Large Hadron Collider
The Large Hadron Collider (LHC) is one of mankind’s greatest engineering milestones in history. It is the world’s largest and most powerful particle accelerator, spanning the length of several standard football fields and reaching energy levels of 7 tera-electronvolts. The Collider was built by the European Organization for Nuclear Research (in French the name translated to Conseil Européen pour la Recherche Nucléaire) or CERN in order to test different theories of particle physics. One of these theories was to prove or disprove the existence of the Higgs Boson particle, a particle that is theorized to be the basic building block of the universe.
The Collider was built in an underground circular tunnel about 17 miles long that is located between the borders of Switzerland and France near Geneva. Construction of the LHC took around thirteen years to complete with the efforts of over 10,000 scientists and engineers from all over the world. Physicists hope that the LHC will lead them into new physics beyond the Standard Model we know today. This gigantic particle accelerator can be the key to answering many of the unanswered fundamental physics problems, such as the existence of an extra dimension, the nature of dark matter and its account of mass in the universe, and the confirmation of the existence of the Higgs Boson particle.
Inside the accelerator, two light speed particles move in opposite directions inside beam pipes that are kept in an ultra-high vacuum environment. The particle beams are guided by a powerful magnetic field created by electromagnets and collide with each other on the other end of the circular tunnels. Since these atomic particles are incredibly small, making them collide requires extreme precision. To increase the chances of collision, more magnets are used to condense the beams before the collision point. The particle beams inside the LHC collide at four specific locations around the circular tunnel, each is the location of the four main particle detectors named ATLAS, CMS, ALICE, and LHCb. These particle detectors are used to collect data and results when the particle beams collide. Two of them, named ATLAS (A Toroidal LHC Apparatus) and CMS (Compact Muon Solenoid), are used for general purposes testing. These two in particular were used to search for the Higgs Boson particle. ALICE (A Large Ion Collider Experiment) and LHCb (Large Hadron Collider beauty) have more for specific roles, such as heavy ion collision. There are three minor particle detector called TOTEM, MoEDAL, and LHCb that are much smaller than the other four and specialize in certain research areas.
The greatest discovery made by the LHC was the confirmation of the existence of the Higgs Boson particle, also known as “the god particle”. Theoretically, this particle gives mass to all matter which allows it to bind together and form various things throughout the universe. In the Standard Model, the Higgs Boson forms an invisible force known as the Higgs field, a cosmic net that slows down moving particles and makes them heavier as they pass through the field. Different particles move at different speeds through the Higgs field. A particle that moves though the field at the speed of light is massless, while particles that move slower than light speed though the field are heavier. In the larger view, this universe-size field essentially holds all of physical existence together by giving different masses to all of the elementary particles.
For the Large Hadron Collider to find the Higgs Boson particle, it smashes two proton beams together in order to recreate the conditions of the Big Bang. The Higgs Boson is the rare by-product produced by the collision that spreads away from the epicenter. Previous attempts to find the elusive Higgs Boson using particle accelerators failed because the energy required for the particle to be seen was enormous. The LHC was built as the largest particle accelerator that can produce the highest planned energy collision needed to produce Higgs Boson. Because the Higgs Boson decays too quickly for particle detectors to detect it directly, the detectors instead collect all the decay signatures that are produced from the collision and use them to reconstruct the original product as much as possible. If the observed decay products match a possible decay process of a Higgs boson, then it’s possible that Higgs boson may have been created. To confirm the existence of the Higgs boson, physicists determine set requirements that must be met. One of these requirements is that the Higgs boson is a scalar particle where the spin (angular momentum) is zero, so the final product that is reconstructed also has a spin of zero. Other set requirements include that the particle has positive parity, has predicted decay patterns, and has constant energy.
On 14 March 2013, CERN tentatively confirmed the existence of the Higgs Boson in a conference. The confirmation of the particle is held as a great discovery in particle physics as it validates the last unknown part of the standard model. At last the LHC had successfully found the elusive particle and opened the door to “new physics.”
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- What is the Higgs Boson?, 2011.
- Dennis Overbye, CERN Physicists may have discovered Higgs Boson Particle?, The New York Times, 2012.
- The Higgs boson: Evolution or Revolution?, CERN, 2011.