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Large Hadron Collider
(LHC)
LHC.svg
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
LHC preaccelerators
p and Pb Linear accelerators for protons (Linac 2) and Lead (Linac 3)
(not marked) Proton Synchrotron Booster
PS Proton Synchrotron
SPS Super Proton Synchrotron
Hadron Colliders
Intersecting Storage Rings CERN, 1971–1984
Super Proton Synchrotron CERN, 1981–1984
ISABELLE BNL, cancelled in 1983
Tevatron Fermilab, 1987–present
Relativistic Heavy Ion Collider BNL, operational since 2000
Superconducting Super Collider Cancelled in 1993
Large Hadron Collider CERN, 2009–
Very Large Hadron Collider Theoretical
Super Large Hadron Collider Proposed

The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator, intended to collide opposing particle beams of either protons at an energy of 7 TeV (1.12 microjoules) per particle, or lead nuclei at an energy of 574 TeV (92.0 microjoules) per nucleus. The term hadron refers to such particles that are composed of quarks. It is expected that it will address the most fundamental questions of physics, hopefully allowing progress in understanding the deepest laws of nature. The LHC lies in a tunnel 27 kilometres (17 mi) in circumference, as much as 175 metres (574 ft) beneath the Franco-Swiss border near Geneva, Switzerland.

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 resumed operations in February 2010, but it will operate at only half of the design collision energy. In 2012 it will be shut down for the repairs necessary to bring it to its full design energy, and then it will start up again in 2013.[10]

Contents

Purpose

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]

Other questions are:

Design

A Feynman diagram of one way the Higgs boson may be produced at the LHC. Here, two quarks each emit a W or Z boson, which combine to make a neutral Higgs.
Map of the Large Hadron Collider at CERN

The LHC is the world's largest and highest-energy particle accelerator.[21][22] The collider is contained in a circular tunnel, with a circumference of 27 kilometres (17 mi), at a depth ranging from 50 to 175 metres (160 to 570 ft) underground.

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.[23] It 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.

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 1,232 dipole magnets keep the beams on their circular path, while an additional 392 quadrupole magnets 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 1,600 superconducting magnets are installed, with most weighing over 27 tonnes. Approximately 96 tonnes of liquid helium is needed to keep the magnets at their operating temperature of 1.9 K (−271.25 °C), making the LHC the largest cryogenic facility in the world at liquid helium temperature.

Superconducting quadrupole electromagnets are used to direct the beams to four intersection points, where interactions between accelerated protons will take place.

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 8.3 teslas (T). The protons will each have an energy of 7 TeV, giving a total collision energy of 14 TeV. At this energy the protons have a Lorentz factor of about 7,500 and move at about 99.9999991% of the speed of light.[24] It will take less than 90 microseconds (μs) for a proton to travel once around the main ring – a speed of about 11,000 revolutions per second. Rather than continuous beams, the protons will be bunched together, into 2,808 bunches, so that interactions between the two beams will take place at discrete intervals never shorter than 25 nanoseconds (ns) apart. However it will be operated with fewer bunches when it is first commissioned, giving it a bunch crossing interval of 75 ns.[25]

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 LINAC 2 generating 50-MeV protons, which feeds the Proton Synchrotron Booster (PSB). There the protons are accelerated to 1.4 GeV and injected into the Proton Synchrotron (PS), where they are accelerated to 26 GeV. Finally the Super Proton Synchrotron (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 20 minutes) to their peak 7-TeV energy, and finally circulated for 10 to 24 hours while collisions occur at the four intersection points.[26]

CMS detector for LHC

The LHC physics program is mainly based on proton–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 ions[27] (see A Large Ion Collider Experiment). 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 then will 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 (or 575 TeV per ion), higher than the energies reached by the Relativistic Heavy Ion Collider. 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 and the Compact Muon Solenoid (CMS), are large, general purpose particle detectors.[22] A Large Ion Collider Experiment (ALICE) and LHCb have more specific roles and the last two TOTEM and LHCf are very much smaller and are for very specialized research. The BBC's summary of the main detectors is:[28]

Detector Description
ATLAS 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 the other general purpose detector will, like ATLAS, hunt for the Higgs boson and look for clues to the nature of dark matter.
ALICE will study a "liquid" form of matter called quark–gluon plasma that existed shortly after the Big Bang.
LHCb equal amounts of matter and antimatter were created in the Big Bang. LHCb will try to investigate what happened to the "missing" antimatter.

Test timeline

The first beam was circulated through the collider on the morning of 10 September 2008.[28] CERN 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.[29] 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.[30] 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, with the full circuit being completed at 14:59.

On 19 September 2008, a quench occurred in about 100 bending magnets 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 in some of the affected magnets. Vacuum conditions in the beam pipe were also lost.[31] 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.[32] Subsequently, CERN released a preliminary analysis of the incident on 16 October 2008,[33] and a more detailed one on 5 December 2008.[34] 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.[35]

In the original timeline of the LHC commissioning, the first "modest" high-energy collisions at a center-of-mass 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.[36] However, due to the delay caused by the above-mentioned incident, the collider was not operational until November 2009.[6] 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.[37]

Timeline
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.[38]
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.[39]
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).[40]

Expected results

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 have been gathered to draw meaningful conclusions.[21]

Current results

The first p-p collisions at energies higher than Fermilab's Tevatron p-pbar collisions have been published on arXiv, yielding greater-than-predicted charged hadron production.[41] The CMS paper reports that the increase in the production rate of charged hadrons when the center-of-mass energy goes from 0.9 TeV to 2.36 TeV exceeds the predictions of the theoretical models used in the analysis, with the excess ranging from 10% to 14%, depending upon which model is used. The charged hadrons were primarily mesons (kaons and pions).[42]

Proposed upgrade

After some years of running, any particle physics experiment typically begins to suffer from diminishing returns: 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, has been proposed,[43] to be made after ten years of LHC 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 1 TeV. This will require an upgrade of the full pre-injector system, the needed changes in the Super Proton Synchrotron being the most expensive.

Cost

With a budget of 9 billion US dollars (approx. €6300M or £5600M as of Jan 2010), the LHC is the most expensive scientific experiment in human history.[44] The total cost of the project is expected to be of the order of 4.6 billion Swiss francs (approx. $4400M, €3100M, or £2800M as of Jan 2010) for the accelerator and 1.16 billion francs (approx. $1100M, €800M, or £700M as of Jan 2010) for the CERN contribution to the experiments.[45]

The construction of LHC was approved in 1995 with a budget of 2.6 billion francs, with another 210 million francs towards the experiments. However, cost overruns, estimated in a major review in 2001 at around 480 million francs for the accelerator, and 50 million francs for the experiments, along with a reduction in CERN's budget, pushed the completion date from 2005 to April 2007.[46] The superconducting magnets were responsible for 180 million francs 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,[47] and also due to faulty parts provided by Fermilab.[48]

Due to lower electricity costs during the summer, it is expected that the LHC will normally not operate over the winter months,[49] although an exception was being 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 will produce a total data output of 15 petabytes per year.[50]

The LHC Computing Grid is being constructed to handle the massive amounts of data produced. It incorporates both private fiber optic cable links and existing high-speed portions of the public Internet, 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 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 to use their computer 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 upcoming experiments at the Large Hadron Collider have sparked fears among the public that the LHC particle collisions might produce doomsday phenomena, involving the production of stable microscopic black holes or the creation of hypothetical particles called strangelets.[51] Two CERN-commissioned safety reviews have examined these concerns and concluded that the experiments at the LHC present no danger and that there is no reason for concern,[52][53][54] a conclusion expressly endorsed by the American Physical Society.[55]

Operational challenges

The size of the LHC constitutes an exceptional engineering challenge with unique operational issues on account of the huge energy stored in the magnets and the beams.[26][56] While operating, the total energy stored in the magnets is 10 GJ (equivalent to 2.4 tons of TNT) and the total energy carried by the two beams reaches 724 MJ (173 kilograms of TNT).[57]

Loss of only one ten-millionth part (10−7) of the beam is sufficient to quench a superconducting magnet, while the beam dump must absorb 362 MJ (87 kilograms of TNT) for each of the two beams. These immense energies are even more impressive considering how little matter is carrying it: 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, would fill the volume of one grain of fine sand.

On 10 August 2008, computer hackers defaced a website at CERN, criticizing their computer security. There was no access to the control network of the collider.[58][59]

Construction accidents and delays

  • On 25 October 2005, a technician was killed in the LHC tunnel when a crane load was accidentally dropped.[60]
  • 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 and KEK. 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.[61] 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.[62][63] 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. The operation was delayed for several months.[64] 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.[34][65] This accident was more recently thoroughly discussed in a February 22, 2010 Superconductor Science and Technology article by CERN physicist Lucio Rossi.[66]
  • Two vacuum leaks were identified in July 2009, and the start of operations was further postponed to mid-November, 2009.[67]

Popular culture

The Large Hadron Collider has gained considerable 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 novels, 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, 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.[68] 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.[69]

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.[70]

CERN employee Katherine McAlpine's "Large Hadron Rap"[71] surpassed 5 million YouTube views.[72][73]

References

Notes

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  2. ^ "Towards a superforce". CERN. 2008. http://public.web.cern.ch/public/en/Science/Superforce-en.html. Retrieved 2008-10-10. 
  3. ^ Roger Highfield (16 September 2008). "Large Hadron Collider: Thirteen ways to change the world". Telegraph. http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/09/16/sciwriters116.xml. Retrieved 2008-10-10. 
  4. ^ CERN Press Office (10 September 2008). "First beam in the LHC – Accelerating science". Press release. http://press.web.cern.ch/press/PressReleases/Releases2008/PR08.08E.html. Retrieved 2008-10-09. 
  5. ^ Paul Rincon (23 September 2008). "Collider halted until next year". BBC News. http://news.bbc.co.uk/2/hi/science/nature/7632408.stm. Retrieved 2008-10-09. 
  6. ^ a b CERN Press Office (9 February 2009). "CERN management confirms new LHC restart schedule". Press release. http://press.web.cern.ch/press/PressReleases/Releases2009/PR02.09E.html. Retrieved 2009-02-10. 
  7. ^ CERN Press Office (19 June 2009). "CERN reports on progress towards LHC restart". Press release. http://press.web.cern.ch/press/lhc-first-physics/. Retrieved 2009-07-21. 
  8. ^ CERN Press Office (20 November 2009). "The LHC is back". Press release. http://press.web.cern.ch/press/PressReleases/Releases2009/PR16.09E.html. Retrieved 2009-11-20. 
  9. ^ a b CERN Press Office (23 November 2009). "Two circulating beams bring first collisions in the LHC". Press release. http://press.web.cern.ch/press/PressReleases/Releases2009/PR17.09E.html. Retrieved 2009-11-23. 
  10. ^ The New York Times (4 February 2010). "Collider to Operate Again, Though at Half Power". Press release. http://www.nytimes.com/2010/02/05/science/05collide.html. Retrieved 2010-02-05. 
  11. ^ Brian Greene (11 September 2008). "The Origins of the Universe: A Crash Course". The New York Times. http://www.nytimes.com/2008/09/12/opinion/12greene.html?_r=1&oref=slogin. Retrieved 2009-04-17. 
  12. ^ "...in the public presentations of the aspiration of particle physics we hear too often that the goal of the LHC or a linear collider is to check off the last missing particle of the Standard Model, this year's Holy Grail of particle physics, the Higgs boson. The truth is much less boring than that! What we're trying to accomplish is much more exciting, and asking what the world would have been like without the Higgs mechanism is a way of getting at that excitement." – Chris Quigg (2005). "Nature's Greatest Puzzles". arΧiv:hep-ph/0502070 [hep-ph]. 
  13. ^ "Why the LHC". CERN. 2008. http://public.web.cern.ch/public/en/LHC/WhyLHC-en.html. Retrieved 2009-09-28. 
  14. ^ "Zeroing in on the elusive Higgs boson". US Department of Energy. March 2001. http://www.science.doe.gov/Accomplishments_Awards/Decades_Discovery/35.html. Retrieved 2008-12-11. 
  15. ^ "Accordingly, in common with many of my colleagues, I think it highly likely that both the Higgs boson and other new phenomena will be found with the LHC."..."This mass threshold means, among other things, that something new—either a Higgs boson or other novel phenomena—is to be found when the LHC turns the thought experiment into a real one." Chris Quigg (February 2008). "The coming revolutions in particle physics". Scientific American. pp. 38–45. http://www.scientificamerican.com/article.cfm?id=the-coming-revolutions-in-particle-physics&page=3. Retrieved 2009-09-28. 
  16. ^ Shaaban Khalil (2003). "Search for supersymmetry at LHC". Contemporary Physics 44 (3): 193–201. doi:10.1080/0010751031000077378. 
  17. ^ Alexander Belyaev (2009). "Supersymmetry status and phenomenology at the Large Hadron Collider". Pramana 72 (1): 143–160. doi:10.1007/s12043-009-0012-0. 
  18. ^ Anil Ananthaswamy (11 November 2009). "In SUSY we trust: What the LHC is really looking for". New Scientist. http://www.newscientist.com/article/mg20427341.200-in-susy-we-trust-what-the-lhc-is-really-looking-for.html. 
  19. ^ Lisa Randall (2002). "Extra Dimensions and Warped Geometries". Science 296: 1422–1427. http://randall.physics.harvard.edu/RandallCV/Sciencearticle.pdf. 
  20. ^ Panagiota Kanti, "Black Holes at the LHC"; http://arxiv.org/pdf/0802.2218v2
  21. ^ a b "What is LHCb". CERN FAQ. CERN Communication Group. January 2008. p. 44. http://cdsmedia.cern.ch/img/CERN-Brochure-2008-001-Eng.pdf. Retrieved 2008-09-12. 
  22. ^ a b Joel Achenbach (March 2008). "The God Particle". National Geographic Magazine. http://ngm.nationalgeographic.com/2008/03/god-particle/achenbach-text. Retrieved 2008-02-25. 
  23. ^ "The Z factory". CERN. 2008. http://public.web.cern.ch/PUBLIC/en/Research/LEP-en.html. Retrieved 2009-04-17. 
  24. ^ "LHC: How Fast do These Protons Go?". yogiblog. http://journal.batard.info/post/2008/09/12/lhc-how-fast-do-these-protons-go. Retrieved 2008-10-29. 
  25. ^ "LHC commissioning with beam". CERN. http://lhc-commissioning.web.cern.ch/lhc-commissioning/. Retrieved 2009-04-17. 
  26. ^ a b Jörg Wenninger (November 2007). "Operational challenges of the LHC" (PowerPoint). p. 53. http://irfu.cea.fr/Phocea/file.php?class=std&file=Seminaires/1595/Dapnia-Nov07-partB.ppt. Retrieved 2009-04-17. 
  27. ^ "Ions for LHC (I-LHC) Project". CERN. 1 November 2007. http://project-i-lhc.web.cern.ch/project-i-lhc/Welcome.htm. Retrieved 2009-04-17. 
  28. ^ a b Paul Rincon (10 September 2008). "'Big Bang' experiment starts well". BBC News. http://news.bbc.co.uk/1/hi/sci/tech/7604293.stm. Retrieved 2009-04-17. 
  29. ^ CERN Press Office (10 September 2008). "First beam in the LHC – Accelerating science". Press release. http://press.web.cern.ch/press/PressReleases/Releases2008/PR08.08E.html. Retrieved 2008-09-10. 
  30. ^ Mark Henderson (10 September 2008). "Scientists cheer as protons complete first circuit of Large Hadron Collider". Times Online. http://www.timesonline.co.uk/tol/news/uk/science/article4722261.ece. Retrieved 2008-10-06. 
  31. ^ "Interim Summary Report on the Analysis of the 19 September 2008 Incident at the LHC" (PDF). CERN. 15 October 2008. https://edms.cern.ch/file/973073/1/Report_on_080919_incident_at_LHC__2_.pdf. Retrieved 2009-09-28. 
  32. ^ CERN Press Office (20 September 2008). "Incident in LHC sector 3-4". Press release. http://press.web.cern.ch/press/PressReleases/Releases2008/PR09.08E.html. Retrieved 2009-09-28. 
  33. ^ CERN Press Office (16 October 2008). "CERN releases analysis of LHC incident". Press release. http://press.web.cern.ch/press/PressReleases/Releases2008/PR14.08E.html. Retrieved 2009-09-28. 
  34. ^ a b CERN Press Office (5 December 2008). "LHC to restart in 2009". Press release. http://press.web.cern.ch/press/PressReleases/Releases2008/PR17.08E.html. Retrieved 2008-12-08. 
  35. ^ CERN Press Office (30 April 2009). "Final LHC magnet goes underground". Press release. http://press.web.cern.ch/press/PressReleases/Releases2009/PR06.09E.html. Retrieved 2009-08-04. 
  36. ^ Mark Henderson (18 September 2008). "'Big bang machine' is back on collision course after its glitches are fixed". Times Online. http://www.timesonline.co.uk/tol/news/uk/science/article4774817.ece. Retrieved 2009-09-28. 
  37. ^ CERN Press Office (21 October 2008). "CERN inaugurates the LHC". Press release. http://press.web.cern.ch/press/PressReleases/Releases2008/PR16.08E.html. Retrieved 2008-10-21. 
  38. ^ CERN (20 November 2009). "The LHC is back". Press release. http://press.web.cern.ch/press/PressReleases/Releases2009/PR16.09E.html. Retrieved 2010-03-02. 
  39. ^ { CERN (30 November 2009). "LHC sets new world record". Press release. http://press.web.cern.ch/press/PressReleases/Releases2009/PR18.09E.html. Retrieved 2010-03-02. 
  40. ^ "Large Hadron Collider to come back online after break". BBC News. 19 December 2010. http://news.bbc.co.uk/2/hi/science/nature/8524024.stm. Retrieved 2010-03-02. 
  41. ^ http://arxiv.org/pdf/1002.0621v2
  42. ^ A. Trafton (5 February 2010). "Record-breaking collisions at LHC produce lots of mesons". rdmag.com. http://www.rdmag.com/News/2010/02/General-Science-Record-breaking-collisions-at-LHC-produce-lots-of-mesons/. Retrieved 2010-03-02. 
  43. ^ F. Ruggerio (29 September 2005). "LHC upgrade (accelerator)". 8th IFCA Seminar. http://chep.knu.ac.kr/ICFA-Seminar/upload/9.29/Morning/session1/Ruggiero-ICFA-05.pdf. Retrieved 2009-09-28. 
  44. ^ (French) A (very) small big bang
  45. ^ "How much does it cost?". CERN. 2007. http://askanexpert.web.cern.ch/AskAnExpert/en/Accelerators/LHCgeneral-en.html#3. Retrieved 2009-09-28. 
  46. ^ Luciano Maiani (16 October 2001). "LHC Cost Review to Completion". CERN. http://user.web.cern.ch/User/LHCCost/2001-10-16/LHCCostReview.html. Retrieved 2001-01-15. 
  47. ^ Toni Feder (2001). "CERN Grapples with LHC Cost Hike". Physics Today 54 (12): 21. doi:10.1063/1.1445534. http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_54/iss_12/21_2.shtml. 
  48. ^ "Bursting magnets may delay CERN collider project". Reuters. 5 April 2007. http://www.reuters.com/article/scienceNews/idUSL054919720070405. Retrieved 2009-09-28. 
  49. ^ Paul Rincon (23 September 2008). "Collider halted until next year". BBC News. http://news.bbc.co.uk/1/hi/sci/tech/7632408.stm. Retrieved 2009-09-28. 
  50. ^ "CERN LHC Computing". CERN. 2008. http://public.web.cern.ch/public/en/LHC/Computing-en.html. Retrieved 2009-09-28. 
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External links


Study guide

Up to date as of January 14, 2010

From Wikiversity

Template:Header About the LHC

The LHC is an international research project based at CERN in Geneva, Switzerland, where scientists, engineers and support staff from 111 nations are combining state-of-the-art science and engineering in one of the largest scientific experiments ever conducted.

The LHC is the latest and most powerful in a series of particle accelerators that, over the last 70 years, have allowed us to penetrate deeper and deeper into the heart of matter and further and further back in time. The next steps in the journey will bring new knowledge about the beginning of our Universe and how it works, as the LHC recreates, on a microscale, conditions that existed billionths of a second after the birth of our Universe.

What is the LHC?

The LHC is exactly what its name suggests - a large collider of hadrons. Strictly, LHC refers to the collider; a machine that deserves to be labelled ‘large’, it not only weighs more than 38,000 tonnes, but runs for 27km (16.5m) in a circular tunnel 100 metres beneath the Swiss/French border at Geneva.

However, the collider is only one of three essential parts of the LHC project. The other two are:

   * the detectors, which sit in 4 huge chambers at points around the LHC tunnel and
   * the GRID, which is a global network of computers and software essential to processing the data recorded by LHC’s detectors.

The LHC’s 27km loop in a sense encircles the globe, because the LHC project is supported by an enormous international community of scientists and engineers. Working in multinational teams, at CERN and around the world, they are building and testing LHC equipment and software, participating in experiments and analysing data. The UK has a major role in leading the project and has scientists and engineers working on all the main experiments.

What will the LHC do?

The LHC will allow scientists to probe deeper into the heart of matter and further back in time than has been possible using previous colliders.

Researchers think that the Universe originated in the Big Bang (an unimaginably violent explosion) and since then the Universe has been cooling down and becoming less energetic. Very early in the cooling process the matter and forces that make up our world ‘condensed’ out of this ball of energy.

The LHC will produce tiny patches of very high energy by colliding together atomic particles that are travelling at very high speed. The more energy produced in the collisions the further back we can look towards the very high energies that existed early in the evolution of the Universe. Collisions in the LHC will have up to 7x the energy of those produced in previous machines; recreating energies and conditions that existed billionths of a second after the start of the Big Bang.

The results from the LHC are not completely predictable as the experiments are testing ideas that are at the frontiers of our knowledge and understanding. Researchers expect to confirm predictions made on the basis of what we know from previous experiments and theories. However, part of the excitement of the LHC project is that it may uncover new facts about matter and the origins of the Universe.

One of the most interesting theories the LHC will test was put forward by the UK physicist Professor Peter Higgs and others. The different types of fundamental particle that make up matter have very different masses, while the particles that make up light (photons) have no mass at all. Peter’s theory is one explanation of why this is so and the LHC will allow us to test the theory. More of the Big Questions about the universe that the LHC may help us answer can be found here.

How does the LHC work?

The LHC accelerates two beams of atomic particles in opposite directions around the 27km collider. When the particle beams reach their maximum speed the LHC allows them to ‘collide’ at 4 points on their circular journey.

Thousands of new particles are produced when particles collide and detectors, placed around the collision points, allow scientists to identify these new particles by tracking their behaviour.

The detectors are able to follow the millions of collisions and new particles produced every second and identify the distinctive behaviour of interesting new particles from among the many thousands that are of little interest.

As the energy produced in the collisions increases researchers are able to peer deeper into the fundamental structure of the Universe and further back in its history. In these extreme conditions unknown atomic particles may appear.

Who benefits?

There are two types of benefit that the LHC project produces for the UK. The less easily measured benefits are:

   * new understanding of the physical world,
   * training of world class scientists and engineers,
   * maintenance of a vibrant, world class UK research base and,
   * a leading role in a major international project.

More easily appreciated are the knowledge, expertise and technology that is spun off from the LHC and can be directly applied to development of new medical, industrial and consumer technologies (more...[1])

The science of the LHC is far removed from everyday life, but the fact that the science is so extreme constantly pushes the boundaries of existing technical and engineering solutions. Simply building the LHC has generated new technology.

The LHC is not primarily about building a better world. Rather, it allows us to test theories and ideas about how the Universe works, its origins and evolution. The questions asked, and answers found, are so fundamental that the information from LHC experiments will only be applied many years in the future, if at all. However, this is an experiment and one of the surprises from the experiment may be new science that can be applied almost immediately.

For Students Exploring the outer limits of knowledge

The LHC is the most exciting science adventure of this decade; a huge international project exploring the boundaries of our knowledge and theories about the world we live in. The LHC experiments will help us understand the origins and evolution of our universe and possibly reshape how we think about the physical world. Screen shot of particle detectives home page

See a young physicist describing how the study of particle physics has affected our lives and our understanding of the universe we live in and hear how the LHC may be our window into a weird world of missing matter and quantum physics.

[2] the fundamental building blocks of nature, [3] the fundamental forces of nature, [4] the quantum world and the hunt for the Higgs boson.

Drive our simulator at www.particledetectives.net and learn how LHC scientists will conduct their experiments. This website includes a collection of resources for 14-16 and 16+ year old students on 'how science works' and particle physics. Your own discoveries or listen to the video clips of students questionning scientists about the LHC project and download Powerpoint presentations on LHC science.

There are simulations and pages of information on particle physics at the Lancaster Particle Physics pages. These are suitable for AS/A2 16+ students. There is a section dedicated to the LHC.

A simple game that illustrates how scientists search for new particles can be found on the Science Museum's website.

UK scientists have major roles in this project, which involves thousands of scientists and engineers from around the world working in harmony, to build and run the biggest experiment in the history of science. The project will continue for at least 15 years, so anyone considering science as a GCSE option now could be working on the LHC ... and contributing to new discoveries … in the future.

The science of the LHC is directly relevant to areas of the A-level (and equivalent) curriculum, but the project is also an example of how science works and there are many role models and career stories among the diverse community of scientists, engineers and administration staff working on the LHC.

A lot of resources on the LHC and particle physics are available and more will be produced over the life of the project. Visit the resources pages on the STFC website to download, or order, a stunning A1 poster of the ATLAS detector and an A5 fold out booklet that describes some of the big questions that researchers expect the LHC to answer. You can also download a poster describing the CMS detector (jpg 69kb) and a booklet describing the evolution of the universe (pdf 9.1mb) from the CMS area of CERN website. The ATLAS experiment has two posters available to download (or order) from the ATLAS store. Booklets, DVDs and other materials are also available. --Ashimjgec08 15:23, 24 May 2009 (UTC)#REDIRECT LHC#REDIRECT lhc


Simple English

File:Location Large Hadron
Map of the Large Hadron Collider at CERN

The Large Hadron Collider (LHC) is the world's biggest and most powerful particle accelerator. It cost 10.4 billion Swiss francs ($10 billion) to build.[1] It's a machine used to shoot very small particles into each other at high speed. When the particles hit each other, their energy is converted into many different particles, and sensitive detectors keep track of the pieces that are created. By looking carefully at the detector data, scientists can study what the particles are made of and how the particles interact. This is the only way to see some particles because very high energy is needed to create them. The LHC's particle collisions have the energy needed.[2]

The LHC starts with atoms, and takes away the atoms' electrons so that protons are left. Protons are parts of atoms with a positive charge. The LHC pushes these protons through a giant circular tunnel 17 miles (27 kilometers) long.[2] The protons are moved around the Large Hadron Collider at very high speeds by giant electromagnets. These magnets have to be very cold to work and they are cooled by a huge cooling system. The protons hit one another at close to the speed of light and break into strange pieces.

The Large Hadron Collider is built underground at CERN, which is in Switzerland, but the LHC is so big that part of it goes underneath France. It is between 50 and 175 metres below the ground.[2] Scientists hope that it will find the Higgs Boson, the only particle predicted to exist by the Standard Model that has not been seen yet. If scientists can find this it will help show that the Standard Model is right and show what the universe is made of.

Some people think the LHC would create a black hole, which would be very dangerous. There are two reasons not to be worried. The first is that although the LHC is powerful, the universe is more powerful. Powerful beams of positively charged particles, called cosmic rays, hit earth all the time but do not create black holes. The second reason is that even if the LHC did make black holes, they would be very tiny. The smaller a black hole is, the shorter its life. Very tiny black holes would die and turn into energy before they could hurt people.[3]

The LHC was first used on September 10, 2008, but it did not work because a cooling system broke, which was important for the magnets that help to move the charged particles. This caused part of the facility to collapse. The winter shutdown meant that it was not used again until November 2009. While it was being repaired, scientists used the Tevatron to try and find the Higgs Boson. When the LHC was restarted in November 2009, it set a new speed record by accelerating protons to 1.18 TeV (teraelectronvolt, or trillion electronvolt).[1] On March 30 2010, the LHC created a collison at 3.5 TeV.[2]

Other websites

References

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