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29/11/2001 Search for charged Higgs bosons 1
Search for charged Higgs bosons in e+e- Search for charged Higgs bosons in e+e- collisions at energies up to collisions at energies up to s=209 GeV s=209 GeV Search for charged Higgs bosons in e+e- Search for charged Higgs bosons in e+e- collisions at energies up to collisions at energies up to s=209 GeV s=209 GeV
History of the History of the analysisanalysis
Data selectionData selection
channelchannel
cscs channel channel
cscs channelcscs channel
resultsresults
P. Colas, B. Fabbro, M-C. Lemaire, E. Locci, B. Tuchming
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IntroductionIntroduction IntroductionIntroduction
• General considerationsGeneral considerations– Charged HiggsesCharged Higgses are predicted in almost any extension of the are predicted in almost any extension of the
Standard Model (In the MSSM, MStandard Model (In the MSSM, MH+H+>M>MWW, except if CP violation)., except if CP violation).
– In case of one HIn case of one H++ and one H and one H--, the couplings to Z, , the couplings to Z, are fixed, are fixed,
thus thus the cross section depends only on the massthe cross section depends only on the mass..
– Decays considered here are Decays considered here are and and cscs, assumed to saturate the , assumed to saturate the
width. The c and s flavours are not explicitly used in the analysis.width. The c and s flavours are not explicitly used in the analysis.
• Experimental signatures:Experimental signatures: – : 2 acoplanar jets: 2 acoplanar jets– cscs : 2 hadronic jets M : 2 hadronic jets Meffeff~M~MH+H+, one tau and missing energy, one tau and missing energy– cscs : 4 jets; 2dijets of equal masses cscs : 4 jets; 2dijets of equal masses
• Then the 3 channels are combined as a function of BR(Then the 3 channels are combined as a function of BR())
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HistoryHistory HistoryHistory
• Papers already publishedPapers already published– 130-172 GeV : PLB 418 (1998) 419130-172 GeV : PLB 418 (1998) 419
– 181-184 GeV : PLB 450 (1999) 467181-184 GeV : PLB 450 (1999) 467
– 189 GeV : PLB 487 (2000) 419189 GeV : PLB 487 (2000) 419
• Proposal : this draftProposal : this draft – 189 -209 GeV 189 -209 GeV – New analyses for each channel, all with LDANew analyses for each channel, all with LDA– cscs and and use the charge asymmetry in WW to use the charge asymmetry in WW to
reject backgroundreject background– cscs re-optimized (with fewer variables)cscs re-optimized (with fewer variables)
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Data Data selectionselection
Data Data selectionselection • Common to the 3 analysesCommon to the 3 analyses
• 618 pb618 pb-1-1 from 189 GeV to 209 GeV from 189 GeV to 209 GeV– Use the WW selectionUse the WW selection
– 189 GeV data re-analysed with the new analyses189 GeV data re-analysed with the new analyses
Data Data analysisanalysis
Data Data analysisanalysis • Similar to other Higgs analysesSimilar to other Higgs analyses
– pre-select events with cutspre-select events with cuts
– use a multivariate analysis (LDA) to select use a multivariate analysis (LDA) to select
optimally the candidatesoptimally the candidates
– calculate CLcalculate CLss with clfft with a discriminant variable with clfft with a discriminant variable
(mass or LDA)(mass or LDA)
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against If two leptons )ore(both must have: sE 1.0
WWZZ,),( elll
well within acceptance 9601 .|cos| 9602 .|cos|
against
165 170missing
missing GeVPT 10missing GeVE 80
GeVm 70
against CMSvis Em 0750.
012 )( E
44 -like
Number of positive charged tracks1Number of negative charged tracks1
Force in 2 jets )/( 23 cGeVm jet
CLASS 11 2( )6Number of charged tracks
In each jet: number of charged tracks 0
selectionselection selectionselection
Selects 45 evts(exp. 40.63)
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selection efficiencyselection efficiency selection efficiencyselection efficiency Background Background
compositioncomposition Background Background
compositioncomposition
W+W- 80%
-> l+l- 6.4%
ZZ 6%
+- 5.3%
We, Zee,… 2.3%
Then corrected for E12=0 cut (8%in ‘ 98, 6.5% in ‘ 99, 7% in 2000)
M H+
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• Multivariate analysisMultivariate analysis– Linearly combine the Linearly combine the
variables of the variables of the
preselection, plus the preselection, plus the
charge-tagged charge-tagged polar polar
angleangle
H
1
2
H
W
W
2
1
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• LDA OptimizationLDA Optimization– 4 variables are 4 variables are
sufficient:sufficient:
1/2 (Q1/2 (Q11coscos11+ Q+ Q22coscos22))
angle angle between taus between taus
event missing Pevent missing PTT
yy2323
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Angle between jets
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Use this optimal linear combination as a discriminant in CL calculation.
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For each s,Signal LDA shape parametrisedby sum of 2 gaussians
and interpolated as a function of Higgs mass
Background :sum of 3 gaussians
LDA LDA
LDA LDA
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Confidence levels calculated with CLFFT
MH+
CL(s+b) / Cb 1-Cb
MH+
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Signal 85 GeV
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cscs cscs
• Select one Select one + 2 jets + missing + 2 jets + missing
energyenergy– if several if several minijets, take the one with minijets, take the one with
min min 22 of the 2C fit (E,p conservation and of the 2C fit (E,p conservation and
equality of the jet-jet and equality of the jet-jet and masses) masses)
– define a first discriminant Ddefine a first discriminant D11 combining : combining :
• the event missing pthe event missing pTT, ,
• the isolation angle the isolation angle isoiso (cone around the (cone around the
containing 5% of the energy)containing 5% of the energy)
• the the 22 of the 2C fit of the 2C fit
• the decay angle of the leptonic Higgs the decay angle of the leptonic Higgs
candidate, multiplied by the candidate, multiplied by the charge charge
• Require DRequire D11>-0.1>-0.1
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cscs cscs
• define a second discriminant Ddefine a second discriminant D22
combining :combining :• the decay angle of the leptonic Higgs the decay angle of the leptonic Higgs
candidate, multiplied by the candidate, multiplied by the charge charge
• a a polarisation estimator polarisation estimator
• Require DRequire D22>-0.3>-0.3
– efficiency from 49.1% for MH=60 GeV efficiency from 49.1% for MH=60 GeV
to 38.8% for MH=80 GeVto 38.8% for MH=80 GeV
• Background compositionBackground composition
– 93% WW93% WW– rest is Werest is We, ZZ and qq, ZZ and qq
Selects 279 evts(289.3 expected)
Year 2000 data
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cscs cscs
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cscscscs cscscscs
•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 2
•calculate m with rescaled jet energies ( fixed) and require m<30 GeV
•Perform a LDA (optimized on a cocktail of higgs masses 80 to 88 GeV) with:
•Production angle
• m
• 25C/Ndof
•E jet min * jet-jet min
•log10 (QCD matrix element)
Cut D3>1.3
Selects 2762 evts
(2892 expected)
BG: 78%WW
10% qq
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cscscscs cscscscs
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cscscscs cscscscs
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cscscscs cscscscs W mass set to 80.45 GeV
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cscscscs cscscscs Confidence levels calculated with CLFFT
MH+ MH+
1-CbCL(s+b) / Cb
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Systematic effectsSystematic effects Systematic effectsSystematic 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 cs and +-0.3% for cscs•for cscs: shift all variables by 1 of their mean:0.5%
background normalisation :•WW cross-section taken from RACOON: lower KORALW by 2.5%•WW cross-section uncertainty 2%• ->leptons cross-section uncertainty 5% for • qq cross-section uncertainty 5%•for cscs: shift all variables by 1 of their mean:0.5%•calorimeter calibration : vary had/em scale by 2%/0.7%
29/11/2001 Search for charged Higgs bosons 23
SystematicsSystematics SystematicsSystematics
%
cs%
cscs%
Signal .MC statothers
2.72.41.
3.22.91.4
1.81.31.2
BG norm.MC statothers
2.11.21.7
4.32.53.5
3.00.52.9
norm
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FINAL FINAL RESULTSRESULTSFINAL FINAL RESULTSRESULTS
95 % C.L. limits in GeV
including systematics
BR(H->)=0 80.4 (exp. 78.2)
BR(H->)=1. 87.7 (exp. 89.2)
Any BR 79.2 (exp. 77.1)
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COMPARISON WITH OTHER EXPERIMENTSCOMPARISON WITH OTHER EXPERIMENTSCOMPARISON WITH OTHER EXPERIMENTSCOMPARISON WITH OTHER EXPERIMENTS
ALEPH DELPHI L3 OPAL
BR=0 80.4(78.2)
77.4(77.0)
77.2(77.1)
76.2(77.1)
BR=1 87.7(89.2)
85.4(89.3)
84.9(83.0)
84.5(86.5)
ANY BR 79.2(77.1)
73.8(75.4)
67.1(75.0)
72.2(74.5)
(*) summer 2001
***
Obs
(exp)