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New physics @ ATLAS

New physics @ ATLAS. Alan Barr University of Oxford. Kings College London 23 rd March 2011. Electroweak symmetry breaking. Hierarchy problem?. WIMPs?. What is the physics at the TeV -scale?. End of 2010 run. 22 July  ICHEP.

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New physics @ ATLAS

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  1. New physics @ ATLAS Alan Barr University of Oxford Kings College London 23rd March 2011

  2. Electroweak symmetry breaking Hierarchy problem? WIMPs? What is the physics at the TeV-scale? Alan Barr, University of Oxford

  3. End of 2010 run 22 July  ICHEP Alan Barr, University of Oxford

  4. Parton-parton luminosity Alan Barr, University of Oxford

  5. Alan Barr, University of Oxford

  6. SUSY & BSM strategy • Precision reliable hermetic detector • Basic kinematics • Understand detector and SM • Look at final states with: Examples given Lepton(s) Proton Jet(s) Photon(s) Proton Invisible(s) Alan Barr, University of Oxford

  7. Basic kinematics Transverse momenta, pT Missing transverse momentum, ETmiss Pseudorapidity, η = - ln tan θ/2 Azimuthal angle differences Δφ Scalar sums of transverse momenta: HT, meff = HT + ETmiss Transverse mass mT = “Stransverse” mass (generalisation of mT to 2 parent particles) Alan Barr, University of Oxford

  8. 1-lepton SUSY 1-lepton + Jets + ETmiss Lepton reduces QCD BGExpect leptons in SUSY cascade decays 1 electron or muonpT>20 GeV 3 jetspT > {60, 30, 30} GeV ETmiss > 125 GeVETmiss > 0.25 * meff mT > 100 GeV meff> 500 GeV First ATLAS SUSY paperarXiv:1102.2357 accepted by PRL Selection based heavily on pre data-takingMC studies e.g. arXiv:0901.0512

  9. 1-lepton SUSY Control regions – some examples Multiple redundant control regions QCD background separately Systematics include (not only) JES, JER, lumi, lepton efficiency, CR stats, extrapolation, … Top C/R distinguished from W+jets using b-tagging Alan Barr, University of Oxford Great care with BG for all analyses presented

  10. 1-lepton SUSY 1-lepton results Likelihood ratio as a function of signal strength Toy MCs for p-values Profile likelihood for nuisance parameters (conservative systematics)Fully simulated backgrounds, signal pointsIncludes systematic uncertainties on signal strength Alan Barr, University of Oxford

  11. 0-lepton SUSY ArXiV:1102.5290 SUSY: Jets + ETmiss Conceptually simple search for squarks and gluinosSeveral overlapping signal regions: Squark decays Gluino decays Alan Barr, University of Oxford

  12. 0-lepton SUSY Robust background determinations • 2-4 measurement methods per background • Examples: • Reversal of cuts & kinematic control regions • Fully data-driven inc. jet transfer functions • Tau re-decay, smear • Z  νν from:Z  ee, Z  μμW  eν, W  μν Alan Barr, University of Oxford

  13. Squark, Gluino interpretations 0-lepton SUSY Exclude non-SM effective cross sections (σ x BR x Acc x Eff):A: 1.3 pb B: 0.35 pb C: 1.1 pb D: 0.11 pb https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/susy-0lepton_01/ Alan Barr, University of Oxford

  14. Multi-lepton SUSY Multi-lepton SUSY ≥ 3 leptons (electron or muon) Expect: Observe no events Top dominates after Z veto Also phenomenological limits: see… https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-039/ Alan Barr, University of Oxford

  15. SUSY with b jets SUSY with b-jets Sensitive to Stop, Sbottom, Gluinoproduction Done for both 1-lepton, 0-lepton channels Top background dominates after b-jet requirementData-driven QCD background determination Paper in the pipeline… Alan Barr, University of Oxford

  16. R-hadrons Stable charged particle search Two independent detector subsystems dE/dx: pixels (Time over threshold) β: tile (ToF resolution ≈ns) 95% confidence limits: Stable gluino > 586 GeV Stable stop > 309 GeV Stable sbottom 294 GeV Alan Barr, University of Oxford

  17. W’ searches Electrons Muons Electron pT> 25 GeV, |η| < 1.37 or 1.52 < |η| < 2.40 MuonpT> 25 GeV, |η| < 1.05 ETmiss > 25 GeV M(W’SSM) > 1.49 TeV arxiv:1103.1391 Alan Barr, University of Oxford

  18. Muons Electrons Z’ searches… M(Z’SSM) > 1.05 TeV Alan Barr, University of Oxford

  19. Dijet inv. mass, angular distributions Compositeness scale, Λ > 9.6 TeV http://arxiv.org/abs/1103.3864 Alan Barr, University of Oxford

  20. Diphoton resonances https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-044/ Alan Barr, University of Oxford

  21. Diphoton + ETmiss Interpret in context of Universal Extra Dimensions ΛR = 20 Alan Barr, University of Oxford

  22. Fourth generation Q search • Di-leptonic channel Approximate mass reconstruction on varying Δη,Δφ Excludes m(Q) < 270 GeV(@95% CL) Alan Barr, University of Oxford

  23. Preliminary conclusions • Excellent operation of LHC and ATLAS • Commissioned physics objects:Jets, e, mu, ETmiss, photons, b-jets, (tau) • Wide variety of such final states studied • Also exotics… R-hadrons, multi-charged particles, stopped gluinos… • Many limits well beyond previous colliders

  24. A few little Extras Alan Barr, University of Oxford

  25. Papers and CONF notes 1/3:SUSY papers and notes https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults Alan Barr, University of Oxford

  26. Papers and CONF notes 2/3:Exotics papers https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResults Alan Barr, University of Oxford

  27. Papers and CONF notes 3/3Exotics Conf notes https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResults Alan Barr, University of Oxford

  28. 0-lepton SUSY Missing transverse momentum Alan Barr, University of Oxford

  29. 0-lepton SUSY meff distributions Cuts shown on mass-sensitive variable in final selection Alan Barr, University of Oxford

  30. 0-lepton SUSY BG example: ETmiss tails One example of very, very, very many background studies Alan Barr, University of Oxford

  31. 1-lepton SUSY Alan Barr, University of Oxford

  32. arXiv:1102.2357 1-lepton SUSY 1-lepton + Jets + ETmiss Alan Barr, University of Oxford

  33. 1-lepton SUSY 1-lepton results Alan Barr, University of Oxford

  34. Profile likelihood • Hatted quantities maximise likelihood • Double hatted quantities maximise L for given value of s • s and s-hat constrained to be non-negative • Likelihood ratio is the test statistic used to calculate the p-value Alan Barr, University of Oxford

  35. 1-lepton SUSY Kinematic distributions Electron channel Muon channel Alan Barr, University of Oxford

  36. Di-photon + ETmiss • S arxiv:1012.4272 Alan Barr, University of Oxford

  37. Multi-lepton SUSY Jets, Electrons, Muons, ETmiss • Charginos and neutralino cascade decays • ≥ 3 leptons (electron or muon)pT > {20, 20, 20(e) or 10 (mu)} GeV • ≥ 2 jets with pT > 50 GeVand |η| < 2.5 • ETmiss > 50 GeV • mll (ossf) Z mass veto (within 5 GeV of mZ) • mll (ossf) photon veto (< 20 GeV) SM: Observe no events Top dominates after Z veto Alan Barr, University of Oxford

  38. SM: H→γγ ATLAS-CONF-2011-025 • Mass range: 110 GeV - 140 GeV • Data-driven estimation of all background components • γγ, γj, jj • Inclusive • only discriminant diphoton inv. mass Sensitivity close to the current Tevatron limits.

  39. Z →ττ mu + had ATLAS-CONF-2011-010 ATLAS-CONF-2011-045 e + had e + mu

  40. R-hadrons Stable massive particle search • Two independent detector subsystems • dE/dx: pixels(Time over threshold) • β: tile (ToF resolution ≈ns) • ETmiss > 40 GeV (trigger) • pT > 50 GeV http://arxiv.org/abs/1103.1984 Alan Barr, University of Oxford

  41. 0-lepton SUSY 0-lepton results Conservative systematics Jet energy scale (~7%) Luminosity (11%) Control region statistics Lepton veto Different MC b-jet fraction MC statisticsHigher orders… more … Alan Barr, University of Oxford

  42. Di-lepton SUSY Dilepton SUSY Alan Barr, University of Oxford

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