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Higgs search in H  ZZ/WW decay channels with the CMS detector

Higgs search in H  ZZ/WW decay channels with the CMS detector. Claude Charlot LLR - École Polytechnique for the CMS collaboration. Outline. LHC & CMS detector SM Higgs at the LHC H  WW  ll  selection H  ZZ  llll selection Expected sensitivity for both channels

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Higgs search in H  ZZ/WW decay channels with the CMS detector

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  1. Higgs search in HZZ/WW decay channels with the CMS detector Claude Charlot LLR - École Polytechnique for the CMS collaboration

  2. Outline • LHC & CMS detector • SM Higgs at the LHC • HWWll selection • HZZllll selection • Expected sensitivity for both channels • Combined sensitivity • 10 TeV projection • Conclusions

  3. The Large Hadron Collider • pp collider at CERN, s=14 TeV • Start operation in late 2009 • 10 TeV for this run • ~200pb-1 expected by automn 2010 • Two general multi-purpose experiments • CMS and ATLAS • understanding EWK symmetry breaking among the main goals

  4. The CMS Detector SUPERCONDUCTING HCAL Scintillating PbWO4 crystals(~80000 ) 36 supermodules (EB) 4 dees (EE) Preshower (EE) 3.8T ECAL COIL Plastic scintillator/brass sandwich ||<2.6 TRACKER ||<2.4 silicium (200m2) PIXEL (rT<11cm) 3 layers (barrel) 2x2disks (fwd) SST (rT<120cm) >8 hits, depending on  MUON MUON BARREL Drift Tube Resistive Plate Cathode Strip Chambers weight: 12,500 t diameter: 15 m length: 21.6 m Drift tubes (||<1.2) Cathode strip chambers (0.9<||<2.4) Resistive plate chambers e: (E)/E ~ 0.5% @100 GeV : (p)/p ~ 1% @100 GeV

  5. SM Higgs at the LHC • Higgs production cross-section (NLO): 0.1-50 fb • gluon fusion dominates at LHC • Especialy at low mH • Factor ~10 @ 100 GeV • Here results for inclusive production • HWW(*) and HZZ(*) are main discovery channels • Highest BRs for mH>~2mW • Clean leptonic decay modes • BR(Wl): 10.8%; BR(Zl+l-):3.4% • Cover high mH region and down to ~2mW

  6. HWWll: selection • Event topology: 2 isolated high pT leptons + ET miss, no hadr. activity • Main backgrounds: tt, Drell-Yan, WW, WZ, ZZ, tW, W+jets Jets: ET>15 GeV ||<2.5 • Preselection to select leptonic WW events • Single lepton triggers • Exactly 2 isolated leptons opp. charge • pT1,2>10 GeV or at least one pT>20 GeV • ETmiss > 30 GeV • mll>12 GeV • Main selection observables • Central jet veto • Angular correlations btw leptons • Dilepton mass, ETmiss, leptons pT • Other discriminants also used in NN analysis After preselection and CJV

  7. HZZllll: selection • Event topology : 4 isolated leptons • Main backgrounds (after presel.): tt, Zbb , ZZ • Preselection to supress backgds involving fake leptons • Single and double lepton triggers • >=2 pairs of opposite charge, matching flavors leptons • pTlepton>5 GeV • mll>12 GeV (all pairs) • m4l>100 GeV (at least one) • Loose isolation • Selection to further reduce irreducible backgds (mH independant ) • Isolation (Iso3+Iso4), IP • pTe>7 GeV, pT>5GeV • 50< mZ<100 GeV • 20<mZ*<100 GeV

  8. Systematics and control from data • Lepton efficiencies measured from Zll candel using tag and probe method • In WW analysis, control of background is crucial • tt and WW from control region close to signal region but with low signal contribution • tt using signal preselection but inverting the CJV (2 jets) • WW using signal preselection and mll>115 GeV • W+jets from P(jetlepton) from jet triggers and using signal selection with only 1 identified lepton (pT>20) and 1 jet (pT>10) • In ZZ analysis, systematic on lepton isolation from UE and pileup estimated using random cone technique • ZZ background normalisation from Z data, using ZZ/Z MC ratio • Zbb by inverting the isolation cuts and using mZ cut to separate from tt and W/Z+jets

  9. HWWll: results • Likelihood ratio method • S = -2lnQ • Q = LS+B/LB • Systematic errors included 14 TeV 1fb-1 14 TeV, ∫Ldt=1fb-1 14 TeV 1fb-1  SM Higgs could be discovered for mH~2mW with 1fb-1

  10. HZZllll: results 14 TeV, ∫Ldt=1fb-1 • Counting experiment • For each mH hypothesis, count events within mH2mH • Sliding window central value (m4l) and  from MC • Systematic errors included  SM-like Higgs could be excluded for 185< mH<250GeV with 1fb-1

  11. HZZ/WW: combined sensitivity • Combine channels using two different approaches: Bayesian and CLs • Different assumptions on correlations between systematic errors • CLs/Bayesian ~0.91 on average  SM-like Higgs could be excluded for mH >140 GeVfor 1fb-1

  12. HZZ/WW: 10 TeV projection • Most important effect is change in cross-section • ggH: 10 TeV/14 TeV is ~0.54 • WW/ZZ: 10 TeV/14 TeV is ~0.65 J. Stirling • Here simple rescaling of signal and main backgrounds yields from the 14 TeV analyses • Full analyses for 10 TeV are underway  1410 TeV is approximately equivalent to a loss of a factor two in sensitivity

  13. Conclusions • New CMS analyses for HWW and HZZ in leptonic modesin the context of an initial scenario • Simple cut based as well as multivariate selections (HWW) have been studied • Methods for background estimation and control from data • SM Higgs could be discovered at 5 around mH=160 GeV in WW decay mode with 1fb-1 • SM Higgs could be excluded for 185<mH<250 GeV in ZZ decay mode with 1fb-1 • Using both channels, SM Higgs could be excluded for mH>140 GeV with 1fb-1 • 10 TeV bottom line: a loss of sensitivity by a factor ~2  CMS is looking forward to the first LHC data!

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