Ashok Kumar Delhi University On behalf of CMS collaboration

1. Higgs searches in CMS Ashok Kumar Delhi University On behalf of CMS collaboration PHYSICS AT LHC 2011 – Perugia June 06-11, 2011

2. Outline of Talk • Higgs phenomenology, production and decay modes at LHC • Standard Model Higgs searches: • H  gg • H  WW • H  ZZ • BSM Higgs: • SUSY Neutral, SUSY Charged, Doubly charged Higgs • CMS Higgs Projections • Significance and exclusion limits • Summary and Outlook

3. Current status of SM Higgs search • Theoretical Limits • mH < 1 TeV from unitarity arguments • If λ cutoff ≈ 1TeV weaker limits: 50≤ mH ≤ 800 GeV • Indirect Constraints • Preferred fit value mH =87-26+35 GeV (68% CL) • mH ≤ 157 GeV (95%CL) & ≤187 GeV (with LEP-2 direct search results) • Experimental Limits • LEP: mH ≥ 114.4 GeV at 95% CL • TEVATRON Run II: 158 ≤ mH ≤ 173 GeV • excluded at 95% CL LEP Electroweak Working Group (LEP EWWG) http://lepewwg.web.cern.ch/LEPEWWG/ Conference Note: arXiv:1103.3233 [hep-ex]

4. Cross sections & Branching Ratios "Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables" (CERN-2011-002, arXiv:1101.0593) • Higgs production cross-section (NLO): 0.1 - 50 pb • Gluon fusion dominates at LHC gg enhances the signal, whereas the irreducible backgrounds come from qqbar At low mass (M < 2MZ) -Dominant bb; huge QCD background -H→tt accessible through VBF -H→WW(*) accessible via gluon-gluon fusion and VBF -H→ gg low BR but good detector resolution -H →ZZ*→4l also accessible For higher masses -H→WW and H→ZZ→4l final-states A. Djouadi arXiv:hep-ph/0503172v2

5. H →gg Analysis Features: • two isolated photons required • looking for a γγ mass peak • large QCD background, estimated from sidebands A fermio-phobic Higgs with mfph < 110 GeV would be excluded, as for this mass range, the yield σ(pp→hfph)xBR(hfph→gg) is ~ 4 The limit on the anomalous production is expected to be about 4 times σ(pp→HSM)xBR(HSM→gg). The projected exclusion reach is comparable to the current limits from LEP and Tevatron

6. H→WW→ll Signature: • Two high pT leptons • MET from neutrinos • Very clean events with little hadronic activity ‣ Most sensitive channel for early studies ‣ Two parallel techniques: Cut-based and boosted decision tree (BDT) Electron-muon WW candidate Event selection: •Exactly two isolated, well identified leptons (e/µ), pT > 20 GeV •Projected MET > 35 (20) GeV for ee/µµ (eµ) channels •Z veto on invariant mass of same flavor leptons •Jet and b-tag veto against events with top quarks Excellentknowledge of backgrounds mandatory: control regions & data- driven methods

7. H→WW: Backgrounds Signal selection mostly relying on opening angle between leptons - ΔΦll -Leptons from H tend to have small angles • Background estimations from data: • SM WW contribution from mll control regions with low signal contamination • Z+jets estimated using inside/outside ratio • from MC applied on data • W+jets and QCD fakes estimated using • a fake-ratio method • Remaining ttbar estimated from additional • soft leptons and soft b-tagged jets BDT takes input from kinematic relations between leptons and MET in addition to cut based variables

8. H→WW→ll • Results from BDT and cut-based analysis virtually the same • Spin correlation used for a Higgs analysis • Search for H→WW sets limits to Higgs production with a fourth generation • Not yet sensitive to SM Higgs -Need factor 3 more data at mH = 160 GeV • However sensitive to some models with 4th fermion family assuming high masses -Exclude them for mH ~ 144 -207 GeV @ 95% C.L. Phys. Lett. B 699 (2011) 25 arXiv:1102.5429

9. CMS-PAS-HIG-08-003 H → ZZ*→ 4l Signal Signature: Isolated high pT 4e, 4m, 2e2m leptons (Clear Higgs mass peak) Dominant Backgrounds: ZZ, Zbb, tt+jets, Z+jets, W+jets, QCD Preselection strategy Single & double lepton triggers 4 loose isolated leptons, oppositely charge pairs mll>12 GeV, m4l>100 GeV Main discrimanting observables: Tight isolation (against tt, Zbb) Impact parameter (against Zbb and tt) 50 < mZ< 100 GeV, 20 < mZ*< 100 GeV Baseline cut-based approach, mH-independent Exclusion is out of reach across the whole mH range, Should a fourth generation of quarks exist, the Higgs boson could be excluded in the range mH < ~ 420 GeV

10. Combination of channels By combining the results for the three channels shown before & assuming twice amount of Data (~ ATLAS + CMS)  Expected exclusion range for SM Higgs: 140 < mH < 200 GeV  The Higgs boson with a mass mH< 500 GeV would be excluded, should a fourth generation of heavy quarks exist

11. Neutral Higgs Boson → TauTau Search for a MSSM Higgs decaying to a pair of taus (Φ = h/H/A) -BR to ττ is about 10 % -Consider ττ decays to e-µ, µ-had, e-had Novel technique for τ pair mass reconstruction: -Likelihood fit to τ momenta -Use all available kinematic information and probability density for τ pT spectra -Improvement in resolution compared to visible mass

12. Limits on Neutral Higgs Boson • No signal excess observed • Set upper limits on σ(pp ➝ ΦX) x BR(Φ ➝ ττ), as a function of the Higgs boson mass yield stringent new bounds in the MSSM parameter space mA versus tan β extending as low as tan β = 23 for mA= 130 GeV. • Significantly extend previous limits CMS-PAS-HIG-10-002

13. Charged Higgs in ttbar decays Charged MSSM Higgs may contribute to ttbar decays tt~(Hb)(Wb)(tau_h v b)(lvb) • Event Selection as for ttbar cross section measurement: • One electron (muon) with pT > 30 (20) GeV • At least two jets ET > 30 GeV • MET > 40 GeV • Hadronic τ pT > 20 GeV [CMS PAS-TOP-10-002] • Backgrounds in two categories: • Fake hadronic τ: use fake rate method to estimate from data • Real hadronic τ: use simulation to estimate background

14. H+ Limits & Exclusion • No signal observed • Set 95% C.L. on BR (t➔bH+) assuming BR(H+➔ τ+v)=1 • Limit ~0.25-0.28 for 80 GeV < mH+ < 140 GeV CMS-PAS-HIG-11-002

15. Doubly Charged Higgs • Extend Standard Model adding scalar triplet: Φ±±, Φ± and Φ0 • Triplet responsible for neutrino masses • Consider model where BR(Φ±± ➔ll)=100% • Final states with three/four isolated leptons (earlier multi-lepton search) • Look for resonance peaks in dilepton mass distributions. CMS-PAS-HIG-11-001 No peak observed ➔ set limit extending reach of previous experiments

16. SM Higgs Projections @ 7 TeV Several Higgs production and decay channels used for projections: -mass range 114 – 600 GeV covered -based upon the cut-and-count methodology (in some cases, cut on the MVA-output) Higher-order cross sections included: -signal gg-fusion at NNLO+NNLL, VBF and VH at NLO, ttH at LO -all backgrounds at NLO

17. Significance and Exclusion Projected CMS sensitivity to SM Higgs Boson searches at √s = 7 TeV, 5 fb-1 -Statistical Exclusions (95%CL): Bayesian limits with a flat prior -Significance: Profile Likelihood method • At √s = 7 TeV with L=5 fb-1, CMS is expected to reach an exclusion sensitivity in the mass range from the LEP limits (114 GeV) to 600 GeV

18. Summary & Outlook With ∫L ~ few pb-1 at √s = 7 TeV CMS experiment have started exploring Higgs Physics. Low mass SM Higgs searches require higher ∫L and √s. Search for SM H→WW alone sets limits to Higgs production with a fourth generation. BSM Higgs searches from CMS ➔ Unfortunately no observations ➔ set limits  Combined projections at √s = 7 TeV with luminosity ~ 5 fb-1, CMS may exclude SM Higgs mass up to 600 GeV.