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ATLAS detector

ATLAS detector. Preparing for first physics at the LHC. Ivo van Vulpen (NIKHEF). Early Top Physics (16). Super Symmetry (8). Commissioning (7). Extra dimensions (3). LHC+ATLAS (3). Conclusions. Introduction (6). Early Top Physics (16). Super Symmetry (8). Commissioning (7).

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ATLAS detector

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  1. ATLAS detector Preparing for first physics at the LHC Ivo van Vulpen(NIKHEF)

  2. Early Top Physics (16) Super Symmetry (8) Commissioning (7) Extra dimensions (3) LHC+ATLAS (3) Conclusions Introduction (6)

  3. Early Top Physics (16) Super Symmetry (8) Commissioning (7) Extra dimensions (3) LHC+ATLAS (3) Conclusions Introduction (6) - The SM- ... and what’s wrong it

  4. Particles Forces 1) Electromagnetism2) Weak nuclear force3) Strong nuclear force Quarks Leptons The Standard Model: Describes all measurements down to distances of 10-19 m

  5. Limits on mh from theoryLimits on mh from exper. “We know everything about the Higgs boson except its mass” Higgs mass (GeV) Triviality Unitarity Λ (GeV) Electroweak Symmetry breaking Electro-Weak Symmetry Breaking:(Higgs mechanism)- Weak gauge bosons and particles have mass- Regulate WW/ZZ scattering λdescribes Higgs’s self-couplings (3h, 4h)

  6. The standard model … boring ? “All measurements in HEP can be explained using the SM” “The Higgs boson will be discovered at the LHC at ~ 150 GeV” No. … there are many mysteries left!

  7. The big questions: • What explains (extreme) tuning of parameters (hierarchy problem) ? • What is dark matter made of ? • Why is gravity so different ?

  8. t W W t h h λtλt b Failure of radiative corr. in Higgs sector: Radiative corrections from top quark mh = 150 = 1354294336587235150–1354294336587235000 Λ2 The hierarchy problem in the SM The hierarchy problem Success of radiative corr. in the SM: predicted observed ? Hierarchy problem: ‘Conspiracy’ to get mh ~ MEW («MPL) Biggest troublemaker is the top quark!

  9. Extra dimensions ? Super-Symmetry ? String theory ? Edward Witten’s latest insight ? • Model is an ‘approximation’ of a more fundamental one.  Model breaks down below 10-19 m(1-10 TeV) New phenomena will appear at distances ~ 10-19 m 2006

  10. Early Top Physics (16) Super Symmetry (8) Commissioning (7) Extra dimensions (3) LHC+ATLAS (3) Conclusions Introduction (6) - The LHC accelerator - Status of construction of the ATLAS detector

  11. The LHC machine Centre-of-mass energy: 14 TeV Energy limited by bending power dipoles 1232 dipoles with B= 8.4 T working at 1.9k  Search for particles with mass up to 5 TeV Luminosity: 1033-1034 cm-2s-1 Phase 1: (low luminosity) 2007-2009 Integrated luminosity ~ 10 fb-1/year Phase 2: (high luminosity) 2009-20xx Integrated luminosity ~ 100 fb-1/year  Search for rare processes 7 x Tevatron 100 x LEP & Tevatron

  12. Tracking (||<2.5, B=2T) : • Silicon pixels and strips • Transition Radiation Detector (e/ separation) • Calorimetry (||<5) : • EM : Pb-LAr • HAD: barrel: Fe/scintillator forward: Cu/W-LAr • Muon Spectrometer (||<2.7) : • air-core toroids with muon chambers The ATLAS detector ~1000 charged particles produced over ||<2.5 at each crossing. Length : ~45 m Radius : ~12 m Weight : ~ 7000 tons Electronic channels : ~ 108 ATLAS floats, … but CMS doesn’t

  13. Last Friday 10:30 hours The ATLAS detector today http://atlaseye-webpub.web.cern.ch/atlaseye-webpub/web-sites/pages/UX15_webcams.htm

  14. Early Top Physics (16) Super Symmetry (8) Commissioning (7) Extra dimensions (3) LHC+ATLAS (3) Conclusions Introduction (6) • Testbeam • Cosmics • Single beam - First Physics runs

  15. The road to physics Time-line for LHC machine and ATLAS preparation Subdetector Installation Cosmics commissioning Testbeam Single beams First LHC collissions First physics runs 2004 2005 2006 2007 2008 2009 Weltmeister !

  16. Muons in the ATLAS cavern ~ 20 million muons enter cavern per hour Simulation ATLAS cavern 0.01 seconds Rate: Cavern 5000 Hzand in ATLAS 25 Hzand go through origin 0.5 Hz  106 events in 3 months Cosmics : tracks in Pixels+SCT+TRT • Useful statistics for debugging. • Check relative position • First alignment studies: (down to ~ 10 m in parts of Pixels/SCT) • First calibration of R-t relation in straws ATLAS Preliminary

  17. TRT We can reconstruct these muons! Muons seen by individual sub-detectors(ATLAS’ first events) Muon chambers Tile calorimeter

  18. Using cosmics to calibrate the EM Calorimeter What can we do with 100 days of cosmics in the ECAL ? In 3 months (50% eff.): 100 muons/cell(over || <=1 and 70 % of  coverage) A muon deposit ~ 300 MeV in ECAL cell ( S/N~ 7 ) check (+ correct) ECAL responseuniformity vs  to ~ 0.5% Test-beam data Test-beam data Entries Muons ATLAS Preliminary Relative Energy Noise Energy GeV Eta (module)

  19. Single beams in LHC Side-view ATLAS detector Beam gas: • 7 TeV protons on residual gas in vacuum Low-PT particles 25 Hz tracks with PT> 1 GeV and |z|<20 cmVertices uniform over ±23 m Timing/Trigger/Tracking Alignment Beam halo: • Straight tracks accompanying beam Rate: 1 kHz with E > 100 GeV 10 Hz with E > 1 TeV 106-107 in 2 months (30% eff.) Alignment in Muon Endcaps Side-view ATLAS detector

  20. ATLAS detector performance on day-1 - Reconstruct (high-level) physics objects: Electrons/photons: Electromagnetic Energy scale Quarks/Gluons: Jet Energy scale + b-tagging Neutrino’s/LSP?: Missing Energy reconstruction Expected detector performance from ATLAS(based on Testbeam and simulations) Performance Expected day-1 Physics samples to improve ECAL uniformity 1% Min. bias, Ze+e- (105 in a few days)e/γ scale 1-2% Ze+e-HCAL uniformity 2-3% single pions, QCD jetsJet scale <10% γ/Z (Zl+l-) + 1 jet or Wjj in ttTracking alignment 20-500 μm Rφ Generic tracks, isol. muons, Zμ+μ-

  21. Plan-de-campagne during first year Process #events 10 fb-1 First year:A new detectorANDa new energy regime Understand ATLAS using cosmics 0 1 1 Understand SM+ATLAS in simple topolgies 2 2 Understand SM+ATLASin complex topologies 3 3 Look for new physicsin ATLAS at 14 TeV

  22. Early Top Physics (16) Super Symmetry (8) Commissioning (7) Extra dimensions (3) LHC+ATLAS (3) Conclusions Introduction (6) Top quarks: • As unknown member of the SM family • As the calibration tool during first LHC runs • As a window to new physics

  23. The top quark: ‘old-physics’, … but not well known We still know little about the top quark u c t s b d - Mass precision <2% - Electric charge ⅔ -4/3 excluded @ 94% C.L. (preliminary) - Spin ½ not really tested – spin correlations - Isospin ½ not really tested - BR(tWb) ~ 100% at 20% level in 3 generations case - V–A decay at 20% level - FCNC probed at the 10% level - Top width ?? - Yukawa coupling ?? The LHC offers an opportunity for precision measurements

  24. Top quark production at the LHC Production: σtt(LHC) ~ 830 ± 100 pb  1 tt-event per second Cross section LHC = 100 x TevatronBackground LHC = 10 x Tevatron 90% 10% t Final states: t 1) Full hadronic (4/9) 6 jets 2) Semi-leptonic (4/9): 1l + 1ν + 4 jets 3) Full leptonic (1/9): 2l + 2ν + 2 jets t  Wb ~ 1W qq ~ 2/3W lν ~ 1/3 Golden channel (l=e,μ) 2.5 million events/year

  25. Top quark physics with b-tag information Top physics is ‘easy’ at the LHC Selection: Lepton + multiple jets+ 2 b-jetskills the dominant background from W+jets Systematic errors on Mtop (GeV)in semi-leptonic channel S/B > 80 Top signal Number of Events hep-ex/0403021 W+jets Top mass (GeV) Could we see top quarks when selection is not based on b-tag ? If so: we could use top quark production to calibrate ATLAS.

  26. Selecting Top quark events without b-tag information • Robust selection cuts • Assign jets to W, top decays Missing ET > 20 GeV Selection efficiency = 5.3% 1 lepton PT > 20 GeV 4 jets(R=0.4) PT > 40 GeV W CANDIDATE TOP CANDIDATE 1) Hadronic top: Three jets with highest vector-sum pT as the decay products of the top 2) W boson: Two jets in hadronic top with highest momentum. in reconstructed jjj C.M. frame.

  27. Results for a ‘no-b-tag’ analysis: 100 pb-1 3-jet invariant mass (70 < Mjj < 90 GeV) Hadronic 3-jet mass electron+muon estimate for L=100 pb-1 Events / 4.15 GeV 100 fb-1 is a few days of nominal low-lumi LHC operation Mjjj (GeV) Yes, we can see top peak (even without b-tag requirement)during first LHC runs

  28. A candle for complex topologies: Calibrate light jet energy scale Calibrate missing ET Obtain enriched b-jet sample Leptons & Trigger Top physics at the LHC “Top quark pair production has it all”: ≥4 jets, b-jets, neutrino, lepton several mass constraints for calibration 4/9 Note the 4 candles: - 2 W-bosons Mw = 80.4 GeV- 2 top quarks & Mt = Mt-bar

  29. MW(had) MW = 78.1±0.8 GeV Events / 5.1 GeV S/B = 0.5 Jet energy scale Determine Light-Jet energy scale • (1) Abundant source of W decays into light jets • Invariant mass of jets should add up to well known W mass (80.4 GeV) • W-boson decays to light jets only  Light jet energy scale calibration (target precision 1%) t t Translate jet 4-vectors to parton 4-vectors

  30. Jet energy scale (using hadronic W-boson) MW (PDG) = 80.425 ± 0.038 GeV Use the known W-boson mass to calibrate the Jet energy scale Before Events Ejet =  x Eparton Rescale jet energy and angles, with correction (PT,η)such that mass of 2 partons gives MW Pro:- Large event sample - Easy to trigger - Small physics backgrounds Con: - Only light quark jets - Limited Range in PT andη After Events Di-jet mass(GeV)

  31. Rate per hourγ+jet Z+jetPT > 20 GeV 6x105 -- PT > 50 GeV 7x103 2x103 Jet Energy Scale (Alternative calibration method ) Use the pT balance between Z/γ and highest pT-jet γ/Z (Ze+e- or μ+μ-) proton proton Pro:- Enlarged PT andη range - Includes 6% of b-jets - Large statistics Con: - Biases from selection / ISR and Z/background - Statistics at large PT limited - Pre-scaled trigger jet

  32. Measuring lepton trigger efficiency from data (2) e/γ reconstruction and trigger- Triggers: 2E15i, E25i, E60 - Lepton reconstruction in ‘busy’ events White: reconstructed electons Blue: reconstructed electons + trigger Why only 85% ? Why did the trigger fire ? Electron pT (GeV) e/γ trig eff (pT) e/ γtrig eff (η)

  33. Miscalibrated detector t Miscalibrated detector or escaping ‘new’ particle Events t Perfect detector Missing ET (GeV) Using top quark events to calibrate missing energy • (3) Known amount of missing energy • 4-momentum of neutrino in each eventcan be constrained from kinematics • Calibration of missing energy vital for all(R parity conserved)SUSY and most exotics! Effect of 3-4 % dead cells on missing ET distribution Calibrate Missing Energy in ATLAS

  34. Using top quark events to obtain a clean sample of b-quarks • (4) Abundant clean source of b-jets • 2 out of 4 jets in event are b-jets  ~50% a-priori purity(extra ISR/FSR jets) • The 2 light quark-jets can be identified (should form W mass) t Calibrate/test b-tagging in complex event topology t

  35. Using top quark events to get clean sample of b-quarks • Use of ttbar sample to provide b enriched jet sample • Cut on MW(had) and Mtop(had) • Look at b-jet prob for 4th jet(must be b-jet if all assignments are correct) W CANDIDATE TOP CANDIDATE W+jets (background) ‘random jet’, no b-enhancement expected ttbar (signal) ‘always b jet if all jet assignment are OK’ B-enrichment expected and observed AOD b-jet probability Clear enhancementobserved! AOD b-jet probability

  36. Inputs Single lepton trigger efficiency Lepton identification efficiency Integrated luminosity At startup around 10-20%. Ultimate precision < 5% What we can provide Top enriched samples Estimate of a light jet energy scale Estimate of the b-tagging efficiency Estimate of Mtop and σtop~20% accuracy. One of ATLAS’ first physics measurements? Summary: top physics duringcommissioning Can reconstruct top and W signal after ~ one week of data taking without using b tagging

  37. Z’, ZH, G(1),SUSY, ? Gaemers, Hoogeveen (1984) 500 GeV 600 GeV 400 GeV Top quarks as a window to new physics Structure in Mtt Resonances in Mtt - Interference from MSSM Higgses H,A tt (can be up to 6-7% effect) Resonanceat 1600 GeV # events Δσ/σ ~ 6 % Cross section (a.u.) Mtt (GeV) Mtt (GeV)

  38. ATLAS 5s sensitivity Flavour changing neutral currents No FCNC in SM: Z/γ u (c,t) u SM: 10-13 , other models up to 10-4 Look for FCNC in top decays u,c t γ/Z(e+e-) Expected limits on FCNC for ATLAS: - Results statistically limited- Sensitivity at the level of SUSY and Quark singlet models

  39. Early Top Physics (16) Super Symmetry (8) Commissioning (7) Extra dimensions (3) LHC+ATLAS (3) Conclusions Introduction (6) - Intro to SUSY • SUSY parameter space (early discovery potential) • ATLAS’ SUSY reach

  40. Fixing the hierarchy problem SUSY: solves the hierarchy problem: All ΔMh terms between particles and super-partners magically cancel fermions Notice minus signNote 2 bosonic partners per fermion bosons - If masses SUSY partners of SM particles (sparticles) not too heavy  ‘natural’ solution to Hierarchy problem SUSY also: Gauge Unification and dark matter candidate

  41. SUSY parameter space SUSY is concept and a-priori not very predictive (many parameters) SUSY has quite a few constraints from data: no sparticles observed yet (SUSY is broken) and cosmology Assumptions (mSUGRA):  R-parity is conserved There is a (stable) Lightest Supersymmetric Particle: LSP • mSUGRA - m0: universal scalar mass (sfermions) - m½: universal gaugino mass - A0: trilinear Higgs-sfermion coupling - sgn(μ): sign of Higgs mixing parameter - tan(β): ratio of 2 Higgs doublet v.e.v

  42. SUSY stuff Fixing parameters at 1016 GeV, the renormalization group equations will give you all sparticle masses at LHC! Evolution of coupling constants Evolution of masses Strength Running mass (GeV) m½ m0 1016 GeV 1016 GeV Energy scale a.u. Energy scale a.u.

  43. gluino Higgs boson LSP (χ10) NLSP SUSY mass spectra Particle (mass) spectrum predicted for each mSUGRA parameter point m0 = 100 GeV m1/2 = 250 GeV A0 = -100 GeV tan  = 10  > 0 Not all mSUGRA points (mass spectra) allowed: LEP:- Mh > 114.4 GeV Cosmology:- LSP is neutral - Limits on LSP mass (upper/lower)

  44. Cosmology and SUSY dark matter WMAP III: 0.121 < Ωmh2 = nLSP x mLSP < 0.135 ρLSP = Relic LSP density x LSP mass The relic LSP density depends on LSP mass:LSP stable, but they can annihilate, so density decreases when LSP annihilation cross section increases. lepton slepton(NLSP) lepton Upper AND lower limitson LSP mass

  45. SUSY might be one of the firstsignals to be observed at the LHC mSUGRA space Allowed mSUGRA space (post WMAP) ATLAS reach in mSUGRA space Focus point SU1 M½ (GeV) M½ (GeV) SU6 ½ SU2 SU3 M0 (GeV) M0 (GeV) M = 1.3 TeV (1 week)M = 1.8 TeV (1 month)M = 3 TeV (300 fb-1) Allowed mSUGRA spaceVery different exp. signatures

  46. In this example: Gluino  2 jets + 2 leptons + LSP (missing energy) Production of SUSY particles at the LHC Superpartners have same gauge quantum numbers as SM particles  interactions have same couplings αS αS Gluino’s / squarks are produced copiously (rest SUSY particles in decay chain)

  47. jet jet jet jet/lepton jet/lepton Common signature large fraction SUSY events LHC day 2: First to discover SUSY Sensitive to hard scale: ATLAS 10 fb-1 (1 year) SUSY Discovery In R-parity conserving models the LSP is stable and escapes detection (mSUGRA) # events/400 GeV Topology: ≥4 jets missing ET (large) leptons/photons Meff (GeV) SUSY events look like top events tt production dominant backgroundremember: we understand this

  48. Early Top Physics (16) Super Symmetry (8) Commissioning (7) Extra dimensions (3) LHC+ATLAS (3) Conclusions Introduction (6) - Intro to Extra Dimensions • Signatures and ATLAS’ reach • Related discoveries

  49. The 3+1 forces of nature Quantum gravitaty: gravitons and mini black holes Most models predict only gravitons can enter extra dimension We should observe decays of Kaluza-Klein excitations of gravitons Quantum theories Strength strong force Weak force no quantum theory gravitation string theory? Electromagn. force ~1040 Energy (GeV)  distance-1 Electroweak scale Planck scale

  50. (4+n)-dim. R small R large massless graviton Gmomentum p0 p1, p2, …, piin extra dimension Cross section (a.u) massive gravitonswith mass m0, m1, m2, …. miwith name G(0), G(1), G(2), …G(i) (4)-dim. Drell-Yan Me+e- (GeV) Kaluza-Klein excitations Each particle that can ‘enter’ the extra dimension (bulk) will appear in our 4 dimensionsas a set of massive states (Kaluza-Klein tower) (Mreal)2 = E2 – px2 – py2 – pz2– pxd2= (m4d)2– pxd2 (m4d)2 = (Mreal)2+ pxd2 Depends on size/shape XD Momentum quantized in the extra dimension. Pxd = i x ΔP , with i = 1,2,3,4,5, … Note: other model can have fermions or gauge bosons in the bulk (Z(i), W(i))

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