Large Hadron Collider

Large Hadron Collider

Overview
The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...

. It is expected to address some of the most fundamental questions of physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

, advancing the understanding of the deepest laws of nature.

The LHC lies in a tunnel 27 kilometres (16.8 mi) in circumference, as deep as 175 metres (574.1 ft) beneath the Franco-Swiss border near Geneva
Geneva
Geneva In the national languages of Switzerland the city is known as Genf , Ginevra and Genevra is the second-most-populous city in Switzerland and is the most populous city of Romandie, the French-speaking part of Switzerland...

, Switzerland. This synchrotron
Synchrotron
A synchrotron is a particular type of cyclic particle accelerator in which the magnetic field and the electric field are carefully synchronised with the travelling particle beam. The proton synchrotron was originally conceived by Sir Marcus Oliphant...

 is designed to collide
Collider
A collider is a type of a particle accelerator involving directed beams of particles.Colliders may either be ring accelerators or linear accelerators.-Explanation:...

 opposing particle beams
Charged particle beam
A charged particle beam is a spatially localized group of electrically charged particles that have approximately the same velocity . The kinetic energies of the particles are typically measured in keV or MeV, much larger than the energies of particles at ambient temperature...

 of either proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

s at an energy of 7 teraelectronvolts
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

 (7 TeV or 1.12 microjoules
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...

) per nucleon, or lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 nuclei
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 at an energy of 574 TeV (92.0 µJ) per nucleus (2.76 TeV per nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...

).
Discussion
Ask a question about 'Large Hadron Collider'
Start a new discussion about 'Large Hadron Collider'
Answer questions from other users
Full Discussion Forum
 
Recent Discussions
Encyclopedia
The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...

. It is expected to address some of the most fundamental questions of physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

, advancing the understanding of the deepest laws of nature.

The LHC lies in a tunnel 27 kilometres (16.8 mi) in circumference, as deep as 175 metres (574.1 ft) beneath the Franco-Swiss border near Geneva
Geneva
Geneva In the national languages of Switzerland the city is known as Genf , Ginevra and Genevra is the second-most-populous city in Switzerland and is the most populous city of Romandie, the French-speaking part of Switzerland...

, Switzerland. This synchrotron
Synchrotron
A synchrotron is a particular type of cyclic particle accelerator in which the magnetic field and the electric field are carefully synchronised with the travelling particle beam. The proton synchrotron was originally conceived by Sir Marcus Oliphant...

 is designed to collide
Collider
A collider is a type of a particle accelerator involving directed beams of particles.Colliders may either be ring accelerators or linear accelerators.-Explanation:...

 opposing particle beams
Charged particle beam
A charged particle beam is a spatially localized group of electrically charged particles that have approximately the same velocity . The kinetic energies of the particles are typically measured in keV or MeV, much larger than the energies of particles at ambient temperature...

 of either proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

s at an energy of 7 teraelectronvolts
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

 (7 TeV or 1.12 microjoules
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...

) per nucleon, or lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 nuclei
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 at an energy of 574 TeV (92.0 µJ) per nucleus (2.76 TeV per nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...

). The term hadron
Hadron
In particle physics, a hadron is a composite particle made of quarks held together by the strong force...

refers to particles composed of quark
Quark
A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly...

s.

The Large Hadron Collider was built by the European Organization for Nuclear Research
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...

 (CERN) with the intention of testing various predictions of high-energy physics, including testing for the existence of the hypothesized Higgs boson
Higgs boson
The Higgs boson is a hypothetical massive elementary particle that is predicted to exist by the Standard Model of particle physics. Its existence is postulated as a means of resolving inconsistencies in the Standard Model...

 and of the large family
Superpartner
In particle physics, a superpartner is a hypothetical elementary particle. Supersymmetry is one of the synergistic theories in current high-energy physics which predicts the existence of these "shadow" particles....

 of new particles predicted by supersymmetry
Supersymmetry
In particle physics, supersymmetry is a symmetry that relates elementary particles of one spin to other particles that differ by half a unit of spin and are known as superpartners...

. It was built in collaboration with over 10,000 scientists and engineers from over 100 countries, as well as hundreds of universities and laboratories.

On 10 September 2008, the proton beams were successfully circulated in the main ring of the LHC for the first time, but 9 days later operations were halted due to an explosion involving helium gas.
On 20 November 2009 they were successfully circulated again, with the first recorded proton–proton collision
Collision
A collision is an isolated event which two or more moving bodies exert forces on each other for a relatively short time.Although the most common colloquial use of the word "collision" refers to accidents in which two or more objects collide, the scientific use of the word "collision" implies...

s occurring 3 days later at the injection energy of 450 GeV per beam. After the 2009 winter shutdown, the LHC was restarted and the beam was ramped up to 3.5 TeV per beam (half its designed energy). On 30 March 2010, the first planned collisions took place between two 3.5 TeV beams, a new world record for the highest-energy man-made particle collisions. The LHC will continue to operate at half energy until the end of 2012; it will not run at full energy (7 TeV per beam) until 2014.

Purpose



Physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

s hope that the LHC will help answer some of the fundamental open questions in physics, concerning the basic laws governing the interactions and forces among the elementary objects
Elementary particle
In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...

, the deep structure of space and time, and in particular the intersection of quantum mechanics
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

 and general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...

, where current theories and knowledge are unclear or break down altogether. Data is also needed from high energy particle experiments to indicate which versions of scientific models are more likely to be correct - in particular to choose between the Standard Model
Standard Model
The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...

 and Higgsless model
Higgsless model
In particle physics, a Higgsless model is a model that does not involve the Higgs boson or in which the Higgs field is not dynamic. Such models must employ a different mechanism of mass generation, electroweak symmetry breaking and unitarity....

s and to validate their predictions and allow further theoretical development. Many theorists expect new physics beyond the Standard Model to emerge at the TeV-scale, based on unsatisfactory properties of the Standard Model. Issues possibly to be explored by LHC collisions include:
  • Is the Higgs mechanism
    Higgs mechanism
    In particle physics, the Higgs mechanism is the process in which gauge bosons in a gauge theory can acquire non-vanishing masses through absorption of Nambu-Goldstone bosons arising in spontaneous symmetry breaking....

     for generating elementary particle
    Elementary particle
    In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...

     mass
    Mass
    Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

    es via electroweak symmetry breaking
    Spontaneous symmetry breaking
    Spontaneous symmetry breaking is the process by which a system described in a theoretically symmetrical way ends up in an apparently asymmetric state....

     actually realised in nature? It is expected that the collider will either demonstrate or rule out the existence of the elusive Higgs boson
    Higgs boson
    The Higgs boson is a hypothetical massive elementary particle that is predicted to exist by the Standard Model of particle physics. Its existence is postulated as a means of resolving inconsistencies in the Standard Model...

    , thereby allowing physicists to determine whether the Standard Model or its Higgsless model alternatives are more likely to be correct.
  • Is supersymmetry
    Supersymmetry
    In particle physics, supersymmetry is a symmetry that relates elementary particles of one spin to other particles that differ by half a unit of spin and are known as superpartners...

    , an extension of the Standard Model
    Beyond the Standard Model
    Physics beyond the Standard Model refers to the theoretical developments needed to explain the deficiencies of the Standard Model, such as the origin of mass, the strong CP problem, neutrino oscillations, matter–antimatter asymmetry, and the nature of dark matter and dark energy...

     and Poincaré symmetry, realised in nature, implying that all known particles have supersymmetric partners
    Superpartner
    In particle physics, a superpartner is a hypothetical elementary particle. Supersymmetry is one of the synergistic theories in current high-energy physics which predicts the existence of these "shadow" particles....

    ?
  • Are there extra dimensions
    Superstring theory
    Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory by modelling them as vibrations of tiny supersymmetric strings...

    , as predicted by various models based on string theory
    String theory
    String theory is an active research framework in particle physics that attempts to reconcile quantum mechanics and general relativity. It is a contender for a theory of everything , a manner of describing the known fundamental forces and matter in a mathematically complete system...

    , and can we detect them?
  • What is the nature of the dark matter
    Dark matter
    In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...

     that appears to account for 23% of the mass of the universe
    Universe
    The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

    ?


Other open questions which may be explored using high energy particle collisions:
  • It is already known that electromagnetism
    Electromagnetism
    Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...

     and the weak nuclear force are just different manifestations of a single force called the electroweak force. The LHC may clarify whether the electroweak force and the strong nuclear force are similarly just different manifestations of one universal unified force, as predicted by various Grand Unification Theories
    Grand unification theory
    The term Grand Unified Theory, often abbreviated as GUT, refers to any of several similar candidate models in particle physics in which at high-energy, the three gauge interactions of the Standard Model which define the electromagnetic, weak, and strong interactions, are merged into one single...

    .
  • Why is the fourth fundamental force (gravity
    Gravitation
    Gravitation, or gravity, is a natural phenomenon by which physical bodies attract with a force proportional to their mass. Gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped...

    ) so many orders of magnitude weaker than the other three fundamental forces
    Fundamental interaction
    In particle physics, fundamental interactions are the ways that elementary particles interact with one another...

    ? See also Hierarchy problem.
  • Are there additional sources of quark
    Quark
    A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly...

     flavour
    Flavour (particle physics)
    In particle physics, flavour or flavor is a quantum number of elementary particles. In quantum chromodynamics, flavour is a global symmetry...

     mixing, beyond those already predicted within the Standard Model
    Standard Model
    The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...

    ?
  • Why are there apparent violations of the symmetry
    Symmetry in physics
    In physics, symmetry includes all features of a physical system that exhibit the property of symmetry—that is, under certain transformations, aspects of these systems are "unchanged", according to a particular observation...

     between matter and antimatter
    Antimatter
    In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles...

    ? See also CP violation
    CP violation
    In particle physics, CP violation is a violation of the postulated CP-symmetry: the combination of C-symmetry and P-symmetry . CP-symmetry states that the laws of physics should be the same if a particle were interchanged with its antiparticle , and left and right were swapped...

    .
  • What are the nature and properties of quark-gluon plasma
    Quark-gluon plasma
    A quark–gluon plasma or quark soup is a phase of quantum chromodynamics which exists at extremely high temperature and/or density. This phase consists of asymptotically free quarks and gluons, which are several of the basic building blocks of matter...

    , believed to have existed in the early universe and in certain compact
    Compact star
    In astronomy, the term compact star is used to refer collectively to white dwarfs, neutron stars, other exotic dense stars, and black holes. These objects are all small for their mass...

     and strange
    Strange matter
    Strange matter is a particular form of quark matter, usually thought of as a "liquid" of up, down, and strange quarks. It is to be contrasted with nuclear matter, which is a liquid of neutrons and protons , and with non-strange quark matter, which is a quark liquid containing only up and down quarks...

     astronomical objects today? This will be investigated by heavy ion collisions in ALICE
    A Large Ion Collider Experiment
    ALICE is one of the six detector experiments at the Large Hadron Collider at CERN. The other five are: ATLAS, CMS, TOTEM, LHCb, and LHCf. 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...

    .

Design


The LHC is the world's largest and highest-energy particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...

. The collider is contained in a circular tunnel, with a circumference of 27 kilometres (16.8 mi), at a depth ranging from 50 to 175 m (164 to 574.1 ) underground.

The 3.8 metres (12.5 ft) wide concrete-lined tunnel, constructed between 1983 and 1988, was formerly used to house the Large Electron–Positron Collider. It crosses the border between Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 and France at four points, with most of it in France. Surface buildings hold ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.

The collider tunnel contains two adjacent parallel beam pipes that intersect at four points, each containing a proton beam, which travel in opposite directions around the ring. Some keep the beams on their circular path, while an additional are used to keep the beams focused, in order to maximize the chances of interaction between the particles in the four intersection points, where the two beams will cross. In total, over are installed, with most weighing over 27 tonnes. Approximately 96 tonnes of liquid helium
Liquid helium
Helium exists in liquid form only at extremely low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values. The density of liquid helium-4 at its boiling point and 1 atmosphere is approximately 0.125 g/mL Helium-4 was first liquefied...

 is needed to keep the magnets, made of copper-clad niobium-titanium
Niobium-titanium
Niobium-titanium is an alloy of niobium and titanium, used industrially as a type II superconductor wire for superconducting magnets...

, at their operating temperature
Operating temperature
An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...

 of 1.9 kelvin (-271.3 °C), making the LHC the largest cryogenic
Cryogenics
In physics, cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures. A person who studies elements under extremely cold temperature is called a cryogenicist. Rather than the relative temperature scales of Celsius and Fahrenheit,...

 facility in the world at liquid helium temperature.
Once or twice a day, as the protons are accelerated from 450 GeV to 7 TeV, the field of the superconducting dipole magnets will be increased from 0.54 to . The protons will each have an energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 of 7 TeV, giving a total collision energy of 14 TeV. At this energy the protons have a Lorentz factor
Lorentz factor
The Lorentz factor or Lorentz term appears in several equations in special relativity, including time dilation, length contraction, and the relativistic mass formula. Because of its ubiquity, physicists generally represent it with the shorthand symbol γ . It gets its name from its earlier...

 of about 7,500 and move at about , or about 3 metres per second slower than the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

 (c). It will take less than for a proton to travel once around the main ring – a speed of about per second. Rather than continuous beams, the protons will be bunched together, into , so that interactions between the two beams will take place at discrete intervals never shorter than apart. However it will be operated with fewer bunches when it is first commissioned, giving it a bunch crossing interval of . The design luminosity of the LHC is 1034 cm−2s−1, providing a bunch collision rate of 40 MHz.

Prior to being injected into the main accelerator, the particles are prepared by a series of systems that successively increase their energy. The first system is the linear particle accelerator
Linear particle accelerator
A linear particle accelerator is a type of particle accelerator that greatly increases the velocity of charged subatomic particles or ions by subjecting the charged particles to a series of oscillating electric potentials along a linear beamline; this method of particle acceleration was invented...

 LINAC 2 generating 50-MeV protons, which feeds the Proton Synchrotron Booster
Proton Synchrotron Booster
The Proton Synchrotron Booster, a synchrotron, is the first and smallest circular proton accelerator in the accelerator chain at the CERN Large Hadron Collider injection complex. The accelerator was built in 1972, and contains four superimposed rings with a radius of 25 meters...

 (PSB). There the protons are accelerated to 1.4 GeV and injected into the Proton Synchrotron
Proton Synchrotron
The Proton Synchrotron is the first major particle accelerator at CERN, built as a 28 GeV proton accelerator in the late 1950s and put into operation in 1959. It takes the protons from the Proton Synchrotron Booster at a kinetic energy of 1.4 GeV and lead ions from the Low Energy Ion Ring at 72...

 (PS), where they are accelerated to 26 GeV. Finally the Super Proton Synchrotron
Super Proton Synchrotron
The Super Proton Synchrotron is a particle accelerator of the synchrotron type at CERN. It is housed in a circular tunnel, in circumference, straddling the border of France and Switzerland near Geneva, Switzerland. The SPS was designed by a team led by John Adams, director-general of what was...

 (SPS) is used to further increase their energy to 450 GeV before they are at last injected (over a period of 20 minutes) into the main ring. Here the proton bunches are accumulated, accelerated (over a period of ) to their peak 7-TeV energy, and finally circulated for 10 to while collisions occur at the four intersection points.

The LHC physics program is mainly based on proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

–proton collisions. However, shorter running periods, typically one month per year, with heavy-ion collisions are included in the program. While lighter ions are considered as well, the baseline scheme deals with lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 ions (see A Large Ion Collider Experiment
A Large Ion Collider Experiment
ALICE is one of the six detector experiments at the Large Hadron Collider at CERN. The other five are: ATLAS, CMS, TOTEM, LHCb, and LHCf. 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 lead ions will be first accelerated by the linear accelerator LINAC 3, and the Low-Energy Ion Ring (LEIR) will be used as an ion storage and cooler unit. The ions will then be further accelerated by the PS and SPS before being injected into LHC ring, where they will reach an energy of 2.76 TeV per nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...

 (or 575 TeV per ion), higher than the energies reached by the Relativistic Heavy Ion Collider
Relativistic Heavy Ion Collider
The Relativistic Heavy Ion Collider is one of two existing heavy-ion colliders, and the only spin-polarized proton collider in the world. It is located at Brookhaven National Laboratory in Upton, New York and operated by an international team of researchers...

. The aim of the heavy-ion program is to investigate quark–gluon plasma, which existed in the early universe.

Detectors



Six detectors have been constructed at the LHC, located underground in large caverns excavated at the LHC's intersection points. Two of them, the ATLAS experiment
ATLAS experiment
ATLAS is one of the six particle detector experiments constructed at the Large Hadron Collider , a new particle accelerator at the European Organization for Nuclear Research in Switzerland...

 and the Compact Muon Solenoid
Compact Muon Solenoid
The Compact Muon Solenoid experiment is one of two large general-purpose particle physics detectors built on the proton-proton Large Hadron Collider at CERN in Switzerland and France. Approximately 3,600 people from 183 scientific institutes, representing 38 countries form the CMS collaboration...

 (CMS), are large, general purpose particle detector
Particle detector
In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify high-energy particles, such as those produced by nuclear decay, cosmic radiation, or reactions in a...

s. A Large Ion Collider Experiment
A Large Ion Collider Experiment
ALICE is one of the six detector experiments at the Large Hadron Collider at CERN. The other five are: ATLAS, CMS, TOTEM, LHCb, and LHCf. 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...

 (ALICE) and LHCb
LHCb
LHCb is one of six particle physics detector experiments collecting data at the Large Hadron Collider accelerator at CERN. LHCb is a specialized b-physics experiment, that is measuring the parameters of CP violation in the interactions of b-hadrons...

, have more specific roles and the last two, TOTEM
TOTEM
TOTal Elastic and diffractive cross section Measurement is one of the six detector experiments at the Large Hadron Collider at CERN. The other five are: ATLAS, ALICE, CMS, LHCb, and LHCf. It shares intersection point IP5 with the Compact Muon Solenoid...

 and LHCf
LHCf
The LHCf is a special-purpose Large Hadron Collider experiment for astroparticle physics, and one of seven detectors in the LHC accelerator at CERN. The other six are: ATLAS, ALICE, CMS, MoEDAL, TOTEM, and LHCb...

, are very much smaller and are for very specialized research. The BBC's summary of the main detectors is:
Detector Description
ATLAS
ATLAS experiment
ATLAS is one of the six particle detector experiments constructed at the Large Hadron Collider , a new particle accelerator at the European Organization for Nuclear Research in Switzerland...

one of two general purpose detectors. ATLAS will be used to look for signs of new physics, including the origins of mass and extra dimensions.
CMS
Compact Muon Solenoid
The Compact Muon Solenoid experiment is one of two large general-purpose particle physics detectors built on the proton-proton Large Hadron Collider at CERN in Switzerland and France. Approximately 3,600 people from 183 scientific institutes, representing 38 countries form the CMS collaboration...

the other general purpose detector will, like ATLAS, hunt for the Higgs boson and look for clues to the nature of dark matter.
ALICE
A Large Ion Collider Experiment
ALICE is one of the six detector experiments at the Large Hadron Collider at CERN. The other five are: ATLAS, CMS, TOTEM, LHCb, and LHCf. 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...

is studying a "fluid" form of matter called quark–gluon plasma that existed shortly after the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

.
LHCb
LHCb
LHCb is one of six particle physics detector experiments collecting data at the Large Hadron Collider accelerator at CERN. LHCb is a specialized b-physics experiment, that is measuring the parameters of CP violation in the interactions of b-hadrons...

equal amounts of matter and antimatter
Antimatter
In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles...

 were created in the Big Bang. LHCb will try to investigate what happened to the "missing" antimatter.

Operational history


The first beam was circulated through the collider
Collider
A collider is a type of a particle accelerator involving directed beams of particles.Colliders may either be ring accelerators or linear accelerators.-Explanation:...

 on the morning of 10 September 2008. CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...

 successfully fired the protons around the tunnel in stages, three kilometres at a time. The particles were fired in a clockwise direction into the accelerator and successfully steered around it at 10:28 local time. The LHC successfully completed its first major test: after a series of trial runs, two white dots flashed on a computer screen showing the protons travelled the full length of the collider. It took less than one hour to guide the stream of particles around its inaugural circuit. CERN next successfully sent a beam of protons in a counterclockwise direction, taking slightly longer at one and a half hours due to a problem with the cryogenics
Cryogenics
In physics, cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures. A person who studies elements under extremely cold temperature is called a cryogenicist. Rather than the relative temperature scales of Celsius and Fahrenheit,...

, with the full circuit being completed at 14:59.

On 19 September 2008, a quench occurred in about 100 bending magnet
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...

s in sectors 3 and 4, causing a loss of approximately six tonnes of liquid helium, which was vented into the tunnel, and a temperature rise of about 100 kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...

 in some of the affected magnets. Vacuum conditions in the beam pipe were also lost. Shortly after the incident CERN reported that the most likely cause of the problem was a faulty electrical connection between two magnets, and that – due to the time needed to warm up the affected sectors and then cool them back down to operating temperature – it would take at least two months to fix it. Subsequently, CERN released a preliminary analysis of the incident on 16 October 2008, and a more detailed one on 5 December 2008. Both analyses confirmed that the incident was indeed initiated by a faulty electrical connection. A total of 53 magnets were damaged in the incident and were repaired or replaced during the winter shutdown.

In the original timeline of the LHC commissioning, the first "modest" high-energy collisions at a center-of-mass
Center of momentum frame
A center-of-momentum frame of a system is any inertial frame in which the center of mass is at rest . Note that the center of momentum of a system is not a location, but rather defines a particular inertial frame...

 energy of 900 GeV were expected to take place before the end of September 2008, and the LHC was expected to be operating at 10 TeV by the time of the official inauguration on 21 October 2008. However, due to the delay caused by the above-mentioned incident, the collider was not operational until November 2009. Despite the delay, LHC was officially inaugurated on 21 October 2008, in the presence of political leaders, science ministers from CERN's 20 Member States, CERN officials, and members of the worldwide scientific community.

Most of 2009 was spent on repairs and reviews from the damage caused by the quench incident. On 20 November, low-energy beams circulated in the tunnel for the first time since the incident. The early part of 2010 saw the continued ramp-up of beam in energies and early physics experiments. On 30 March 2010, LHC set a record for high-energy collisions, by colliding proton beams at a combined energy level of 7 TeV. The attempt was the third that day, after two unsuccessful attempts in which the protons had to be "dumped" from the collider and new beams had to be injected. The first proton run ended on 4 November 2010. A run with lead ions started on 8 November 2010, and ended on 6 December 2010. This allowed the ALICE experiment to study matter under extreme conditions similar to those shortly after the Big Bang.

CERN has declared that the LHC will run through to the end of 2012, with a short technical stop at the end of 2011. The energy for 2011 will be 3.5 TeV per beam. In 2013 the LHC will go into a long shutdown to prepare for higher-energy running starting in 2014.

Timeline

Date Event
10 Sep 2008 CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...

 successfully fired the first protons around the entire tunnel circuit in stages.
19 Sep 2008 Magnetic quench occurred in about 100 bending magnet
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...

s in sectors 3 and 4, causing a loss of approximately 6 tonnes of liquid helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

.
30 Sep 2008 First "modest" high-energy collisions planned but postponed due to accident.
16 Oct 2008 CERN released a preliminary analysis of the accident.
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 accident.
23 Nov 2009 First particle collisions in all four detectors at 450 GeV.
30 Nov 2009 LHC becomes the world's highest-energy particle accelerator achieving 1.18 TeV per beam, beating the Tevatron
Tevatron
The Tevatron is a circular particle accelerator in the United States, at the Fermi National Accelerator Laboratory , just east of Batavia, Illinois, and is the second highest energy particle collider in the world after the Large Hadron Collider...

's previous record of 0.98 TeV per beam held for eight years.
28 Feb 2010 The LHC continues operations ramping energies to run at 3.5 TeV for 18 months to two years, after which it will be shut down to prepare for the 14 TeV collisions (7 TeV per beam).
30 Mar 2010 The two beams collided at 7 TeV (3.5 TeV per beam) in the LHC at 13:06 CEST, marking the start of the LHC research program.
8 Nov 2010 Start of the first run with lead ions.
6 Dec 2010 End of the run with lead ions. Shutdown until early 2011.
13 Mar 2011 Beginning of the 2011 run with proton beams.
21 Apr 2011 LHC becomes the world's highest-luminosity hadron accelerator achieving a peak luminosity of 4.67·1032 cm−2s−1, beating the Tevatron's previous record of 4·1032 cm−2s−1 held for one year.
17 Jun 2011 The high luminosity experiments ATLAS and CMS reach 1 fb-1 of collected data.
23 Oct 2011 The high luminosity experiments ATLAS and CMS reach 5 fb-1 of collected data.

Findings


CERN scientists estimate that, if the Standard Model is correct, a single Higgs boson may be produced every few hours. At this rate, it may take about two to three years to collect enough data to discover the Higgs boson unambiguously. Similarly, it may take one year or more before sufficient results concerning supersymmetric particles
Superpartner
In particle physics, a superpartner is a hypothetical elementary particle. Supersymmetry is one of the synergistic theories in current high-energy physics which predicts the existence of these "shadow" particles....

 have been gathered to draw meaningful conclusions. On the other hand, some extensions of the Standard Model predict additional particles, such as the heavy W' and Z' gauge bosons
W' and Z' bosons
In particle physics, W' and Z' bosons refer to hypothetical new gauge bosons that arise from extensions of the electroweak symmetry of the Standard Model. They are named in analogy with the Standard Model W and Z bosons....

, whose existence might already be probed after a few months of data collection.

The first physics results from the LHC, involving 284 collisions which took place in the ALICE
A Large Ion Collider Experiment
ALICE is one of the six detector experiments at the Large Hadron Collider at CERN. The other five are: ATLAS, CMS, TOTEM, LHCb, and LHCf. 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...

 detector, were reported on 15 December 2009. The results of the first proton–proton collisions at energies higher than Fermilab's Tevatron proton–antiproton collisions were published by the CMS collaboration
Compact Muon Solenoid
The Compact Muon Solenoid experiment is one of two large general-purpose particle physics detectors built on the proton-proton Large Hadron Collider at CERN in Switzerland and France. Approximately 3,600 people from 183 scientific institutes, representing 38 countries form the CMS collaboration...

 in early February 2010, yielding greater-than-predicted charged-hadron
Hadron
In particle physics, a hadron is a composite particle made of quarks held together by the strong force...

 production.

After the first year of data collection, the LHC experimental collaborations started to release their preliminary results concerning searches for new physics beyond the Standard Model in proton-proton collisions. No evidence of new particles was detected in the 2010 data. As a result, bounds were set on the allowed parameter space of various extensions of the Standard Model, such as models with large extra dimensions, constrained versions of the Minimal Supersymmetric Standard Model
Minimal Supersymmetric Standard Model
The Minimal Supersymmetric Standard Model is the minimal extension to the Standard Model that realizes supersymmetry, although non-minimal extensions do exist. Supersymmetry pairs bosons with fermions; therefore every Standard Model particle has a partner that has yet to be discovered...

, and others.

On 24 May 2011 it was reported that quark–gluon plasma (the densest matter besides black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...

s) has been created in the LHC.

Between July and August 2011, results of searches for the Higgs boson and for exotic particles, based on the data collected during the first half of the 2011 run, were presented in conferences in Grenoble
and Mumbai.
In the latter conference it was reported that, despite hints of a Higgs signal in earlier data, ATLAS and CMS exclude with 95% confidence level the existence of a Higgs boson with the properties predicted by the Standard Model over most of the mass region between 145 and 466 GeV.
The searches for new particles did not yield signals either, allowing to further constrain the parameter space of various extensions of the Standard Model, including its supersymmetric extensions
Supersymmetry
In particle physics, supersymmetry is a symmetry that relates elementary particles of one spin to other particles that differ by half a unit of spin and are known as superpartners...

.

Proposed upgrade


After some years of running, any particle physics
Particle physics
Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...

 experiment typically begins to suffer from diminishing returns
Diminishing returns
In economics, diminishing returns is the decrease in the marginal output of a production process as the amount of a single factor of production is increased, while the amounts of all other factors of production stay constant.The law of diminishing returns In economics, diminishing returns (also...

: each additional year of operation discovers less than the year before. The way around the diminishing returns is to upgrade the experiment, either in energy or in luminosity. A luminosity upgrade of the LHC, called the Super LHC
Super Large Hadron Collider
The Super Large Hadron Collider is a proposed upgrade to the Large Hadron Collider to be made after around ten years of operation...

, has been proposed, to be made in 2018 after ten years of operation.

The optimal path for the LHC luminosity upgrade includes an increase in the beam current (i.e. the number of protons in the beams) and the modification of the two high-luminosity interaction regions, ATLAS and CMS. To achieve these increases, the energy of the beams at the point that they are injected into the (Super) LHC should also be increased to . This will require an upgrade of the full pre-injector system, the needed changes in the Super Proton Synchrotron
Super Proton Synchrotron
The Super Proton Synchrotron is a particle accelerator of the synchrotron type at CERN. It is housed in a circular tunnel, in circumference, straddling the border of France and Switzerland near Geneva, Switzerland. The SPS was designed by a team led by John Adams, director-general of what was...

 being the most expensive. Currently the collaborative research effort of LHC Accelerator Research Program
LHC Accelerator Research Program
The U.S. LHC Accelerator Research Program coordinates research and development in the United States related to the Large Hadron Collider at CERN...

, LARP is conducting research into how to achieve these goals.

Cost


With a budget of 7.5 billion euros (approx. $9bn or £6.19bn as of Jun 2010), the LHC is one of the most expensive scientific instruments ever built. The total cost of the project is expected to be of the order of 4.6bn Swiss franc
Swiss franc
The franc is the currency and legal tender of Switzerland and Liechtenstein; it is also legal tender in the Italian exclave Campione d'Italia. Although not formally legal tender in the German exclave Büsingen , it is in wide daily use there...

s (approx. $4.4bn, €3.1bn, or £2.8bn as of Jan 2010) for the accelerator and SFr 1.16bn (approx. $1.1bn, €0.8bn, or £0.7bn as of Jan 2010) for the CERN contribution to the experiments.

The construction of LHC was approved in 1995 with a budget of SFr 2.6bn, with another SFr 210M towards the experiments. However, cost overruns, estimated in a major review in 2001 at around SFr 480M for the accelerator, and SFr 50M for the experiments, along with a reduction in CERN's budget, pushed the completion date from 2005 to April 2007. The superconducting magnets were responsible for SFr 180M of the cost increase. There were also further costs and delays due to engineering difficulties encountered while building the underground cavern for the Compact Muon Solenoid
Compact Muon Solenoid
The Compact Muon Solenoid experiment is one of two large general-purpose particle physics detectors built on the proton-proton Large Hadron Collider at CERN in Switzerland and France. Approximately 3,600 people from 183 scientific institutes, representing 38 countries form the CMS collaboration...

, and also due to faulty parts provided by Fermilab. Due to lower electricity costs during the summer, it is expected that the LHC will normally not operate over the winter months, although an exception was made to make up for the 2008 start-up delays over the 2009/10 winter.

Computing resources


Data produced by LHC, as well as LHC-related simulation, was estimated at approximately 15 petabyte
Petabyte
A petabyte is a unit of information equal to one quadrillion bytes, or 1000 terabytes. The unit symbol for the petabyte is PB...

s per year (max throughput while running not stated).

The LHC Computing Grid
LHC Computing Grid
The Worldwide LHC Computing Grid is a computer network designed by CERN to handle the massive amounts of data produced by the Large Hadron Collider .-Description:A design report was published in 2005....

 was constructed to handle the massive amounts of data produced. It incorporated both private fiber optic cable links and existing high-speed portions of the public Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

, enabling data transfer from CERN to academic institutions around the world.

The Open Science Grid is used as the primary infrastructure in the United States, and also as part of an interoperable federation with the LHC Computing Grid.

The distributed computing
Distributed computing
Distributed computing is a field of computer science that studies distributed systems. A distributed system consists of multiple autonomous computers that communicate through a computer network. The computers interact with each other in order to achieve a common goal...

 project LHC@home
LHC@home
LHC@home is a distributed computing project for particle physics on the Berkeley Open Infrastructure for Network Computing platform. LHC@home consists of two applications: SixTrack, which went live in September 2004, is used to upgrade and maintain the particle accelerator Large Hadron Collider ...

 was started to support the construction and calibration of the LHC. The project uses the BOINC
Berkeley Open Infrastructure for Network Computing
The Berkeley Open Infrastructure for Network Computing is an open source middleware system for volunteer and grid computing. It was originally developed to support the SETI@home project before it became useful as a platform for other distributed applications in areas as diverse as mathematics,...

 platform, enabling anybody with an Internet connection and either Windows, Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

 or Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

 to use their computer's idle time to simulate how particles will travel in the tunnel. With this information, the scientists will be able to determine how the magnets should be calibrated to gain the most stable "orbit" of the beams in the ring.

Safety of particle collisions


The experiments at the Large Hadron Collider sparked fears among the public that the particle collisions might produce doomsday phenomena, involving the production of stable microscopic black holes
Micro black hole
Micro black holes are tiny black holes, also called quantum mechanical black holes or mini black holes, for which quantum mechanical effects play an important role....

 or the creation of hypothetical particles called strangelet
Strangelet
A strangelet is a hypothetical particle consisting of a bound state of roughly equal numbers of up, down, and strange quarks. Its size would be a minimum of a few femtometres across . Once the size becomes macroscopic , such an object is usually called a quark star or "strange star" rather than a...

s. Two CERN-commissioned safety reviews examined these concerns and concluded that the experiments at the LHC present no danger and that there is no reason for concern, a conclusion expressly endorsed by the American Physical Society
American Physical Society
The American Physical Society is the world's second largest organization of physicists, behind the Deutsche Physikalische Gesellschaft. The Society publishes more than a dozen scientific journals, including the world renowned Physical Review and Physical Review Letters, and organizes more than 20...

.

Operational challenges


The size of the LHC constitutes an exceptional engineering challenge with unique operational issues on account of the amount of energy stored in the magnets and the beams. While operating, the total energy stored in the magnets
Superconducting magnetic energy storage
Superconducting Magnetic Energy Storage systems store energy in the magnetic field created by the flow of direct current in a superconducting coil which has been cryogenically cooled to a temperature below its superconducting critical temperature....

 is (equivalent to 2.4 tons of TNT
TNT equivalent
TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT...

) and the total energy carried by the two beams reaches 724 megajoule.

Loss of only one ten-millionth part (10−7) of the beam is sufficient to quench a superconducting magnet
Superconducting magnet
A superconducting magnet is an electromagnet made from coils of superconducting wire. They must be cooled to cryogenic temperatures during operation. In its superconducting state the wire can conduct much larger electric currents than ordinary wire, creating intense magnetic fields...

, while the beam dump
Beam dump
A beam dump is a device that absorbs a beam. This may be a beam of photons such as a laser beam, or a beam of electrically charged particles.- Optical beam dumps :An optical beam dump is an optical element used to absorb a beam of light...

 must absorb 362 megajoule for each of the two beams. These energies are carried by very little matter: under nominal operating conditions (2,808 bunches per beam, 1.15×1011 protons per bunch), the beam pipes contain 1.0×10−9 gram of hydrogen, which, in standard conditions for temperature and pressure
Standard conditions for temperature and pressure
Standard condition for temperature and pressure are standard sets of conditions for experimental measurements established to allow comparisons to be made between different sets of data...

, would fill the volume of one grain of fine sand.

Construction accidents and delays



  • On 25 October 2005, José Pereira Lages, a technician, was killed in the LHC when a switchgear
    Switchgear
    The term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults...

     that was being transported fell on him.
  • On 27 March 2007 a cryogenic magnet support broke during a pressure test involving one of the LHC's inner triplet (focusing quadrupole) magnet assemblies, provided by Fermilab
    Fermilab
    Fermi National Accelerator Laboratory , located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics...

     and KEK
    KEK
    , known as KEK, is a national organization whose purpose is to operate the largest particle physics laboratory in Japan, which is situated in Tsukuba of Ibaraki prefecture. Established in 1997. The term "KEK" is also used to refer to the laboratory itself, which employs approximately 900 employees...

    . No one was injured. Fermilab director Pier Oddone stated "In this case we are dumbfounded that we missed some very simple balance of forces". This fault had been present in the original design, and remained during four engineering reviews over the following years. Analysis revealed that its design, made as thin as possible for better insulation, was not strong enough to withstand the forces generated during pressure testing. Details are available in a statement from Fermilab, with which CERN is in agreement. Repairing the broken magnet and reinforcing the eight identical assemblies used by LHC delayed the startup date, then planned for November 2007.
  • Problems occurred on 19 September 2008 during powering tests of the main dipole circuit, when an electrical fault in the bus between magnets caused a rupture and a leak of six tonnes of liquid helium
    Liquid helium
    Helium exists in liquid form only at extremely low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values. The density of liquid helium-4 at its boiling point and 1 atmosphere is approximately 0.125 g/mL Helium-4 was first liquefied...

    . The operation was delayed for several months. It is currently believed that a faulty electrical connection between two magnets caused an arc, which compromised the liquid-helium containment. Once the cooling layer was broken, the helium flooded the surrounding vacuum layer with sufficient force to break 10-ton magnets from their mountings. The explosion also contaminated the proton tubes with soot
    Soot
    Soot is a general term that refers to impure carbon particles resulting from the incomplete combustion of a hydrocarbon. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolyzed fuel particles such as cenospheres,...

    . This accident was thoroughly discussed in a 22 February 2010 Superconductor Science and Technology article by CERN physicist Lucio Rossi.
  • Two vacuum leaks were identified in July 2009, and the start of operations was further postponed to mid-November 2009.


Popular culture


The Large Hadron Collider gained a considerable amount of attention from outside the scientific community and its progress is followed by most popular science media. The LHC has also sparked the imaginations of authors of works of fiction, such as novel
Novel
A novel is a book of long narrative in literary prose. The genre has historical roots both in the fields of the medieval and early modern romance and in the tradition of the novella. The latter supplied the present generic term in the late 18th century....

s, TV series, and video games, although descriptions of what it is, how it works, and projected outcomes of the experiments are often only vaguely accurate, occasionally causing concern among the general public.

The novel Angels & Demons, by Dan Brown
Dan Brown
Dan Brown is an American author of thriller fiction, best known for the 2003 bestselling novel, The Da Vinci Code. Brown's novels, which are treasure hunts set in a 24-hour time period, feature the recurring themes of cryptography, keys, symbols, codes, and conspiracy theories...

, involves antimatter
Antimatter
In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles...

 created at the LHC to be used in a weapon
Antimatter weapon
An antimatter weapon is a hypothetical device using antimatter as a power source, a propellant, or an explosive for a weapon. Antimatter weapons do not currently exist due to the cost of production and the limited technology available to produce and contain antimatter in sufficient quantities for...

 against the Vatican. In response CERN published a "Fact or Fiction?" page discussing the accuracy of the book's portrayal of the LHC, CERN, and particle physics in general. The movie version of the book has footage filmed on-site at one of the experiments at the LHC; the director, Ron Howard
Ron Howard
Ronald William "Ron" Howard is an American actor, director, and producer. He came to prominence as a child actor, playing Opie Taylor in the sitcom The Andy Griffith Show for eight years, and later the teenaged Richie Cunningham in the sitcom Happy Days for six years...

, met with CERN experts in an effort to make the science in the story more accurate.

In The Big Bang Theory
The Big Bang Theory
The Big Bang Theory is an American sitcom created by Chuck Lorre and Bill Prady, both of whom serve as executive producers on the show, along with Steven Molaro. All three also serve as head writers...

, the episode "The Large Hadron Collision" features the Large Hadron Collider prominently - albeit as a concept (the collider itself is not shown).

The novel FlashForward
Flashforward (novel)
Flashforward is a science fiction novel by Canadian author Robert J. Sawyer first published in 1999. The novel is set in 2009. At CERN, the Large Hadron Collider accelerator is performing a run to search for the Higgs boson. The experiment has a unique side effect: the entire human race loses...

, by Robert J. Sawyer
Robert J. Sawyer
Robert James Sawyer is a Canadian science fiction writer. He has had 20 novels published, and his short fiction has appeared in Analog Science Fiction and Fact, Amazing Stories, On Spec, Nature, and many anthologies. Sawyer has won over forty awards for his fiction, including the Nebula Award ,...

, involves the search for the Higgs boson at the LHC. CERN published a "Science and Fiction" page interviewing Sawyer and physicists about the book and the TV series based on it.

CERN employee Katherine McAlpine
Katherine McAlpine
Katherine McAlpine is an American science journalist. In 2008 while working for CERN, McAlpine wrote, produced and performed in the YouTube video "Large Hadron Rap" under the pseudonym "alpinekat"...

's "Large Hadron Rap" surpassed 6.7 million YouTube
YouTube
YouTube is a video-sharing website, created by three former PayPal employees in February 2005, on which users can upload, view and share videos....

 views. The band Les Horribles Cernettes
Les Horribles Cernettes
Les Horribles Cernettes is an all-female parody pop group, self-labelled "the one and only High Energy Rock Band", founded by employees of CERN which performs at CERN and other HEP related events. Their musical style is often described as doo-wop...

 was founded by female members of CERN. The name was chosen so to have the same initials as the LHC.

See also



  • Bose–Einstein statistics
    Bose–Einstein statistics
    In statistical mechanics, Bose–Einstein statistics determines the statistical distribution of identical indistinguishable bosons over the energy states in thermal equilibrium.-Concept:...

  • Boson
    Boson
    In particle physics, bosons are subatomic particles that obey Bose–Einstein statistics. Several bosons can occupy the same quantum state. The word boson derives from the name of Satyendra Nath Bose....

  • Compact Linear Collider
    Compact Linear Collider
    The Compact Linear Collider is a proposed linear particle accelerator under design at CERN. CLIC is separate from the International Linear Collider project, and differs from it using normal conducting cavities to achieve a higher planned energy of several TeV.Currently research is in progress to...

  • International Linear Collider
    International Linear Collider
    The International Linear Collider is a proposed linear particle accelerator. It is planned to have a collision energy of 500 GeV initially, and, if approved after the project has published its Technical Design Report, planned for 2012, could be completed in the late 2010s. A later upgrade to 1000...

  • List of accelerators in particle physics


External links