Search for MSSM neutral Higgs bosons in the decay channel AH with the ATLAS detector

1
Search for MSSM neutral Higgs bosons in the decay
channel A/H?µµ- with the ATLAS detector

• Giorgos Dedes , Nectarios Benekos , Sandra Horvat
  , Sergey Kotov, Hubert Kroha, and Susanne
  Mohrdieck Möck
• Max-Planck-Institut für Physik, München
• Deutsche Physikalische Gesellschaft,
  Dortmund 2006

2
Outline

• The bbA, A-gtmm- decay channel
• Muon distributions (ATLFAST Full Simulation)
• b-jet distributions (ATLFAST Full Simulation)
• Analysis results
• Cut optimization
• Additional cuts improvements
• Summary

3
Processes

• bbH/A, H/A-gt mm- for tanb 30 , L 30fb-1

4
Data Samples

• ATLFAST
• Pythia
• No filters

• Full Simulation
• Pythia

• bbA
• MultiLeptonFilter
• Generated only events with
• plT gt 5 GeV , hl lt2.7

• tt
• HiggsMultiLeptonFilter
• Generated only events with
• mll gt 180 GeV, plT gt 5 GeV , hl lt 2.7
• Approximately 10 of events passed in the
  specified mass range

5
Muon Reconstruction (bbA sample, 300 GeV)
Dpt/pt of matched muons
Deta/eta of matched muons
sFull 3.4
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 gt 5 GeV , h lt 2.7
• no muon isolation

MeV
Efficiency in eta
Efficiency in phi

• Average muon
• reconstruction efficiency 90

6
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 gt 15 GeV , h lt 2.5
• Likelihood b-tagging variable used (gt0.9)
• 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

7
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 eta
bjet phi
Number of reco bjets
8
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
9
Selection Cuts (TDR)
Fully simulated data
1.
Normalized number of events
10
Results TDR cuts

• bbA, A-gt mm- for tanb 30 , L 30fb-1

Z background
A boson invariant mass (ATLFAST)
A boson invariant mass (Full Sim)
MeV
MeV
11
Results TDR cuts

• bbA, A-gt mm- 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
12
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
13
Additional Cut (in FullSim)

• Muons from A are mostly back to back in the phi
  plane (single body decay)
• ?f-gt 3.14
• In the case of tt background this is not so
  pronounced -gt broader distribution

Muons ?f
Normalized number of events

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

?f gt 2.7
14
Summary

• Study of the A(H) discovery potential in the A -gt
  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 ?fµµ used and
  improved signal significance