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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,

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Presentation on theme: "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,"— Presentation transcript:

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 Deutsche Physikalische Gesellschaft, 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 59.6 fb
Higgs mass 150 GeV 200 GeV 300 GeV 350 GeV 450 GeV sxBR bbA 59.6 fb 20.9 fb 4.2 fb 2.2 fb 0.7 fb bbH 57.2 fb 20.8 fb

4 Data Samples Full bbH/A tt Z Z+jets ATLFAST (CBNT – 8.7.0)
Pythia No filters ATLFAST (CBNT – 8.7.0) Full (AOD ) bbH/A mH/A = 150 GeV 20k events --- mH/A = 200 GeV (only A) mH/A = 300 GeV 32k events mH/A = 350 GeV mH/A = 450 GeV 18k events tt 1M events 90k events Z Z+jets 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 Muon Reconstruction (bbA sample, 300 GeV)
Dpt/pt of matched muons Deta/eta of matched muons sFull = 3.4% sATLFAST = 3.2% ATLFAST FullSim 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 Average muon reconstruction efficiency ~ 90%

6 b-jet Recostruction (bbA sample, 300 GeV)
Dpt/pt of matched bjets Deta/eta of matched muons sATLFAST = 18% sFull = 24% ATLFAST FullSim 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 Muon/b-jet Distributions (bbA sample, 300 GeV)
ATLFAST FullSim 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 ETmiss Distributions In data contribution from muons made ETmiss broader MET_Calo + MET_Cryo + MET_Muon bbA sample ATLFAST FullSim 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
Selection Cuts (TDR) Fully simulated data bbA tt Event Loop pTm > 20 GeV pTmiss < 20 GeV pT2m < 100 GeV m2m = mA ± dm N(b- jets) = 0 N(b- jets) > 0 pT /MeV pT > 20 GeV , trigger selection pTmiss < 20 GeV 2. pTmiss /MeV 1. Normalized number of events pT2m /MeV 3. pT2m < 100 GeV N(b-jets) > 0 4.

10 A boson invariant mass (ATLFAST) A boson invariant mass (Full Sim)
Results – TDR cuts bbA, A-> m+m- for tanb = 30 , L= 30fb-1 150GeV 200GeV 300GeV 350GeV 450GeV S/√B ATLFAST 14.3 (7.6*) 6.5 (2.9*) 1.9 1.0 0.3 S/√B Full simulation --- 5.4 1.7 0.5 *Z background A boson invariant mass (ATLFAST) A boson invariant mass (Full Sim) bbA tt bbA + tt Z bbA tt bbA + tt MeV MeV

11 H/A boson invariant mass (ATLFAST) H/A boson invariant mass (Full Sim)
Results – TDR cuts bbA, A-> m+m- for tanb = 30 , L= 30fb-1 150GeV 200GeV 300GeV 350GeV 450GeV S/√B ATLFAST 14.3 (7.6*) 6.5 (2.9*) 1.9 1.0 0.3 S/√B Full simulation --- 5.4 1.7 0.5 *With Z background included H/A boson invariant mass (ATLFAST) H/A boson invariant mass (Full Sim) bbA tt bbA + tt Z bbA tt bbA + tt MeV MeV

12 Full Simulation optimized Normalized number of events
Cuts Optimization We tune the selection cuts in fast and full simulation by maximizing signal/background ratio for each step TDR cuts ATLFAST optimized Full Simulation optimized ETmiss 20 GeV 17 GeV 26 GeV pT2m 100 GeV 48 GeV 50 GeV pTbjet --- 35 GeV bbA (full) tt (full) tt (fast) bbA (fast) 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) Δφ-> 3.14 In the case of tt background this is not so pronounced -> broader distribution Muons Δφ Normalized number of events bbA tt The value of this cut is obtained through the same method for optimizing signal/background ratio Δφ > 2.7 150GeV 200GeV 300GeV 350GeV 450GeV S/√B ATLFAST (opt) / (TDR) 26.8 / 14.3 10.1 / 6.5 3.0 / 1.9 1.5 / 1.0 0.7 / 0.3 S/√B Full simulation (opt) / (TDR) --- 7.2 / 5.4 2.4 / 1.7 0.4 / 0.5 S/√B Full simulation (+ Δφ) 19.8 2.5 0.4

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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