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The ATLAS Experiment at the CERN Large

A 30 minute tour

Peter Krieger University of Toronto

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 0 The of Particle

SU(3)C  SU(2)L  U(1)Y  e  μ     Consistent with all existing experimental data     μ     BUT  e L  L   L  No Higgs yet  u c  t   19 free parameters (, couplings etc)        three (?) generations of fundamental fermions d s b  L  L  L  (need )  Charge ratios of quarks and (GUTs)   No gravity (need string ?) ± 0 0 W ,Z Higgs H A Number candidates for physics beyond the SM g Expected scale for new physics ~ 1 TeV

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 1 Beyond the Standard Model

Hierarchy problem: there are two fundamental scales that we know -17 of: the electroweak scale and the Planck scale: MEW / Mplanck  10

Naturalness problem: radiative corrections to the mass of a fundamental scalar (e.g. the Higgs) scale like 2 where  is the energy scale to which the theory remains valid. This yields a fine-tuning problem for the Higgs mass unless:

Could be gravity if there a) There is new physics at the ~ TeV energy scale are extra dimensions b) There is some symmetry protecting the Higgs mass against large radiative corrections (Supersymmetry)

If the Higgs is not discovered with a mass < 800 GeV, expect the dynamics of WW, ZZ scattering to reveal new physics at this energy scale

We MUST see something at LHC

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 2 Vector Boson Scattering

2 Cross-section grows with s  E CM . Eventually violates unitarity (probability) unless there are additional processes. Need to add

with M H 1 TeV

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 3 Constraints on the Higgs Mass

LEP Direct Search Limit

MH > 114 GeV Low mass Higgs is favoured

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 4 Supersymmetry

Each SM boson (fermion) has a fermionic (bosonic) supersymmetric partner with IDENTICAL MASS and Standard Model COUPLINGS μ   leptons sleptons  μ   ~ μ~ ~  e       e      gauginos              μ          ~   ~   ~  ± ~ ± 0 ~ 0 ~  e    e    W W h h g g 0 ~ 0 0 ~ 0 ~ Z Z H H u c t ~u ~c t              ~ 0 ~ 0        ~   ~  A A d s b d ~s b ~       H ± H ± quarks squarks

Obviously we do not see such particles. So we say SUSY is a broken symmetry. However, most motivations for SUSY require a mass scale of less than about 1 TeV

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 5 Force Unification with and without SUSY

Weak-scale SUSY seems to allow for force unifications at high energy (running of coupling constants with energy):

No SUSY with SUSY

Assumes a TeV scale SUSY particle mass spectrum

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 6 R-

R-Parity is a quantum number which distinguishes SM and supersymmetric particles

R = (1)3(BL)+2S

Most supersymmetric models assume R-Parity Conservation

This has two important consequences:

Supersymmetric particles must be produced in pairs There must be some Lightest Supersymmetric Particle or LSP

~0 This LSP is usually the lightest neutralino  1 which can be a good Cold Dark Matter candidate.

This to an experimental signature of large transverse missing energy. In the case of pair production of squarks and gluinos at the LHC, the standard signature is jets + missing energy

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 7 Cosmological Issues

Evidence is that dark matter is predominantly “cold”, e.g. non-relativistic. Popular candidate is the WIMP (Weakly Interacting Massive Particle). The LSP can be a very good candidate for this.

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 8 Some Basic Collider Physics How does one calculate the rate for some physics process at a collider ? M = sum of all contributing processes, here for e+e-  W+W-

Define cross-section   |M|2 units of (length)2 f bunch crossing frequency Define luminosity L  N A ~Number of ~ cross-sectional size of the beams particle bunches times numbers of particles in each Instantaneous production rate N = L  bunch P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 9 Hadron vs Colliders

Bending a charged particle in a costs energy emitted in the form of :

2 2 4 4 e   1 4 E = •  or E 3  m4

For fixed radius machine (i.e. in the LEP tunnel at CERN with  = 6.28km) synchrotron radiation loss for is less that that for by the amount

Cannot (feasibly) build electron 4  m  of arbitrarily high energy. Need either:  e  1013    hadron collider  mp   linear electron positron collider

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 10 The at CERN

Proton- collider installed into the 27km circumference LEP ring at CERN in Geneva Switzerland:

 pp centre-of-mass energy of 14 TeV  constituent centre-of-mass energies ~ 1-2 TeV  luminosity of 1033 cm-2s-1 (low luminosity) 1034 cm-2s-1 (high luminosity)  proton bunch spacing of 25 ns (40MHz collision frequency)

Physics goals: whatever TeV-scale physics is there to be discovered

• • Extended gauge • Supersymmetry • Compositeness • Extra dimensions • Low-scale gravity

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 11 CERN Aerial View

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 12 LHC Accelerator Chain

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 13 The CERN Large Hadron Collider

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 14 Cutaway View LHC/ATLAS (Graphic)

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 15 The LHC Tunnel

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 16 Quadrupole from Canada

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 17 The proton-proton total cross-section

 = 1034 cm-2/s · 100mb · 10-27cm-2/mb = 109/s L tot LHC 109/s · 25ns  25 interactions / bunch crossing This is referred to as “pileup”

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 18 Min-Bias Events at High Luminosity (1034 cm-2s-1)

High rate results in large detector occupancies

High charged particle multiplicity visible in tracking detector

ATLAS H

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 19 Production cross-sections at the LHC

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 20 Higgs Branching Fractions vs MH

In terms of discovery potential, MH matters a lot. Low mass is tricky due to huge QCD backgrounds.

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 21 Higgs Discovery Significance at ATLAS

Ldt = 30 fb1 Vector boson fusion  important in the low ATLAS mass region

for example, VBF H   + 

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 22 LHC luminosity profile and physics reach

early physics O(1fb-1)

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 23 Collider Detectors

Events reconstructed based on particles stable enough to be detected

Tracking EM Hadronic Detector Detector Calorimeters

0 nK, L  e±

μ ±  ± , p

0 nK, L

Charged e±,  particle , ------, jets------particle ID

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 24 Calorimeters vs Magnetic

A calorimeter measures particle / energies via total energy deposition in the device e.g. absorption of entire particle / jet energy through a showering process (EM or hadronic). Magnetic spectrometers measure particle momenta via curvature in a known magnetic field (usually solenoidal, but also toroidal in the case of the ATLAS muon ). For a given design, the depth of a calorimeter capable of providing full containment of high energy particles scales like ln(E). For a magnetic spectrometer, the resolution p/p, for a given detector size, scales like sqrt(E). Magnetic spectrometers must get larger at higher energies, to achieve the same momentum resolution.

In ATLAS, most of the detector volume is occupied by the muon spectrometer.

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 25 The ATLAS Detector

people shown for scale

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 26 ATLAS Event Slice

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 27 The ATLAS Canada Collaboration

Alberta 42 University/Lab Carleton Montreal 150 People, including engineers, McGill Simon technicians and students Fraser Regina 20 Undergraduate students Toronto 60 Graduate Students TRIUMF 20 Postdocs UBC Victoria York Other Important Activities High Level Trigger Focus has been on LAr Calorimetry ATLAS Computing TRT Electronics Four NSERC funded projects: ATLAS Upgrades (SLHC) Hadronic Endcap Calorimeter Beam Conditions Monitors Beam Testing / Analysis Hadronic Forward Calorimeter Calorimeter Calibration Endcap Signal Cryogenic Feedthroughs Physics Studies / Analysis Radiation Hardness Studies Front-End Board Electronics Pixel Testing and Assembly

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 28 ATLAS Collaboration (Status October 2007)

37 Countries 167 Institutions 2000 Scientific Authors total (1600 with a PhD) CANADA: ~ 4% of collaboration

Albany, Alberta, NIKHEF Amsterdam, Ankara, LAPP Annecy, Argonne NL, Arizona, UT Arlington, Athens, NTU Athens, Baku, IFAE Barcelona, Belgrade, Bergen, Berkeley LBL and UC, HU Berlin, Bern, Birmingham, Bogota, Bologna, Bonn, Boston, Brandeis, Bratislava/SAS Kosice, Brookhaven NL, Buenos Aires, Bucharest, Cambridge, Carleton, Casablanca/Rabat, CERN, Chinese Cluster, Chicago, Chile, Clermont-Ferrand, Columbia, NBI Copenhagen, Cosenza, AGH UST Cracow, IFJ PAN Cracow, DESY, Dortmund, TU Dresden, JINR Dubna, Duke, Frascati, Freiburg, Geneva, Genoa, Giessen, Glasgow, Göttingen, LPSC Grenoble, Technion Haifa, Hampton, Harvard, Heidelberg, Hiroshima, Hiroshima IT, Indiana, Innsbruck, Iowa SU, Irvine UC, Istanbul Bogazici, KEK, Kobe, Kyoto, Kyoto UE, Lancaster, UN La Plata, Lecce, Lisbon LIP, Liverpool, Ljubljana, QMW London, RHBNC London, UC London, Lund, UA Madrid, Mainz, Manchester, Mannheim, CPPM Marseille, Massachusetts, MIT, Melbourne, Michigan, Michigan SU, Milano, Minsk NAS, Minsk NCPHEP, Montreal, McGill Montreal, FIAN Moscow, ITEP Moscow, MEPhI Moscow, MSU Moscow, Munich LMU, MPI Munich, Nagasaki IAS, Nagoya, Naples, New Mexico, New York, Nijmegen, BINP Novosibirsk, Ohio SU, Okayama, Oklahoma, Oklahoma SU, Oregon, LAL Orsay, Osaka, Oslo, Oxford, Paris VI and VII, Pavia, Pennsylvania, Pisa, Pittsburgh, CAS Prague, CU Prague, TU Prague, IHEP Protvino, Regina, Ritsumeikan, UFRJ Rio de Janeiro, Rome I, Rome II, Rome III, Rutherford Appleton , DAPNIA Saclay, Santa Cruz UC, Sheffield, Shinshu, Siegen, Simon Fraser Burnaby, SLAC, Southern Methodist Dallas, NPI Petersburg, Stockholm, KTH Stockholm, Stony Brook, Sydney, AS Taipei, Tbilisi, Tel Aviv, Thessaloniki, Tokyo ICEPP, Tokyo MU, Toronto, TRIUMF, Tsukuba, Tufts, Udine/ICTP, Uppsala, Urbana UI, Valencia, UBC Vancouver, Victoria, Washington, Weizmann Rehovot, FH Wiener Neustadt, Wisconsin, Wuppertal, Yale, Yerevan P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 29 Canadian Contributions to ATLAS LAr Calorimeter

Hadronic Endcap Calorimeter Wheels Cryogenic feedthroughs

Electromagnetic Endcap Calorimeter Wheels

Hadronic Forward Calorimeter Modules

Electromagnetic Forward Calorimeter Module

Liquid Front-End Electronics

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 30 P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 31 P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 32 Insertion of HEC Wheels into Endcap Cryostat

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 33 P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 34 P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 35 Insertion of the Forward Calorimeter

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 36 The ATLAS Forward Calorimeter

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 37 The ATLAS Cavern, June 2003

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 38 The ATLAS Cavern June 2004

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 39 ATLAS Cavern February 2008

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 40 ATLAS Endcap View

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 41 ATLAS Detector (Endcap Calorimeter Out)

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 42 Muon Big Wheel Installation (Sept 2006)

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 43 Muon System Installation

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 44 Muon Chambers

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 45 The ATLAS Inner Detector

• Detector components installed in 4 steps • Barrel SCT + TRT • 2 End-Caps SCT + TRT • Full pixel detector + Be beam pipe

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 46 Installation of SCT into TRT

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 47 Inner Detector Barrel Installed in ATLAS

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 48 Inner Detector Endcap Installation May 2007

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 49 ATLAS Commissioning: Timeline

1: Combined Beam Tests 2: Detector Installation, Commissioning 2.5: Spring ’08: Global cosmic run 3: Single beam 4: First LHC collisions

5: First Physics

2004 2005 2006 2007 2008

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 50 Running ATLAS: Main Control Room

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 51 Commissioning with Cosmic Ray Events

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 52 TileCal

LAr

TileCal

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 53 53 LHC Cooldown Status February 2008

Presented during the most recent ATLAS week, which took place this past week.

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 54 Current LHC Schedule

12 23 34 45 56 67 78 81

1 1 2 2 3 Power limitation 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 30 30 31 31 32 32 33 33 34 34 35 35

Flushing Warm up LHC cold May 1st Cool-down Powering Tests Inner triplets interconnections CV maintenance

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 55 Summary

The LHC Experimental programme represents the largest international scientific collaboration even undertaken. The work of thousands of people over the past two decades is about to come to fruition. This promised to be an exciting and rewarding period, and one that will likely set the direction taken in both the experimental and theoretical sides of the fields for the next few decades.

P.Krieger, University of Toronto WNPPC'08, Banff, February 2008 56