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High Mass Higgs at the Tevatron Matthew Herndon, University of Wisconsin Madison Higgs Days 2012

g g s. High Mass Higgs at the Tevatron Matthew Herndon, University of Wisconsin Madison Higgs Days 2012. The Higgs Boson. SM postulates a mechanism of electroweak symmetry breaking via the Higgs mechanism Interaction with the Higgs field results in masses for the W and Z vector bosons,

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High Mass Higgs at the Tevatron Matthew Herndon, University of Wisconsin Madison Higgs Days 2012

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  1. g g s High Mass Higgs at the Tevatron Matthew Herndon, University of Wisconsin Madison Higgs Days 2012

  2. The Higgs Boson • SM postulates a mechanism of electroweak symmetry breaking via the Higgs mechanism • Interaction with the Higgs field results in masses for the W and Z vector bosons, • Possible mass terms for the fermions • Also expect and observable quanta of the field: Higgs boson • Directly testable hypothesis by searching for the Higgs boson A primary goal of the Tevatron and LHC Now directly testable by measuring Higgs properties!

  3. The Higgs Boson • Where to concentrate you search • One answer: where your experiment excels • Higgs decay to pairs of mass vector bosons with leptonic decays • Where the data says to look(just before final analyses) SM LEP Direct search: mH > 114GeV SM (Tevatron) indirect constraint: mH < 152GeV LHC: 115.5 < mH < 129 LHC: Look around 125 GeV Some Hints that optimizing the analysis at low mass was called for.

  4. Tevatron Performance Over 10 fb-1! Enough data to make an impact at low mass 9.7/fb used in analysis

  5. Tevatron Higgs History • After LP 2007 we had predicted expected preface enhancements and extrapolated to 10fb-1 • Improvement factors based on studies in data • Expectation: 3σ evidence for Higgs possible at 115GeV • 125 was a harder mass. • Needed to exceed the expectations

  6. SM Higgs Production and Decay • High mass: HWWll decay available (ZZ used - contribution small) • Takes advantage of large ggH production cross section • Alternative production mechanisms • WHWWW, ZHZWW, VBF: qqHqq->WWjj • Significant contribution in events with 1, 2 or more jets and same sign leptons, three leptons events. Helps at low mass

  7. Analysis Technique • Expanded acceptance • Expanded lepton acceptance in areas with weak/no dedicated lepton Id • Multiple analysis channels beyond HWW: HZZ, HWW (lepton + jets), VH (same sign, trilepton, extra jets) and VBF (extra jets) • Analyze specific event topologies • Isolate subsets of signal/background processes for optimal discrimination • Optimize inputs to discriminants as a function of mass • Use of jet kinematics to find vector bosons and identify VBF events • Control regions • Check modeling of primary backgrounds • Measure background cross sections where possible: Z, WW, WZ, ttbar • Apply advanced techniques • Add only order 10-20% sensitivity to the analysis but needed in regions where the spin correlation is not enough such as at low mass

  8. SM Higgs: HWW W+ H μ+ W+ W- ν e- W- • HWWll - signature: Two high pT leptons and MET • The most powerful analysis channel • Primary backgrounds: WW and top in di-lepton decay channel • Excellent physics based discriminants Spin correlation: Charged leptons go in the same direction ν

  9. CDF WW 2+ Jet Analysis • Signals • VHVWWl+l- MET jj analysis, VHBHWW + forward jets, ggHWWjj • Analysis improvements • Implementation of MCs with good 2+ jets modeling for backgrounds • Use of jets kinematics: Energy and rapidity • Use of dijet variables mass, delta rapidity • Optimization of variables as a function of mH 25% imrpvement

  10. UW contribution CDF HWW Search • Combination of CDF H  WW searches As sensitive as individual Hbb searches as low mass • most sensitive analysis for mH > 128GeV Observed limit 2.98

  11. DØ HWWll Search Exp limit 1.19@165 – most powerful single Tevatron channel • ll – signature subdivided by jet topology & lepton charge • Further subdivided by lepton flavor • BDT for DY suppression • Example: HWWeμ + MET • High purity channel

  12. DØ H: ljj • ljj(jj): lepton + jets signature • HWWljj, VHljjjj, WHlnubb • High and low mass analysis at once • At high mass takes advantage of large Wjj branching ratio • Classifies events by number and type of b tag • BDT based discriminant

  13. DØ HWW Search Combination of DØ H  WW searches hWW combined sensitivity more powerful that any of the low mass H analysis Observed limit 4.56

  14. Tevatron Higgs Combination Exclusion driven by HWW No interesting WW signal observed Obs. Exclusion 147-180 GeV

  15. Conclusions • LHC has observed a boson with mass ~125 GeV! • What we have measured so far almost certainly means it plays a part in electroweak symmetry breaking. • The Tevatron experiments have achieved sensitivity to the SM Higgs boson production cross section at high and low mass • The sensitivity of the CDF and DØ high mass searches make them a primary element of the Tevatron search at mass around 125 GeV We exclude at 95% C.L. the production of a SM Higgs boson of 147-180 GeV The observed data in HWW is compatible with a SM Higgs boson but not constraining

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