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| Degree of
interaction among quarks in liquid gold-gold collisions. Image
credit: RHIC
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Using high-speed collisions
between gold atoms, scientists think they have re-created one of the
most mysterious forms of matter in the universe -- quark-gluon
plasma. This form of matter was present during the first microsecond
of the Big Bang and may still exist at the cores of dense, distant
stars.
UC Davis physics professor Daniel Cebra is one of 543 collaborators
on the research. His main role was building the electronic listening
devices that collect information about the collisions, a job he
compared to "troubleshooting 120,000 stereo systems."
Now, using those detectors, "we look for trends in what happened
during the collision to learn what the quark-gluon plasma is like,"
he said.
"We have been trying to melt neutrons and protons, the building
blocks of atomic nuclei, into their constituent quarks and gluons,"
Cebra said. "We needed a lot of heat, pressure and energy, all
localized in a small space."
The scientists produced the right conditions with head-on collisions
between the nuclei of gold atoms. The resulting quark-gluon plasma
lasted an extremely short time -- less than 10-20 seconds, Cebra
said. But the collision left tracings that the scientists could
measure.
"Our work is like accident reconstruction," Cebra said. "We see
fragments coming out of a collision, and we construct that
information back to very small points."
Quark-gluon plasma was expected to behave like a gas, but the data
shows a more liquid-like substance. The plasma is less compressible
than expected, which means that it may be able to support the cores
of very dense stars.
"If a neutron star gets large and dense enough, it may go through a
quark phase, or it may just collapse into a black hole," Cebra said.
"To support a quark star, the quark-gluon plasma would need
rigidity. We now expect there to be quark stars, but they will be
hard to study. If they exist, they're semi-infinitely far away."
The project is led by Brookhaven National Laboratory and Lawrence
Berkeley National Laboratory, with collaborators at 52 institutions
worldwide. The work was done in Brookhaven's Relativistic Heavy Ion
Collider (RHIC).
Original Source:
UC Davis News Release
