LHC Experiments
There are four main experimental complexes at the LHC. Basically at each spot where the two accelerator rings cross one another, there is a laboratory complex (either a big lab complex or a small town - however you want to look at it) with a couple dozen big buildings or so that house a bunch of laboratories and other geeky physics stuff. Each complex is called simply an 'experiment' - even though each site will in fact be the place of many different experiments. When people speak of the LHC they say there are four experiments.
There is some mission overlap between the various experiments which should foster both competition and carefulness on the part of their respective scientists. There are most definitely Nobel Prizes on the line for a few of these physicists - should they make key discoveries. But there is also the prospect of ending up a laughingstock for prematurely announcing a discovery that doesn't pan out. The media will no doubt play up this aspect of things to add some human drama to the physics (which makes pretty dull news for the masses. (except for the masses of quarks and gluons - couldn't resist.))
In fact, the more research I do the more I become convinced that the four experiments have been given different names and different staff, different facilities and different websites... but they seem to be doing largely the same stuff from a mission perspective. So below I detail as best i can what each experiment purports to be up to, but from what I can gather, each experiment is just a town full of geeks sitting on an intersection of the two rings and they all figure that banging protons together and looking at the debris is what they are supposed to do.
Of course I should note that I am not a physicist and that though I now have an account at the CERN website which makes me feel sorta warm and geeky fuzzy, I still have access to only braindead public stuff, so I could be wrong about the unclear division of labor between the experiments (but I don't think so.)
Below are some facts and figures and photos and maybe a bit of editorializing on the four experiments.
ALICE (A Large Ion Collider Experiment) Here 700 scientists and engineers will perform experiments involving collisions of lead atoms that have been stripped of their electron clouds. These big, fat atomic nuclei will be slammed together at LHC energies in order to create and study a hypothetical new phase of matter called a quark-gluon plasma. They will study the various particles that come out of the collisions and hopefully come to a better understanding of a few aspects of supersymmetry.
If you would like to poke around inside Alice, this link will take you to a fine site where you can take a virtual tour. When I first hit this site I thought it was a slide show... and a rather dull one at that. Until I realized that the photos are fully 3D and you can zoom in and out as well as mouse around and see in 360 degrees.
http://aliceinfo.cern.ch/Public/en/Chapter4/Chapter4VirtualTour.html
ATLAS (A Toroidal LHC Apparatus) Here 3000 scientists and engineers will slam protons together at ultra high energy in order to recreate conditions as close as possible to those that occurred at the beginning of the universe. They are hoping that when they recreate these conditions they will be able to shed some light on several major questions about the nature of the universe.
- Dark matter: Only a small percentage of the matter in the universe turns out to be normal matter like we are used to - only about 4% in fact. The rest is of some other type. For now scientists are calling the other types dark matter and dark energy. Scientists on the ATLAS experiments hope to discover whether dark matter is made of as yet undiscovered particles and if so they hope to find a couple, give them funny names and take their pictures.
- Extra spatial dimensions: They also are hoping to find evidence for extra spatial dimensions. Physicists are mystified about why gravity is such a wimpy force compared to the other forces of nature. They cannot understand why a simple child's magnet can lift a paperclip and thus overpower the gravity of the entire earth. One theory to explain the weakness of gravity is that gravity might be exerting itself in other, unseen spatial dimensions, thus diluting its effect in the three spatial dimensions we are readily able to perceive. Physicists are hoping to discover evidence of gravitons being absorbed into extra dimensional spaces. And if the occasional black hole happens to get created during this investigation; well, the math says it will evaporate immediately. (It should be noted that cosmic ray collisions with matter particles take place regularly at much much higher energies than those that can ever be created at the LHC. Physicists state that if a black hole could be created and sustained then it already would have been created as the result of natural cosmic ray collisions - so they are not the least bit worried. Someone though, might also note that cosmic rays do not generally occur in unremitting streams and that there are not generally ever sustained periods of 20 cosmic ray collisions occurring every 25 nanoseconds in nature anywhere as far as I know... but hey, if half a hundred black holes do somehow manage to merge into one that doesn't immediately evaporate, what the heck, right?) At any rate if a killer black hole decides to make liars of all the King's best geeks and show up at the LHC, it will be the ATLAS guys who have the front row seats.
- The Higgs boson: Arguably the most important thing and certainly the most talked about and anticipated thing that ATLAS will be used for is the discovery of the Higgs boson. The Higgs is the particle that physicists believe to be responsible for the mass of the quarks and gluons (gluons should be massless but aren't(!)). (They still don't have any idea why electrons, muons, taus, and neutrinos have their mass.) If it is discovered at the LHC - and everything I read leads me to believe that they really are expecting to find the thing - it will be discovered by the ATLAS team.
LHC.b. (LHC beauty experiment) Scientists here will perform high energy experiments that deal with a subatomic property that physicists call beauty (either because they are weird, or because they didn't want to be studying 'bottoms' which is the other name physicists have for this property). They talk about beauty alot on the various sites, but from what I gather they are really just doing general investigations into quarks of whatever sort happen to show up. I can't really determine what they are doing here that the ATLAS guys don't also claim to be doing. I will keep looking into it, but for now my conclusion is that LHC.b is doing more or less the same thing as ATLAS with a slightly different set of detection equipment. (Hopefully someone from CERN will read this and tear me a new one in the comments section, at which point I shall hastily revise this post in light of my new illumination...) [Illumination is what they call it when the collider is working... :-) ]
CMS (Compact Muon Solenoid). In a fit of colossal irony, the detector in the Compact Muon Solenoid is the heaviest scientific instrument ever constructed. It weighs 28 million pounds - which makes it heavier than the Eiffel tower.
Here's one small piece of it being delivered:
Now, what would a story about High Energy Particle Physics be without a rap video? Yes. I was sceptical too... but this is actually pretty damned informative.
Further reading:
Vanity Fair article:
Great slide deck
United States involvement in the LHC
Lecture by Nobel Laureate Frank Wilczek on the LHC
[I will likely continue polishing this entry over the next week or so, but for now I am itching to get back to AI and digital sentience...]
Need to research these experiments and incorporate them into the post:
Totem - Will measure the size of protons and how they scatter, among other things
LHCf - Will simulate cosmic rays, naturally occurring charged particles from outer space
-j
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