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Higgs Physics – Activities in Bonn/Siegen. Jörn Große-Knetter ATLAS-Higgs-D Treffen München, 28.11.2006. 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

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higgs physics activities in bonn siegen

Higgs Physics – Activities in Bonn/Siegen

Jörn Große-Knetter

ATLAS-Higgs-D Treffen

München, 28.11.2006

Hggs-D meeting MPI 11/2006

outline
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 Hinvisible
  • Other non-VBF studies not shown here
  • Plans/potential for collaboration

Hggs-D meeting MPI 11/2006

slide3

Forward Jet Studies(Iris Rottländer)

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

matching between truth jets (hadron level) and reco jets within a ΔR

different jet algos – eff. vs. eta and Pt

Cone 07

Cone 04

●:Tower

o: Topo

Hggs-D meeting MPI 11/2006

slide4

Different MC Generators and Topologies

Pythia QCD Forwardjets

Herwig QCD Dijets

Pythia 6.3 VBF H->tautau->ll

Herwig VBF H->tautau->ll

  • 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)

Hggs-D meeting MPI 11/2006

central jet veto nlo talea k chling
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??

Hggs-D meeting MPI 11/2006

survial probability w r t central jet veto
Survial Probability w.r.t central jet veto

Signal 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

Hggs-D meeting MPI 11/2006

survial probability w r t central jet veto1
Survial Probability w.r.t central jet veto

Zjj(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

Hggs-D meeting MPI 11/2006

id for vbf h lh a veenendaal
-ID for VBF Hlh(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 Wlepton + jets background
  • Own production (CSC not ready)  low MC statistics

Hggs-D meeting MPI 11/2006

comparison taurec tau1p3p
Comparison tauRec/tau1P3P

avg. over all pT

10 GeV < pT < 20 GeV

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

Hggs-D meeting MPI 11/2006

slide10

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

  • Idea:jjZμμandjjZμμwith 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   μμ4νMC (works!)
  • apply „usual“ selection and mass reconstruction

shape of background

can be extracted precisely

from data itself

towards mass determination:

- subtract BG prediction

- Gaussian fit  mass

Hggs-D meeting MPI 11/2006

prospects for mass determination with limited luminosity
Prospects for mass determination with limited luminosity

30fb-1, only  mm decay

6 out of 8 fits fine

120fb-1,  mm decay

=30fb-1, ll decays?

all fits fine

Hggs-D meeting MPI 11/2006

invisible higgs boson decays
Invisible Higgs boson decays

invisble Higgs decays: SUSY HLSP LSP, ADD, Majoron,…

95% CL exclusion

with 30 fb-1

VBF result assumes trigger on jets up to h = 4.9

VBF most sensitive, but how to trigger on 2 jets + missing energy?

 LVL1 trigger study for jets including FCAL

Hggs-D meeting MPI 11/2006

ongoing lvl1 trigger study guilherme hanninger
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”:

Hggs-D meeting MPI 11/2006

estimation of lvl1 trigger efficiencies rates
Estimation of LVL1 trigger efficiencies, rates

topological cuts:

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

Hggs-D meeting MPI 11/2006

plans collaboration options
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 HWW analysis?

Hggs-D meeting MPI 11/2006

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