Search for charged Higgs bosons in e+e- collisions at energies up to  s=209 GeV

1. Search for charged Higgs bosons in e+e- collisions at energies up to s=209 GeV P. Colas, B. Fabbro, M-C. Lemaire, E. Locci, B. Tuchming History of the analysis Data selection tntn channel cstn channel cscs channel results Search for charged Higgs bosons

2. Introduction • General considerations • Charged Higgses are predicted in almost any extension of the Standard Model (In the MSSM, MH+>MW, except if CP violation). • In case of one H+ and one H-, the couplings to Z, g are fixed, thus the cross section depends only on the mass. • Decays considered here are tn and cs, assumed to saturate the width. The c and s flavours are not explicitly used in the analysis. • Experimental signatures: • tntn : 2 acoplanar jets • cstn : 2 hadronic jets Meff~MH+, one tau and missing energy • cscs : 4 jets; 2dijets of equal masses • Then the 3 channels are combined as a function of BR(tn) Search for charged Higgs bosons

3. History • Papers already published • 130-172 GeV : PLB 418 (1998) 419 • 181-184 GeV : PLB 450 (1999) 467 • 189 GeV : PLB 487 (2000) 419 • Proposal : this draft • 189 -209 GeV • New analyses for each channel, all with LDA • cstn and tntn use the charge asymmetry in WW to reject background • cscs re-optimized (with fewer variables) Search for charged Higgs bosons

4. Data analysis • Similar to other Higgs analyses • pre-select events with cuts • use a multivariate analysis (LDA) to select optimally the candidates • calculate CLs with clfft with a discriminant variable (mass or LDA) Data selection • Common to the 3 analyses • 618 pb-1 from 189 GeV to 209 GeV • Use the WW selection • 189 GeV data re-analysed with the new analyses Search for charged Higgs bosons

5. CLASS 11 Number of charged tracks -like Force in 2 jets or missing tntn selection Number of positive charged tracks Number of negative charged tracks In each jet: number of charged tracks against If two leptons both must have: against missing missing Selects 45 evts (exp. 40.63) against well within acceptance Search for charged Higgs bosons

6. tntnselection efficiency Background composition W+W-80% gg-> l+l-6.4% ZZ 6% t+t-g5.3% Wen, Zee,… 2.3% MH+ Then corrected for E12=0 cut (8%in ‘ 98, 6.5% in ‘ 99, 7% in 2000) Search for charged Higgs bosons

7. tntn • Multivariate analysis • Linearly combine the variables of the preselection, plus the charge-tagged t polar angle Search for charged Higgs bosons

8. LDA Optimization • 4 variables are sufficient: 1/2 (Q1cosq1+ Q2cosq2) angle a between taus event missing PT y23 Search for charged Higgs bosons

9. Angle between t jets Search for charged Higgs bosons

10. Use this optimal linear combination as a discriminant in CL calculation. Search for charged Higgs bosons

11. For each s, Signal LDA shape parametrised by sum of 2 gaussians and interpolated as a function of Higgs mass Background : sum of 3 gaussians LDA LDA LDA LDA Search for charged Higgs bosons

12. tntn Confidence levels calculated with CLFFT CL(s+b) / Cb 1-Cb MH+ MH+ Search for charged Higgs bosons

13. Signal 85 GeV Search for charged Higgs bosons

14. cstn • Select one t + 2 jets + missing energy • if several t minijets, take the one with min c2 of the 2C fit (E,p conservation and equality of the jet-jet and tn masses) • define a first discriminant D1 combining : • the event missing pT, • the isolation angle qiso (cone around the t containing 5% of the energy) • the c2 of the 2C fit • the decay angle of the leptonic Higgs candidate, multiplied by the t charge • Require D1>-0.1 Search for charged Higgs bosons

15. cstn • define a second discriminant D2 combining : • the decay angle of the leptonic Higgs candidate, multiplied by the t charge • a t polarisation estimator • Require D2>-0.3 • efficiency from 49.1% for MH=60 GeV to 38.8% for MH=80 GeV • Background composition • 93% WW • rest is Wen, ZZ and qq Year 2000 data Selects 279 evts (289.3 expected) Search for charged Higgs bosons

16. cstn Search for charged Higgs bosons

17. cscs • 4 jet preselection (>9 charged tracks, Ech>0.1 s, anti-ISR cuts, y34>0.003, T<0.9) • 5C fit with ABCFIT (as in WW) -> pairing with min c2 • calculate Dm with rescaled jet energies (b fixed) and require Dm<30 GeV • Perform a LDA (optimized on a cocktail of higgs masses 80 to 88 GeV) with: • Production angle • Dm • c25C/Ndof • E jetmin * qjet-jetmin • log10 (QCD matrix element) BG: 78%WW 10% qq Cut D3>1.3 Selects 2762 evts (2892 expected) Search for charged Higgs bosons

18. cscs Search for charged Higgs bosons

19. cscs Search for charged Higgs bosons

20. cscs W mass set to 80.45 GeV Search for charged Higgs bosons

21. cscs Confidence levels calculated with CLFFT 1-Cb CL(s+b) / Cb MH+ MH+ Search for charged Higgs bosons

22. Systematic effects • Systematic effects on signal and BG normalisation are taken into account by smearing (s+b)/b • signal normalisation : • cross-section +-1% (rad. corr.) • calorimeter calibration : vary had/em scale by 2%/0.7%: • +-0.5% for cstn and +-0.3% for cscs • for cscs: shift all variables by 1s of their mean:0.5% • background normalisation : • WW cross-section taken from RACOON: lower KORALW by 2.5% • WW cross-section uncertainty 2% • gg ->leptons cross-section uncertainty 5% for tntn • qq cross-section uncertainty 5% • for cscs: shift all variables by 1s of their mean:0.5% • calorimeter calibration : vary had/em scale by 2%/0.7% Search for charged Higgs bosons

23. Systematics tn cs cscs tntn % % % norm Signal . 2.7 3.2 1.8 MC stat 2.4 2.9 1.3 1.4 others 1. 1.2 BG norm. 2.1 4.3 3.0 MC stat 1.2 2.5 0.5 others 1.7 3.5 2.9 Search for charged Higgs bosons

24. FINAL RESULTS 95 % C.L. limits in GeV including systematics BR(H->tn)=080.4(exp. 78.2) BR(H->tn)=1.87.7(exp. 89.2) Any BR 79.2(exp. 77.1) Search for charged Higgs bosons

25. COMPARISON WITH OTHER EXPERIMENTS * * * (*) summer 2001 Obs (exp) Search for charged Higgs bosons