The Large Hadron Collider was built by the European Organization for Nuclear Research (CERN) with the intention of testing various predictions of high-energy physics, including the existence of the hypothesized Higgs boson[1] and of the large family of new particles predicted by supersymmetry.[2] It is funded by and built in collaboration with over 10,000 scientists and engineers from over 100 countries as well as hundreds of universities and laboratories.[3]
On 10 September 2008, the proton beams were successfully circulated in the main ring of the LHC for the first time.[4] On 19 September 2008, the operations were halted due to a serious fault between two superconducting bending magnets.[5] Repairing the resulting damage and installing additional safety features took over a year.[6][7] On 20 November 2009 the proton beams were successfully circulated again,[8] On 23 November 2009, the first proton–proton collisions were recorded, at the injection energy of 450 GeV per particle.[9] On 18 December 2009 the LHC was shut down after its initial commissioning run, which achieved proton collision energies of 2.36 TeV, with multiple bunches of protons circulating for several hours and data from over one million proton-proton collisions. The LHC will now be down until February 2010. During the intervening interval, improvements in magnet protection, etc, will be carried out with the aim of permitting research at 3.5 TeV per beam during the 2010 operational period. [10]
Contents
A simulated event in the CMS detector, featuring the appearance of the Higgs boson.
Physicists hope that the LHC will help answer the most fundamental questions in physics, questions concerning the basic laws governing the interactions and forces among the elementary objects, the deep structure of space and time, especially regarding the intersection of quantum mechanics and general relativity, where current theories and knowledge are unclear or break down altogether. These issues include, at least:[11]
• Is the Higgs mechanism for generating elementary particle masses via electroweak symmetry breaking indeed realised in nature?[12] It is anticipated that the collider will either demonstrate (or rule out) the existence of the elusive Higgs boson(s), completing (or refuting) the Standard Model.[13][14][15]
• Is supersymmetry, an extension of the Standard Model and Poincaré symmetry, realised in nature, implying that all known particles have supersymmetric partners?[16][17][18] These may clear up the mystery of dark matter.
• Are there extra dimensions,[19] as predicted by various models inspired by string theory, and can we detect them?
Other questions are:
• Are electromagnetism, the strong nuclear force and the weak nuclear force just different manifestations of a single unified force, as predicted by various Grand Unification Theories?
• Why is gravity so many orders of magnitude weaker than the other three fundamental forces? See also Hierarchy problem.
• Are there additional sources of quark flavours, beyond those already predicted within the Standard Model?
• Why are there apparent violations of the symmetry between matter and antimatter? See also CP violation.
• What was the nature of the quark-gluon plasma in the early universe? This will be investigated by ion collisions in ALICE.
Date Event
10 Sep 2008 CERN successfully fired the first protons around the entire tunnel circuit in stages.
19 Sep 2008 Magnetic quench occurred in about 100 bending magnets in sectors 3 and 4, causing a loss of approximately 6 tonnes of liquid helium.
30 Sep 2008 First "modest" high-energy collisions planned but postponed due to accident.
16 Oct 2008 CERN released a preliminary analysis of the incident.
21 Oct 2008 Official inauguration.
5 Dec 2008 CERN released detailed analysis.
20 Nov 2009 Low-energy beams circulated in the tunnel for the first time since the incident.[37]
23 Nov 2009 First particle collisions in all 4 detectors at 450 GeV.[9]
30 Nov 2009 LHC becomes the world's highest energy particle accelerator achieving 1.18 TeV per beam, beating the Tevatron's previous record of 0.98 TeV per beam held for 8 years.[38]
Early 2010 The LHC expected to continue operation ramping energies up to 3.5 TeV, then later in the year up to 5 TeV per beam.[39]
End of 2010 The LHC will be shut down and work will begin on it to allow it to operate at 7 TeV per beam.
[edit] Expected results
pages from CERN