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Preparing for LHC physics in ATLAS Ivo van Vulpen. Complex SM. SUSY/Higgs. Early physics. Now. Calibrations. Detector commissioning. Look for new physics in ATLAS at 14 TeV . 3. Higgs/SUSY . 2. Understand SM+ATLAS in complex topologies. Top quark pairs . 1.

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  1. Preparing for LHC physicsin ATLASIvo van Vulpen Complex SM SUSY/Higgs Early physics Now Calibrations Detector commissioning

  2. Look for new physicsin ATLAS at 14 TeV 3 Higgs/SUSY 2 Understand SM+ATLASin complex topologies Top quark pairs 1 Understand SM+ATLAS in simple topologies W/Z 0 Understand ATLAS Testbeam/cosmics LHC start-up programme Integrated luminosity 1 fb–1 100 pb–1 10 pb–1 Andreas Hoecker Time LHC startup

  3. The ATLAS detector at day-1  Expected detector performance from ATLAS(based on testbeam, cosmics-data and simulations) Performance Expected day-1 Physics samples to improve ECAL uniformity 1-2% Ze+e-, minimum biase/γ scale 2% Ze+e-HCAL uniformity 3% jets, single pionsJet scale <10% γ/Z+jet, Wjj in tt eventsTracking alignment 10-200 μm Rφ tracks, isolated μ, Zμ+μ-  First job is to get a combined ATLAS detector operational

  4. Maaike LimperCaroline MagrathEgge van der Poel First SM peaks & an early discovery J/ Y Number of events Number of events ATLAS preliminary, 10 pb-1 ATLAS preliminary, 1 pb-1 Mμμ (GeV) Mμμ (GeV) Events per day at day 1 (L=1031):4200 (800) J/ (У)  +- 160 Z  +- Reconstruction efficiencies, Muon spectrometer alignment,Detector and trigger performance, Tracking momentum scale, ECAL uniformity, E/p scale, …

  5. First SM peaks & an early discovery J/ Y Number of events Number of events ATLAS preliminary, 10 pb-1 ATLAS preliminary, 1 pb-1 Mμμ (GeV) Mμμ (GeV) Drell-Yan (SM) +- Early discoveries:Heavy resonances  lepton pairs e+e- Mμμ (GeV)

  6. Top quark physics 90% 10% t t Top quark pair-production: σtt(LHC) ~ 833 ± 100 pb 1 top quark pair per second Focus on semi-leptonic decays (4/9) Top analyses: SM: Top, single-top non-SM: Mtt, FCNC (tZc), H+/-

  7. Martijn GosselinkAlexander Doxiadis Commissioning analysis:- Missing ET > 20 GeV - 1 lepton PT > 20 GeV - 3(4) jets PT > 40(20) GeV Top = 3-jet combination with highest sum PT Note: No b-tag information used 100 pb-1 muon analysis ~ 500 events Mjjj (GeV) Top quark physics “Top quark pair production has it all”: ≥4 jets, b-jets, neutrino, lepton a) Early cross-section measurement b) Unique calibration opportunities  Background to many new physics signals

  8. Alexander DoxiadisManuel KaylErik van der Kraaij Manouk RijpstraMartijn Gosselink Menelaos Tsiakiris Rate/jet Non-prompt Fake Muon 1.3·10-3 97% 3% Electron 1.0·10-3 62% 38% Number of events W-boson transverse mass (GeV) Top quark physics(understanding ATLAS in complex topologies) • Extra/Fake isolated leptonsEstimate rate for arbitrary event-topology (multi-jet QCD) • 2) Calibrate ET-miss scale: • MT(W) using constrained fits • 3) Extra jets: tt+jets • Low mass Higgs boson: tt+h(bb)

  9. Martijn GosselinkManuel Kayl The Higgs boson • LHC reach (ATLAS+CMS): 5 fb-1 needed for 5σ discovery- mh < 130 GeV: tth(hbb). Difficult. > 130 GeV: hWW(*) and hZZ(*) Direct: mh >114.4 GeV at 95% CL EW-fit+direct: mh< 182 GeV at 95% CL - 5σdiscovery - 95% CL exclusion 1 fb-1 WW bb LEP direct search Luminosity needed for discovery (fb-1) ZZ LEP direct search Higgs branching fraction Higgs decay ATLAS + CMS Gluonstau’s 100 200 300 500 1000 Higgs boson mass (GeV) Higgs boson mass (GeV) Note: to prove we see the SM Higgs boson requires (much) more data

  10. Max BaakGijs van den Oord No lose approach:Something should regularize vector boson scattering in SM • “No-lose” theorem: W-W scattering: Stat. Significance [SD] W.Z W.Z W.Z W.Z theory + experiment Higgs boson mass (GeV) The Higgs boson(vector boson fusion: W+W-hW+W- l+vl-v) - In combination with gg hWW- Less statistics, but clear signature5-dimensional fit… based fully on background control samples 1 fb-1 data: ~2.5 sigma -- background signal + bkg Number of events mh = 170 GeV Transverse Higgs boson mass (GeV)

  11. ATLAS 100 pb-1 800700600500400300200100 0 Mass spectrum gluino Particle mass (GeV) m0 = 100 GeV m1/2 = 250 GeV tan  = 10 Higgs boson(LEP) LSP (ΩDM) Supersymmetry SUSY: - boson/fermion symmetry, SM particles have partners, LSP - broken  many models/topologies (GMSB, AMSB,NUHM,mSUGRA) mSUGRAtan(β)=10 g-2 m0 (GeV) (WMAP) stau LSP m1/2 (GeV)

  12. Supersymmetry(decay chains and event topologies) 800700600500400300200100 0 Mass spectrum Particle mass (GeV) ≥4 jets 0,1,2 leptons (a lot of) missing ET SUSY events look like top events

  13. ATLAS’ inclusive SUSY searches Inclusive search (1 lepton) Number of events ATLAS reach: ~ 1 TeV for 1 fb-1 Effective mass (GeV) Note: Much more data required to:- is excess sign of supersymmetry ? - reconstruct (part of) particle spectrum and underlying parameters

  14. Alex KoutsmanFolkert KoetsveldNicole Ruckstuhl Data-driven background estimates(Nikhef’s main contribution to ATLAS SUSY search) Determine SM background in signal region: a) Extrapolate three SM backgrounds separately to signal region b) Account for SUSY signal events in sidebands SM: tt(lvqq) SUSY SM: tt(lvlv) SM:W+jets MT (GeV) MT (GeV) MT (GeV) MT (GeV) sideband sideband sideband sideband ET-miss (GeV) ET-miss (GeV) ET-miss (GeV) ET-miss (GeV)

  15. Calabi-Yau More exotic scenario’s “An experimentalist cannot afford to have a theoretical predjudice” • Extra space-dimensions: - Kaluza-Klein excitations: G(n) ,Z(n) - Mini black holes • Z’, ZH, W’, WH • Little/Twin Higgs • … Manouk Rijpstra WH tbtt Number of events Little Higgs300 fb-1 Great collaboration between experiment and theory ahead mass (GeV)

  16. Summary and outlook 2007: o ATLAS Detector paper o Update ATLAS analysis potential (CSC Notes, focus on early data) 2008: o Detector commissioningo Full dress rehearsal Simulate chain with mock data (data transfer, trigger, Grid-analyses) o Focus on first data: J/ψ, top-cross-section … Higgs, SUSY

  17. Back-up slides

  18. The Higgs boson Higgs production Signal significance cross-section (pb) Higgs boson mass (GeV) Higgs boson mass (GeV)

  19. The Higgs boson(properties and extensions to SM) ATLAS 300 fb-1Bosons: Γz/ΓW & Γγ/ΓW ~ 10-20%Fermions:Γτ/ΓW & Γb/ΓW ~ 40-50% Higgs boson properties: ΔM/M = 0.1% for 130<mh<450 GeV ΔΓ/Γ< 10% for mh>300 GeV Couplings SM-like ? Scalar ? Higgs self-coupling (λ) ~3000 fb-1 Precision coupling ratio Higgs boson mass (GeV) Extensions to SM: Simplest SM extension (MSSM):2 complex Higgs Doublets  5 Higgs bosons (3 neutral) MSSM searches:- Entire MSSM parameter space covered by at least one Higgs boson - Sometimes more Higgs bosons observable [link to SUSY]

  20. Supersymmetry Evolution of masses R-parity is conserved - Stable Lightest Supersymmetric Particle: LSP mass (GeV) mSUGRA: (5 parameters) - A0, sign(μ), tan (β) - m0: universal scalar mass - m½: universal gaugino mass Num ber of events m0 = 100 GeV m1/2 = 250 GeV tan  = 10 1016 10Log(Energy scale) (GeV) ATLAS mSUGRA reach

  21. Supersymmetry(exclusive searches) ATLAS 300 fb-1 cleaned SUSY signal 1) Exclusive search (end-point spectra) Num ber of events Standard model Di-lepton mass (GeV)

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