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

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  1. 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

  2. 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

  3. Processes • bbH/A, H/A-> m+m- for tanb = 30 , L= 30fb-1

  4. 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

  5. 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

  6. 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%

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

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