search for mssm neutral higgs bosons in the decay channel a h with the atlas detector
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Search for MSSM neutral Higgs bosons in the decay channel A/H→ μ + μ - with the ATLAS detector. Giorgos Dedes , Nectarios Benekos , Sandra Horvat , Sergey Kotov, Hubert Kroha, and Susanne Mohrdieck – M ö ck Max-Planck-Institut f ü r Physik, M ü nchen

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search for mssm neutral higgs bosons in the decay channel a h with the atlas detector

Search for MSSM neutral Higgs bosons in the decay channel A/H→μ+μ-with the ATLAS detector

Giorgos Dedes , Nectarios Benekos , Sandra Horvat , Sergey Kotov, Hubert Kroha, and Susanne Mohrdieck – Möck

Max-Planck-Institut für Physik,München

DeutschePhysikalischeGesellschaft, Dortmund 2006

outline
Outline
  • The bbA, A->m+m- decay channel
  • Muon distributions (ATLFAST – Full Simulation)
  • b-jet distributions (ATLFAST – Full Simulation)
  • Analysis results
  • Cut optimization
  • Additional cuts – improvements
  • Summary
processes
Processes
  • bbH/A, H/A-> m+m- for tanb = 30 , L= 30fb-1
data samples
Data Samples

ATLFAST

  • Pythia
  • No filters

Full Simulation

  • Pythia

bbA:

MultiLeptonFilter:

  • Generated only events with

plT > 5 GeV , |hl|<2.7

tt:

HiggsMultiLeptonFilter:

  • Generated only events with

mll> 180 GeV, plT > 5 GeV , |hl|< 2.7

  • Approximately 10% of events passed in the specified mass range
muon reconstruction bba sample 300 gev

ATLFAST

FullSim

Muon Reconstruction (bbA sample, 300 GeV)

Dpt/pt of matched muons

Deta/eta of matched muons

sFull = 3.4%

Average muon

reconstruction efficiency ~ 90%

sATLFAST = 3.2%

Deta/eta of matched muons

Efficiency in pt

ATLFAST (8.7.0): CBNT

Full sim (10.0.4): AOD

  • high-pt muons
  • pT > 5 GeV , |h|< 2.7
  • no muon isolation

MeV

Efficiency in eta

Efficiency in phi

b jet recostruction bba sample 300 gev

Dpt/pt of matched bjets

Deta/eta of matched muons

ATLFAST

FullSim

b-jet Recostruction (bbA sample, 300 GeV)

sATLFAST = 18%

sFull = 24%

Dphi/phi of matched bjets

Efficiency in pt

ATLFAST (8.7.0): CBNT

Full sim (10.0.4): AOD

  • pT > 15 GeV , |h|< 2.5
  • Likelihood b-tagging variable used (>0.9)
  • Gen_AOD container for truth

MeV

Efficiency in eta

Efficiency in phi

  • Full simulation: Average b-jet efficiency of ~ 45%
  • ATLFAST: Average b-jet efficiency of ~ 35%
muon b jet distributions bba sample 300 gev

ATLFAST

FullSim

Muon/b-jet Distributions(bbA sample, 300 GeV)
  • Very good agreement between fast and full simulation

Single muon pt

Single muon phi

Single muon eta

Normalized number of events

MeV

Number of reco muons

bjet pt

H pt

MeV

MeV

bjet phi

bjet eta

Number of reco bjets

e t miss distributions

ATLFAST

FullSim

ETmiss Distributions
  • In 10.0.4 data contribution from muons made ETmiss broader

MET_Calo + MET_Cryo + MET_Muon

bbA sample

  • The contribution in missing energy from the muon spectrometer

is- p2mx(y)

We correct by adding this value to

MET_Topox(y) + MET_Cryox(y)

instead of MET_Muonx(y)

MeV

MET_Topo + MET_Cryo + MET_Muon

bbA sample

MeV

MET_Topo + MET_Cryo + reco dimuon PT

MET_Topo + MET_Cryo + MET_TruthMu

bbA sample

bbA sample

MeV

MeV

selection cuts tdr

pT > 20 GeV , trigger selection

pTmiss< 20 GeV

2.

pTm> 20 GeV

pT /MeV

pTmiss /MeV

pTmiss < 20 GeV

pT2m< 100 GeV

N(b-jets) > 0

pT2m< 100 GeV

3.

4.

Event Loop

tt

N(b- jets) = 0

N(b- jets) > 0

bbA

pT2m/MeV

m2m = mA±dm

m2m = mA±dm

Selection Cuts (TDR)

Fully simulated data

1.

Normalized number of events

results tdr cuts

bbA

tt

bbA + tt

bbA

tt

bbA + tt

Z

Results – TDR cuts
  • bbA, A-> m+m- for tanb = 30 , L= 30fb-1

*Z background

A boson invariant mass (ATLFAST)

A boson invariant mass (Full Sim)

MeV

MeV

results tdr cuts1

bbA

tt

bbA + tt

bbA

tt

bbA + tt

Z

Results – TDR cuts
  • bbA, A-> m+m- for tanb = 30 , L= 30fb-1

*With Z background included

H/A boson invariant mass (ATLFAST)

H/A boson invariant mass (Full Sim)

MeV

MeV

cuts optimization

bbA (full)

tt (full)

bbA (fast)

tt (fast)

Cuts Optimization
  • We tune the selection cuts in fast and full simulation by maximizing signal/background ratio for each step

Normalized number of events

pTbjet /MeV

additional cut in fullsim

bbA

tt

Additional Cut (in FullSim)
  • Muons from A are mostly back to back in the phi plane (single body decay)

Δφ-> 3.14

  • In the case of tt background this is not so pronounced -> broader distribution

Muons Δφ

Normalized number of events

  • The value of this cut is obtained through the same method for optimizing signal/background ratio

Δφ > 2.7

summary
Summary
  • Study of the A(H) discovery potential in the A -> μ+μ-decay channel , using ATLFAST and fully simulated data
  • ATLFAST and Full simulation are in good agreement except for b-jet efficiency (better in fullsim) and Etmiss (correction applied)
  • Selection cuts were optimized leading to the improvement of the signal significance
  • Additional selection on pTbjet and Δφμμ used and improved signal significance
ad