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Discovery potential for the MSSM H/A  →μ + μ - decays with the ATLAS detector

Discovery potential for the MSSM H/A  →μ + μ - decays with the ATLAS detector … and other even more exotic particles. Univ. of Athens Dimitris Fassouliotis C. Kourkoumelis P. Ioannou K. Nikolopoulos Z. Roupas Inst. of Physics, Belgrade M. Milosavljevi ć. Layout:

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Discovery potential for the MSSM H/A  →μ + μ - decays with the ATLAS detector

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  1. Discovery potential for the MSSM H/A →μ+μ- decays with the ATLAS detector … and other even more exotic particles • Univ. of Athens • Dimitris Fassouliotis • C. Kourkoumelis • P. Ioannou • K. Nikolopoulos • Z. Roupas • Inst. of Physics, Belgrade • M. Milosavljević • Layout: • Muon reconstruction in ATLAS • Motivation • Event Selection • Results The project is co-funded by the European Social Fund and National Resources- (EPEAEK II) PYTHAGORAS II

  2. The ATLAS Detector

  3. December 2005

  4. Cosmic Data Station 13

  5. First measured point Calorimeter correction Refit @ vertex Matching with the inner tracks and combined fit Overview of muon identification IMuon system as tracker • standalone Muon system • combination of muon and ID track • Eloss-calorimeter IIMuon system as tagger • starting point is ID track • muon identification by extrapolation and matching to muon segments/hits IIICalorimetry tagging HEP 2006 - D. Fassouliotis UoA

  6. Muon Reconstruction performance pT resolution vs pT

  7. In many cases a decay into a hadronic final state has a much higher branching ratio ( ), but it is also impossible to distinguish from the QCD backgounds. Why do we like leptonic final states?

  8. μ- μ+ Η/Α μ- μ- Ζ* μ+ μ+ Η Ζ MSSM SUSY Higgs Expected events for 30 fb-1 Standard Model Higgs Expected events for 100 fb-1 HEP 2006 - D. Fassouliotis UoA

  9. μ- νμ μ+ μ Ζ’ W’ νμ μ- W μ μ+ W’ Ζ More Exotic Signatures with 1,2,3 leptons in the final state HEP 2006 - D. Fassouliotis UoA

  10. MSSM • 5 Physical Higgs Bosons: h, H, A, H+, H- • on Born level:2 Parameters tanb, mA mass limit mh < MZ • Large loop corrections  mh < 133 GeV (+-3GeV) corrections depend on 5 SUSY parameters: Xt,M0,M2,Mgluino, m • 5 parameters fixed in4 benchmark scenariosconsidered • scan performed over tanb, mA Mhmax scenario(maximum allowed Mh, conservative tanβ limits)

  11. (direct production) (associated production) • H/A →μ+μ- • In the framework of the MSSM, the A→ll decay channel isstrongly enhanced, for large values of tanβ. • Still, Br(H/A→μμ)/ Br(H/A→ττ)~(mµ/mτ)2 • However, the μ+μ-presents the advantage of • Cleaner signal • Complete reconstruction Associated production σxBR (fb) (Dominated by Drell-Yan background) For mA>150 GeV/c2 A and H are degenerate in mass, enlarging the discovery potential

  12. Signature: 2 muons + 2 b-jets Main backgrounds: irreducible (both μ from Z σ=39. x 103fb) reducible (both μ from Ws σ=9.5 x 103fb) The complete study was performed on fully simulated samples (signal mA=300 GeV/c2, tanβ=30) • Selection criteria: • muon pT • muon isolation • b-tagging • missing energy • Accoplanarity • mass window

  13. Muon pT

  14. Missing ET

  15. Accoplanarity

  16. Mass window HEP 2006 - D. Fassouliotis UoA

  17. Signature: 2 muons + 2 b-jets Main backgrounds: irreducible (both μ from Z σ=39. x 103fb) reducible (both μ from Ws σ=9.5 x 103fb) The complete study was performed on fully simulated samples (signal mA=300 GeV/c2, tanβ=30) • Selection criteria: • muon pT • muon isolation • b-tagging • missing energy • Accoplanarity • mass window • Cut value PμT>50 GeV/c Eem<5, Nch≤2 in cone ΔR=0.2 ≥ 1 bjet Emis<50 GeV α<0.75 Δm = 2 gaussian sigmas

  18. Before applying a mass window: Signal Efficiency: 34% Zbbar Rejection : ~400 ttbar Rejection : ~200 Mass distributions for signal and backgrounds after cuts based on the fully simulated samples normalized to an integrated luminosity of 30 fb-1 Lack of bkg statistics but good agreement with fast simulation analysis HEP 2006 - D. Fassouliotis UoA

  19. (a) (c) (b) (d) (e) With reference the fully simulated mA=300 GeV/c2, tanβ=30 sample We performed a study for different tanβ values HEP 2006 - D. Fassouliotis UoA

  20. (a) (c) (b) (d) (e) With reference the fully simulated mA=300 GeV/c2, tanβ=30 sample We performed a study for different mA values HEP 2006 - D. Fassouliotis UoA

  21. …and we got the following significance plot on the mA – tanβ plane HEP 2006 - D. Fassouliotis UoA

  22. Conclusions • Physics at LHC will be exciting • ATLAS detector presents a great opportunity to exploit the physics potential offered by LHC • An example of the work on Physics studies of our group was presented in this talk • Still, great effort is put on Reconstruction software improvement Software validation (Part of it will be presented by K. Nikolopoulos in HEP2006) HEP 2006 - D. Fassouliotis UoA

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