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ATLAS Results and Plans

ATLAS Results and Plans. Monika Wielers RAL – STFC On behalf of the ATLAS collaboration. Outline. ATLAS and 2011 operation Physics Results SM Beyond SM Summary and Outlook Disclaimer: I can only show some select examples but not the full wealth of the ATLAS results

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ATLAS Results and Plans

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  1. ATLAS Results and Plans Monika Wielers RAL – STFC On behalf of the ATLAS collaboration

  2. Outline • ATLAS and 2011 operation • Physics Results • SM • Beyond SM • Summary and Outlook • Disclaimer: I can only show some select examples but not the full wealth of the ATLAS results • All public results can be found here • https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ Monika Wielers (RAL)

  3. The ATLAS Detector Muon Spectrometer (<2.7): air-core toroids with gas-based muon chambers; /pT < 10% up to E~1TeV Length: ~46m Radius: ~12 m Weight: 7000t Inner Detector: Si pixel, Si strips, Transition Radiation Detector (TRT) in || < 2.5; /pT ~ 3.810-4pT(GeV)  0.015 Electro-magnetic calorimeter (<3.2 with fine granularity in || < 2.5): Pb-LArAccordion, /E ~ 10%/√E(GeV) Hadronic calorimeter (<4.9): Fe/scintillator Tiles (central), Cu/W-LAr (fwd); /E ~ 50%/√E(GeV)  3% in ||<3 Monika Wielers (RAL)

  4. Operation • Proton-proton collisions at s = 7 TeV • Data taking eff. in 2011: 93.5% • Fraction of good quality data: 90-96% • Pb – Pb collisions • 287 TeV on 287 TeV • In total 158 b-1 collected • 0.9 b-1 in 2010 • Overall error on integrated luminosity • 2010: 3.4%; 2011: 3.9% Monika Wielers (RAL)

  5. Standard Model Physics • Soft QCD (minimum bias, underlying event) • Production of Jets, b’s, prompt photons …. • W, Z production • Top production • Higgs • …. Monika Wielers (RAL)

  6. Inclusive jet spectrum (Ldt = 1.9 fb-1) • Jets are typically reconstructed with anti-kT algorithm with R=0.4 or 0.6, but also other jet algorithms (cone, kT, …) are being tested. • Jet spectrum measured using 2010 and 2011 data • 2011 data normalised to 2010 data • Not only the overall spectrum is measured but also d2/dpTd • MC prediction based on Pythia reweighted with NLO ad LO PDF ratio • Very good agreement data-MC • Biggest effect on systematics arising from JES uncertainties • 2.5% uncert.(2010) in wide kinematic range (ultimate goal: 1%) Will appear very soon in arXiv Monika Wielers (RAL)

  7. W/Z production (Ldt = 33-36 pb-1) • Measured in leptonic decay channels: Wl, Zll, l =e, • “Clean” signature: high pT isolated leptons or a high pT isolated lepton and missing ET • Comparison of W vs Z cross section gives reasonable agreement with NNLO predictions • Universality of PDFs and pQCD work up to kinematic range of W and Z at LHC • We also measure W/Z + jets cross-section and di-boson production (W, Z, WW, WZ, ZZ) Z Sub. to Phys Rev D arXiv:1109.5141 hep-ex] ATLAS Monika Wielers (RAL)

  8. Dominantly decay: tWb Cross-section measured in lepton+jets channel Signatures one lepton (e or , ETmiss, jjbb (37.9%) dilepton (ee,  or e, ETmiss, bb (6.46%) Use likelihood fit for cross section extraction tt = 176.5  5-10 (stat + sys)  7 (lumi) pb good agreement with SM prediction Main systematic uncert. JES ISR+FSR mt=175.9  0.9  2.7 GeV (Tevatron: 173.20.60.9GeV) Top cross section and mass (Ldt = 0.7 fb-1) +13 ATLAS-CONF-2011-121 Monika Wielers (RAL)

  9. Summary: SM cross section (Ldt = 0.035-1.04 fb-1) • Good agreement with SM expectations (within present uncertainties) • Experimental precision starts to challenge theory – need for more precise calculations Inner error: statistical Outer error: total Monika Wielers (RAL)

  10. Search in the range 110 to 600 GeV Higgs searches Gluon-gluon fusion VBF Associated production “golden”-plated channels Monika Wielers (RAL)

  11. Selection 2 well identified high-pT isolated photons 22489 events with 100<m<160 GeV Position measurement use position in 1st and 2nd EM calo layer Use also track position if photon converted Sample dominated by real  events Sample sub-divided in 9 categories (based on , conversions, pT transverse to  thrust axis) Fit spectrum for each category: Falling exponential →Bkgd Crystal Ball + Gaussian with wide σ → Signal Main systematic uncertainty arising from photon reconstruction and identification efficiency + signal  H (Ldt = 4.9 fb-1) ATLAS-CONF-2011-161  0 Monika Wielers (RAL)

  12. H (Ldt = 4.9 fb-1) Consistency of the data with the background-only expectation ATLAS-CONF-2011-161 • Excluded (95% CL): • 114 ≤ mH ≤ 115 GeV, 135 ≤ mH≤ 136 GeV • Maximum deviation from background-only expectation observed for mH~126 GeV: • Local p0-value: 0.27% or 2.8σ • global p0-value: includes probability for such an excess to appear anywhere in the investigated mass range (“Look-Elsewhere-Effect”): ~7% (1.5σ) • expected from SM Higgs: ~ 1.4σ Expected from SM Higgs Monika Wielers (RAL)

  13. HZZ(*)4l (Ldt ~ 4.8 fb-1) ATLAS-CONF-2011-162 • Selection • Two isolated same-flavour lepton pairs (e or ) with opposite charge • One lepton pair close to Z mass • mH dependent cuts on the 2nd pair • Main backgrounds • ZZ, Z+jets, Z+bb, ttbar • A total of 71 events are selected (110-600 GeV mass range) • 24 4μ, 30 2e2μ and 17 4e • Dominant systematics • Higgs x-sections ~15% • Zbb, Z+jets backgrounds (~40%) • ZZ* background (~15%) Monika Wielers (RAL)

  14. HZZ(*)4l (Ldt ~ 4.8 fb-1) ATLAS-CONF-2011-162 • Exclusion limits (95% C.L.) • Observed • 135<mH<156 GeV, 181<mH<415 GeV (except 234-255) • Expected: • 137<mH<158 GeV, 185<mH<400 GeV • Largest deviations • mH=125 GeV: p0=1.8%, mH=244 GeV: p0=1.1%, mH=500 GeV: p0=1.4% • if ‘look-elsewhere effect” considered, none of the local excesses is significant by itself Monika Wielers (RAL)

  15. HWW(*)l l  (Ldt = 2.05 fb-1) • HWW(*) covers mass range 110-300GeV • Most sensitive channel ~ 130-180 GeV • Selection • Two oppositely charged isolated leptons (e or ) • Large missing ET • mll>15GeV, |MZ-Mll|>15GeV • Plus different cuts for 0 and 1-jet case to reduce bkgd • Challenge: 2  no mass reconstruction/peak  “counting channel” • Main backgrounds (estimated with data driven methods) • top, WW, W+jets, Z+jets Monika Wielers (RAL)

  16. Consistency of the data with the background-only expectation HWW(*)l l (Ldt = 2.05 fb-1) • Excluded (95% CL): 145 < mH < 206 GeV (expected: 134-200 GeV) • Observed limit within 2σ of expected: max deviation 1.9 σ for mH ~ 130 GeV Change in selection cuts Monika Wielers (RAL)

  17. Higgs Combination (Ldt ~ 1-5 fb-1) Observed Predicted ATLAS-CONF-2011-163 Monika Wielers (RAL)

  18. Higgs Combination (Ldt ~ 1-5 fb-1) LEP ATLAS+CMS Combination ATLAS today • 95% CL in mass ranges 112.7-115.5, 131-237, 251-453 GeV ATLAS-CONF-2011-163 Monika Wielers (RAL)

  19. Higgs Combination (Ldt ~ 1-5 fb-1) • Consistency of observed results with the background-only hypothesis • Maximum deviation for mH~126 GeV • Local p0-value: 210-4 3.6σ • ~ 2.8σ H, 2.1σ H4l, 1.4σ Hll • Expected from SM: ~2.4σ (~1.4σ per channel) • Global p0-value : ~1% 2.3σ ATLAS-CONF-2011-163 Monika Wielers (RAL)

  20. Searches for new physics beyond SM Monika Wielers (RAL)

  21. Susy Searches (Ldt ~ 1-2 fb-1) • Susy signatures: • For each sparticle complex decay chain • Searches subdivided in three main categories 1) Powerful generic searches for R-parity conservation • Sparticles produced in pairs, decay to Lightest Susy Particle (LSP) • Search for 2, 3, or 4 jets, ETmiss and veto leptons • different jet multiplicity sensitive to different squark or gluino pair prod. • Combine channels to optimise search for different topologies • For limits use “simplified model” within MSSM • Only gluinos and squarks of 1st 2 generations are produced • Other sparticle masses= 5 TeV • Only allowed decays: • , • squark/gluino mass limits are less strong for LSP mass > 200 GeV! ATLAS-CONF-2011-155 mLSP=0 GeV, 195 GeV, 395 GeV Monika Wielers (RAL)

  22. Susy Searches (Ldt ~ 2 fb-1)  1 0 2) Searches for 3rd generation squarks • Squarks from 1st and 2nd generations and gluinos may be heavy, naturalness requires not too heavy 3rd gen. squarks and gauginos • Look for O(100-500 GeV) light stop and sbottom from gluino decays or direct pair production • Example: direct sbottom pair prod. • . • Selection: • 2 b-jets, no other jets, large missing ET, lepton veto • Assuming 100% BR, sbottoms are excluded up to 385 GeV (for LSP < 60 GeV) 3) Long lived particles from: • Degeneracies (e.g. MSSM with m(chargino)=m( ) or AMSB) • Weak couplings (e.g. GMSB decays of NLSP into gravitino LSP) • Heavy virtual intermediate states (gluino decays in split SUSY) Will appear very soon in arXiv Monika Wielers (RAL)

  23. Susy Summary of current limits • Lots of parameter space already excluded with 1fb-1 of data! 1TeV Monika Wielers (RAL)

  24. Other Searches • Wide spectrum of analyses • additional heavy gauge bosons • Extra-dimensions • Leptoquarks • Excited quarks • 4th generation particles • Black holes • Contact interactions • Majorana neutrinos • Technicolour particles • … Monika Wielers (RAL)

  25. High mass di-lepton resonance (Ldt ~ 1.2 fb-1) arXiv:1108.1582 • Selection • 2 high pT opposite-sign isolated leptons (e or ) • No significant excess observed using 1 fb-1 of data • Limit setting • Normalisation under Z peak • SSM Z’ limits: • MZ’ >1.83 (1.83 exp) TeV • Limits available for other models • Contact interactions Will appear very soon in arXiv Monika Wielers (RAL)

  26. Summary of exotic searches 1TeV Monika Wielers (RAL)

  27. Summary and Outlook • LHC and ATLAS performing extremely well • Many, many nice analyses carried out (could not do justice here) • Main results • SM works extremely well so far • Excess of events for Higgs masses around 126GeV observed • So far no hints yet for physics beyond the SM • Quite some of our limits surpassed previous limits with fraction of the 2011 data! • Outlook • Analysis of complete dataset under way • LHC running in 2012 • Expect even more luminosity • In Feb decision if we stay at s=7 TeV or move to 8 TeV • Would be nice to collect 20fb-1 • 5σ evidence at mH~125 GeV with ~3σ per channel • 5σ evidence down to ~116 GeV (ATLAS+CMS combined) • exclude mH~125 GeV if the excess is due to a fluctuation Monika Wielers (RAL)

  28. Backup Monika Wielers (RAL)

  29. Electron Identification • Match EM cluster to ID track • Loose (jet rejection factor ~500): • EM shower shape in middle layer, hadronic leakage • Medium (~5000): • +EM strip layer, track quality and track/cluster matching • Tight (50000): • +E/p, TRT high threshold hits, tighter track cuts to remove photon conversions • Measure reconstruction and ID efficiencies using tag-and-probe in We, Zee, J/ψee events Monika Wielers (RAL)

  30. Photon Identification  0 loose • Distinguish unconverted photons and those converted in the ID volume • Identification cut optimised separately for both categories • Loose: • EM shower shape in middle layer, hadronic leakage • Tight: • Tight middle layer cuts, +EM strip layer, • Measure reconstruction and ID efficiencies using Zee tag-and-probe, correct for electron-photon differences using MC for unconv. photons Look for substructures in 1st EM layer for /0 separation tight Monika Wielers (RAL)

  31. Muon identification • `Combined’ muon: • Match ID track with MS track • Combine parameters • `Segment-tagged’ muon: • ID track matched to MS track segment • Used for regions with too few MS hits for momentum meas. • Measure efficiency using tag-and-probe in Z events • >96% and agrees with MC to better than 1% • Momentum resolution measured from Z mass distribution • Design: <3.5% (pT<200GeV); <10% (pT<1TeV) Monika Wielers (RAL)

  32. Jet and missing ET • Jets • reconstructed from calorimeter clusters using anti-kT algorithm, R=0.4 or 0.6 • Jet energy scale (i.e. EM  hadronic) calibrated using MC • Checked with data, e.g. track jets, jet-photon pT balance • Missing transverse energy • calculated using e/μ/jets plus unassociated calorimeter clusters in |η| < 4.5 • Clusters calibrated as EM or hadronic depending on topology • Correction for muon energy in calorimeter Monika Wielers (RAL)

  33. Luminosity Measurement • Measure event rates in lumi. detectors • BCM: diamond sensors z=±1.84m, |η|~ 4.2 • LUCID: Cerenkov tubes z = ± 17m, 5.6< |η| < 6.0 • L = visnbfr / σvis, μvis = interaction rate / BX • Calibrate rates (i.e. measure σvis) using van der Meer (beam separation) scans • Separate beams in steps of known distance to measure beam profiles ΣxΣy • Length scale checked using ATLAS primary vertex position • L = nbfrn1n2 / 2ΣxΣy • Main systematic (3%) from measurement of beam currents • Overall error on integrated L • 2010: 3.4% • 2011: 3.9% Measure for each BCID Monika Wielers (RAL)

  34. Example: Z with 20 vertices A potential issue for: Trigger Lepton Isolation Vertexing Jet Energy Scale/Resolution Missing transverse energy Work in progress to better understand impact of pile-up Pile-up before Sep 2011 after Monika Wielers (RAL)

  35. H: unconverted categories Monika Wielers (RAL)

  36. H: converted categories Monika Wielers (RAL)

  37. ATLAS CMS Comparison ATLAS-CMS in H Monika Wielers (RAL)

  38. ATLAS CMS Comparison ATLAS-CMS in H4l Monika Wielers (RAL)

  39. ATLAS CMS Comparison ATLAS-CMS in HWW Monika Wielers (RAL)

  40. ATLAS CMS Comparison ATLAS-CMS Higgs combination Monika Wielers (RAL)

  41. ATLAS CMS Comparison ATLAS-CMS Higgs combination LEP ATLAS+CMS Combination ATLAS today Excluded (95% CL): 135 < mH < 156 GeV,181 < mH < 415 GeV (except 234-255 GeV) Excluded (95% CL): 127 < mH < 600 GeV Monika Wielers (RAL)

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