LR11713
Collider Reaches Hottest Temperature Ever Achieved - 4 trillion degrees Celcius
The PHENIX Collaboration at Brookhaven National Laboratory's
Relativistic Heavy Ion Collider (RHIC) has found that collisions of
gold ions traveling at nearly the speed of light create matter at a
temperature of about 370 MeV (about 4 trillion degrees Celsius).
This is the hottest temperature ever reached in a laboratory, and
about one hundred thousand times hotter than the center of the Sun.
This temperature is higher than the temperature needed to melt
protons and neutrons into a plasma of quarks and gluons. Such a
plasma filled the universe a few microseconds after it came into
existence. At RHIC, the plasma is a freely flowing liquid with almost
no frictional resistance, or viscosity. The matter is formed, and
the quoted temperature reached, in less time than it takes light
to travel across a single proton. The temperature was determined
by looking at the color, or energy distribution, of the light emitted -
similar to the way one can tell that an iron rod is hot by looking at
its glow. Light interacts very little with the hot liquid produced at
RHIC, so bears accurate witness to the early conditions. We deduce
the yield of photons from the production of electron pairs beyond those
from particle decays. By matching theoretical models of the expanding
plasma to the data, we infer the initial temperature of the liquid.
