Something I have wanted to do for a while is write about CERN and the LHC. CERN is a European Organization for Nuclear Research. Whenever I hear nuclear I tense up and think about nuclear reactors and how dangerous nuclear power plants can be (they get lots of bad publicity). But CERN is the leading organization in particle research. Something, consequently, that I am interested it. I find it really nerdy to tell my friends that I have a secret love for quantum physics and the idea of dark matter and energy really gets the juices flowing. J So let the nerdy-ness begin. I am very excited about the latest experiments going on at CERN with the LHC-Large Hadron Collider. This is the largest and highest energy particle accelerator. I think the reason I am such a big fan is the fact that we are on the precipice of discovery only ever dreamed of. We are at the point where we can discover new, exciting, particles and test many theory’s that have, until this point, been un-testable. Wow right, it really is exacting. Any who I wanted to write today because it is really hard to find good resources that explain what experiments are being performed at the LHC. Granted you can find each of these experiments website but most of us are not particle physicist and we don’t speak monkey. J So I am going to try and compile a list and brief description of each experiment being preformed and also how awesome they are…
ATLAS (A Toroidal LHC ApparatuS) is the first experiment. This experiment is designed to observe phenomena that involve highly massive particles which were not observable using earlier lower-energy accelerators and might shed light on new theories of particle physics beyond the Standard Model. The Standard Model is something we talked about in class last night so I am now an expert (go ahead and laugh). The standard Model is how scientist currently perceive atoms and there structure. You have a nucleus housing protons and storm clouds housing the electrons (this is a gross simplification). The exciting thing about ATLAS is that we might be able to better understand the structure and composition of the atom and all of the partials involved.
The Compact Muon Solenoid (CMS) is the next experiment. This is a general purpose experiment to test all physics at the TeV scale. TeV is a unit electrical voltage. The LHC are performing experiments with so much more energy than has ever been tested. We just don’t know what that kind of energy will do to a particle, hence CMS. Another component of the CMS experiment is to discover the Higgs Boson particle. This is a theoretical particle that has never been observed, only postulated. The theory is that this particle is what gives us mass. It is a highly debated and scrutinized topic in physics. The media refer to it as the “God particle”. It is really exciting to think that this experiment might be able to observe this particular particle and give us a better understanding of how mass is created. Here is a neat website I found that explains Higgs Boson http://www.exploratorium.edu/origins/cern/ideas/higgs.html. This experiment will also study the physics of the standard model as well as other aspects of heavy ion collisions.
The LHCb (standing for "Large Hadron Collider beauty" where "beauty" refers to the bottom quark) experiment is our next experiment. The LHCb particularly aimed at measuring the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark). (Thanks Wikipedia) CP violation is a violation of the idea of CP symmetry. CP symmetry is the combination of C and P symmetry. Ok, got it…what is C and P symmetry?? It states that the laws of physics should be the same if a particle were interchanged with its antiparticle (C symmetry, or charge conjugation symmetry), and left and right were swapped (P symmetry, or parity symmetry). So this experiment is testing whether or not this CP symmetry actually exists or if some other physical property is occurring.
Next is ALICE. ALICE is optimized to study heavy ion collisions. Pb-Pb nuclei collisions will be studied at a centre of mass energy of 2.76 TeV per nucleon. The resulting temperature and energy density are expected to be large enough to generate a quark-gluon plasma, a state of matter wherein quarks and gluons are deconfined. (I don’t think our world would function these days without Wikipedia) So umm…a quark-gluon plasma you say…what exactly is that?? Let’s start with quarks. These are subatomic partials that exist in the atom. Quarks combined to form Hadrons, the most stable of which are protons and neutrons. Gluons are the expression of quark interactions and are indirectly related to proton and neutron binding in the nucleus. The quark-gluon plasma contains quarks and gluons, just as normal (baryonic) matter does. The difference between these two phases of QCD is that in normal matter each quark either pairs up with an anti-quark to form a meson or joins with two other quarks to form a baryon (such as the proton and the neutron). In the QGP, by contrast, these mesons and baryons lose their identities and dissolve into a fluid of quarks and gluons. In normal matter quarks are confined; in the QGP quarks are deconfined. In classical QCD quarks are the Fermionic components of mesons and baryons while the gluons are considered the Bosonic components of such particles. The gluons are the force carriers or bosons of the QCD color force while the quarks by themselves are their Fermionic matter counterparts. On a side note both ATLAS and CMS are also testing QCD. It makes you want to enroll in particle physics right now huh?? J
Total Cross Section, Elastic Scattering and Diffraction Dissociation (TOTEM) is next. The experiment does what its name suggests: testing total cross section, elastic scattering and diffraction dissociation. Ok and that means?? Here is some information from CERNs website (http://public.web.cern.ch/public/en/lhc/TOTEM-en.html): The TOTEM experiment studies forward particles to focus on physics that is not accessible to the general-purpose experiments. Among a range of studies, it will measure, in effect, the size of the proton and also monitor accurately the LHC's luminosity.
To do this TOTEM must be able to detect particles produced very close to the LHC beams. It will include detectors housed in specially designed vacuum chambers called 'Roman pots', which are connected to the beam pipes in the LHC. Eight Roman pots will be placed in pairs at four locations near the collision point of the CMS experiment.
Although the two experiments are scientifically independent, TOTEM will complement the results obtained by the CMS detector and by the other LHC experiments overall.
The LHCf ("Large Hadron Collider forward") is a special-purpose Large Hadron Collider experiment for astroparticle (cosmic ray) physics. LHCf scientists study proton-proton collisions at the LHC that are similar to the collisions of ultra-high-energy cosmic rays with the earth's atmosphere. Their results contribute to the measurement of the energy of these cosmic rays by the large cosmic-ray experiments at the Pierre Auger Observatory in Argentina and the Telescope Array in Utah. (http://www.uslhc.us/LHC_Science/Experiments/LHCf)
Those are the experiments and this is a gross simplification of what they do. Here are the links to each experiments website in case you want to study up on them. It was a very exciting birthday for me this year as the first collisions started at the LHC on March 30th. J I love particle physics and I admit to knowing nothing about it! but that doesn’t stop me from jumping feet first.
ALICE-- http://aliceinfo.cern.ch/Public/Welcome.html
ATLAS-- http://atlas.ch/
CMS-- http://cms.web.cern.ch/cms/index.html
LHCB-- http://lhcb-public.web.cern.ch/lhcb-public/
TOTEM-- http://totem-experiment.web.cern.ch/totem-experiment/
LHCF-- http://public.web.cern.ch/public/en/lhc/LHCf-en.html
