The LHC, Large Hadron Collider

1. History

The Large Hadron Collider (LHC) was built by the European Organization for Nuclear Research (CERN). It is located one hundred meters underneath the ground between Switzerland and France.

Have you ever wondered what conditions were like right after the Big Bang occurred billions of years ago? Well physicists working on the LHC are trying to do just this. They are trying to produce head on collisions of two beams at a very high energy. The scientists use two beams of subatomic particles, known as “Hadrons,” which are either protons or lead ions. They then place these beams on opposite sides in the circular accelerator, with the beams increasing their energy each time around. Scientists believe that when these two particles finally cross paths and collide, the resulting factor will result in the same conditions of the world right after the big bang occurred.

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On September 10, 2008, Scientists were for the first time successful in their experiments regarding the LHC. Proton beams were successfully able to spin in the main ring of the LHC for the first time. However, the following day, the LHC was forced to shut down for repairs. There had been an accident between two superconductor metals resulting in repairs, which took over a year to complete. The following year, the first proton on proton collision was tested. The resulting factor produced energies of 2.36 TeV. However, the LHC was again shut down for reparations. Recently the LHC has reopened, and it was ready for experimentation in February, producing an even greater energy. Physicists recorded the energy as being 3.5 TeV, but this is only half of the energy the system was created to produce. The LHC is planned to reclose again in 2012, and to open the following year, 2013, to try to reach the designated energy.

Scientists working in Geneva, Switzerland at CERN, and all around the world study the energies produced by the LHC. (sources 1,2)



2. Purpose


The LHC was created to resolve important unanswered questions in particle physics. For example, the LHC will eventually help scientist to completet the standard model of particle physics (As of now the model contains gaps).1



standardmodel.jpg The picture to the left is the standard model of particle physics. The video to the right explains the standard model.










The missing part of the standar model is the higgs boson. The higgs boson is an undiscovered particel that is essential to the standard model. The higgs was first hypothosized in 1964, but it has yet to actually be discovered. Specifically at the LHC the ATLAS and CMS experiments are searching for evidence of the higgs boson. (sources 1,2)

3. How the LHC Works

The LHC is the most recent addition to the experiments created at CERN. The LHC is a twenty-seven kilometer ring of superconducting magnets with accelerating structures created to increase the energy of the beams while they are circulating through the tunnel. The machine is able to get the two beam particles, coming from opposite sides, to travel close to the speed of light. Inside the machine, the beam particles are kept on track by a strong magnetic field, which is created by using the superconducting magnets. The magnets have to remain at an extremely cold temperature, about -271 degrees Celsius, in order for them to be able to conduct electricity without resistance or loss of energy. In order for the metals to stay chilled at such an extreme temperature, the accelerator is hooked up to liquid helium. This helps keep the metals at the correct temperature, and is used for other parts of the accelerator as well.

Once the beam particles collide, thousands of new particles are created for scientists to observe. The detectors, found around collision areas, show different behavior habits of the new particles.

Millions of protons race toward each other at a time, but many times these protons never collide with another proton. However, sometimes, two protons will collide. Scientists will then observe this collision and see if it had any significance in their overall purpose. Many times, the collisions do not produce any profound results. (sources 3,4)



4. Experiments Within the LHC complex are six other experiments that are currently being conducted by the physicists at CERN. These are, ATLAS, CMS, ALICE, LHCb, TOTEM, and LHCf.


ALICE—A Large Ion Collider Experiment:


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The ALICE experiment was created to show conditions that occurred right after the Big Bang. For this experiment, the LHC collides lead ions together, creating a mixture called quark-gluon plasma. Quark-gluon plasma is a type of matter that scientists believe emerged after the Big Bang.
The ALICE experiment n the LHC creates temperatures that are extremely hotter than the sun. In fact, it generates temperatures over 100,000 times hotter that the center of the sun does! Scientists have concluded that with these extreme conditions, they will be able to melt the protons and neutrons, which in turn will free the quarks from their strong bonds with the gluons. In turn, they will create plasma-gluon, which was believed to have existed after the Big Bang. ALICE is twenty-six meters long, sixteen meters high, and sixteen meters wide. (sources 1,4)



ATLAS:
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ATLAS is a very diverse machine that is able to test different aspects of physics. It has participated in the search for the Higgs Boson and particles that could create dark matter. It is located in Meyrin, Switzerland, and is forty-six meters long, twenty-five meters high, and twenty-five meters wide. ALTAS has a large magnet system, which helps measure the particles momentum. It’s collision energy is 3.5 TeV, and as of December of 2009, it has had 917,131 collisions.
Hundreds of physicists work with the ATLAS experiment, hoping to discover something that will change the course of physics. (sources 1, 5)


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CMS:

CMS is one of the largest experiments located in the LHC section at CERN. Like ATLAS, the CMS is a multi-purpose experiment, and has helped search for the Higgs Boson as ell as extra dimensions and particles that make up dark matter. Unlike the other six experiments, the CMS was built above ground, and then transferred underground. It is twenty-one meters long, fifteen meters wide, and fifteen meters high. It is created around a large magnet that helps keep the protons on the right track during the experiment. (sources 1, 6)

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LHCb: The LHCb, part of CERN, is located in Ferney-Voltaire, France. LHCb stands for large hadron collider beauty. The word beauty refers to the bottom quark, or b cork. The actual experiment specializes in finding the slight differences between matter and antimatter by analyizing the beauty quark. According to the LHC website, this experiment will help scientists understand why we live in a world composed of almost all matter, but no antimatter. (sources 1,2)










TOTEM: TOTal Elastic and diffractive cross section Measurement



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The TOTEM experiment is located in Cessy, France. It is 440 meters long, 5 meters high and 5 meters wide. This means its length is just over a quarter of a mile. Fifty scientist are required to operate the TOTEM experiment. The TOTEM experiment studies forward particels in order to collect data not accessible to general-purpose experiments. For example, this experiment can measure the size of a proton and monitor the LHC's luminosity. To do this detectors housed in specially designed vacuum chambers, called Roman pots, are used. The results and data collected by TOTEM go along with the results and data collected by CMS. (sorces 1,2)


LHCf.jpg
LHCf: The LHCf, Large Hadron Collider forward, is located in Meyrin, Switzerland. It is the smallest of the six experiments at CERN. The LHCf consists of two detectors that stimulate cosmic rays using forward particles. This is done by measuring the energy and numbers of neutral pions produced by the experiment. This helps scientists understand larege-scale cosmic ray experiments that can cover over one thousand kilometers. (sources 1,2)












Sources:
1. http://en.wikipedia.org/wiki/Large_Hadron_Collider
2. http://public.web.cern.ch/public/en/LHC/LHC-en.html
3. http://www.lhc.ac.uk/about-the-lhc/how-does-the-lhc-work.html
4. http://angelsanddemons.cern.ch/video/how-lhc-works
5. http://atlas.ch/
6. http://cms.web.cern.ch/cms/Detector/index.html