Physicists Puzzle Over Unexpected Findings In "Little" Big Bang

Science Daily | University of Rochester ^ | 11/13/2002

[sourcery]

Scientists have recreated a temperature not seen since the first microsecond of the birth of the universe and found that the event did not unfold quite the way they expected, according to a recent paper in Physical Review Letters. The interaction of energy, matter, and the strong nuclear force in the ultra-hot experiments conducted at the Relativistic Heavy Ion Collider (RHIC) was thought to be well understood, but a lengthy investigation has revealed that physicists are missing something in their model of how the universe works. "It's the things you weren't expecting that are really trying to tell you something in science," says Steven Manly, associate professor of physics and astronomy at the University of Rochester and co-author of the paper. "The basic nature of the interactions within the hot, dense medium, or at least the manifestation of it, changes depending on the angle at which it's viewed. We don't know why. We've been handed some new pieces to the puzzle and we're just trying to figure out how this new picture fits together."

At RHIC in Brookhaven, NY., Manly and his collaborators on the PHOBOS experiment wanted to probe the nature of the strong nuclear force that helps bind atoms together. They smashed two atoms of gold together at velocities near the speed of light in an attempt to create what's called a "quark-gluon plasma," a very brief state where the temperature is tens of thousands of times higher than the cores of the hottest stars. Particles in this hot-soup plasma stream out, but not without bumping into other particles in the soup. It's a bit like trying to race out of a crowded room--the more people in your way, the more difficult to escape. The strength of the interactions between particles in the soup is determined by the strong force, so carefully watching particles stream out could reveal much about how the strong force operates at such high temperatures.

To simplify their observations, the researchers collided the circular gold atoms slightly off-center so that the area of impact would not be round, but shaped rather like a football--pointed at each end. This would force any streaming particles that headed out one of the tips of the football to pass through more of the hot soup than a particle exiting the side would. Differences in the number of particles escaping out the tip versus the side of the hot matter could reveal something of the nature of that hot matter, and maybe something about the strong force itself.

But a surprise was in store. Right where the gold atoms had collided, particles did indeed take longer to stream out the tips of the football than the sides, but farther from the exact point of collision, that difference evaporated. That defied a treasured theory called boost invariance.

"When we first presented this at a conference in Stony Brook, the audience couldn't believe it," says Manly. "They said, 'This can't be. You're violating boost invariance.' But we've gone over our results for more than a year, and it checks out."

Aside from revealing that scientists are missing a piece of the physics puzzle, the findings mean that understanding these collisions fully will be much more difficult than expected. No longer can physicists measure only the sweet spot where the atoms initially collided--they now must measure the entire length of the plasma, effectively making what was a two-dimensional problem into a three-dimensional one. As Manly says, this "dramatically increases the computing complexity" of any model researchers try to devise.

Modeling and understanding such collisions are extremely important because the way that the plasma cools--condensing like steam turning into water against a shower door--might shed some light on the mechanism that gives matter its very mass. Where mass itself comes from has been one of physicists chief conundrums for decades. Manly hopes that if we can understand exactly why the quark-gluon plasma behaves as it does, we might gain an insight into some of the rudiments of the world we live in.

"Understanding all the dynamics of the collision is really critical for actually trying to get the information we want," says Manly. "It may be that we have an actual clue here that something fundamental is different--something we just don't understand." Smiling, he adds, "Yet."

Editor's Note: The original news release can be found here.

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Note: This story has been adapted from a news release issued for journalists and other members of the public. If you wish to quote any part of this story, please credit University Of Rochester as the original source. You may also wish to include the following link in any citation:

http://www.sciencedaily.com/releases/2002/11/021113071031.htm

[griffin]

:) Thing about the Big Dog is if you recognize Him he won't bite...but if you turn your back and run your a hurtin' unit....

Otherwise....I'm thinking that non-constant time is an assumption due to the nature of the experiment. Doesn't Relativity add into their data transformations and models in terms of time references? Not sure where I was going with that....

My point is that I guess we alreay have a theory that helps to model time as a non-constant with respect to speed of particles. From our perspective it would appear that the particles decay slower in motion that they would at a stand still. Since you appear to be thinking in cartisiean (sp?) coordinate system, as we look at the particle decay in terms of individual axises, would the particle not decay faster along one axis than the other two since component velocity varies according to what direction the particle is going relative to the observation reference frame?

I have a hard time thinking of this in anything other than a polar system. I'm not thinking about it deep enough. I can't see how time could allow space expansion in only one dimension unless the energy capacity of one dimension needs to be maxed out before another dimension is needed....to expand the time/space continuum. :(

In any case, this is pretty cool.

[MattAMiller]

So you're saying that we think of space as being east to west, north to south, and up and down.

And the way that we think about time is past to present which is as inacurate as thinking about space as simply east to west.

Do I have it right?

[Scully]

Late-night ping!

[MHGinTN]

Yes! I'm conjecturing that space has three expressions or variables, linear, planar, volumetric and these variable expressions came in a progression as the spacetime bubble errupted into the universe we have now. [I've tried thinking of past as similar to linear, present as planar, and future as volumetric ... that sort of notion.]

[El Gato]

the event did not unfold quite the way they expected

Good, thats how we learn things. If everything goes just like you expected, you only learn that your understanding was OK. If things don't go the way you thought, you get to figure out why, and "Why" sometimes leads to the most amazing things. Like quantum mechanics itself.

[John Locke]

This is a fascinating result. The first and less interesting aspect is that all our current equations modeling the situation are wrong. Badly wrong.

The system has four coordinates: distance along the beam (z), distance from the center of the beam (r), angle of rotation from a reference line (eg vertical) (theta) and time into the experiment (t for clock time and tau for proper time).

A little paper on the background can be found at:
www.phys.jyu.fi/homepages/ruuskane/bielefld.pdf

The so-called "boost invariance", formally "Lorentz invariance under transformations along the beam direction" allows us to simplify the equations so the the rate at which stuff flies out of the collision depends on (r) and (tau) alone, with axial and azimuthal symmetry. Without that assumption, we cannot remove the (z) coordinate and so have to work in three dimensions not two. (Nobody has yet challenged the assumption of azimuthal - theta - symmetry)

But much the more important aspect is this: "boost invariance" is not just an arbitrary assumption; it is derivable directly from the Theory of Relativity. If this experiment holds up, and if no other fudge factor can be found, this is the first hard evidence against the ToR since the Michaelson-Gale experiment. We live in interesting times.

[Nick Danger]

So the government is now funding the destruction of gold, atom by atom. This proves it... it's a plot by the central bankers to enslave us all! Join the moron particles and escape, before it's too late.

[PatrickHenry]

Late-night ping!

Early morning catching up ping.

[PatrickHenry]

This is a fascinating result. The first and less interesting aspect is that all our current equations modeling the situation are wrong. Badly wrong.

This could be huge. An enormous amount of our recently-acquired knowledge comes as a result of such collisions. If we've been missing out on some information because of an incorrect assumption, it may be necessary to go back and re-run a load of ancient, now classic experiments again and review the observations. But I may be reading more into this than is warranted. I'll await the opinions of our heavyweights in this area.

[AndrewC]

This could be huge. An enormous amount of our recently-acquired knowledge comes as a result of such collisions.

Nah! It was cuz this guy was runnin the machine.

[Moonman62]

But much the more important aspect is this: "boost invariance" is not just an arbitrary assumption; it is derivable directly from the Theory of Relativity.

But isn't "boost invariance" an assumption of the ToR, essentially a belief that the laws of physics are the same under a change in velocity?

And it should be noted that Relativity has been confirmed by many different experiments over the past century, and now we may have a special case where it doesn't hold.

[PatrickHenry]

Self-search bump.

[AndrewC]

Splifford the bat says: Always remember:

A mind is a terrible thing to waste; especially on just-so stories
Just say no to narcotic drugs, alcohol abuse, and corrupt ideological doctrines.