• A visualization 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.

    Image: Brookhaven National Laboratory

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Explained: Quark-gluon plasma

By colliding particles, physicists hope to recreate the earliest moments of our universe, on a much smaller scale.


For a few millionths of a second after the Big Bang, the universe consisted of a hot soup of elementary particles called quarks and gluons. A few microseconds later, those particles began cooling to form protons and neutrons, the building blocks of matter.

Over the past decade, physicists around the world have been trying to re-create that soup, known as quark-gluon plasma (QGP), by slamming together nuclei of atoms with enough energy to produce trillion-degree temperatures.

“If you’re interested in the properties of the microseconds-old universe, the best way to study it is not by building a telescope, it’s by building an accelerator,” says Krishna Rajagopal, an MIT theoretical physicist who studies QGP.

Quarks and gluons, though they make up protons and neutrons, behave very differently from those heavier particles. Their interactions are governed by a theory known as quantum chromodynamics, developed in part by MIT professors Jerome Friedman and Frank Wilczek, who both won Nobel prizes for their work. However, the actual behavior of quarks and gluons is difficult to study because they are confined within heavier particles. The only place in the universe where QGP exists is inside high-speed accelerators, for the briefest flashes of time.

In 2005, scientists at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory reported creating QGP by smashing gold atoms together at nearly the speed of light. These collisions can produce temperatures up to 4 trillion degrees — 250,000 times warmer than the sun’s interior and hot enough to melt protons and neutrons into quarks and gluons.

The resulting super-hot, super-dense blob of matter, about a trillionth of a centimeter across, could give scientists new insights into the properties of the very early universe. So far, they have already made the surprising discovery that QGP is a nearly frictionless liquid, not the gas that physicists had expected.

By doing higher-energy collisions, scientists now hope to find out more about the properties of quark gluon plasma and whether it becomes gas-like at higher temperatures. They also want to delve further into the very surprising similarities that have been seen between QGP and ultracold gases (near absolute zero) that MIT’s Martin Zwierlein and others have created in the laboratory. Both substances are nearly frictionless, and theoretical physicists suspect that string theory may explain both phenomena, says Rajagopal.

At the Large Hadron Collider in Geneva, MIT faculty Gunther Roland, Wit Busza and Boleslaw Wyslouch are among the physicists planning to double the temperature achieved at Brookhaven, offering a glimpse of an even-earlier stage of the universe’s formation.


Topics: Large Hadron Collider, Nuclear science and engineering, Physics, Explained

Comments

Can the baryons have an atom-like structure? Similarity of structures can be broken at most for sizes smaller than the Planck length (about 10^-35 m). The baryons are about 20 powers of ten bigger. The triplet neutron-proton scattering length is approximately 5.4 fm. The singlet neutron-proton effective range is approximately 2.7 fm whereas the triplet neutron-proton effective range is approximately 1.7 fm. It leads to conclusion that outside the core of nucleons (and other baryons) is obligatory the Titius-Bode law for the strong interactions: R(d)=A+dB, where A=0.7 fm, B=0.5 fm whereas d=0,1,2,4. Then, diameter of the last 'orbit' is 5.4 fm, radius of last orbit is 2.7 fm whereas radius of the last but one orbit is 1.7 fm. The magnetic moments of nucleons lead to the massive core in baryons. When the relativistic nucleons collide the orbits are destroyed and there appears the liquid-like plasma composed of the cores of baryons.
when quark gluon plasma is "frictionless" does that mean that is a "homogeneous, pure, row, primary energy" form, since, I think, friction arises from "different" types of energy.? In a brief paragraph about the string theory it says: (that there are strings "floating in space"...)what does "space" means, is there, yet, a more "primitive, primary" form of energy in that theory?.
Is it possible to add a deceleration module (inverse accelerator) to a particle accelerator prior to the detector? I can imagine numerous advantages to developing such an apparatus.
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