Hggs-D meeting MPI 11/2006 1

Higgs Physics – Activities in Bonn/Siegen

Jörn Große-Knetter

ATLAS-Higgs-D TreffenMünchen, 28.11.2006

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Outline• VBF Fusion:

• forward jet tagging• central jet veto: NLO with SHERPA, different

underlying event / PS models• tau tagging• Zjj background estimate for H from data• W+jets background studies (M. Rast, not shown

here)• LVL1 trigger studies for Hinvisible

• Other non-VBF studies not shown here

• Plans/potential for collaboration

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comparison of different jet algorithms (cone, KT with diff. par‘s), different generators (PYTHIA/HERWIG) and processes (dijet/VBF)

efficiencies, fake rates, out of jet corrections

different jet algos – eff. vs. eta and Pt matching between truth jets (hadron level) and reco jets within a ΔR

Forward Jet Studies (Iris Rottländer)

Cone 07 Cone 04 ● : Tower o: Topo

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• Jets from hard process found easier than jets from shower• Forward region: jets from VBF found easier than jets from QCD• Maybe slight dependence on generator (shower & fragmentation model)

Pythia QCD ForwardjetsHerwig QCD DijetsPythia 6.3 VBF H->tautau->llHerwig VBF H->tautau->ll

Different MC Generators and Topologies

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Central Jet Veto, NLO (Talea Köchling)• Goal: study effects of NLO on sensitivity esp. jet veto with SHERPA

• Def.: 1st and 2nd jet tagging jets, 3rd jet apply veto Signal: 3rd jet properties (including underlying event)

momentum: SHERPA3j>PYTHIA>SHERPA2JEt>HERWIG

rapidity: SHERPA agree well, HERWIG slightly wider, PYTHIA??

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Survial Probability w.r.t central jet vetoSignal w/o underlying event Signal with underlying event

Veto jets with Pt > x GeV)Veto jets with Pt > x GeV)• SHERPA H+2j and H+3j agree well „NLO“ effect seems small?

• signficant difference among different MC generators

• reason not yet understood

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Survial Probability w.r.t central jet vetoZjj(EW) w/o underlying event Zjj(QCD) with underlying event

Veto jets with Pt > x GeV)Veto jets with Pt > x GeV)• SHERPA H+2j and H+3j agree well only for EW process

• signficant difference in QCD process

• reason not yet understood

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-ID for VBF Hlh (A. Veenendaal) from VBF Higgs decay have relatively low pT

• Check performance of ID of hadronic decays for this channel – tauRec and 1P3P

• Look for best discrimination method against Wlepton + jets background

• Own production (CSC not ready) low MC statistics

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Comparison tauRec/tau1P3P

• Find best working point: tauRec better for pT>20GeV, 1P3P for pT<20GeV

• Combine both algorithms?

10 GeV < pT < 20 GeVavg. over all pT

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• Idea: jjZμμ and jjZμμ with identical topology

muons are MIPS same energy deposition in calorimeters (checked!)

only difference: momentum spectra of muons

• Method: select Z μμ events

„randomise“ μ-momenta according to Z μμ4ν MC (works!)

apply „usual“ selection and mass reconstruction

shape of backgroundcan be extracted precisely from data itself

towards mass determination:

- subtract BG prediction

- Gaussian fit mass

VBF, H: determination of bkgr. from data (M. Schmitz)

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Prospects for mass determination with limited luminosity 30fb-1, only decay

6 out of 8 fits fine

120fb-1, decay=30fb-1, ll decays?

all fits fine

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Invisible Higgs boson decaysinvisble Higgs decays: SUSY HLSP LSP, ADD, Majoron,…

VBF most sensitive, but how to trigger on 2 jets + missing energy? LVL1 trigger study for jets including FCAL

95% CL exclusion with 30 fb-1VBF result assumes trigger on jets up to = 4.9

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Ongoing LVL1 Trigger Study (Guilherme Hanninger)

Goal: determine efficiencies and rates for various options of trigger menues for combinations of ET miss + central jet + forward jet

“plain cuts”:

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Estimation of LVL1 trigger efficiencies, rates

• Maybe forward + central good for background rejection? • Gain from using topological cuts: re-define boundaries?• QCD: LVL1 output rates extremely sensitive to ETmiss

topological cuts:

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Plans, collaboration options• Tools:

– Forward jet tagging:• Continue jet efficiency, jet energy scale studies• Effects of pile-up, underlying event

– Tau ID:• Check other background to VBF Higgs sample• Look for improvement in the few-10GeV pT region, revise LLH/NN

with Higgs and its backgrd. samples• Analysis:

– Study central jet veto• tune cuts to be less sensitive to MC models• Continue SHERPA studies

– Continue invisible Higgs trigger studies: LV2, EF ?– Continue Zjj background studies: e-channel– Background studies (e.g. W+jets bg.)– Start HWW analysis?