The Large Hadron Collider is a particle accelerator housed in a 27km circular tunnel underneath the border between France and Switzerland. The instrument allows scientists to smash protons together at extremely high speeds and it is hoped that this will tell them more about what happened in the first moments after the Big Bang. Experiments here may also demonstrate the existence of the Higgs boson, a particle which is postulated to confer mass to other particles.
When on 30 March 2010, the accelerator began colliding protons together with a total energy of 7,000 billion electon volts, it became the most powerful particle collider ever.
Image: Installation of the silicon tracking detector in the CMS experiment (credit: CERN)
The LHC investigates the first moments after the Big Bang.
Researchers introduce the Large Hadron Collider.
The Large Hadron Collider, constructed in tunnels below Geneva, is the world's largest particle accelerator. Scientists using the LHC will recreate conditions less than a billionth of a second after the Big Bang.
BBC News reports from the Large Hadron Collider.
Reporting from the Large Hadron Collider at CERN, David Shukman finds out what scientists hope the experiment will tell them.
The Large Hadron Collider (LHC) is the world's largest and most powerful particle collider, and the largest single machine in the world, built by the European Organization for Nuclear Research (CERN) from 1998 to 2008.
The LHC was built in collaboration with over 10,000 scientists and engineers from over 100 countries, as well as hundreds of universities and laboratories. It lies in a tunnel 27 kilometres (17 mi) in circumference, as deep as 175 metres (574 ft) beneath the Franco-Swiss border near Geneva, Switzerland.
Its aim is to allow physicists to test the predictions of different theories of particle physics and high-energy physics like the Standard Model, and particularly prove or disprove the existence of the theorized Higgs boson and of the large family of new particles predicted by supersymmetric theories. The discovery of a particle matching the Higgs boson was confirmed by data from the LHC in 2013. The LHC is expected to address some of the unsolved questions of physics, advancing human understanding of physical laws. It contains seven detectors, each designed for certain kinds of research.
As of 2015, the LHC remains the largest and most complex experimental facility ever built. Its synchrotron is designed to collide two opposing particle beams of either protons at up to 4 teraelectronvolts (4 TeV or 0.64 microjoules), or lead nuclei (574 TeV per nucleus, or 2.76 TeV per nucleon), with energies increased to around 6.5 TeV (13 TeV collision energy) in 2015. Collision data was also anticipated to be produced at an unprecedented rate of tens of petabytes per year, to be analysed by a grid-based computer network infrastructure connecting 140 computing centers in 35 countries (by 2012 the LHC Computing Grid was the world's largest computing grid, comprising over 170 computing facilities in a worldwide network across 36 countries).
The LHC went live on 10 September 2008, with proton beams successfully circulated in the main ring of the LHC for the first time, but nine days later a faulty electrical connection led to the rupture of a liquid helium enclosure, causing both a magnet quench and several tons of helium gas escaping with explosive force. The incident resulted in damage to over 50 superconducting magnets and their mountings, and contamination of the vacuum pipe, and delayed further operations by 14 months. On November 20, 2009 proton beams were successfully circulated again, with the first recorded proton–proton collisions occurring three days later at the injection energy of 450 GeV per beam. On March 30, 2010, the first collisions took place between two 3.5 TeV beams, setting a world record for the highest-energy man-made particle collisions, and the LHC began its planned research program.
The LHC has discovered a massive 125 GeV boson (which subsequent results confirmed to be the long-sought Higgs boson) and several composite particles (hadrons) like the χb (3P) bottomonium state, created a quark–gluon plasma, and recorded the first observations of the very rare decay of the Bs meson into two muons (Bs0 → μ+μ−), which challenged the validity of existing models of supersymmetry.
The LHC operated at 3.5 TeV per beam in 2010 and 2011 and at 4 TeV in 2012. Proton–proton collisions are the main operation mode. It collided protons with lead nuclei for two months in 2013 and used lead–lead collisions for about one month each in 2010, 2011 and 2013. After the end of the 2012-2013 run, the LHC went into shutdown for upgrades to increase beam energy to 6.5 TeV per beam and beams successfully circulated in the machine again in April 2015.