions of quarks in quantum chromodynamics. ... In quantum chromodynamics (QCD), color or color charge refers to a certain property of the subatomic particles called quarks. ... In mathematics, an abelian group is a commutative group, i. ... Electric charge is a fundamental FATTY STASHEconserved property of some subatomic particles, which determines their electromagnetic interactions. ... In mathematics, an abelian group is a commutative group, i. ...

How is this studied theoretically?

One consequence of this difference is that the colour charge is too large for perturbative computations which are the mainstay of QED. As a result, the main theoretical tools to explore the theory of the QGP is lattice gauge theory and the AdS/CFT correspondence. The transition temperature (approximately 170 MeV) 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. In quantum chromodynamics (QCD), color or color charge refers to a certain property of the subatomic particles called quarks. ... In quantum mechanics, perturbation theory is a set of approximation schemes for describing a complicated quantum system in terms of a simpler one. ... Quantum electrodynamics (QED) is a quantum field theory of electromagnetism. ... Lattice gauge theory is a method to deal with gauge theory that is useful for computer-assisted calculations. ... In physics, the AdS/CFT correspondence is the equivalence between a string theory or supergravity defined on some sort of Anti de Sitter space and a conformal field theory defined on its boundary whose dimension is lower by one. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ...

How is this created in the lab?

The QGP can be created by heating matter up to a temperature of 170 MeV. This can be done in the lab by colliding two large nuclei at high energy. Gold and lead nuclei have been used to do this at CERN and BNL. The resulting hot volume is called a fireball. Once created, this fireball is expected to expand under its own pressure, and cool while expanding. By carefully studying this flow, experimentalists hope to put the theory to test. Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... General Name, Symbol, Number Gold, Au, 79 Chemical series transition metals Group, Period, Block 11 (IB), 6, d Density, Hardness 19300 kg/m3, 2. ... General Name, Symbol, Number Lead, Pb, 82 Chemical series Poor metals Group, Period, Block 14(IVA), 6 , p Density, Hardness 11340 kg/m3, 1. ... Plural: nuclei In chemistry and physics, the nucleus (atomic nucleus) is the collection of protons and neutrons in the center of an atom that carries the bulk of the atoms mass and positive charge. ... CERN logo CERN is the European Organization for Nuclear Research, the worlds largest particle physics laboratory, situated on the border between France and Switzerland, just west of Geneva. ... BNL is short for Barenaked Ladies, a Canadian alternative rock band. ... Pressure is the application of force to a surface, and the concentration of that force in a given area. ...

How does this fit into the general scheme of physics?

QCD is one part of the modern theory of particle physics called the Standard Model. Other parts of this theory deal with electroweak interactions and neutrinos. The theory of electrodynamics has been tested and found correct to a few parts in a trillion. The theory of weak interactions has been tested and found correct to a few parts in a thousand. Perturbative aspects of QCD have been tested to a few percents. In contrast, non-perturbative aspects of QCD have barely been tested. The study of the QGP is part of this effort to consolidate the grand theory of particle physics. The acronym QCD can mean: Quantum chromodynamics Quintessential Player This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Particles explode from the collision point of two relativistic velocity (100 GeV) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... In physics, the electroweak theory presents a unified description of two of the four fundamental forces of nature: electromagnetism and the weak nuclear force. ... The neutrino is an elementary particle. ... Quantum electrodynamics (QED) is a quantum field theory of electromagnetism. ... In physics, the electroweak theory presents a unified description of two of the four fundamental forces of nature: electromagnetism and the weak nuclear force. ... The acronym QCD can mean: Quantum chromodynamics Quintessential Player This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

The study of the QGP is also a testing ground for finite temperature field theory, a branch of theoretical physics which seeks to understand particle physics under conditions of high temperature. Such studies are important to understand the early evolution of our universe: the first hundred microseconds or so. While this may seem esoteric, this is crucial to the physics goals of a new generation of observations of the universe (WMAP and its successors). Artist depiction of the WMAP satellite at the L2 point The Wilkinson Microwave Anisotropy Probe (WMAP) is a NASA satellite whose mission is to survey the sky to measure the temperature of the radiant heat left over from the Big Bang. ...

Expected Properties

Thermodynamics

The cross-over temperature from the normal to the QGP phase is about 170 MeV, corresponding to an energy density of a little less than 1 [[GeV]] / [[fm]]³. For relativistic matter, pressure and temperature are not independent variables, so the equation of state is a relation between the energy density and the pressure. This has been found through lattice computations, and compared to both perturbation theory and string theory. This is still a matter of active research. Response functions such as the specific heat and various quark number susceptibilities are currently being computed. An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... Albert Einsteins theory of relativity is a set of two theories in physics: special relativity and general relativity. ... In physics and thermodynamics, an equation of state is a constitutive equation describing the state of matter under a given set of physical conditions. ... Lattice gauge theory is a method to deal with gauge theory that is useful for computer-assisted calculations. ... This article describes perturbation theory as a general mathematical method. ... String theory is a physical model whose fundamental building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that were the basis of most earlier physics. ... The specific heat capacity (symbol c or s, also called specific heat) of a substance is defined as heat capacity per unit mass. ...

Flow

The equation of state is an important input into the flow equations. The speed of sound is currently under investigation in lattice computations. The mean free time of quarks and gluons have been computed using perturbation theory as well as string theory. Lattice computations have been slower here, although the first computations of transport coefficients have recently been concluded. These indicate that the mean free time of quarks and gluons in the QGP may be comparable to the average interparticle spacing: hence the QGP is a liquid as far as its flow properties go. This is very much an active field of research, and these conclusions may evolve rapidly. The incorporation of dissipative phenomena into hydrodynamics is another recent development that is still in an active stage. The speed of sound varies depending on the medium through which the sound waves pass. ... Molecules in a fluid constantly collide off each other. ... This article describes perturbation theory as a general mathematical method. ... String theory is a physical model whose fundamental building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that were the basis of most earlier physics. ... Lattice gauge theory is a method to deal with gauge theory that is useful for computer-assisted calculations. ... The Pitch Drop Experiment at the University of Queensland. ... Molecules in a fluid constantly collide off each other. ...

Excitation spectrum

Does the QGP really contain (almost) free quarks and gluons? The study of thermodynamic and flow properties would indicate that this is an over-simplification. Many ideas are currently being evolved and will be put to test in the near future. It has been found recently that some mesons built from heavy quarks (such as the charm quark) do not dissolve until the temperature reaches about 350 MeV. This has led to speculation that many other kinds of bound states may exist in the plasma. Some static properties of the plasma (similiar to the Debye screening length) constrain the excitation spectrum. For other uses of this term, see: Quark (disambiguation) 1974 discovery photograph of a possible charmed baryon In particle physics, the quarks are subatomic particles thought to be elemental and indivisible. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ...

The Experimental Situation

Unfortunately, those aspects of the QGP which are easiest to compute are not the ones which are the easiest to probe in experiments. While the balance of evidence points towards the QGP being the origin of the detailed properties of the fireball produced in the RHIC, this is the main barrier which prevents experimentalists from declaring a sighting of the QGP. The Relativistic Heavy Ion Collider (RHIC) is a heavy-ion collider located at and operated by the Brookhaven National Laboratory in Upton, New York. ...

The important classes of experimental observations are

• Single Particle Spectra
• Strangeness production
• Photon and muon rates (and J/ψ melting)
• Elliptic flow
• Jet Quenching
• Fluctuations
• Hanbury-Brown and Twiss effect and correlations

For more details, see the web pages of the RHIC experiments [4] (http://www.bnl.gov/rhic). The Relativistic Heavy Ion Collider (RHIC) is a heavy-ion collider located at and operated by the Brookhaven National Laboratory in Upton, New York. ...

See also

• Quantum Chromodynamics
• Hadrons (that is mesons and baryons) and confinement
• Quantum Electrodynamics
• Plasma Physics
• Relativistic plasma
• Quark Matter

Quantum chromodynamics (QCD) is the physical theory describing one of the fundamental forces, the strong interaction. ... In particle physics, a hadron is a subatomic particle which experiences the strong nuclear force. ... In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... In particle physics, the baryons are a family of subatomic particles including the proton and the neutron (collectively called Greek barys, meaning heavy, as they are heavier than the other main groups of particles. ... This article refers to a particle physics phenomenon. ... Quantum electrodynamics (QED) is a quantum field theory of electromagnetism. ... This article is about plasma in the sense of an ionized gas. ... Quark Matter refers to any of a number of phases of matter built out of quarks and gluons. ...

News

April 2005: Formation of quark matter has been tentatively confirmed by results obtained at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC). The consensus of the four RHIC research groups is that they have created a quark-gluon liquid of very low viscosity. However, contrary to the widespread assumption, it is yet unknown from theoretical predictions whether the QCD "plasma", especially close to the transition temperature should behave like a gas or fluid. April is the fourth month of the year in the Gregorian Calendar and one of four with the length of 30 days. ... 2005 is a common year starting on Saturday of the Gregorian calendar and is the current year. ... Aerial view of Brookhaven National Laboratory. ... The Relativistic Heavy Ion Collider (RHIC) is a heavy-ion collider located at and operated by the Brookhaven National Laboratory in Upton, New York. ... A liquid will assume the shape of its container. ... The Pitch Drop Experiment at the University of Queensland. ...

References and external links

• The Relativistic Heavy Ion Collider (http://www.bnl.gov/rhic/) at Brookhaven National Laboratory (http://www.bnl.gov/)
• The Alice Experiment (http://pcaliweb02.cern.ch/NewAlicePortal/en/index.html) at CERN (http://www.cern.ch)
• The Indian Lattice Gauge Theory Initiative (http://theory.tifr.res.in/~sgupta/ilgti)
• Quark matter reviews: 2004 theory (http://arxiv.org/pdf/hep-ph/0402251), 2004 experiment (http://arxiv.org/pdf/nucl-ex/0405007)
• Lattice reviews: 2003 (http://arxiv.org/pdf/hep-ph/0303042), 2005 (http://arxiv.org/pdf/hep-ph/0505073)
• BBC article mentioning Brookhaven results (http://news.bbc.co.uk/1/hi/sci/tech/4462209.stm)
• Physics News Update article on the quark-gluon liquid, with links to preprints (http://www.aip.org/pnu/2005/split/728-1.html)