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Search for a SM Higgs Boson in the WW Dilepton Decay Channel with 200/pb CDF II Data

This paper presents a study on the search for a SM Higgs boson in the WW dilepton decay channel using 200/pb CDF II data. The analysis aims to understand the dynamics of electroweak symmetry breaking and the mass generation of gauge bosons and fermions. The Higgs production and decay modes are discussed, as well as the approach and event selection criteria used in the analysis. The results obtained are preliminary but promising, indicating progress in the optimization of the approach.

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Search for a SM Higgs Boson in the WW Dilepton Decay Channel with 200/pb CDF II Data

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  1. Search for a SM Higgs Bosonin the WW Dilepton Decay Channel with 200/pb CDF II Data Shan-Huei Chuang UW−Madison for the CDF Collaboration 2004 PHENOMENOLOGY SYMPOSIUM Madison WI April 27 2004

  2. Why Do Higgs? And ggh0WW*? • Electroweak symmetry breaking dynamics? • Mass generation of electroweak gauge bosons and fermions? • Indication of the scale of new physics where the Standard Model will fail? HIGGS major leading-order production mechanism dominant decay mode in high mass region • TeVatron provides an opportunity with pp collision. Shan-Huei Chuang @ PHENO 04

  3. W+ (spin 1) h0 W− ν(spin ½, right-handed) How to Approach Higgs? l+(spin ½, right-handed) tendency of collinearity l−(spin -½, left-handed) SPIN-ZERO parity conservation spin conservation makes two distinctive higgs features: small dilepton angular separation small dilepton invariant mass ν(spin -½, left-handed) in the rest frame of the higgs boson Shan-Huei Chuang @ PHENO 04

  4. |ηµ| < 1.0 |ηe| < 2.0 Event Selection • Select events that have • “well-detected” two electron/mµons, each with Et > 20 GeV • missing Et > 25 GeV • no jets with Et > 15 GeV and |η| < 2.5 • ΔΦ(missing Et, closest lepton or jet) > 20° for missing Et < 50 GeV • not 76 < MZee/µµ < 106 GeV • opposite lepton charge signs • dilepton invariant mass Mll < ½MH • Use a binned maximum likelihood method on the ∆Φll distribution of selected events • Extract the 95% CL σ·BR(ggh0WW) limit  Shan-Huei Chuang @ PHENO 04

  5. Signal Acceptance MC study shows the tendency of small HWW* dilepton invariant mass, which is not a property of other SM background processes. SM ggHWW* signal acceptance in each dilepton channel for each higgs mass Shan-Huei Chuang @ PHENO 04

  6. Signal and Background Expectations Shan-Huei Chuang @ PHENO 04

  7. Q: Why do we separate the to-be-fitted into data, h0WW*, WW and all other SM backgrounds? • A: Because of the different dis- • tribution shape expectations • h0WW* − small ΔΦ • WW − large ΔΦ • all other SM − any Dilepton ΔΦDistribution Shan-Huei Chuang @ PHENO 04

  8. Limit on σ·BR(ggHWW*) as a fun-ction of Higgs Mass at √ŝ = 1.96 TeV CDF Run II Preliminary, Lint ≈ 200 pb-1 BR(Wlv)2 included Shan-Huei Chuang @ PHENO 04

  9. Conclusion • We studied the production of ggh0WW*lvlv (l = {e,µ}) at TeVatron. • We extracted 95% C.L. limits on higgs production at √ŝ = 1.96 TeV as a function of the higgs mass. • Our results are good yet pre-liminary. We are making pro-gress on the optimization of our approach while waiting for data increase to advance the results. Shan-Huei Chuang @ PHENO 04

  10. Backup • Indirect searches: • For Mtop = 174.3±5.1 GeV, • logMH = 1.98+0.21−0.22 • MH = 96+60−38 GeV • MH < 219 GeV @ 95% CL • For Mtop = 178 ± 4.3 GeV, • logMH = 2.07+0.20−0.21 • MH = 117+67−45 GeV • MH < 251 GeV @ 95% CL • LARGE uncertainties! • LEP2 direct searches: • MH > 114.4 GeV @ 95% CL Shan-Huei Chuang @ PHENO 04

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