Hot and Dense QCD:
The Physics of the Quark-Gluon-Plasma
Introduction into Quark-Gluon-Plasma Physics:
Hadronic matter - matter susceptible to the strong interaction force -
is described by quantum-chromo-dynamics (QCD). The basic constituents
of QCD are quarks which interact through the exchange of gluons.
It is believed that shortly after the creation of the universe in
the Big Bang all matter was in a state called the Quark Gluon Plasma (QGP).
Due to the rapid expansion of the universe, this plasma went through
a phase transition to form hadrons - most importantly nucleons - which
constitute the building blocks of (nuclear) matter as we know it today.
The investigation of QGP properties, such as its equation of state,
will improve our understanding of the
development of the early universe and the behavior of QCD under extreme
Timeline of the history of the Universe and the evolution of matter from
the Big Bang to the present.
The existence of a QGP can be theoretically inferred through
lattice gauge simulations of QCD
(see also the page on our group's activities in that sector), which
provide the only rigorous method to compute the QCD equation of state.
These simulations predict a phase transition of confined hadronic matter
(such as protons and neutrons) to a deconfined state in
which hadrons are dissolved into quarks and gluons. Further information,
however, such as the critical temperature and energy-density for that
phase-transition, depend crucially on the parameters of the simulation
and the extrapolation from the discretized quantities on the lattice
to the continuum of the real world.
Conditions for creating this highly excited state of primordial matter
under controlled laboratory conditions using relativistic heavy ion
collisions are currently being provided
Relativistic Heavy Ion Collider (RHIC) at
Brookhaven National Laboratory . RHIC collides
gold nuclei at center of mass energies of
130 GeV and 200 GeV per nucleon-nucleon pair
and thus creates a state of matter at the highest temperatures and densities
possible in a laboratory environment. Experiments at RHIC
have yielded many interesting and
sometimes surprising results,
which have not yet been fully evaluated or understood by theory.
Two views of one of the first full-energy collisions between
gold ions at Brookhaven Lab's Relativistic Heavy Ion Collider,
as captured by the
Solenoidal Tracker At RHIC (STAR) detector.
The tracks indicate the paths taken by thousands of subatomic particles
produced in the collisions as they pass through the
STAR Time Projection Chamber, a large, 3-D digitial camera.
The central problem in the study of the QGP is that
the deconfined quanta of a QGP are not directly
observable due to the fundamental confining property of the
physical QCD vacuum. If we could see free quarks and gluons
(as in ordinary plasmas) it would be trivial to verify the QCD
prediction of the QGP state. However, nature chooses to hide those
constituents within the confines of color neutral composite many
body systems - hadrons. One of the main tasks in relativistic
heavy-ion research is to find clear and unambiguous connections
between the transient quark gluon plasma state and the observable
hadronic final state.
QGP Research at Duke
Our group has a longstanding tradition in QGP related research.
We are active in the following areas:
An autogenerated list of recent publications (from 1998 onwards)
by the Duke Nuclear/High Energy
Theory Group on QGP related topics can be found
- Heavy-Ion Phenomenology:
- Hadronization via parton recombination and fragmentation
- the phenomenology of jet quenching
- charge and baryon number fluctuations
- balance functions
- Hydrodynamical description of Relativistic Heavy-Ion Collisions
- Microscopic transport models
- Parton Cascade Models
- Ultra-Relativistic Quantum Molecular Dynamics
- Hybrid Macro+Micro transport approaches