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Hunting the invisible at the LHC

Hunting the invisible at the LHC. Alan Barr. https:// twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults. Motivation. The usual blah blah ? Dark Matter … Naturalness of the Higgs boson mass… Electroweak unification… Radiative electroweak symmetry breaking….

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Hunting the invisible at the LHC

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  1. Hunting the invisible at the LHC Alan Barr https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults

  2. Motivation • The usual blah blah? • Dark Matter … • Naturalness of the Higgs boson mass… • Electroweak unification… • Radiative electroweak symmetry breaking…

  3. Motivation – as a pragmatist Lots of effort to build it: let’s make good use of it…

  4. 1 pb 1 fb Integrated luminosity: 2 fb-1(Mid 2012) 5 fb-1(All of 2011)

  5. Missing momentum… invisibles

  6. Missing momentum (ETmiss) signatures: challenges in 2011 Data collectedInt. Lumi: ~5 fb-1 • Instantaneous luminosity: 3.65×1033 cm−2s−1 • Trigger: ETmiss-only trigger: threshold up to 180 GeV • Others available • Pile-up: up to • Calorimeter response (in-time and out-of-time) • Jet and ETmissresolution • Particle ID

  7. Pile-up: track ↔ jet association A spectacular 9-jet + ETmiss eventAll nine jets associated to same primary vertex(even in presence of many other vertices)

  8. Uncertainties? Standard Model backgrounds Instrumental backgrounds Expected Signal?

  9. Momentum imbalance… PATHOLOGIES PHYSICS Mismeasurement? Cosmics? Noise? Beam halo? Neutrinos? WIMPs?

  10. JETS + MISSING MOMENTUM From collisions Jets Jets PTmiss

  11. JETS From collisions Jets: Had. CalorimeterE.M. CalorimeterTracks from vertexIn-time b,c quark jets can decayto neutrinos

  12. JETS + MISSING MOMENTUM Measurements Jets:  cut Reduce: Had. CalorimeterE.M. CalorimeterTracks from vertex Measure remainderat small 

  13. JETS + MISSING MOMENTUM From cosmics Reduce by: (a) requiring tracks with jets (b) look for muonhits Measure remainder: (a) no beam (b) timing

  14. JETS + MISSING MOMENTUM From beam halo Reduce by requiring tracks with jets Measure remainder with single beam / timing

  15. JETS + MISSING MOMENTUM Calorimeter noise Reduce by requiring tracks with jets Measure remainder (a) no beam (b) timing

  16. Neutrinos Z ( ) + jets (+ jets) W ( l) + jets

  17. Analysis philosophy * We have some fast-sim for signal Dedicated analysis for different final states State of the art Monte Carlo Validated GEANT-4 detector simulation* Multiple redundant control regions (CR) Multiple cross-checks & validation regions (VR) Appropriate kinematic & ID variables Uncertainties based on measurements wherever possible Signal systematics in limits

  18. Lots of different final states… Try to make it simple…

  19. Jets: anti kT, R=0.4, emhad calibration B-tagged jets: secondary vertex fitter Typically at point: (εB~60%, εlight<1%) Leptons (either e or µ), isolated Trigger requires: (e > 25, µ > 20), soft lep down to (7,6) GeV Tau: 1- or 3- prong hadronic pT > 20GeV Photon: isolated ? ETMiss: Missing transverse momentum -ve sum pT of: jets, leptons, unclustered ET Disappearing track LEGEND

  20. ATLAS-CONF-2012-034 ATLAS-CONF-2012-033 arXiv:1203.5763 ATLAS-CONF-2012-037 ATLAS SUSY review: missing momentum ATLAS-CONF-2012-003 2 fb-1 ATLAS-CONF-2012-036 arXiv:1112.3832 ATLAS-CONF-2012-023 ATLAS-CONF-2012-041 2 fb-1 5 fb-1 ArXiv:1111.4116 1fb-1 ATLAS-CONF-2012-001 ATLAS-CONF-2012-005 ATLAS-CONF-2012-002 ATLAS-CONF-2011-096 ?

  21. ATLAS-CONF-2012-034 ATLAS-CONF-2012-033 ATLAS-CONF-2012-037 ATLAS-CONF-2012-041 5fb-1 Full 2011 dataset ?

  22. ATLAS-CONF-2012-033 No leptons, ≥(2-6) jets + ETmiss Squarks, Gluinos Page 22

  23. ATLAS-CONF-2012-033 Small Δm Gluinos/cascades Squarks Different mass scales Total of 11 signal regions

  24. ATLAS-CONF-2012-033 Control regions for each significant BGMultijet BG determined from data-driven smearing method Smaller backgrounds, e.g. diboson: MC only

  25. ATLAS-CONF-2012-033 meff (incl.): scalar sum of ET of all jets and ETmiss MC scaled by ~0.75 (based on control regions)Band shows JES, JER, MC stats

  26. ATLAS-CONF-2012-033

  27. ATLAS-CONF-2012-033 Non-disjoint SRs: exclusion based on best expected significance MSUGRA/CMSSM Simplified gluino-squark-neutralino model

  28. ATLAS-CONF-2012-037 No leptons ≥(6-9) jets + ETmiss Gluinos cascadesGluinos 4 x tops Page 28

  29. ATLAS-CONF-2012-037 QCD background: stochastic term  HT Independent of jet multiplicity • Final variable quantifies significance of Etmiss •  Multi-jets dominated control regions •  Subtract (subdominant) “leptonic” backgrounds • QCD background is reliably predicted (~20%) • Tested in further control regions and cross-checked with jet-smearing method

  30. ATLAS-CONF-2012-037 SR: 7j80 Top validation region SR: 9j55

  31. ATLAS-CONF-2012-037 Most discrepant 7j80 p-value 0.07

  32. ATLAS-CONF-2012-037 arXiv:1203.5763 ATLAS-CONF-2012-003 Simplified gluino/top model

  33. ATLAS-CONF-2012-033 ATLAS-CONF-2012-037 ATLAS-CONF-2012-041 5 fb-1 MSUGRA/CMSSM interpretation Gluino mass > ~850 GeV

  34. Nothing so far…

  35. …and to knowledge, self-control; and to self-control, perseverance… Forecast of fraction of “interesting” points “discovered” 1105.1024 Allanach, AJB, Dafinca, Gwenlan

  36. Tough points…. 1105.1024

  37. Tough points…. 1105.1024

  38. Tough points…. 1105.1024

  39. Tough points…. 1105.1024

  40. ATLAS-CONF-2012-034 ATLAS-CONF-2012-033 arXiv:1203.5763 ATLAS-CONF-2012-037 ATLAS-CONF-2012-003 2 fb-1 ATLAS-CONF-2012-036 2 fb-1 ArXiv:1112.3832 ATLAS-CONF-2012-023 ATLAS-CONF-2012-041 5 fb-1 ArXiv:1111.4116 1 fb-1 ATLAS-CONF-2012-001 ATLAS-CONF-2012-005 ATLAS-CONF-2012-002 ATLAS-CONF-2011-096 ?

  41. arXiv:1203.5763 2 fb-1 ATLAS-CONF-2012-023 ATLAS-CONF-2012-001 ATLAS-CONF-2012-005 ATLAS-CONF-2012-002 EW gauginos, staus

  42. Three-lepton + ETmiss ATLAS-CONF-2012-023 Direct EW gaugino

  43. Three-lepton + ETmiss Searches for direct gaugino productionChargino + neutralino 3 leptons + 2 LSP OSSF pair(s) allowed (mll > 20) ATLAS-CONF-2012-023 pT (µ) > 20,10,10 GeV pT (e) > 25,10,10 GeV ETmiss> 50 GeV Z enriched(within 10 GeVof mZ) Z depleted(+b jet veto)

  44. 3-lepton + Etmiss - gauginos Via slepton ATLAS-CONF-2012-023 LSP Chargino-1

  45. ATLAS-CONF-2012-035 ATLAS-CONF-2012-001 4 lepton + ETmiss Direct gauginos L-violating RPV

  46. ATLAS-CONF-2012-035 ATLAS-CONF-2012-001 L-violating RPV  LSP λ121gut ~ 0.032

  47. ATLAS-CONF-2012-003 2 fb-1 ATLAS-CONF-2012-036 arXiv:1112.3832 arXiv:1111.4116 ATLAS-CONF-2011-096 1 fb-1

  48. arXiv:1112.3832 2 jets only(veto on third jet) Direct sbottom

  49. Direct sbottom 2 jets only – veto on third jet ArXiv:1112.3832 (Pure MC predictions in parentheses)

  50. Direct Sbottom 2 jets only – veto on third jet ArXiv:1112.3832

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