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Higgs Searches using Vector Boson Fusion

Higgs Searches using Vector Boson Fusion. Why a “Low Mass” Higgs (1). M H <251 GeV (95% C.L.). Why a “Low Mass” Higgs (2). s = 206.7 GeV B-tag probab. 0.99 0.99 0.14 0.01 ZZ Hypothesis : M Z =91.7GeV M Z =100.2GeV s/b = 4.7. CHECK lep CONCLUSIONS. 2.2 s fluctuation

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Higgs Searches using Vector Boson Fusion

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  1. Higgs Searches using Vector Boson Fusion

  2. Why a “Low Mass” Higgs (1) MH<251 GeV (95% C.L.)

  3. Why a “Low Mass” Higgs (2) s = 206.7 GeV B-tag probab. 0.990.99 0.140.01 ZZ Hypothesis: MZ=91.7GeV MZ=100.2GeV s/b = 4.7 CHECK lep CONCLUSIONS 2.2s fluctuation (3.4% Prob.) MH>114.1GeV

  4. ATLAS-SN-2003-024 EPJ Direct, C: 32 Suppl. 2 (2004) pp.19-54 -- Detector Effects, Pile-up studies -- Channel-by-channel discussion

  5. Forward jets f h Higgs Decay General Properties Two quarks emitted in the forward region No color flow in the central part of the detector Require two forward (Tagging) jets and Veto extra jet Activity in the central region

  6. Forward Jet Distribution HWW 2l 2ν

  7. Jet Reconstruction Efficiency Probability to find a jet in a Cone of r=0.2 around a parton Note the calorimeter structure And the end of the detector

  8. The effect of Pile-up Energy released in the calorimeters from Minimum bias interactions Low luminosity = 1033 cm-2s-1 High luminosity = 1034 cm-2s-1

  9. Fake Veto from Pile-up Events can be vetoed because Of a Jet from Minimum Bias Low luminosity = 1033 cm-2s-1 High luminosity = 1034 cm-2s-1

  10. Fakes from Pile-up

  11. Comments on the IVB Signature • Clearly depends on the Tagging and Veto performances. Last evaluation rather old (Summer ’01) • Can we Identify jets in the Forward Region? (low signal/noise ratio) • How well can we reconstruct low PT jets in the central region? • The studies I showed assume a model for Minimum Bias, as in Pythia 5.7, 4 years ago. Systematic can be >~ 2

  12. Higgs Decays WW and tau tau decays are the alternatives Tau can be searched in 2 lepton final state, and One lepton and one hadron LEP

  13. HWW2 lep. decay • Main Backgrounds • Top production • WW (electroweak production can be very similar to signal) • Drell-Yan • Selection • Forward tagging • Jet Veto • Mll < 75GeV, ETmiss > 30GeV • Tau rejection (Ztau tau) • Lepton Symmetry • Transverse mass

  14. Transverse Mass MT MT before the angular cut on the leptons 160 GeV e/ Channel Define: MT<175GeV Signal region MT>175GeV Background region

  15. Lepton Angular Correlation Signal Region Background Region

  16. Higgs Mass Reconstruction S=1.02fb B=2.28fb S=8.24fb B=2.44fb

  17. Hττ Define x1 and x2 as the visible energy of the tau decay products Use collinear approximation and assume all decay products (including) neutrino in the same direction Mtt=mll/(x1x2)1/2

  18. Mass Reconstruction in the Tau Channel for 30 fb-1 Di-Lepton Tau Decays Lepton-Hadron Tau decays

  19. Discovery Potentials

  20. Comments • Finding the Higgs is a tough job… • Possible with 10 fb-1? • Depend on several channels exploiting different detector characteristics • Still do not include NLO corrections • Systematic from the minimum bias model used • I didn’t show any neural network analysis • The most “interesting” mass region is also the most difficult

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