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The Large Hadron Collider Machine, Experiments, Physics Introduction to the lecture

The Large Hadron Collider Machine, Experiments, Physics Introduction to the lecture. Johannes Haller Thomas Schörner-Sadenius Hamburg University Summer Term 2009. A) WORKING LANGUAGE, STYLE. Style: informal!

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The Large Hadron Collider Machine, Experiments, Physics Introduction to the lecture

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  1. The Large Hadron ColliderMachine, Experiments, PhysicsIntroduction to the lecture Johannes HallerThomas Schörner-Sadenius Hamburg UniversitySummer Term 2009

  2. A) WORKING LANGUAGE, STYLE • Style: informal! • – The material will not always be presented in the theoretically most rigorous style but in a rather pedagogical way. • – Many of the contents are difficult to understand – and it would be a pity if you got lost on the way. • Please ask all questions! I hope I can answer most of them immediately; if not, I will think about them and come back with an answer in the next session. Very often only your questions will bring out the full truth, in the sense that I am partially “betriebsblind” and will have problems to spot places where you might have problems.  You help your fellow students, and you help me in improving the lecture. • If NO objections: ENGLISH! • – … good opportunity for practice … • – … but only reasonable if nobody gets lost … • – … and if we can make sure that everybody understands everything … • Requires your active participation (questions, discussion, criticism). If objections: – slides in english, – but german as working language. Please bring typos, errors, etc. in thelecture / in the slides to my attention! UHH SS09: LHC

  3. B) LECTURERS JunProf. Dr. Johannes Haller – Studies in Heidelberg – First HEP contact: DESY summer student (1997, H1 and HASYLAB) – Diploma in Heidelberg (OPAL experiment) – Dissertation Heidelberg: Search for supersymmetry at HERA (H1). – CERN fellow (2004-2006): Work on the ATLAS trigger; search for new physics. – UHH JunProfessor: Priorities are ATLAS (trigger and new physics) and ILC. Dr. Thomas Schörner-Sadenius– First HEP contact: Internship at the Crystal Barrel Experiment (CERN, 1996) – Diploma at LMU Munich (1998): (“Search for Higgs bosons …”), OPAL ToF. – Dissertation MPI f. Physik München / LMU (2001): QCD studies at H1. – CERN fellow (2001-03): Work on ATLAS trigger and on EW physics at OPAL (LEP).– UHH WissAss (03-08): ZEUS calorimeter, run coordination, QCD, 6m Tagger, …-- DESY: Head of Analysis Centre (since 2009) UHH SS09: LHC

  4. C) ORGANISATIONAL MATTERS – Date: Wednesday, 14:00-15.30, HS III. – Working language: English (if no strong protests). - Web page: www.desy.de/~schorner/lehre/ss09/lhc.html - Outline - Slides - News - Seminar – Contacts: johannes.haller@desy.de thomas.schoerner@desy.de – Slides Hopefully on web evening before lecture . – Purpose - Experimental lecture on all aspects of the Large Hadron Collider (LHC) project: Accelerator, detectors, physics. - We do NOT intend to provide the theo- retical basics for particle physics (field theory, Standard Model, gauge principle, etc.) – these topics have been discussed in other lectures. – Prerequisits: - at least “Nuclear and Particle Physics” (Kern- und Teilchenphysik, P5) - better: “Advanced Particle Physics” (Teilchenphysik für Fortgeschrittene) – Credits: - Active participation in the lecture - presentation in seminar on LHC and associated issues. User: lectures Password: sadenius UHH SS09: LHC

  5. D) OUTLINE • (0) Introduction, organisation, overview (TSS) • Accelerators and the LHC (TSS) • Basics of pp physics: factorisation, PDFs, minimum bias, QCD, underlying events (TSS) • Detectors 1: Trigger, DAQ, Lumi (TSS) • Detectors 2: Calorimetry (TSS) • SM physics 1: Electroweak, QCD (TSS) • SM physics 2: Top (TSS) • SM physics 3: Higgs (JH) • Detectors 3: Tracking (JH) • Beyond the SM (JH) • SUSY 1: Theory (JH) • SUSY 2: Experiment (JH) • SLHC, VLHC and LHeC (JH) • LHC at Hamburg University (JH) • For more details, dates etc. please refer to: • http://www.desy.de/~schorner/lehre/ss09/lhc.html UHH SS09: LHC

  6. UHH SS09: LHC

  7. E) LITERATURE, FURTHER INFORMATION Status of the Standard Model – LEP and SLD Collaborations et al., “Precision Electroweak Measurements on the Z Resonance”, hep-ex/0509008, Phys. Rept. 427 (2006) 257. – LEP Collaborations and LEP EWWG, “A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model”, hep-ex/0511027. – Scripts for the following lectures: - Das Elektroschwache Standarmodell, http://www.desy.de/~schorner/lehre/ws0607/ew.html - Physik jenseits des Standard-Modells, http://www.desy.de/~haller/lehre/ss07/vorlesung/bsm.html - Teilchenphysik f. Fortgeschrittene, http://www.desy.de/~schorner/lehre/ss06/teilchen2.html Higgs– LEP Higgs WG, “Search for the standard model Higgs boson at LEP”, Phys.Lett.B565 (2003) 61, hep-ex/0306033. – V. Büscher and K. Jakobs, “Higgs boson searches at hadron colliders”, hep-ph/0504099. SUSY – S. Martin, “A Supersymmetry Primer”, hep-ph/9709356. – Haber and Kane, “The Search for Supersymmetry”, Phys. Rept. 117 (1985) 75. Other new physics – R. N. Mohapatra, „Unification and Supersymmetry“, Springer, 1991 – John Ellis, "Beyond the standard model for hill walkers", hep-ph/9812235. – Salavat Abdullin et al., "Tevatron-for-LHC Report: Preparations for Discoveries", hep-ph/0608322. UHH SS09: LHC

  8. E) LITERATURE, FURTHER INFORMATION LHC experiments – http://atlas.web.cern.ch/Atlas/index.html – http://cms.cern.ch TEVATRON experiments – http://www-d0.fnal.gov – http://www-cdf.fnal.gov HERA experiments – http://www-zeus.desy.de – http://www-h1.desy.de LEP experiments – http://opal.web.cern.ch/Opal/PPwelcome.html – http://aleph.web.cern.ch/aleph/ – http://l3.web.cern.ch/l3 – http://delphiwww.cern.ch/ Sources of literature, data bases etc. – http://www-library.desy.de/spires/hep – http://arxiv.org – http://pdg.lbl.gov Physics at the LHC: – ATLAS Collaboration: “Physics TDR” , CERN-LHCC-99-15, http://atlas.web.cern.ch/Atlas/index.html Documentation  Proposal & TDR -- ATLAS Collaboration: “Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics”, http://arxiv.org/abs/0901.0512 – CMS Collaboration: “Physics TDR”, CERN-LHCC-06-001, http://cmsdoc.cern.ch/cms/cpt/tdr/ptdr1_final_colour.pdf UHH SS09: LHC

  9. F) SEMINAR • We want to organise a seminar (instead of “Übungen”). • Exact date to be discussed / defined. • Middle / end of term? • 1-2 days? Weekend? Continuously during term? • Talks 25` • Possible topics (suggestions, need to be defined more strictly): • Calorimetry • Tracking • Triggering • Higgs physics • Aspects of SUSY • LHC and cosmology • Beyond the LHC • Forward and diffractive physics • Jet finding at the LHC • Limit-Setting • The Monte Carlo method • Electroweak fits Organisational Meeting for Seminar: Wednesday, April 29, 15:30 (after the lecture) UHH SS09: LHC

  10. 1.0 INTRODUCTION When starting a lecture on the LHC there are 4 questions which have to be answered: Why are we not satisfied with the current state of particle physics (i.e. the Standard Model)? What kind of extensions of the SM could we think of? What kind of machine do we need to increase our knowledgeand to go further than the SM? How could we possibly find (=detect) ‘new’ physics? In today’s quick overview I will briefly address these questions. You are not necessarily expected to understand all details of today’s lecture; having participated in former specializedHEP lectures might help. Otherwise you will (partially) be enlightened during the course of the lecture. UHH SS09: LHC

  11. 1.1 INTRODUCTION: THE STANDARD MODEL The Standard Model (SM) • - Renormalisable (local) gauge field theory with complex group structure: SU(3)C×SU(2)L×U(1)Y. • - Incorporates Glashow-Salam-Weinberg model (=QED + weak theory) and QCD. • - Complex Lagrangian (shown before EWSM)! Particle content of the Standard Model • - 6 quarks (plus their antiquarks) (spin ½) • - 3 charged and 3 neutral leptons (spin ½) • - Fermions organised in three families or generations! • - 8 gluons, W±, Z0, γ (spin 1) • - … what about the Higgs boson? • Particle interactions in the SM • Mediated by the exchange of one of the gaugebosons (g,W±,Z0,γ), depending on particle charges (EM, weak, color). • Calculable using perturbation methods (if hard energy scale present and couplings small), or (for QCD) on the lattice. H(?) UHH SS09: LHC

  12. 1.1 INTERMEZZO: QED AND QCD SM is invariant under local gauge transformationsand renormalisable. Postulate of local gauge leads to existence of gauge bosonsand fixes form of interactions. Using Euler-Lagrange equation on Lagrange density gives equations of motion (e.g. Dirac equation). Remember: QED – Gauge transformation (change of phase): – in accordance to that: covariant derivative and gauge boson A with fixed behaviour under gauge transformation: – Physics invariant! Noether theorem  conserved quantity: electric charge! Remember: QCD – Gauge transformation: Rotation in color space: – more complex structure of covariant derivative and of gluon fields under transformation (non-abelian theory with gluon self-interaction): – Physics (Lagrange density) invariant under color transformations. Remember: GSW Theory … next page k: rotation angles in color space, fjkl: structure constants j: rotation matrices (Gell-Mann, 33) UHH SS09: LHC

  13. 1.1 INTERMEZZO: GSW Glashow-Salam-Weinberg: SU(2)L×U(1)Y – covariant derivative: – The Wj are new vector fields (with their own kinetic terms). It follows: Invariant, if: – To get also the photon, include further U(1) IA (masses neglected): – Go from W,B fields to W,Z,photon: – Using … … we arrive at: UHH SS09: LHC

  14. 1.1 THE STANDARD MODEL: SUCCESSES H Z Z Z Z t Success of the SM: – No measurement to-date in contradiction to SM predictions!– SM does not only describe, but can predict – for example mass of top quark (in 1992!): – Underlying effect: Virtual corrections – higher order terms in perturbative SM expansions! Quadratic/logarithmic sensitivity to Mt, MH! – Especially combined fits to masses of t, W, H interesting (using variety of LEP/ TEVATRON data): – LEP: There are exactly 3 interacting neutrinos (plus perfect description of Z boson line shape)! UHH SS09: LHC

  15. 1.1 THE STANDARD MODEL: SUCCESSES Even Higgs mass predicted: – MH ~ 76 GeV, MH < 144 GeV (Δχ2=2.7, CL=95%). – But: Direct searches (yellow area) give higher limits: … first hint towards a problem? Going into a bit more detail: – Overall agreement of data with SM predictions is excellent: UHH SS09: LHC

  16. 1.1 THE STANDARD MODEL: SUCCESSES More EW physics: Cross-section ee WW (LEP): – Requires calculation of many diagrams! … and EW physics at HERA: – Electroweak unification established at HERA!– Neutral = charged current at high Q2! Photon: W boson: (MW)2 UHH SS09: LHC

  17. 1.1 THE STANDARD MODEL: SUCCESSES Also strong interactions precisely measured and described: – For example the strong coupling constant αS: – Or the proton structure from deep inelastic electron-proton scattering (HERA): Average αS(MZ) : 1% uncertainty: UHH SS09: LHC

  18. 1.1 THE STANDARD MODEL: SUCCESSES Jet cross-sections at HERA and Tevatron: Testing – Coupling αS; – PDFs fi;– Factorisation– PDF universality– QCD dynamics– … UHH SS09: LHC

  19. 1.2 PROBLEMS OF THE SM – large number of free (a-priori unknown) parameters: – Particle masses, mixing angles, couplings, … – Explanation for values in fundamental theory? – Gauge structure? – Why exactly three (?) generations? – Connection fermions – bosons? – Connection leptons – quarks (charge!)? Connection SU(2)L, U(1)Y and SU(3)C? – Without Higgs: SM diverges at 1 TeV! – Development of SM: story of avoiding singularities! – Only scalar boson can avoid divergencies. – Nature of EW symmetry breaking? – SM decoupled from gravitation! – In SM, no unification of couplings, masses etc. – Hoping for more fundamental theory to unify these parameters? – Hierarchy and fine-tuning problems? – Question of dark matter? – No SM candidate! UHH SS09: LHC

  20. 1.3 POSSIBLE EXTENSIONS OF THE SM Spin SM particles SUSY partners 1/2 Leptonen (e, ne, …) Quarks (u, d, …) Sleptonen (e, ne, …) Squarks (u, d, …) ~ ~ ~ ~ 1 Gluonen W Z0 Photon (g) Gluinos Wino Zino Photino ( g ) ~ 0 Higgs Higgsino 2 Graviton Gravitino Spin 0 1/2 1/2 3/2 Arguments for SUSY: – Why not? - compatible with all experimental data! – Last extension of Poincare group of SRT (after translation, rotation, Lorentz trafo, C,P,T). – Explanation of spin? – removes fermion-boson asymmetry! – Leads to unification of interactions (GUT). – Solves hierarchy problem. – Introduces dark matter candidate (LSP). – Predicts MH < 130 GeV. – Allows introduction of gravity – is limit of string theories at low energies. Discovery of SUSY similarly fundamental like discovery of antimatter! Many proposals on the market, some quite esoteric. Hottest candidates for discoveries at the LHC: – (one or more) Higgs bosons (note that “only” the SM Higgs boson would not solve too many of the above mentioned problems!). – Supersymmetry: - Symmetry between fermions and bosons proposed by Wess and Zumino in 1973.- introduce SUSY partner for all SM particles.- SUSY must be broken symmetry! UHH SS09: LHC

  21. 1.3 POSSIBLE EXTENSIONS OF THE SM – SUSY – Unification of gauge couplings in SUSY models! – Solution to hierarchy problem via SUSY corrections to Higgs diagrams! – Unification of masses! UHH SS09: LHC

  22. 1.3 POSSIBLE SM EXTENSIONS: SUSY ¶ SM Fits – precise measurement of Mt, MW allows exclusion SM and confirmation of SUSY? ¶ currently: … heavy SUSY prefered! UHH SS09: LHC

  23. 1.3 POSSIBLE SM EXTENSIONS: SUSY • If gravitation ~ 1/r2 expect rotational curves v(r) ~ 1/sqrt(r) (Kepler) Galaxy NGC6503 Solar system New form of invisible matter:Dark Matter = SUSY particles ? UHH SS09: LHC

  24. 1.4 MOTIVATION FOR THE LHC History of particle physics: Discoveries mostly done at hadron machines (cf. Livingston plot): – ISR: hard interactions  QCD! – SppS: W and Z! – Tevatron: top Quark UHH SS09: LHC

  25. 1.4 MOTIVATION FOR THE LHC Higgs, SUSY, ED, CI, …… all propose “new” physics at high energy scales and high particle masses Other view: We are interested in the smallest possible structures of matter • need high energy Problem in ring accelerators: synchrotron radiation! Loss per turn proportional to inverse of ring radius, to fourth power of energy and to fourth inverse power of particle mass: • Choose the heaviest reasonable particles in the largest possible radius! • … Large Hadron Collider ! History of particle physics: Discoveries mostly done at hadron machines (cf. Livingston plot): – ISR: hard interactions  QCD! – SppS: W and Z! – Tevatron: top Quark UHH SS09: LHC

  26. 1.5 LHC PHYSICS PROGRAM OVERVIEW Other BSM models: – Contact interactions – Extra dimensions – Technicolor – Extra Z bosons – … Forward and diffractive physics: – Total cross-section measurements – Understand diffraction – Saturation phenomena – Low-x physics Heavy ions: – Quark-gluon plasma – … … you name it … Standard Model physics: – Top: all quantum numbers – W,Z (and possibly PDFs from that?) – QCD studies (jets, prompt photons, strong coupling αS, …) important as background to all BSM studies! – Heavy flavours (b physics) All SM topics also have relevance for physics beyond the SM – either as backgrounds or because BSM physics could reveal itself in SM signatures … Higgs physics: – SM Higgs: Quantum numbers? – Higgs in SM extensions? – Little Higgs Supersymmetry: – Discover! – Understand: Which model? – What can we tell about physics at the highest scales (unification?). UHH SS09: LHC

  27. 1.6 THE LHC AND ITS EXPERIMENTS UHH SS09: LHC

  28. 1.6 THE LARGE HADRON COLLIDER – proton-proton collider, √s = 14 TeV = 14·1012 eV– frequeny: 40 MHz (25 ns, +overlays) – max. luminosity: 1034 cm-2s-1, 100fb-1/a. – Start: Delayed until autumn 2009– Experiments ATLAS, CMS (LHCb, ALICE) UHH SS09: LHC

  29. 1.6 THE ATLAS EXPERIMENT - Length ~40 m- Diameter ~25 m- Weight ~7000 t- 108 channels (2MB/event) - ‘Inner Detector’ (tracking)- Numerous calorimeters- Large muon system ~40 Nations~150 Institutes~2000 physicists - central: solenoid around ID, Toroids in muon system- End caps: Toroidal fields UHH SS09: LHC

  30. 1.6 ATLAS: CAVERN UHH SS09: LHC

  31. 1.6 ATLAS: STATUS (~MÄRZ 2007) Requirements: – 5% pT resolution for muons (1 TeV)– 20 μm spatial resolution– EM energy scale to 0.1% – uniformity: 1% UHH SS09: LHC

  32. 1.6 ATLAS: ‘INNER DETECTOR’: TRACKING ‘Transition Radiation Tracker (TRT)’ - 0.42•106 channels- =170m pro tube- || <2.5 Pixel detector: - 3 barrel layers - 2•4 end discs - 140•106 channels- R=12m,z,R=~70m- || <2.5 Silicon Tracker: - 4 barrel layers, || <1.4 - 2•9 end discs, 1.4 <  < 2.5- area 60 m2- 6.2•106 channels- R=16m, z,R=580m UHH SS09: LHC

  33. 1.6 ATLAS: CALORIMETERS ‘Hadronic Tile’ - 463000 scintillating ‘tiles’- 10000 PMTs- granularity 0.1•0.1 - : <1.0, (0.8-1.7)- L=11.4 m, Rout=4.2 m ‘Hadronic LArEndcaps’ - Steel aboserber - 4400 channels- 0.1•0.1 / 0.2•0.2- 1-5  ‘EM LAr Accordeon’ - Lead absorber - 174000 channels- 0.025•0.025- : <2.5, <3.2 ‘Forward LAr’ - 30000 ‘rods’, each 1mm- Cell size 2-5cm2 (4 rods)- : <3.1, <4.9- copper / tungsten ‘LAr Pre-Sampler’ Compensates energy loss in front of calorimeters UHH SS09: LHC

  34. 1.6 ATLAS: MUON SYSTEM ‘Cathode Strip Chambers’ - 67000 wires- space=60m, t=7ns ‘Resistive Plate Chambers’ - 354000 channels- space=1cm- Trigger signals in 1ns ‘Thin Gap Chambers’ - 440000 channels- ~MWPCs ‘Monitored Drift Tubes’ - 3 cylinders at R=7, 7.5, 10m- 3 layers at z=7, 10, 14 m- 372000 tubes, 70-630 cm- space=80m, t=300ps (24-bit FADCs) UHH SS09: LHC

  35. 1.6 ATLAS: TRIGGER AND DAQ Cross-sections at the LHC: – Factors 109 between bread-and-butter physics and interesting processes like Higgs, SUSY … – In addition, extremely high rate (25 MHz) with large event sizes (2 MB)  need fast and efficient rejection of uninteresting events Task of the trigger (and DAQ): – Identify, select and read-out interesting events and reject the others in short time: ATLAS: 3-layer system: UHH SS09: LHC

  36. UHH SS09: LHC

  37. Transverse slice through CMS detector Click on a particle type to visualise that particle in CMS Press “escape” to exit ¶ Almost complete coverage of full solid angle … with “individual” detection capabilities for all particle types. UHH SS09: LHC

  38. 1.6 PARTICLES IN CMS ¶ Almost complete coverage of full solid angle … with “individual” detection capabilities for all particle types. UHH SS09: LHC

  39. 1.6 SUSY EVENT IN CMS • Squark produktion • ET,miss = 360 GeV • ET,jet = 330, 140, 60 GeV φ η UHH SS09: LHC

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