Detector Optimization Studies and Light Higgs Decay into Muons at CLIC
Higgs search in H ZZ/WW decay channels with the CMS detector
description
Transcript of Higgs search in H ZZ/WW decay channels with the CMS detector
Higgs search in HZZ/WW decay channels with the CMS detector
Claude CharlotLLR - École Polytechnique
for the CMS collaboration
C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 2
Outline
LHC & CMS detector SM Higgs at the LHC HWWll selection HZZllll selection Expected sensitivity for both channels Combined sensitivity 10 TeV projection Conclusions
C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 3
The Large Hadron Collider
pp collider at CERN, s=14 TeV
Start operation in late 2009 10 TeV for this run ~200pb-1 expected
by automn 2010 Two general multi-
purpose experiments CMS and ATLAS
understanding EWK symmetry breaking among the main goals
C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 4
The CMS Detector
MUON BARREL
ECAL
Cathode Strip Chambers Drift Tube
Resistive Plate
SUPERCONDUCTINGCOIL
TRACKER
HCALPlastic scintillator/brasssandwich
silicium (200m2) PIXEL (rT<11cm)3 layers (barrel)2x2disks (fwd)SST (rT<120cm)>8 hits, depending on
||<2.6
||<2.4
Scintillating PbWO4 crystals (~80000 )36 supermodules (EB)4 dees (EE)Preshower (EE)
Drift tubes (||<1.2)Cathode strip chambers (0.9<||<2.4)Resistive plate chambers
MUON
e: (E)/E ~ 0.5% @100 GeV: (p)/p ~ 1% @100 GeV
3.8T
weight: 12,500 tdiameter: 15 mlength: 21.6 m
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SM Higgs at the LHC Higgs production cross-section
(NLO): 0.1-50 fb gluon fusion dominates at LHC
Especialy at low mH Factor ~10 @ 100 GeV
Here results for inclusive production
HWW(*) and HZZ(*) are main discovery channels Highest BRs for mH>~2mW
Clean leptonic decay modes BR(Wl): 10.8%; BR(Zl+l-):3.4%
Cover high mH region and down to ~2mW
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HWWll: selection Event topology: 2 isolated high pT leptons + ET
miss, no hadr. activity Main backgrounds: tt , Drell-Yan, WW, WZ,
ZZ, tW, W+jets
Main selection observables Central jet veto Angular correlations btw leptons Dilepton mass, ET
miss, leptons pT
Other discriminants also used in NN analysis
After preselection and CJV
Preselection to select leptonic WW events Single lepton triggers Exactly 2 isolated leptons opp. charge
pT1,2>10 GeV or at least one pT>20 GeV
ETmiss > 30 GeV
mll>12 GeV
Jets:ET>15 GeV
||<2.5
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HZZllll: selection Event topology : 4 isolated leptons Main backgrounds (after presel.): tt, Zbb , ZZ
Preselection to supress backgds involving fake leptons
Single and double lepton triggers >=2 pairs of opposite charge, matching flavors leptons
pTlepton>5 GeV
mll>12 GeV (all pairs) m4l>100 GeV (at least one) Loose isolation
Selection to further reduce irreducible backgds (mH independant )
Isolation (Iso3+Iso4), IP pT
e>7 GeV, pT>5GeV
50< mZ<100 GeV 20<mZ*<100 GeV
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Systematics and control from data
Lepton efficiencies measured from Zll candel using tag and probe method
In WW analysis, control of background is crucial tt and WW from control region close to signal region but with low
signal contribution tt using signal preselection but inverting the CJV (2 jets) WW using signal preselection and mll>115 GeV
W+jets from P(jetlepton) from jet triggers and using signal selection with only 1 identified lepton (pT>20) and 1 jet (pT>10)
In ZZ analysis, systematic on lepton isolation from UE and pileup estimated using random cone technique
ZZ background normalisation from Z data, using ZZ/Z MC ratio Zbb by inverting the isolation cuts and using mZ cut to separate
from tt and W/Z+jets
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HWWll: results Likelihood ratio method S = -2lnQ
Q = LS+B/LB
Systematic errors included
14 TeV, ∫Ldt=1fb-1
14 TeV 1fb-1
14 TeV 1fb-1
SM Higgs could be discovered for mH~2mW with 1fb-1
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HZZllll: results Counting experiment For each mH hypothesis, count
events within mH2mH Sliding window central value
(m4l) and from MC Systematic errors included
14 TeV, ∫Ldt=1fb-1
SM-like Higgs could be excluded for 185< mH<250GeV with 1fb-1
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HZZ/WW: combined sensitivity Combine channels using two different approaches: Bayesian and CLs
Different assumptions on correlations between systematic errors CLs/Bayesian ~0.91 on average
SM-like Higgs could be excluded for mH >140 GeV for 1fb-1
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HZZ/WW: 10 TeV projection
1410 TeV is approximately equivalent to a loss of a factor two in sensitivity
Most important effect is change in cross-section ggH: 10 TeV/14 TeV is ~0.54 WW/ZZ: 10 TeV/14 TeV is ~0.65
J. Stirling
Here simple rescaling of signal and main backgrounds yields from the 14 TeV analyses Full analyses for 10 TeV are
underway
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Conclusions
New CMS analyses for HWW and HZZ in leptonic modes in the context of an initial scenario
Simple cut based as well as multivariate selections (HWW) have been studied
Methods for background estimation and control from data SM Higgs could be discovered at 5 around mH=160 GeV in
WW decay mode with 1fb-1
SM Higgs could be excluded for 185<mH<250 GeV in ZZ decay mode with 1fb-1
Using both channels, SM Higgs could be excluded for mH>140 GeV with 1fb-1
10 TeV bottom line: a loss of sensitivity by a factor ~2
CMS is looking forward to the first LHC data!