Looking for neutralinos at the Large Hadron Collider

July 9, 2008 By Miranda Marquit feature

“We are looking at the heavens, and using the very biggest things to help up predict what will happen with the very smallest things,” David Toback tells PhysOrg.com. Toback is a professor at Texas A&M University in College Station, and he believes that there is a way to combine cosmology and particle physics in a way that can help us learn more about the universe.

“We’re interested in the dark matter question,” Toback continues. “Our current best guess is that the particles we know and love only make up about four percent of the stuff in the universe. Twenty-three percent of the universe is dark matter. The rest is dark energy. But I’m interested in dark matter, which should be made of particles. We want to know the properties of the bulk of the matter in the universe. This is a question that interests both cosmologists and particle physicists.”

Toback and his colleagues at Texas A&M, Richard Arnowitt, Bhaskar Dutta, Alfredo Gurrola, Teruki Kamon and Abram Krislock, have been working on a model that allows them to use information obtained from the Large Hadron Collider (LHC) to predict the amount of dark matter left over from the beginning of the universe. Their work is published in Physical Review Letters: “Determining the Dark Matter Relic Density in the Minimal Supergravity Stau-Neutralino Coannihilation Region at the Large Hadron Collider.”

“Our goal is to see whether our understanding of particles in the universe, the theory of supersymmetry, is correct. If it is, it will explain one of the most important questions in particle physics and cosmology in one fell swoop,” Toback says.

Supersymmetry is a theory that predicts that all elementary particles with spin are paired to other particles whose spin differs by half a unit. “One of the things that makes it special,” Toback says, “is that supersymmetry is a theory that predicts new particles. And one of the particles predicted is called a neutralino.” Neutralinos are thought to be heavy and stable, and they represent the leading candidate to explain the amount of cold dark matter indirectly detected in the universe.

The problem is that no one has been able to measure dark matter directly yet. This is where the LHC comes in. This $6 billion project is scheduled to begin operation later this summer, smashing protons into each other. The LHC is the largest and highest energy particle accelerator in the world, and Toback thinks that there’s a good chance that neutralinos could be produced from the collisions between protons. The data produced by the LHC will be made available to scientists around the world, including the team at Texas A&M.

“If our results are correct we now know much better where to look for this dark matter particle at the LHC,” Toback explains. “We’ve used precision data from astronomy to calculate what it would look like at the LHC, and how quickly we should be able to discover and measure it.” He and his colleagues have even gone so far to be show that with their measurements with LHC data they would be able to predict the amount of dark matter in the universe. This could be compared to what is seen from the WMAP satellite. “If we get the same answer,” he continues, “that would give us enormous confidence that the supersymmetry model is correct. If nature shows this, it would be remarkable.”

Toback says that the work he is doing with his peers at Texas A&M could make a connection between particle physics and cosmology. “If this works out, we could do real, honest to goodness cosmology at the LHC. And we’d be able to use cosmology to make particle physics predictions.”

Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

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1.8 / 5 (10) Jul 09, 2008
I found one in my cereal this morning. it tasted like plasma.
1.8 / 5 (8) Jul 09, 2008
Is it bad that the one I found tasted like Dark Matter?
1.9 / 5 (9) Jul 09, 2008
Yeah, I took a dark matter earlier, and Im pretty sure there were some strangelets in there from yesterday.
2.9 / 5 (8) Jul 09, 2008
You are all so politically incorrect. It should be called Albedo-Challenged Matter.
2.3 / 5 (7) Jul 09, 2008
Mmm, Neutralinos. Now with Strangelets!
2.9 / 5 (8) Jul 09, 2008
Ok, I have been reading this forum for ages but never registered. But now finally I have to react. I am just a dumb person with interest in physics and astronomy. But nobody has ever proved that dark energy and matter are real. Isn't is possible that our models of gravity and universe expansion on a large scale are just wrong? It seems that scientist want to hold on to their proven theories instead of admitting something could be wrong with their models.
4.4 / 5 (10) Jul 09, 2008
Igorus, it is indeed possible the models are wrong, which is why these scientists are constantly searching for ways to test them. Of course some scientists are biased, since they're human, but there are so many new scientists looking to make a name for themselves, I can't imagine a flawed model lasting very long in the face of a better model.

This is not to say that the model that predicts dark matter is right, only that it is currently the best model out there.
4.1 / 5 (7) Jul 09, 2008
Igorus, I dont know much about the evidence for dark energy, but the effects of dark matter can be qiantifiably measured and observed. Matter has strung its self along the stringy clumps of dark matter that are slung around the universe. My personal favorite theory on the subject is that in the process of symmetry breakdown, as the grand unified energy disseminated into the lesser constants of the strong force, the weak force, EM force, and some say matter, mass, gravity, and even 4D as we know it, particular aspects of this energy crystallized on the "other side", where further interaction with the rest of the universe was impossible except through gravity. These other forces were able to produce matter, just as in our spacetime, but the particles are of a different nature. I believe our scientists have predicted some of these particles based on symmetry breaking theory, and are trying to create them in the LHC. I say good luck and Im glad its on the other side of the world.
1.7 / 5 (11) Jul 10, 2008
Dark Matter is ad hoc for "Our theory is broken and we dont know where the matter is".

In other words dont believe it.
4.8 / 5 (8) Jul 10, 2008
start LHC already....
5 / 5 (3) Jul 10, 2008
Dark matter and dark energy are just working theories they seem to be pretty popular with scientists nowadays (mostly cause its a puzzle that needs solving - an opportunity for new scientists) but it is quite possible that some new observations and models will get rid of them sooner or later.
3 / 5 (2) Jul 10, 2008
@Igorus - This is perfectly valid point, and one which everyone in the scientific community has to ask. However look at what you wrote

"It seems that scientist want to hold on to their proven theories instead of admitting something could be wrong with their models."

and you will realize that you have sort of answered your own question. The theories, or models if you prefer, work for most of the phenomena we see. But to explain everything they need these new elements, like dark matter. Any new theory of gravity has to work as well or better than our current theories.
1.5 / 5 (4) Jul 10, 2008
Personally, I like dark matter, but the whole dark energy thing just dosent feel right.
4 / 5 (1) Jul 13, 2008
Personally, I like dark matter, but the whole dark energy thing just dosent feel right.

how that mercury? energy is not so different from matter (E=mc²). i think if there is dark matter there will be dark energy as well...
4 / 5 (1) Jul 13, 2008
Right, of course dark matter is energetic in nature, but I meant to say dark energy as it applies to expansion theory. it just seems kind of ad hoc to me, but perhaps It just I just havnt understood it yet. Can anyone explain how energy causes our universe to expand?
1 / 5 (1) Jul 13, 2008
I'll be ripped to shreds, but here's my interpretation:

Consider surface waves on water.

You drop a pebble into a clam body of water and it sends out ripples; the ripples expand outwards at an accelerating rate (due to gravity here on earth) as they race towards their original "ground state" before the energy (pebble) was added.

The "dark energy" is the unknown energy that is pulling everything back towards the ground state in the Universe before the Big Bang, which some suggest was the collision of "branes."

As the waves become smaller, the faster they go until until they reach the fastest speed they can go which is the total energy of the system.
1 / 5 (2) Jul 14, 2008
Whatever happened to the elecritic universe, earls? But no it's not dark matter. It's light matter - very light matter!

5 / 5 (1) Jul 15, 2008
That light matter crap is bogus. Maybe the stars are held in place by a giant tortoise.
not rated yet Jul 15, 2008
Yes, but it's a tortoise that weighs VERY LITTLE.
1 / 5 (2) Jul 16, 2008
5 / 5 (2) Jul 16, 2008
I'll be ripped to shreds, but here's my interpretation:

Consider surface waves on water.

You drop a pebble into a clam body of water and it sends out ripples; the ripples expand outwards at an accelerating rate (due to gravity here on earth) as they race towards their original "ground state" before the energy (pebble) was added.

The "dark energy" is the unknown energy that is pulling everything back towards the ground state in the Universe before the Big Bang, which some suggest was the collision of "branes."

As the waves become smaller, the faster they go until until they reach the fastest speed they can go which is the total energy of the system.
Waves travel at a constant speed in homogeneous media (determined by the strength of the restoring force and the density of the medium.) Dark energy is a theoretical type of energy with positive energy but negative pressure.

The mathematics of all reasonable physical models requires that the invariance of physical laws under rotation, translation in space, and at different times require that (angular and linear) momentum as well as total energy is conserved. This conservation combined with the accelerating expansion of the universe require a form of energy with negative pressure and positive energy (negative pressure to explain the acceleration and positive energy to explain the missing energy (after normal and dark matter are considered) necessary to give the universe the curvature we observe (essentially flat.) As an added bonus, the addition of a constant (that was originally employed to describe a static universe) to einstein's equations reproduce the same effects as dark energy (indeed, that is what is generally assumed (and that the constant is a result of "vacuum energy.")

Dark matter is simply what is used to explain an unexplained additional acceleration in the motion of stars toward the edge of most galaxies. Since the stars still rotate in stable orbits, the force must follow an inverse square law (just like gravity.) Since this is equivalent to having additional mass in galaxies, it is much simpler to assume that there is a form of matter that we cannot see (since the number of stars in a galaxy is correlated with the amount of (normal) matter.) This assertion is further validated by the discovery of gravitational lensing without the presence of significant numbers of stars (essentially the discovery of patches of only dark matter since large enough amounts of gas would likely begin to collapse and trigger a burst of star formation that would be visible.)

Thus dark energy and dark matter are both acceptable and reasonable extension of current theories to explain new phenomena (why create completely new theories if the current ones explain the same things more simply.)
1 / 5 (2) Jul 16, 2008
Light matter is just as good an explanation of phenomena currently attributed to both dark matter and dark energy, and also explains a whole load of other stuff like galaxy morphology, molecular clouds etc.

5 / 5 (1) Jul 16, 2008
I briefly read the material on light matter, but I just can not visualize how an outside force could by pushing the stars into tight orbits. It would be like balancing a broomstick on the end of your finger with a ball on the end. wouldnt the applied force have to shift constantly to keep them balanced? Dark matter seems like a more elegant and simple expalnation.
1 / 5 (2) Jul 16, 2008
The key thing is that a local reduction of density of anti-gravity matter has the same effect as a local presence of attractive matter. Once you've got that it's much easier to visualise. I'm adding a maths page later today which will explain the point I hope.

not rated yet Jul 16, 2008
not rated yet Aug 02, 2008
Let's review the messed-up logic:

1A) Because the Big Bang is perfectly proven undisputed fact obtained during a direct telephone call to God The Creator himself, the fact that the Big Bang occurred just like we know for certain that it did logically implies that these little black holes dissipate.
1B) We have spent billions of Euros on this thing to prove whether the Big Bang occurred or not, because we are not sure that the facts support a key criterion on which the Big Bang depends.

2A) Because input stimuli in the LHC happen in nature all of the time, the LHC is perfectly safe.
2B) We have spent billions of Euros on this thing, because we have never observed the outcomes of the LHC in nature.

1A and 1B cannot both be true. 2A and 2B cannot both be true.

To produce different outcomes than seen in nature, evidently the LHC actually does induce different input stimuli than possible outside of the laboratory, or else we would have already been able to observe the LHC's wonderful outputs already in nature. Even people with very high IQs can be very stupidly illogical. Book smarts are not street smarts!

5 / 5 (1) Aug 04, 2008
1A) Black holes dissipate as a result of Hawking radiation, not because the Big Bang formed in a certain way.

1B) The LHC does not exist to "prove whether the
Big Bang occurred". It exists to, among other things, determine what conditions were like in the early moments of the Bang. Learning these things will not prove they happened.

2A) That's the idea.

2B) True. Some things in nature are hard to observe. This is why laboratories exist.

Logician, sometimes "logic" can be improved with some reading and education. I would encourage you to start with Wikipedia and some good scientific cosmology books, perhaps Stephen Hawking's "A Brief History of Time". God is big enough to handle these kinds of scientific questions -- don't be afraid to ask them.

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