STAR QM08 Highlights I
Characterizing the new state of matter discovered at RHIC: first steps
By Tim Hallman, STAR Collaboration
The discovery phase at RHIC has yielded overwhelming evidence
for the creation of a
new state of matter in central heavy ion collisions — the
hottest and densest yet examined in the laboratory. It is highly
opaque to colored probes such as quarks and gluons, but not to
photons. Elliptic flow measurements suggest the matter behaves
as a relativistic quantum liquid with minimal shear viscosity.
It produces copious mesons and baryons with yield ratios and
flow properties that suggest their formation via the coalescence
of partons having the degrees of freedom of valence quarks in a
hot thermal bath.
These phenomena — not observed prior to the start of the RHIC program — constitute important discoveries which now raise a new challenge: quantitative characterization of the matter’s properties. First steps toward this goal were the subject of STAR presentations at Quark Matter 2008. Ultimately the full capability of RHIC II, including increased luminosity and significant detector upgrades, will be required to accomplish a) extension of the phenomena discovered with light quarks to hadrons containing charm and bottom, b) high efficiency and high luminosity for quarkonia studies and rare probes such as direct γ + jet c) precision, differential particle identified correlations and fluctuations, and d) acceptance to study the initial-state gluon distribution (i.e. Color-Glass Condensate) in the entrance channel nuclei. Dramatic new developments related to stochastic cooling of RHIC beams put this future within reach years earlier than originally projected.
Read the full RHIC News story here (pdf).
The Relativistic Heavy Ion Collider at Brookhaven National
Laboratory is a world-class scientific research facility primarily
funded by the U.S. Department of Energy Office of Science. Hundreds
of physicists from around the world use RHIC to study what the
universe may have looked like in the first few moments after its
creation. What physicists learn from these collisions may help us
understand more about why the physical world works the way it does,
from the smallest subatomic particles, to the largest stars.