searches for the standard model higgs boson at lhc a. nikitenko, ic, london. on leave from itep,...
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Searches for the Standard ModelSearches for the Standard ModelHiggs boson at LHCHiggs boson at LHC
A. Nikitenko, IC, London. On leave from ITEP, MoscowA. Nikitenko, IC, London. On leave from ITEP, Moscow
ICHEP2006, EW session, July 28, 2006ICHEP2006, EW session, July 28, 2006
CERN, Building 40
CMS ATLAS
Emphasize will be given to the new CMS PTDR results obtained at L=2x1033cm-2s-1
http://cmsdoc.cern.ch/cms/cpt/tdr/
CERN/LHCC 2006-001 CERN/LHCC 2006-021
Published printed in July 2006
LHC : 27 km long100m underground
General Purpose,pp, heavy ions
General Purpose,pp, heavy ions
CMS+TOTEM
ATLAS
Heavy ions, pp
ALICE
pp, B-Physics,CP Violation
The CMS Detector The CMS Detector today at point 5today at point 5
The ATLAS The ATLAS Barrel Toroid.Barrel Toroid.End of November 2005End of November 2005
SM Higgs mass constraints from the data and theorySM Higgs mass constraints from the data and theory
Indirect constraints from precision EW data : MH < 260 GeV at 95 %CL (2004) MH < 186 GeV with Run-I/II prelim. (2005) MH < 166 GeV (2006)
ExperimentExperiment SM theorySM theory
The triviality (upper) bound andvacuum stability (lower) bound asfunction of the cut-off scale “triviality” : Higgs self-coupling remains finite Direct limit from LEP: MH > 114.4 GeV
NLO
SM Higgs boson couplings and Br. ratiosSM Higgs boson couplings and Br. ratios
v is vev of Higgs field = 246 GeV
Right bottom plot includes uncertainties fromthe quark masses mt, mb, mc and s(MZ)
tree level couplingsDjouadi, Kalinowski, Spira
• Discovery of the inclusive Higgs boson Discovery of the inclusive Higgs boson production with decay modes:production with decay modes:– H->ZZ->4lH->ZZ->4l– H->H->– H->WW->2lH->WW->2l
H->ZZH->ZZ(*)(*)->4->4ll - golden mode - golden mode (first studies in CMS in 1995)(first studies in CMS in 1995)
Background: tt, ZZ, Background: tt, ZZ, llllbb (“Zbb”)bb (“Zbb”)
Selections :Selections :- lepton isolation in tracker and calolepton isolation in tracker and calo- lepton impact parameter, lepton impact parameter, , ee vertex , ee vertex - mass windows Mmass windows MZ(*)Z(*), M, MHH
H->ZZ->ee
H->ZZ->4lH->ZZ->4l
• New elements of analysis:
– ZZ background: NLO k factor depends on m4l
– background from side bands or from ZZ/Z; (gg->ZZ is
added as 20% of LO qq->ZZ, no good generator yet)
Signal and background at 5 sigma discoverySignal and background at 5 sigma discovery
ee ee
CMSCMSat 5at 5 sign. sign.
CMSCMSat 5at 5 sign. sign.
H->ZZ->4lH->ZZ->4l
Signal significance: new vs old results; no big changeSignal significance: new vs old results; no big change
~ 125 GeV~ 125 GeV
CP property with H->ZZ->4lCP property with H->ZZ->4l
d d ( () ~ H + ) ~ H + I + I + 22 A, A,H scalar, A – pseudoscalar,H scalar, A – pseudoscalar,=tan(=tan(), ), = +/- = +/- /2 --> A/2 --> A
C2 = Br / SM Br SM
CC22 needed to exclude SM h needed to exclude SM h
CMS CMS
Inclusive H->
CMS plot of the ECAL TDR time : December 1997CMS plot of the ECAL TDR time : December 1997
Went then from hybrid silicon + gas chamber trackerWent then from hybrid silicon + gas chamber tracker to all silicon tracker to all silicon tracker
CMSCMS CMSCMS
Discovery potential of H->
SMSM
light h->light h-> in MSSM in MSSMinclusive searchinclusive search
CMS CMS ECAL TDRECAL TDR
CMS PTDRCMS PTDR ATLASATLAS
NLONLO
count. expcount. exp
NLONLO
cut basedcut based
NLONLO
optimized*optimized*
TDR (LO)TDR (LO) New, NLONew, NLO
Cut basedCut based
New, NLONew, NLO
likelihoodlikelihood
~ 7.5~ 7.5 6.06.0 8.28.2 3.93.9 6.36.3 8.78.7
Significance for SM Higgs MSignificance for SM Higgs MHH=130 GeV for 30 fb=130 GeV for 30 fb-1-1
* NN with kinematics and * NN with kinematics and isolation as input, s/b per event isolation as input, s/b per event
Discovery of SM H->Discovery of SM H-> in associated ttH and WH in associated ttH and WH
production at high luminosityproduction at high luminosity Discovery of Wh, h->Discovery of Wh, h->Discovery of tth, h->Discovery of tth, h->
Significance of tth, h->Significance of tth, h->for 100 fbfor 100 fb-1-1
L=1034 cm-2 s-1
L=1034 cm-2 s-1
CMS
CMS
Accuracy of the Higgs boson mass Accuracy of the Higgs boson mass measurement with H->ZZ->4l and H->measurement with H->ZZ->4l and H->
Stat. error onlyStat. error only
Early discovery with H->WW->2l2Early discovery with H->WW->2l2
• New elements of analysisNew elements of analysis– PPTT Higgs and WW bkg. as at Higgs and WW bkg. as at
NLO (re-weighted in PYTHIA)NLO (re-weighted in PYTHIA)– include box gg->WW bkg.include box gg->WW bkg.– NLO Wt cross section after jet NLO Wt cross section after jet
veto veto • Backgrounds from the data Backgrounds from the data
(and theory)(and theory)– tt from the data; uncertainty tt from the data; uncertainty
16% at 5 fb16% at 5 fb-1-1
– WW from the data; uncertainty WW from the data; uncertainty 17% at 5 fb17% at 5 fb-1-1
– Wt and gg->WW bkg from theor. Wt and gg->WW bkg from theor. uncertainty 22% and 30% uncertainty 22% and 30%
after cuts: - ET
miss > 50 GeV - jet veto in < 2.4 - 30 <pT
l max<55 GeV - pT l min > 25 GeV - 12 < mll < 40 GeV
Discovery reach with H->WW->2lDiscovery reach with H->WW->2l
Excluded cross section timesBranching Ratio at 95% C.L. CMS Phys. TDR 2006CMS Phys. TDR 2006
very similar to old results w/o syst.
Luminosity needed for 5 Luminosity needed for 5 discovery discoveryfor incl. Higgs boson production for incl. Higgs boson production
Discovery of qqH associated Discovery of qqH associated production (Weak Boson Fusion)production (Weak Boson Fusion)
qq->qqHqq->qqH
(written in 2005)
Jet veto (“rapidity gap”) in VBF (WW->H) productionfirst discussed in :Yu. Dokshitzer, V. Khoze and S. Troyan, Sov.J.Nucl. Phys. 46 (1987) 712Yu. Dokshitzer, V. Khoze and T. Sjostrand, Phys.Lett., B274 (1992) 116
From D. Zeppenfeld; talk on TeV4LHC, 2004
First, full simulation analysis ofFirst, full simulation analysis ofqqH, H->qqH, H->->l+jet ->l+jet
Discovery in Standard ModelDiscovery in Standard Model
discoverydiscoveryof light hof light h in MSSM in MSSM
CMSCMSSMSM
Summary of SM Higgs boson discovery: Summary of SM Higgs boson discovery:
Signal Significance for 30 fbSignal Significance for 30 fb-1-1
with K factors
ATLAS h->ATLAS h-> sensitivity is now comparable with CMS sensitivity is now comparable with CMSCMS ttH, H->bb does not have even 3 CMS ttH, H->bb does not have even 3 with 60 fb with 60 fb-1-1
ATL-PHYS-PUB-2003/030
Measurement of the SM Higgs boson couplingsMeasurement of the SM Higgs boson couplings
ConclusionsConclusions• The latest simulation studies show: The latest simulation studies show:
– Inclusive h->2Inclusive h->2 could be discovered with < 10fb could be discovered with < 10fb-1-1
– almost no change in the discovery potential with almost no change in the discovery potential with H->ZZ->4l and H->WW->2l. H->ZZ->4l and H->WW->2l. – tth, h->bb is lost as CMS discovery channel even with tth, h->bb is lost as CMS discovery channel even with
60 fb60 fb-1-1
– qqh, h->qqh, h-> “survived” after full simulation ! The “survived” after full simulation ! The biggest discovery reach in Mbiggest discovery reach in MAA-tan -tan
– Mass measurement 0.1-1.0 % precisionMass measurement 0.1-1.0 % precision– Width measurement 10-5 % precision, MWidth measurement 10-5 % precision, MHH > 200 GeV > 200 GeV– CP with H->ZZCP with H->ZZ– Ratio of couplings: ~ 5-30 % Ratio of couplings: ~ 5-30 %
BACKUP
discrepancy from the SM for light h
M. Duhrssen et al.,hep-ph/0407190
Can MSSM be distinguished from SM in the area of only light Higgs discovery ?
Total weight 12500 tOverall diameter 15 mOverall length 21.6 m
Physics runs 2008-2009Physics runs 2008-2009
First , we should First , we should “discover” Standard Model“discover” Standard Model
~ 10~ 107-87-8 Z->ll, W->l Z->ll, W->l on tape during on tape during physics run in 2008-09 (~ 10fbphysics run in 2008-09 (~ 10fb-1 -1 ?)?)
Z, W, tt cross sections and expectedZ, W, tt cross sections and expectednumber of events after trigger in CMSnumber of events after trigger in CMS with 10 fbwith 10 fb-1-1
W/Z+nJ+X NLOpredictions at LHCwith cuts :
pTl > 15 GeV
|l| < 2.4 pT
j > 20 GeV |j| < 4.5 Rlj > 0.4 Rll > 0.2
W/Z bb + X |b| < 2.5
J. Campbell, R.K. Ellis, D. Rainwaterhep-ph/0308195
~ 106 tt->+X with 10 fb-1
W/Z+nJets is very important background for Higgs at LHC
topologytopology Background for Higgs channel (one example)Background for Higgs channel (one example)
W+1j+XW+1j+X gg->h->WW*->2l gg->h->WW*->2l W+2j+XW+2j+X MSSM gg->bbH, H->MSSM gg->bbH, H->->->ll+jet (one b-tag)+jet (one b-tag)W+3j+XW+3j+X VBF qq->qqh, h->VBF qq->qqh, h->->->ll+jet + 2 tag. jets+jet + 2 tag. jetsW+4j+XW+4j+X VBF qq->qqh, h->WW->VBF qq->qqh, h->WW->lljj + 2 tag jetsjj + 2 tag jetsZ+1j+XZ+1j+X MSSM gg->bbH, H->MSSM gg->bbH, H->->l+jet (one b-tag)->l+jet (one b-tag)Z+2j+XZ+2j+X VBF qq->qqh, h->VBF qq->qqh, h->->->ll+jet + 2 tag jets+jet + 2 tag jetsZ+4j+XZ+4j+X VBF qq->qqh, h->ZZ->VBF qq->qqh, h->ZZ->lllljj + 2 tag jetsjj + 2 tag jets
Zbb,Zcc, Wbb, Wcc (W/Z+QQ+nj) are as important as W/Z+njZbb,Zcc, Wbb, Wcc (W/Z+QQ+nj) are as important as W/Z+nj
• Discovery potential for the Higgs boson(s) Discovery potential for the Higgs boson(s) in CMS is updated in comparison with in CMS is updated in comparison with
Higgs Summary Note, CMS Note 2003 :Higgs Summary Note, CMS Note 2003 :– Latest trigger tableLatest trigger table– Bkg estimates from “data” and exp. Bkg estimates from “data” and exp.
systematicssystematics– Advanced generators for multi-jet events: Advanced generators for multi-jet events:
ALPGEN, MadGraph, CompHEP, TopRexALPGEN, MadGraph, CompHEP, TopRex– almost all analyses use full G4 simulation data almost all analyses use full G4 simulation data
New elements of PTDR 2006 analysis:New elements of PTDR 2006 analysis: - splitting into categories depending of R- splitting into categories depending of R99=E(3x3)/E=E(3x3)/Escsc and and regions regions
- usage of LLR for discovery, systematic- usage of LLR for discovery, systematic - - “optimized analysis” – NN with kinematics and “optimized analysis” – NN with kinematics and isolation as input, isolation as input, s/b per events/b per event
barrel with large Rbarrel with large R99 barrel with small Rbarrel with small R99
endcaps with large Rendcaps with large R99 endcaps with small Rendcaps with small R99
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