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Standard Model Higgs Searches at LHC

Standard Model Higgs Searches at LHC. Suyong Choi Korea U. SM Higgs Production and Decay. SM Higgs Production Cross Sections at 7 TeV. SM Higgs Production Cross Sections at 14 TeV. Branching Fractions. SM Higgs . Sensitivity depends on Backgrounds Mass resolution.

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Standard Model Higgs Searches at LHC

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  1. Standard Model Higgs Searches at LHC Suyong Choi Korea U

  2. SM Higgs Production and Decay

  3. SM Higgs Production Cross Sections at 7 TeV

  4. SM Higgs Production Cross Sections at 14 TeV

  5. Branching Fractions

  6. SM Higgs • Sensitivity depends on • Backgrounds • Mass resolution More info in https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CrossSections

  7. SM Higgs Search Channels • – good mass resolution • - clean, good mass resolution • - not clean, worse mass resolution • – statistics • – statistics, clean • - clean, good mass resolution • Overall, they are very complicated analyses

  8. SM Higgs searches at CMS and ATLAS

  9. CMS SM Higgs Channels

  10. ATLAS SM Higgs Channels

  11. Boosted selection 1 jet pT>150 GeV VBF selection

  12. W/Z+H

  13. Event categories divided into • 2 classes where the smallest of two photons is less or greater than 0.94 • 2 classes where the largest is in endcap or barrel • Total of 2x2=4 classes Mass resolution for

  14. Excess: SM signal x5

  15. Consistency • P-value - Probability that background to produce fluctuation as large as observed 2.3 @123.5 GeV

  16. Upper Limit Data disfavors Higgs in 127 – 131 GeV @ 95% CL

  17. ATLAS Mass resolution 1.7 GeV

  18. ATLAS • 114 – 115, 135-136 GeVexcluded @ 95% CL

  19. ZZ selection • A second lepton pair: • for 4e, 4 • Two sets of cuts for low-mass and high-mass Higgs • Signal efficiencies

  20. Higgs mass resolutions

  21. Backgrounds • Reducible - , , • Irreducible - • All derived from data 72 observed exepected Theory:

  22. low mass region • 13 events observed • expected • No significant excess

  23. Limits from 340~465 GeV 180~305 GeV 134~158 GeV expected exclusion: 130-160 GeV, 182-420 GeV

  24. ATLAS 71 events observed 629 events expected Below 180 GeV, 8 events observed 9.31.5 events expected 2e2μ events (m=123.6 GeV, m=124.3 GeV), one 4μ event(m=124.6 GeV)

  25. ATLAS

  26. ATLAS 135 – 156 GeV excluded 181-234 GeV excluded 255-415 GeV excluded

  27. Further selections • mass-dependent selection • , , ,

  28. Yields after signal selection • Experimental uncertainties only • Signal efficiency uncertainty ~ 20% • Background uncertainty in signal region ~ 15%

  29. Limits 129-270 GeV Excluded @ 95%CL 127-270 GeV expected exclusion

  30. ATLAS

  31. ATLAS

  32. ATLAS • 2.05 fb-1 110 events observed 9110 expected If Higgs of certain mH existed

  33. 145 – 206 GeV excluded @ 95% CL • Excpected exclusion: 134 – 200

  34. Dilepton trigger • Veto events with 3rd lepton • Cuts to reject Fake Missing ET • Final selection • MET cut – mass dependent • MT

  35. Backgrounds • MET modelingusing events • reweighting according to n-jets, boson pT • Less reliance on MC simulation • Data driven methods to estimate non-resonant backgrounds • Top pair, single top, WW, W+jets,

  36. Limits 270-440 GeV excluded at 95% CL

  37. CMS Combination

  38. Expected exclusion: 117 – 543 GeV

  39. Global p-value 1.9 with LEE in 110~145 GeV 0.6 with LEE in 110~600 GeV

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