Advanced Topics in Particle Physics Probing the High Energy Frontier at the LHC Ulrich Husemann, Klaus Reygers, Ulrich Uwer University of Heidelberg Winter Semester 2009/2010 CERN = European Laboratory for Partice Physics the world’s largest particle physics laboratory, founded 1954 Historic name: “Conseil Européen pour la Recherche Nucléaire” Lake Geneva Proton-proton2500 employees, collider almost 10000 guest scientists from 85 nations Jura Mountains 8.5 km Accelerator complex Prévessin site (approx. 100 m underground) (France) Meyrin site (Switzerland) Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 2 Large Hadron Collider: CMS Experiment: Proton-Proton and Multi Purpose Detector Lead-Lead Collisions LHCb Experiment: B Physics and CP Violation ALICE-Experiment: ATLAS Experiment: Heavy Ion Physics Multi Purpose Detector Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 3 The Lecture “Probing the High Energy Frontier at the LHC” Large Hadron Collider (LHC) at CERN: premier address in experimental particle physics for the next 10+ years LHC restart this fall: first beam scheduled for mid-November LHC and Heidelberg Experimental groups from Heidelberg participate in three out of four large LHC experiments (ALICE, ATLAS, LHCb) Theory groups working on LHC physics → Cornerstone of physics research in Heidelberg → Lots of exciting opportunities for young people Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 4 Scope of this Lecture Goal: Overview of most important physics topics pursued at the LHC High-pT physics (mostly ATLAS and CMS) Flavor physics (mostly LHCb) Heavy ion physics (mostly ALICE) Target audience: Master/Diploma and graduate students with prior knowledge of theoretical and experimental particle physics Builds upon previous lecture(s) “Experimental Particle Physics” & “Introduction to the Standard Model” Part of program of the “Heidelberg Graduate School of Fundamental Physics” Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 5 Organizational Issues Advanced Topics in Particle Physics: “Probing the High Energy Frontier at the LHC” Date: Mondays, 14:00–16:00 c.t. (2 SWS) Room: INF 227 / HS 2 Lecturers: Ulrich Husemann (KIP & DESY, ATLAS): High-pT Physics Tel.: 06221-54xxxx, E-Mail: [email protected] Klaus Reygers (PI, ALICE): Heavy Ion Physics Tel.: 06221-549317, E-Mail: [email protected] Ulrich Uwer (PI, LHCb): Flavor Physics Tel.: 06221-549226, E-Mail: [email protected] Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 6 Preliminary Schedule # Date To p ic Lecturer 1 10/12/09 Introduction All 2 10/19/09 The LHC Multipurpose Experiments U. Husemann 3 10/26/09 Hadron Collider Basics U. Husemann 4 11/02/09 QCD, Factorization, Jets U. Husemann 5 11/09/09 W and Z Boson Production U. Husemann 6 11/16/09 To p Q u ar k Pro d u ct i o n U. Husemann 7 11/23/09 Higgs Physics U. Husemann 8 11/30/09 Supersymmetry U. Husemann 9 12/07/09 Exotic Models: Extra Dimensions etc. U. Husemann 10 12/14/09 U. Uwer 11 12/21/09 U. Uwer 12 01/11/10 U. Uwer 13 01/18/10 K. Reygers 14 01/25/10 K. Reygers 15 02/01/10 K. Reygers Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 7 Literature The Particle Data Book, of course: http://pdg.lbl.gov Detailed papers on LHC machine and detectors published back-to-back in open-access journal before startup: Machine: 2008 JINST 3 S08001 ALICE: 2008 JINST 3 S08002 ATLAS: 2008 JINST 3 S08003 CMS: 2008 JINST 3 S08004 LHCb: 2008 JINST 3 S08005 More detailed literature lists for the individual topics later (few books, many review articles) Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 8 Chapter 1 Introduction A Little LHC History The early days 1977: LEP tunnel to be built large enough for another ring 1984: First LHC workshops in Lausanne → superconducting 10 T (= 17 TeV) pp collider in LEP tunnel → feasibility of magnet design shown in late 1980ies 1990: Aachen workshop → evaluation of LHC physics potential 1992: Évian workshop → experiment proposals 1993: US congress terminates SSC (Superconducting Super Collider, 40 TeV) → integrate US physics community 1994: Approval by CERN Council Initial plan: two stages (10 TeV in 2004, 14 TeV in 2008, due to budget constraints), later changed to 14 TeV in 2005 Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 10 A Little LHC History Construction phase 1998: civil engineering starts (experimental caverns and surface buildings) 2000: LEP terminated and dismantled from 2000: (pre-) production of magnets 2005–2007: magnet installation [atlas.ch] Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 11 A Little LHC History LHC startup September 10, 2008: first beam event, experiments (partly) switched on September 19, 2008: magnet incident stops LHC operation November 2009: LHC restart Further details on LHC history: CERN Courier (issue of October 2008) [CERN] Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 12 LHC Physics Program Main LHC goal: search for the Higgs boson and physics beyond the standard model → high-pT & flavor physics Broader physics program considered early on: Collisions at four points around the ring: two with large collision rates, two with medium collision rates Allow LHC operation with heavy ions (lead) Optimize design of machine and detector for above goals, given technical constraints: Tunnel: re-use from LEP accelerator → 27 km circumference Magnets: maximum B field strength with available technology for superconducting dipole magnets → 9 Tesla → approx. 15 TeV center of mass energy Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 13 High-pT Physics @ LHC Hadron collider physics = discovery physics at the highest available energies (“energy frontier”), complementary to precision physics at e+e– colliders CERN Sp!S: 1982–1990 → W and Z boson discovery, searches for top quarks, SUSY… Fermilab Tevat ro n : 1987–2010 (2011?) → top quark discovery, Bs flavor oscillations, searches for Higgs, SUSY, exotics… Next step in energy: explore energies around 1 TeV (“terascale”) → relevant scale for electroweak physics Machine & detector design goals: Highest possible energies and collision rates Versatile multi-purpose detectors Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 14 Protons or Antiprotons? Sp!S and Tevatron: proton-antiproton colliders At leading order many processes dominated by quark- antiquark annihilation, e.g. W and Z production, but: no valence antiquarks in proton → antiprotons p p + + + ν¯", " e ,µ u, d u, d ± Z ¯ ¯ W ¯ ¯ d, u − u, d − − " , ν" e ,µ p¯ p¯ Particle and its antiparticle can be accelerated in the same structure (single beam pipe, same magnets, …) Problem: protons are “cheap”, but antiprotons are hard to produce (in proton beam dump) and to accumulate (“cooling”) → performance of collider limited by antiproton availability Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 15 Protons! At LHC energies: Interesting final states with a few 100 GeV (Higgs, top, …) produced by partons that carry small fraction x of proton momentum (more details on proton structure later) Important HERA result: gluons dominate at small x → don’t need valence antiquarks, e.g. for top pair production q W– p ! #’ " b t Ȟ p ȝ W+ ȝ+ Caveat: need separate acceleration structures (two rings or double ring) Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 16 Heavy Ion Physics @ LHC Heavy ion collisions: study strongly interacting matter at extreme energy densities → expect new phase of matter: quark-gluon plasma Experience from previous heavy ion programs, e.g. CERN fixed target program: ions from SPS Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory: 200 GeV gold-gold collisions LHC: explore highest available energy densities Design goals: Allow for acceleration of heavy ions in addition to protons Dedicated experiment for heavy ion collisions: ALICE Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 17 Flavor Physics @ LHC Flavor physics: indirect search for new phenomena in very rare decays via loop effects → multi-TeV Central tool in flavor physics: B hadrons → long history of fixed-target and collider experiments, e.g. LEP and Tevat ro n multi-purpose experiments ARGUS & CLEO: e+e– collider experiments on ϒ(4S) resonance BABAR & Belle (“B Factories”): experiments at asymmetric e+e– collider on ϒ(4S) resonance LHC: extremely high production rate of B hadrons Specialized interaction region with lower collision rates Dedicated experiment optimized for detecting B hadron decays Probing the High Energy Frontier at the LHC, U Heidelberg, Winter Semester 09/10, Lecture 1 18 Chapter 2 The LHC Accelerator Chain Pre-Accelerator Chain LHC beam to consist of: 2808 proton bunches with spacing of 25 ns (40 MHz, distance: 7.5 m), complicated bunch structure High intensity bunches (1011 protons/ bunch) with small longitudinal and transverse spread (“emittance”) Cannot accelerate beams from zero to 7 TeV in a single structure → need chain of pre-accelerators Re-use existing pre-accelerators