Quark-Gluon Plasma Discovery - Brookhaven National Lab

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Discussion Overview

The discussion revolves around the recent discovery of quark-gluon plasma (QGP) at Brookhaven National Lab, specifically focusing on the conditions under which it was created, the implications of this discovery, and comparisons with experiments at CERN. Participants explore the significance of the temperatures achieved during collisions and the nature of the QGP state.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants note that quark-gluon plasma requires heavy ions for sufficient quark involvement, questioning the effectiveness of nucleons in achieving this state.
  • There is a discussion about whether lead ions, which are heavier than gold, would produce higher temperatures in collisions, with some participants asserting that CERN has not yet used lead ions in the LHC.
  • Concerns are raised about the measurement of temperature in the QGP state, with one participant suggesting that the definition of temperature in this context is complicated due to the short lifetime of the plasma.
  • Participants debate the significance of QGP despite its short lifetime, with some linking it to the Big Bang theory and questioning why such experiments do not lead to expansive phenomena akin to the early universe.
  • One participant emphasizes that the goal of high-energy experiments is not to replicate the Big Bang but to study the standard model of particle physics, including the Higgs particle and phenomena like QGP.
  • A later reply clarifies that the reported temperature of 4 trillion degrees Celsius pertains to the jets produced in the collision rather than the QGP itself, suggesting a need for caution in interpreting these measurements.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the implications of the QGP discovery, the effectiveness of different ion collisions, and the interpretation of temperature measurements. The discussion remains unresolved on several points, particularly regarding the significance of the findings and the nature of the QGP state.

Contextual Notes

There are limitations in the discussion related to the assumptions about temperature definitions in non-equilibrium states, the specific conditions under which QGP is formed, and the varying experimental goals of different particle accelerators.

ionowattodo
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Lately, I've heard that the scientists at Brookhaven National Lab were able to create a collision between gold ions that generated 4 trillion degrees Celsius. They said that this amount of energy in the collision was more than enough, according to their calculations, to melt the nucleons into a plasma of quarks and gluons. Link: http://www.bnl.gov/rhic/news2/news.asp?a=1074&t=pr
However, at CERN, they have a particle accelerator at 17 miles in circumference, much larger than the one at Brookhaven National Lab (2.4 miles in circumference.) So how come they didn't report similar news earlier, or maybe with the news of the 3.5 TeV particle collision lately?

I'm fairly new at this subcategory of physics, so a discussion about this new discovery could hopefully benefit my knowledge on such science. Any ideas on this?
 
Physics news on Phys.org
Quark-gluon plasma requires heavy ions; with nucleons not enough quarks are involved.
 
tom.stoer said:
Quark-gluon plasma requires heavy ions; with nucleons not enough quarks are involved.

I thought scientists at CERN fired lead ions? If lead is heavier than gold chemically, wouldn't it create a much greater temperature due to the collision of more quarks?
 
ionowattodo said:
I thought scientists at CERN fired lead ions?

Not in the LHC yet.
 
The LHC right now concentrates on calibration and checking standard results. It is best done with cleaner events. Proton and heavy ions are both parts of the ultimate physics program.
 
I see.

Did the scientists at Brookhaven National Lab confirm the temperature of the collision event? Correct me if I'm wrong, but I think that they measured the wavelengths of the released particles and calculated the temperature from there.
 
yes, something like that;

it's not straightforward to define a temperature; temperature means that we have thermodynamical equilibrium,whereas the qg-plasma state has of course a very short lifetime; so this is "on the edge"
 
If QGP has a very short lifetime, why is it so significant to scientists? I've heard that some people think it leads to the Big Bang theory, but if this collision event really does recreate something similar to the Big Bang, how come it didn't expand tremendously into an entirely new universe? Also, how can it be possible to accelerate particles (maybe even nucleons at the very least) without the aid of man-made machines?
 
As for every high-energy experiment with the LHC we come a bit closer to the Big Bang, but not really close!

The Tevatron has ~ 1TeV c.o.m. energy, the LHC will have 14TeV (both in hadron collisions, of course much higher for heavy ions). The Planck energy is ~1016 TeV. In addition the Big Bang is different as spacetime emerged from it, therefore the high energy density was realized in the hole (tiny) universe with Planck length ~ 10-35m. Today the tiny volume with QGP is surrounded by a gigantic (nearly empty) spacetime into which the plasma can expand, whereas after the Big bang the plasma could only expand by "creating new spacetime".
 
  • #10
tom.stoer said:
As for every high-energy experiment with the LHC we come a bit closer to the Big Bang, but not really close!

If the experiments at the LHC and Brookhaven National Lab weren't even approaching the energies needed to replicate the Big Bang, what's the point of even initiating the experiment? Since these experiments deal with quantum particles, the scientists have to reach a specific amount of energy input on the particles in order to obtain a result similar to the Big Bang.
 
  • #11
The answer is simple: the scientists do not want to study the big bang as they are aware of the fact that they are still some orders of magnitude away from it. Instead they want to study the standard model, especially the Higgs particle, perhaps physics beyond the standard model like SUSY, QGP etc.
 
  • #12
ionowattodo,

I saw your post a few days ago, you may find these posts of interest, in jal's "perfect symmetery" thread. This has to do with BNL's findings concerning quark-gluon-plasma. See what you think. Starting with https://www.physicsforums.com/showpost.php?p=2582244&postcount=89", consisting in part of quark-gluon-plasma. Plenty to think about, enjoy and welcome to PF.

Rhody...

P.S. I just read your response in post #6. See jal's response in https://www.physicsforums.com/showpost.php?p=2588442&postcount=92" about half way down the page. A good explanation of how the temperature was calculated:
I realize that when writing for the the news media that things have got to be “dumbed down” to make it understandable.
The repeating of “measuring the temperature of the quark-gluon plasma as 4 trillion degrees Celsius,” should be clarified.
The temperature of the “ball/bubble of plasma/liquid/fire” is not being measured.

What is being measured are the temperatures of the jets NOT THE TEMPERATURE OF THE PERFECT LIQUID.

Therefore, the presumption and assumption that the perfect liquid is at those “temperatures” needs to be taken with a grain of salt.
 
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