'Littlest' quark-gluon plasma revealed by physicists using Large Hadron Collider

September 3, 2015
CMS detector at CERN's Large Hadron Collider. Credit: CERN

Researchers at the University of Kansas working with an international team at the Large Hadron Collider have produced quark-gluon plasma—a state of matter thought to have existed right at the birth of the universe—with fewer particles than previously thought possible.

The material was discovered by colliding protons with at high energy inside the supercollider's Compact Muon Solenoid detector. Physicists have dubbed the resulting plasma the "littlest liquid."

"Before the CMS experimental results, it had been thought the medium created in a proton on lead collisions would be too small to create a ," said Quan Wang, a KU postdoctoral researcher working with the team at CERN, the European Organization for Nuclear Research. Wang performed key analysis for a paper about the experiment recently published in APS Physics.

"Indeed, these collisions were being studied as a reference for collisions of two lead nuclei to explore the non-quark-gluon-plasma aspects of the collisions," Wang said. "The analysis presented in this paper indicates, contrary to expectations, a quark-gluon plasma can be created in very asymmetric proton on lead collisions."

The unexpected discovery was said by senior scientists associated with the CMS detector to shed new light on high-energy physics.

"This is the first paper that clearly shows multiple particles are correlated to each other in proton-lead collisions, similar to what is observed in lead-lead collisions where quark gluon plasma is produced," said Yen-Jie Lee, assistant professor of physics at MIT and co-convener of the CMS heavy-ion physics group. "This is probably the first evidence that the smallest droplet of quark gluon plasma is produced in proton-lead collisions."

The KU researcher described quark-gluon plasma as a very hot and dense state of matter of unbound quarks and gluons—that is, not contained within individual nucleons.

"It's believed to correspond to the state of the universe shortly after the Big Bang," Wang said. "The interaction between partons—quarks and gluons—within the quark-gluon plasma is strong, which distinguishes the quark-gluon plasma from a gaseous state where one expects little interaction among the constituent particles."

While high-energy particle physics often focuses on detection of subatomic particles, such as the recently discovered Higgs Boson, the new quark-gluon-plasma research instead examines behavior of a volume of such particles.

Quan Wang is at the Large Hadron Collider. Credit: University of Kansas

Wang said such experiments might help scientists to better understand cosmic conditions in the instant following the Big Bang.

"While we believe the state of the universe about a microsecond after the Big Bang consisted of a quark-gluon plasma, there is still much that we don't fully understand about the properties of quark-gluon plasma," he said. "One of the biggest surprises of the earlier measurements at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory was the fluid-like behavior of the quark-gluon . Being able to form a in proton-lead collisions helps us to better define the conditions needed for its existence."

Wang continues his research at CERN's Large Hadron Collider, performing analysis and working on the operations of a Zero Degree Calorimeter maintained by KU.

"You have to see the apparatus," he said. "It is amazing."

Explore further: Physicists find surprising 'liquid-like' particle interactions in Large Hadron Collider

More information: APS Physics, physics.aps.org/articles/v8/61

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14 comments

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baudrunner
not rated yet Sep 03, 2015
What happens to the plasma over time when the experiment is discontinued? Are all the original particles restored to their pre-collision state with no losses incurred? Inquiring minds want to know.
shavera
5 / 5 (9) Sep 03, 2015
The plasma lasts for a very very tiny fraction of a second. It freezes out into hadrons pretty rapidly.

No, there are new particles created from the energy of momentum contained in the colliding species.
RealityCheck
3 / 5 (2) Sep 03, 2015
A few days ago (September 1), PO had an article here on quark-gluon plasma creation at the Relativistic Heavy Ion Collider (RHIC), a particle collider for nuclear physics research at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory...

http://phys.org/n...tml#nRlv

billpress11
not rated yet Sep 04, 2015
Quote from article:
"Researchers at the University of Kansas working with an international team at the Large Hadron Collider have produced quark-gluon plasma—a state of matter thought to have existed right at the birth of the universe—"

There's no exact spot that the Big Bang happened. In fact, the Big Bang happened everywhere in the Universe.
http://www.univer...-happen/
What is the Big Bang?

According to the big bang theory, the universe began by expanding from an infinitesimal volume with extremely high density and temperature.

http://www.ugcs.c...Bang.htm

These 3 sources are leaving me a little puzzled. If the BB happened everywhere at once why is there a need for the inflationary period? In two yes, in the other it is not need to explain the flatness of the universe.
shavera
4.5 / 5 (8) Sep 04, 2015
bill: Yes, we know there's no "spot" the big bang happened. What they mean is that the very very early universe, just "after" the bang, the state of matter would have been a quark gluon plasma. Energy densities would have been too high for quarks to stay bound together into individual particles (hadrons).

According to the big bang theory, the universe began by expanding from an infinitesimal volume with extremely high density and temperature.


Not precisely accurate. Our region of the universe, which is likely just one small sub-volume, was at one time very very very small. Was it a single point? Maybe. Was it a very very small volume? maybe. We can't really say yet. So the word "infinitesimal" here is... so-so. If you mean colloquially "very very small" yes, it's fine. If you mean mathematically "the limit of 1/x as x grows arbitrarily large", then... maybe.
shavera
4.5 / 5 (8) Sep 04, 2015
why is there a need for the inflationary period?


Even if it did happen everywhere at once, what are the odds that "at once" is perfectly uniform? Maybe some parts were a little hotter, some a little cooler. Some expanding a little faster or slower. We can approximate what that should maybe look like, but those results predict more variation in temperature across universe we can observe.

So the idea that's been largely accepted as likely, but not "known to be true" is the idea that the very first instant it expands *so fast* that there isn't time for these small variations in temperature to cross from one region to another. Our subvolume is an even tinier fraction of the early universe volume if you wouldn't include inflation, so our tiny subvolume wouldn't have a lot of temperature differences across it in that case. This kind of fits what we observe presently.
billpress11
not rated yet Sep 04, 2015
Quote shavera: "Our subvolume is an even tinier fraction of the early universe volume if you wouldn't include inflation, so our tiny subvolume wouldn't have a lot of temperature differences across it in that case. This kind of fits what we observe presently."

If your statement "fits" with observation what would ever give you the idea that the BB happened everywhere at once? The "everywhere" at once would not be needed because we would have no way of knowing what is "outside" our tiny fraction of the universe would we? Do we have any evidence of anything beyond our "subvolume"?
shavera
4.3 / 5 (6) Sep 04, 2015
happened everywhere at once: because there's no central point everything is radiating away from. Everything is uniformly expanding (think "loaf of bread" rather than "balloon"/"explosion")

And, no, by fact of relativity, we can't ever know beyond our own little part of the universe. You could believe it's filled with vanilla custard and unicorns if you'd like.

Science isn't about getting at the *truth per se*. It's an attempt to define what is true by what we can observe and making as few additional assumptions as possible about what we observe. The "truth" could be something entirely different than what we observe.

So the *scientific answer* to what lies beyond our universe is "more of the same." Why? Because we would have to speculate without observation about it. We'd have to make assumptions unfounded on evidence.
billpress11
3 / 5 (2) Sep 04, 2015
Quote shavera: "So the *scientific answer* to what lies beyond our universe is "more of the same." Why? Because we would have to speculate without observation about it. We'd have to make assumptions unfounded on evidence."

This part I can say I agree with. But that is exactly why we cannot say the BB happened everywhere at once beyond our field of view but in an inflationary micro-second within our field of view. You cannot have it both ways.
docile
Sep 04, 2015
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nikola_milovic_378
1 / 5 (1) Sep 04, 2015
Why are so many scientists working to uncover the cause of the creation of matter in the universe? Why none of them recognize that what they are doing Sisyphean task? Because it's big earnings resulting from a system that does not understand what the universe is and how it formed.
I believe that most scientists know that they will not find the CERN never God particle, because some know that it is not certain people to prove it, they do not know even nothing of its existence, which is many millions of years younger than the origin of matter. These phenomena in collisions of particles, are nothing more than restore these broken particles in its original position. Imagine how to observe people who demolished the building to find out what it is made. Well made of what is already there, and you znatiželjici do not know.
nikola_milovic_378
not rated yet Sep 06, 2015
If the experiment is performed in a vacuum (without any gas), how can you talk of a gaseous about the quark gluon plasma? How do you get to that place anything other than fragments of two protons? If there is anything further, so that there is something wrong with the experiment.
docile
Sep 06, 2015
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docile
Sep 06, 2015
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