Finding Mach Cones in QGP

Wednesday, August 26, 2009

Bryon Neufeld has spent his time at Duke studying what happens when quarks and gluons scatter in heavy ion collisions. Just as particles scatter, so too must newly minted PhDs. Neufeld left Duke on August 1 to head out to Los Alamos to begin a post-doctoral fellowship in the Nuclear Theory Division at the Los Alamos National Laboratory. There, he will work with Ivan Vitev as he continues to tease out the secrets of the elusive Quark-Gluon-Plasma (QGP).

What is QGP?

In the first few instants after the Big Bang, physicists believe that all matter and energy in the universe was in the form of QGP—a super-dense, super-hot state of matter in a super-tiny space. Experimental physicists are pretty confident that they have created small amounts of QGP, lasting for just milliseconds, by smashing together the nuclei of gold ions in the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory in Long Island. Some of the results seem to indicate that there might be mach cones present in the QGP. A mach cone is the emission pattern produced when an object moves through a medium faster than sound can move through that medium.

Calculating Mach Cones

Neufeld’s advisor, Berndt Mueller, suggested that Neufeld look at the possibility of mach cones in QGP through the eyes of a theoretical physicist. During heavy ion collisions, quarks and gluons scatter, essentially forming projectiles that zip through the QGP. How were those high-energy projectiles interacting with the QGP? Were they causing mach cones?

Several years later and who-knows-how-many calculations later, Neufeld can say: “The work I have done gives the first rigorous presentation that a projectile in the QGP does generate a mach cone in the medium.” Neufeld has published his results in the Physical Review C and other journals. He says his work opens the door to study other properties of QGP, such as the speed of sound and viscosity.

When asked, “Why study QGP?” Neufeld replies, “We don’t know what we’ll learn. That’s why we’re doing it. But I do know that the physics research of today is the technology of tomorrow, and studying QGP is one aspect of that pursuit.”


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