Now Detector commissioning Calibrations Early physics SUSY/Higgs Preparing for LHC physics in ATLAS Ivo van Vulpen Complex SM

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

ECAL uniformity 1-2% Z  e + e -, minimum bias e/ γ scale 2%Z  e + e - HCAL uniformity 3%jets, single pions Jet scale <10% γ /Z+jet, W  jj in tt events Tracking alignment μ m R φ tracks, isolated μ, Z  μ + μ - Performance Expected day-1 Physics samples to improve  Expected detector performance from ATLAS (based on testbeam, cosmics-data and simulations) The ATLAS detector at day-1  First job is to get a combined ATLAS detector operational

ATLAS preliminary, 1 pb -1 J/  Y  Number of events M μμ (GeV) First SM peaks & an early discovery M μμ (GeV) Reconstruction efficiencies, Muon spectrometer alignment, Detector and trigger performance, Tracking momentum scale, ECAL uniformity, E/p scale, … Events per day at day 1 (L=10 31) : 4200 (800) J/ ( У )   +  Z   +  - ATLAS preliminary, 10 pb -1 Maaike Limper Caroline Magrath Egge van der Poel

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

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

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 M jjj (GeV) Commissioning analysis: - Missing E T > 20 GeV - 1 lepton P T > 20 GeV - 3(4) jets P T > 40(20) GeV Top = 3-jet combination with highest sum P T Note: No b-tag information used 100 pb -1 muon analysis ~ 500 events Martijn Gosselink Alexander Doxiadis

1)Extra/Fake isolated leptons Estimate rate for arbitrary event- topology (multi-jet QCD) 2) Calibrate E T -miss scale: M T (W) using constrained fits 3) Extra jets: tt+jets Low mass Higgs boson: tt+h(  bb) Top quark physics (understanding ATLAS in complex topologies) Rate/jet Non-prompt Fake Muon 1.3· % 3% Electron 1.0 · % 38% Alexander Doxiadis Manuel Kayl Erik van der Kraaij Manouk Rijpstra Martijn Gosselink Menelaos Tsiakiris Number of events W-boson transverse mass (GeV)

Direct: m h >114.4 GeV at 95% CL EW-fit+direct: m h < 182 GeV at 95% CL Direct: m h >114.4 GeV at 95% CL EW-fit+direct: m h < 182 GeV at 95% CL The Higgs boson LEP direct search Higgs decay Higgs boson mass (GeV) Higgs branching fraction ZZ WW bb Gluons tau’s Luminosity needed for discovery (fb -1 ) Higgs boson mass (GeV) σ discovery - 95% CL exclusion ATLAS + CMS LEP direct search - LHC reach (ATLAS+CMS): 5 fb -1 needed for 5σ discovery - m h 130 GeV: h  WW (*) and h  ZZ (*) 1 fb -1 Note: to prove we see the SM Higgs boson requires (much) more data Martijn Gosselink Manuel Kayl

- In combination with gg  h  WW - Less statistics, but clear signature 5-dimensional fit … based fully on background control samples The Higgs boson (vector boson fusion: W + W -  h  W + W -  l + vl - v) Transverse Higgs boson mass (GeV) Number of events m h = 170 GeV -- background signal + bkg 1 fb -1 data: ~2.5 sigma Max Baak Gijs van den Oord Higgs boson mass (GeV) Stat. Significance [SD] “No-lose” theorem: W-W scattering: No lose approach: Something should regularize vector boson scattering in SM W.Z theory + experiment

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

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

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

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 E T -miss (GeV) E T -miss (GeV) E T -miss (GeV) E T -miss (GeV) SUSY SM:W+jetsSM: tt(lvlv) SM: tt(lvqq) sideband M T (GeV) Alex Koutsman Folkert Koetsveld Nicole Ruckstuhl M T (GeV)

More exotic scenario’s Extra space-dimensions: - Kaluza-Klein excitations: G (n),Z (n) - Mini black holes Z’, Z H, W’, W H Little/Twin Higgs … “An experimentalist cannot afford to have a theoretical predjudice” Calabi-Yau Great collaboration between experiment and theory ahead Manouk Rijpstra W H  tb tt mass (GeV) Number of events Little Higgs 300 fb -1

Summary and outlook 2007: o ATLAS Detector paper o Update ATLAS analysis potential (CSC Notes, focus on early data) 2008: o Detector commissioning o 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

Back-up slides

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

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

Supersymmetry mSUGRA: (5 parameters) - A 0, sign(μ), tan (β) - m 0 : universal scalar mass - m ½ : universal gaugino mass mSUGRA: (5 parameters) - A 0, sign(μ), tan (β) - m 0 : universal scalar mass - m ½ : universal gaugino mass R-parity is conserved - Stable Lightest Supersymmetric Particle: LSP 10 Log(Energy scale) (GeV) Evolution of masses mass (GeV) m 0 = 100 GeV m 1/2 = 250 GeV tan  = 10 Num ber of events ATLAS mSUGRA reach

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