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

2. 23/03/2011Alan Barr, University of Oxford2 Electroweak symmetry breaking Hierarchy problem? What is the physics at the TeV-scale? WIMPs?

3. 23/03/2011Alan Barr, University of Oxford3 22 July  ICHEP End of 2010 run

4. Parton-parton luminosity 23/03/2011Alan Barr, University of Oxford4

5. 23/03/2011Alan Barr, University of Oxford5

6. SUSY & BSM strategy Precision reliable hermetic detector Basic kinematics Understand detector and SM Look at final states with: 23/03/2011Alan Barr, University of Oxford6 Proton Lepton(s) Jet(s) Invisible(s) Photon(s) Examples given

7. Basic kinematics 23/03/2011Alan Barr, University of Oxford7 Transverse mass m T = Transverse momenta, p T Scalar sums of transverse momenta: H T, m eff = H T + E T miss Missing transverse momentum, E T miss “Stransverse” mass (generalisation of m T to 2 parent particles) Azimuthal angle differences Δφ Pseudorapidity, η = - ln tan θ/2

8. 1-lepton + Jets + E T miss 8 1-lepton SUSY 1 electron or muon p T >20 GeV 3 jets p T > {60, 30, 30} GeV E T miss > 125 GeV E T miss > 0.25 * m eff m T > 100 GeV m eff > 500 GeV Selection based heavily on pre data-taking MC studies e.g. arXiv:0901.0512 First ATLAS SUSY paper arXiv:1102.2357 accepted by PRL Lepton reduces QCD BG Expect leptons in SUSY cascade decays

9. Control regions – some examples 23/03/2011Alan Barr, University of Oxford9 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 1-lepton SUSY Great care with BG for all analyses presented

10. 1-lepton results 23/03/2011Alan Barr, University of Oxford10 1-lepton SUSY Likelihood ratio as a function of signal strength Toy MCs for p-values Profile likelihood for nuisance parameters (conservative systematics) Fully simulated backgrounds, signal points Includes systematic uncertainties on signal strength

11. SUSY: Jets + E T miss 23/03/2011Alan Barr, University of Oxford11 0-lepton SUSY Squark decays Gluino decays Conceptually simple search for squarks and gluinos Several overlapping signal regions: ArXiV:1102.5290

12. Robust background determinations 23/03/2011Alan Barr, University of Oxford12 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  μμ W  eν, W  μν 0-lepton SUSY

13. 23/03/2011Alan Barr, University of Oxford13 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 Squark, Gluino interpretations https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/susy-0lepton_01/

14. Multi-lepton SUSY 23/03/2011Alan Barr, University of Oxford14 Multi-lepton SUSY https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-039/ Also phenomenological limits: see… Expect: Observe no events Top dominates after Z veto ≥ 3 leptons (electron or muon)

15. SUSY with b-jets 23/03/2011Alan Barr, University of Oxford15 SUSY with b jets Done for both 1-lepton, 0-lepton channels Paper in the pipeline… Sensitive to Stop, Sbottom, Gluino production Top background dominates after b-jet requirement Data-driven QCD background determination

16. Stable charged particle search 23/03/2011Alan Barr, University of Oxford16 95% confidence limits: Stable gluino > 586 GeV Stable stop > 309 GeV Stable sbottom 294 GeV R-hadrons Two independent detector subsystems dE/dx: pixels (Time over threshold) β: tile (ToF resolution ≈ns)

17. W’ searches 23/03/2011Alan Barr, University of Oxford17 Electrons Muons arxiv:1103.1391 Electron p T > 25 GeV, |η| < 1.37 or 1.52 < |η| < 2.40 Muon p T > 25 GeV, |η| < 1.05 E T miss > 25 GeV M(W’ SSM ) > 1.49 TeV

18. Z’ searches… 23/03/2011Alan Barr, University of Oxford18 Electrons Muons M(Z’ SSM ) > 1.05 TeV

19. Dijet inv. mass, angular distributions 23/03/2011Alan Barr, University of Oxford19 http://arxiv.org/abs/1103.3864 Compositeness scale, Λ > 9.6 TeV

20. Diphoton resonances 23/03/2011Alan Barr, University of Oxford20 https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-044/

21. Diphoton + E T miss 23/03/2011Alan Barr, University of Oxford21 Interpret in context of Universal Extra Dimensions ΛR = 20

22. Fourth generation Q search Di-leptonic channel 23/03/2011Alan Barr, University of Oxford22 Approximate mass reconstruction on varying Δη, Δφ Excludes m(Q) < 270 GeV (@95% CL)

23. Preliminary conclusions Excellent operation of LHC and ATLAS Commissioned physics objects: Jets, e, mu, E T miss, 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 Excellent operation of LHC and ATLAS Commissioned physics objects: Jets, e, mu, E T miss, 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 23/03/2011

24. EXTRAS A few little 23/03/2011Alan Barr, University of Oxford24

25. Papers and CONF notes 1/3: SUSY papers and notes https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults 23/03/2011Alan Barr, University of Oxford25

26. https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResults 23/03/2011Alan Barr, University of Oxford26 Papers and CONF notes 2/3: Exotics papers

27. Papers and CONF notes 3/3 Exotics Conf notes 23/03/2011Alan Barr, University of Oxford27 https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResults

28. 23/03/2011Alan Barr, University of Oxford28 0-lepton SUSY Missing transverse momentum

29. m eff distributions 23/03/2011Alan Barr, University of Oxford29 0-lepton SUSY Cuts shown on mass-sensitive variable in final selection

30. BG example: E T miss tails 23/03/2011Alan Barr, University of Oxford30 0-lepton SUSY One example of very, very, very many background studies

31. 23/03/2011Alan Barr, University of Oxford31 1-lepton SUSY

32. 1-lepton + Jets + E T miss 23/03/2011Alan Barr, University of Oxford32 arXiv:1102.2357 1-lepton SUSY

33. 1-lepton results 23/03/2011Alan Barr, University of Oxford33 1-lepton SUSY

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 23/03/2011Alan Barr, University of Oxford34

35. Kinematic distributions 23/03/2011Alan Barr, University of Oxford35 1-lepton SUSY Electron channel Muon channel

36. Di-photon + E T miss S 23/03/2011Alan Barr, University of Oxford36 arxiv:1012.4272

37. Jets, Electrons, Muons, E T miss Charginos and neutralino cascade decays ≥ 3 leptons (electron or muon) pT > {20, 20, 20(e) or 10 (mu)} GeV ≥ 2 jets with p T > 50 GeV and |η| < 2.5 E T miss > 50 GeV m ll (ossf) Z mass veto (within 5 GeV of m Z ) m ll (ossf) photon veto (< 20 GeV) 23/03/2011Alan Barr, University of Oxford37 Multi-lepton SUSY SM: Observe no events Top dominates after Z veto

38. 38 SM: H→γγ 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. ATLAS-CONF-2011-025

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

40. Stable massive particle search Two independent detector subsystems dE/dx: pixels (Time over threshold) β: tile (ToF resolution ≈ns) E T miss > 40 GeV (trigger) p T > 50 GeV 23/03/2011Alan Barr, University of Oxford40 http://arxiv.org/abs/1103.1984 R-hadrons

41. 0-lepton results Alan Barr, University of Oxford41 0-lepton SUSY Conservative systematics Jet energy scale (~7%) Luminosity (11%) Control region statistics Lepton veto Different MC b-jet fraction MC statistics Higher orders… more …

42. Dilepton SUSY 23/03/2011Alan Barr, University of Oxford42 Di-lepton SUSY