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

C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 5

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

C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 6

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

C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 7

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

C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 8

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

C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 9

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

C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 10

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

C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 11

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

C. Charlot, LOUISE09, Higgs search in H->ZZ/WW decay channels with the CMS detector 13

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!