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A visualization of particles jets in the CMS. Yellow is the path of the particles, while blue and red represent energy detected from the particles.  (Source: CERN/Imperial College of London)
Discovery of dark matter's behavior would solve many outstanding mysteries in physics

Dark matter makes up five times more of the universe's mass than visible matter (~25% vs ~5%), yet scientists have yet to directly observe this ultra-abundant substance.  Scientists also have yet to observe dark energy, which may well beat out normal energy in universal abundance.  This lack of direct observations means that scientists know precious little about two of the most important physical components of our universe.

That could soon change.  CERN's Large Hadron Collider, a 17-mile long circular underground track that is chilled to almost zero degrees Kelvin, is recording incredibly violent collisions, the likes of which haven't been seen since billions of years ago.  Those collisions will likely produce exotic substances like dark matter, which will be analyzed by the LHC's instruments, unlocking long debated mysteries of physics.

Scientists think they are making progress in the hunt for the SUSY – also known as supersymmetric particle, or 'sparticle'.  Scientists believe the sparticle may be the mysterious dark matter, given its theoretical stability.

In order to detect sparticles, scientists must probe the matter resulting from the collision for the absence of energy and momenta signals -- the sign that a sparticle was produced, rather than a standard particle.  This lack of energetic emissivity is the reason why dark matter is dark -- it does not transfer energy to photons, like standard particles.

More specifically, the researchers are trying to detect a "jet" of particles traveling in the same direction, post proton-beam collision, that lack a significant amount of detected energy and momentum.  

Professor Oliver Buchmueller [profile], a faculty member at the Department of Physics at Imperial College London who is doing research at CERN, describes the LHC team's findings, stating [press release], "We need a good understanding of the ordinary collisions so that we can recognise the unusual ones when they happen. Such collisions are rare but can be produced by known physics. We examined some 3-trillion proton-proton collisions and found 13 'SUSY-like' ones, around the number that we expected. Although no evidence for sparticles was found, this measurement narrows down the area for the search for dark matter significantly."

The CMS (compact muon solenoid) detector was co-designed by faculty at the Imperial College, one of Europe's best physics schools.  

Professor Geoff Hall [profile], another Imperial College physics faculty member working at CERN, describes the recent detection of "SUSY-like" streams of particles, stating, "We have made an important step forward in the hunt for dark matter, although no discovery has yet been made. These results have come faster than we expected because the LHC and CMS ran better last year than we dared hope and we are now very optimistic about the prospects of pinning down Supersymmetry in the next few years."

Later this year, physicists will run more trials, which they hope will verify the existence of dark matter in the stream.  They also hope that the theory of supersymmetry will be verified as an accurate description of dark matter, allowing the Standard Model of particle physics to be officially extended.

Looking ahead there's also much hope that the higher-energy collisions might yield a legendary Higgs boson, which would offer much more insight into the behavior of the universe.  The LHC's other major detector -- ATLAS (A Toroidal LHC ApparatuS) -- was designed to search for the Higgs boson.



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RE: Here We Go Again
By JediJeb on 2/2/2011 12:07:50 PM , Rating: 2
I was thinking along these lines a while back, concerning the idea of Expansion. We conclude that the universe is expanding, and with recently determined values of the Hubble constant that it will expand forever. We also determine the distances to far off galaxies by their redshift in that the more red shifted they are the farther away they are. This is because the faster they are moving away the more red shifted they will be. But that would mean that galaxies were moving away from us faster billions of years ago than they were millions of years ago because galaxies that are only millions of light years distant are less redshifted. Would that not imply the opposite of the expansion belief, in that the speed at which galaxies are moving away has slowed over time, not sped up? If the expansion is speeding up then the farther away galaxies should be less redshifted and not more, since what we are seeing is not what is happening now but what happened in the far past. How can we base what is happening now on 10 billion year old data?

Dark matter can be effected by the same observations, we are using billion year old data to describe what is happening now. Do the models account for the temporal gradient in the data as data points taken from different observations not only differ in their x,y,z coordinates but also in time coordinates? Imagine if you had a field that was one light year across yet experienced changes in season the same as we see here in a year cycle. Your instantaneous view of that field would show parts of it as it appeared in spring, summer, fall and winter all at once. Without compensating for that temporal variation you would assume that the field existed in different forms of seeds sprouting, growing, maturing, and dying all at once then in reality they did not.

Just something I have wondered about.


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