# large hadron collider ![[220px-lhc.svg.png|300]] layout of the lhc complex general properties accelerator type: synchrotron beam type: proton heavy ion target type: collider beam properties maximum energy: 6.8 tev per beam (13.6 tev collision energy) maximum luminosity: 1×1034/(cm2⋅s) physical properties circumference: 26-659 metres (16.565 miles) location: near geneva switzerland across the border of france and switzerland coordinates: 46°14′06″n 06°02′42″e / 46.23500°n 6.04500°e institution: cern dates of operation: 2010 13 years ago - present preceded by: large electron-positron collider large hadron collider (lhc) ![[250px-lhc.svg.png|300]] plan of the lhc experiments and the preaccelerators lhc experiments atlas: a toroidal lhc apparatus cms: compact muon solenoid lhcb: lhc-beauty alice: a large ion collider experiment totem: total cross section elastic scattering and diffraction dissociation lhcf: lhc-forward moedal: monopole and exotics detector at the lhc faser: forward search experiment snd: scattering and neutrino detector lhc preaccelerators p and pb: linear accelerators for protons (linac 4) and lead (linac 3) (not marked): proton synchrotron booster ps: proton synchrotron sps: super proton synchrotron cern complex ![[cernacceleratorcomplex2022.png|300]] current particle and nuclear facilities lhc: accelerates protons and heavy ions leir: accelerates ions sps: accelerates protons and ions psb: accelerates protons ps: accelerates protons or ions linac 3: injects heavy ions into leir linac4: accelerates ions ad: decelerates antiprotons elena: decelerates antiprotons isolde: produces radioactive ion beams medicis: produces isotopes for medical purposes the large hadron collider (lhc) is the world's largest and highest-energy particle collider. it was built by the european organisation for nuclear research (cern) between 1998 and 2008 in collaboration with over 10-000 scientists and hundreds of universities and laboratories across more than 100 countries. it lies in a tunnel 27 kilometres (17 mi) in circumference and as deep as 175 metres (574 ft) beneath the france-switzerland border near geneva the first collisions were achieved in 2010 at an energy of 3.5 teraelectronvolts (tev) per beam about four times the previous world record. the discovery of the higgs boson at the lhc was announced in 2012. between 2013 and 2015 the lhc was shut down and upgraded after those upgrades it reached 6.5 tev per beam (13.0 tev total collision energy.) at the end of 2018 it was shut down for maintenance and further upgrades reopening over three years later in april 2022 the collider has four crossing points where the accelerated particles collide. nine detectors each designed to detect different phenomena are positioned around the crossing points. the lhc primarily collides proton beams but it can also accelerate beams of heavy ions such as in lead-lead collisions and proton-lead collisions the lhc's goal is to allow physicists to test the predictions of different theories of particle physics including measuring the properties of the higgs boson searching for the large family of new particles predicted by supersymmetric theories and studying other unresolved questions in particle physics # background the term hadron refers to subatomic composite particles composed of quarks held together by the strong force (analogous to the way that atoms and molecules are held together by the electromagnetic force.) the best-known hadrons are the baryons such as protons and neutrons hadrons also include mesons such as the pion and kaon which were discovered during cosmic ray experiments in the late 1940s and early 1950s a collider is a type of a particle accelerator that brings two opposing particle beams together such that the particles collide. in particle physics colliders though harder to construct are a powerful research tool because they reach a much higher center of mass energy than fixed target setups. analysis of the byproducts of these collisions gives scientists good evidence of the structure of the subatomic world and the laws of nature governing it. many of these byproducts are produced only by high-energy collisions and they decay after very short periods of time. thus many of them are hard or nearly impossible to study in other ways # purpose many physicists hope that the large hadron collider will help answer some of the fundamental open questions in physics which concern the basic laws governing the interactions and forces among elementary particles and the deep structure of space and time particularly the interrelation between quantum mechanics and general relativity these high-energy particle experiments can provide data to support different scientific models. for example the standard model and higgsless model required high-energy particle experiment data to validate ir predictions and allow further theoretical development. the standard model was completed by detection of the higgs boson by the lhc in 2012 lhc collisions have explored other questions including **+** do all known particles have supersymmetric partners as part of supersymmetry in an extension of the standard model and poincare symmetry **+** are there extra dimensions as predicted by various models based on string theory and can we detect them **+** what is the nature of the dark matter a hypothetical form of matter which appears to account for 27% of the mass-energy of the universe other open questions that may be explored using high-energy particle collisions include **+** it is already known that electromagnetism and the weak nuclear force are 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 **+** why is the fourth fundamental force (gravity) so many orders of magnitude weaker than the other three fundamental forces? see also hierarchy problem **+** are there additional sources of quark flavour mixing beyond those already present within the standard model **+** why are there apparent violations of the symmetry between matter and antimatter? see also cp violation **+** what are the nature and properties of quark-gluon plasma thought to have existed in the early universe and in certain compact and strange astronomical objects today? this will be investigated by heavy ion collisions mainly in alice but also in cms atlas and lhcb. first observed in 2010 findings published in 2012 confirmed the phenomenon of jet quenching in heavy-ion collisions # design the collider is contained in a circular tunnel with a circumference of 26.7 kilometres (16.6 mi) at a depth ranging from 50 to 175 metres (164 to 574 ft) underground. the variation in depth was deliberate to reduce the amount of tunnel that lies under the jura mountains to avoid having to excavate a vertical access shaft there. a tunnel was chosen to avoid having to purchase expensive land on the surface and to take advantage of the shielding against background radiation that the earth's crust provides ![[locationlargehadroncollider.png|300]] map of the large hadron collider at cern the 3.8-metre (12 ft) wide concrete-lined tunnel constructed between 1983 and 1988 was formerly used to house the large electron-positron collider. the tunnel crosses the border between switzerland 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 ![[220px-lhcquadrupolemagnets.jpg|300]] superconducting quadrupole electromagnets are used to direct the beams to four intersection points where interactions between accelerated protons take place the collider tunnel contains two adjacent parallel beamlines (or beam pipes) each containing a beam which travel in opposite directions around the ring. the beams intersect at four points around the ring which is where the particle collisions take place. some 1-232 dipole magnets keep the beams on ir circular path (see image) while an additional 392 quadrupole magnets are used to keep the beams focused with stronger quadrupole magnets close to the intersection points in order to maximize the chances of interaction where the two beams cross. magnets of higher multipole orders are used to correct smaller imperfections in the field geometry. in total about 10-000 superconducting magnets are installed with the dipole magnets having a mass of over 27 tonnes. about 96 tonnes of superfluid helium-4 is needed to keep the magnets made of copper-clad niobium-titanium at ir operating temperature of 1.9 k (−271.25 °c) making the lhc the largest cryogenic facility in the world at liquid helium temperature. lhc uses 470 tonnes of nb-ti superconductor during lhc operations the cern site draws roughly 200 mw of electrical power from the french electrical grid which for comparison is about one-third the energy consumption of the city of geneva the lhc accelerator and detectors draw about 120 mw thereof. each day of its operation generates 140 terabytes of data when running an energy of 6.5 tev per proton once or twice a day as the protons are accelerated from 450 gev to 6.5 tev the field of the superconducting dipole magnets is increased from 0.54 to 7.7 teslas (t.) the protons each have an energy of 6.5 tev giving a total collision energy of 13 tev. at this energy the protons have a lorentz factor of about 6-930 and move at about 0.999999990 c or about 3.1 m/s (11 km/h) slower than the speed of light (c.) it takes less than 90 microseconds (μs) for a proton to travel 26.7 km around the main ring. this results in 11-245 revolutions per second for protons whether the particles are at low or high energy in the main ring since the speed difference between these energies is beyond the fifth decimal rather than having continuous beams the protons are bunched together into up to 2-808 bunches with 115 billion protons in each bunch so that interactions between the two beams take place at discrete intervals mainly 25 nanoseconds (ns) apart providing a bunch collision rate of 40 mhz. it was operated with fewer bunches in the first years. the design luminosity of the lhc is 1034 cm−2s−1 which was first reached in june 2016. by 2017 twice this value was achieved ![[republic of bob/citation needed (wikinovel)/attachments/cernlhcprotonsource.jpg|300]] the lhc protons originate from the small red hydrogen tank before being injected into the main accelerator the particles are prepared by a series of systems that successively increase ir energy. the first system is the linear particle accelerator linac4 generating 160 mev negative hydrogen ions (h− ions) which feeds the proton synchrotron booster (psb.) there both electrons are stripped from the hydrogen ions leaving only the nucleus containing one proton. protons are then accelerated to 2 gev and injected into the proton synchrotron (ps) where they are accelerated to 26 gev. finally the super proton synchrotron (sps) is used to increase ir energy further to 450 gev before they are at last injected (over a period of several minutes) into the main ring. here the proton bunches are accumulated accelerated (over a period of 20 minutes) to ir peak energy and finally circulated for 5 to 24 hours while collisions occur at the four intersection points the lhc physics programme is mainly based on proton-proton collisions. however during shorter running periods typically one month per year heavy-ion collisions are included in the programme. while lighter ions are considered as well the baseline scheme deals with lead ions (see a large ion collider experiment.) the lead ions are first accelerated by the linear accelerator linac 3 and the low energy ion ring (leir) is used as an ion storage and cooler unit. the ions are then further accelerated by the ps and sps before being injected into lhc ring where they reach an energy of 2.3 tev per nucleon (or 522 tev per ion) higher than the energies reached by the relativistic heavy ion collider. the aim of the heavy-ion programme is to investigate quark-gluon plasma which existed in the early universe ## detectors nine detectors have been built in large caverns excavated at the lhc's intersection points. two of them the atlas experiment and the compact muon solenoid (cms) are large general-purpose particle detectors. alice and lhcb have more specialised roles while the other five - totem moedal lhcf snd and faser - are much smaller and are for very specialised research. the atlas and cms experiments discovered the higgs boson which is strong evidence that the standard model has the correct mechanism of giving mass to elementary particles ![[viewinsidedetectoratthecmscavernlhccern.jpg|300]] cms detector for lhc ## computing and analysis facilities data produced by lhc as well as lhc-related simulation were estimated at about 200 petabytes per year the lhc computing grid was constructed as part of the lhc design to handle the massive amounts of data expected for its collisions. it is an international collaborative project that consists of a grid-based computer network infrastructure initially connecting 140 computing centres in 35 countries (over 170 in more than 40 countries as of 2012.) it was designed by cern to handle the significant volume of data produced by lhc experiments incorporating both private fibre optic cable links and existing high-speed portions of the public internet to enable data transfer from cern to academic institutions around the world. the lhc computing grid consists of global federations across europe asia pacific and the americas the distributed computing project lhc@home was started to support the construction and calibration of the lhc. the project uses the boinc platform enabling anybody with an internet connection and a computer running mac os x windows or linux to use ir computer's idle time to simulate how particles will travel in the beam pipes. with this information the scientists are able to determine how the magnets should be calibrated to gain the most stable "orbit" of the beams in the ring. in august 2011 a second application (test4theory) went live which performs simulations against which to compare actual test data to determine confidence levels of the results by 2012 data from over 6 quadrillion (6×1015) lhc proton-proton collisions had been analysed. the lhc computing grid had become the world's largest computing grid in 2012 comprising over 170 computing facilities in a worldwide network across more than 40 countries # future plans ## "high-luminosity" upgrade after some years of running any particle physics experiment typically begins to suffer from diminishing returns: as the key results reachable by the device begin to be completed later years of operation discover proportionately less than earlier years. a common response is to upgrade the devices involved typically in collision energy luminosity or improved detectors. in addition to a possible increase to 14 tev collision energy a luminosity upgrade of the lhc called the high luminosity large hadron collider started in june 2018 that will boost the accelerator's potential for new discoveries in physics starting in 2027. the upgrade aims at increasing the luminosity of the machine by a factor of 10 up to 1035 cm−2s−1 providing a better chance to see rare processes and improving statistically marginal measurements ## proposed future circular collider cern has several preliminary designs for a future circular collider (fcc) - which would be the most powerful particle accelerator ever built - with different types of collider ranging in cost from around €9 billion (us$10.2 billion) to €21 billion. it would use the lhc ring as preaccelerator similar to how the lhc uses the smaller super proton synchrotron. it is cern's opening bid in a priority-setting process called the european strategy for particle physics update and will affect the field's future well into the second half of the century. as of 2023 no fixed plan exists and it is unknown if the construction will be funded # safety of particle collisions the experiments at the large hadron collider sparked fears that the particle collisions might produce doomsday phenomena involving the production of stable microscopic black holes or the creation of hypothetical particles called strangelets. 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 endorsed by the american physical society the reports also noted that the physical conditions and collision events that exist in the lhc and similar experiments occur naturally and routinely in the universe without hazardous consequences including ultra-high-energy cosmic rays observed to impact earth with energies far higher than those in any human-made collider # 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 inspired works of fiction including novels tv series video games and films cern employee katherine mcalpine's "large hadron rap" surpassed 8 million youtube views as of 2022 the band les horribles cernettes was founded by women from cern. the name was chosen so to have the same initials as the lhc national geographic channel's world's toughest fixes season 2 (2010) episode 6 "atom smasher" features the replacement of the last superconducting magnet section in the repair of the collider after the 2008 quench incident. the episode includes actual footage from the repair facility to the inside of the collider and explanations of the function engineering and purpose of the lhc the song "munich" off of the 2012 studio album scars & stories by the fray is inspired by the lhc. lead singer isaac slade said in an interview with the huffington post "there's this large particle collider out in switzerland that is kind of helping scientists peel back the curtain on what creates gravity and mass. some very big questions are being raised even some things that einstein proposed that have just been accepted for decades are starting to be challenged. they're looking for the god particle basically the particle that holds it all together. that song is really just about the mystery of why we're all here and what's holding it all together you know?" the large hadron collider was the focus of the 2012 student film decay with the movie being filmed on location in cern's maintenance tunnels ## fiction the novel angels & demons by dan brown involves antimatter created at the lhc to be used in a weapon 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 met with cern experts in an effort to make the science in the story more accurate the novel flashforward by robert j. sawyer 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 # see also **+** list of accelerators in particle physics **+** accelerator projects - compact linear collider - future circular collider - international linear collider - very large hadron collider // republic of bob