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Large Hadron Collider at CERN

Large Hadron Collider at CERN. Steve Playfer University of Edinburgh 15th Novemebr 2008. LHC vital statistics. Ring is 27km in circumference and between 50 and 200m underground Will collide two 7 TeV proton beams with beam currents of 600mA Using E=mc 2 we get 14TeV=>0.15g (a fly)

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Large Hadron Collider at CERN

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  1. Large Hadron Collider at CERN Steve Playfer University of Edinburgh 15th Novemebr 2008

  2. LHC vital statistics • Ring is 27km in circumference and between 50 and 200m underground • Will collide two 7 TeV proton beams with beam currents of 600mA Using E=mc2 we get14TeV=>0.15g (a fly) Total energy stored in each beam is 350MJ • 1232 superconducting NbTi dipole magnets to bend beams round the ring • Beam pipe has vacuum of 10-13 atmospheres • Total power required to run LHC is 120MW • Total cost to construct LHC was 3Billion Euros More details at http://lhc.web.cern.ch/lhc/

  3. LHC Dipoles • Magnets are cooled to 1.9K by superfluid 3He • Field ramps from 0.5T to 8.3T during injection • Both beams are in the same cryostat

  4. LHC RF Cavities • Needed to accelerate beams from 400GeV to 7TeV during injection • Also needed to replace synchrotron energy losses • 8 cavities/beam • Frequency 400 MHz • Accelerating gradient 5MV/m

  5. LHC Status Temperature of dipole magnets CMS Experiment SPS ring injects 400GeV protons ALICE Experiment LHCb Experiment ATLAS Experiment

  6. LHC Operation • Proton beams are injected from the SPS at 400GeV and then accelerated to 7TeV. This is known as a “fill”. • The lifetime of the stored beams is ~10 hours. • There will be 2808 bunches of protons in each direction. Each bunch contains 1011 protons and travels round the ring in 0.9ms. • The bunch spacing is ~7m or 25ns, the bunch length is 7.5cm, and the crossing rate is 40MHz at each of the four interaction points. • There are several interactions during a bunch crossing. • The expected data rate is 100MB/s per experiment or ~10 PetaBytes/year!

  7. LHC Detectors • ATLAS is a general purpose detector (GPD) 46mx25mx25m, 7000Tonnes, central magnetic solenoid 2T and muon toroids 4T • CMS is another GPD, 21mx15mx15m, 12500Tonnes, central magnetic solenoid 4T • GPDs look for new heavy particles • Each collaboration has 2000 physicists (10% from UK) • LHCb is a forward spectrometer with a dipole bending magnet (4Tm) • Designed to study b quarks • Collaboration has 650 physicists (20% from UK) • ALICE is designed to look at heavy ion collisions

  8. ATLAS

  9. Beam view Simulation of ATLAS Event Charged Particles Side view Jets of Energy Muon Tracks

  10. CMS

  11. LHCb Bending Magnet Particle ID (RICH) Tracking System Calorimeter Muon detectors Vertex Locator Décembre 2005

  12. Higgs field in a vacuum (lots of politicians doing nothing) Particle (PM) acquires mass from interaction with Higgs field Higgs boson (rumour) is self-excitation of the Higgs field The “Waldegrave” challenge: In 1993 a minister asked for a one page explanation of the Higgs boson Winner : David Miller (UCL)

  13. Constraints on Higgs mass Top quark and W boson masses from Tevatron/LEP MH > 115 GeV from direct search at LEP2 (1996-2001)

  14. Higgs production at LHC Protons are made of quarks (mostly u,d) and gluons (g) Main production mechanisms are gluon-gluon fusion: g + g top quarks + Higgs (from t+t ) and “central” production by quark scattering: u + d d + u + Higgs (from W + W) _ Higgs is accompanied by “jets” of energy from quarks Main decays of Higgs boson: H b quarks (b + b) , tau leptons ( ,  _

  15. Higgs Cross-section MH=120GeV  ~ 30pb Large MH  < 1pb Total LHC cross-section  ~ 125mb Expected data samples are ~ 50/fb per year

  16. Higgs Decays MH=120GeV main decays are to bb and  MH>160GeV main decay is W+W-

  17. We might find something else? • Extra dimensions • Mini black holes • Supersymmetric partners of the known particles … We’re not sure what we will discover at the LHC!

  18. LHC turn-on 10/9/08 Big media publicity day (I was at the Scottish parliament) No collisions happened! Proton beams were circulated in each direction for a short time.

  19. Why the LHC won’t destroy the world Centre of mass energy of proton-proton collisions ECM=14TeV Can be achieved by colliding a high energy proton with a proton at rest ECM = sqrt(2Epmp) with Ep ~105 TeV Primary cosmic rays (protons) interact with the Earth’s upper atmosphere. Highest observed energy cosmic rays are Ep ~108 TeV which gives ECM>>14TeV. There are even more energetic collisions in the centres of galaxies, black holes etc. LHC collisions are the highest energy in a laboratory

  20. The incident on 19/10/08 http://jwenning.web.cern.ch/jwenning/documents/LHC/Talks/Glasgow-Seminar.Jan09.ppt • During power testing of a dipole magnet at high current (9kA) there was an electrical arc due to sudden high resistance • Burnt a hole in a cryogenic circuit causing a large liquid Helium leak (6 Tonnes) • Energy released was sufficient to displace and damage 30 magnets • Safety interlocks restricted damage to one sector

  21. LHC Schedule is being revised • Official CERN statements • Installation/repair of magnets by March 2009 • Interconnections & installation of improved safety systems by May 2009 • Machine cold by end of June 2009 • Injection & commissioning July-Sept. 2009 • First collisions for Physics at 10TeV in Oct.-Nov. 2009 • My optimistic projections after that • Collisions at 14TeV in June-Nov. 2010 Luminosity ~1033cm-2s-1, Data sample ~3/fb • Design goals for 1 year reached in 2012 Luminosity 1034cm-2s-1, Data sample 50/fb • Prove existence of Higgs Boson (or not?) by 2012 • Upgrades of detectors (and LHC) in 2014 & 2018

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