240 likes | 244 Views
Trilepton+top signal from chargino-neutralino decays of MSSM charged Higgs bosons. 17 June 2004, 9 th Nordic LHC Physics Workshop, Copenhagen. Introduction. Introduction (cont). Introduction (cont). Event Production. Used HERWIG for event production and ATLFAST for fast detector simulation
E N D
Trilepton+top signal from chargino-neutralino decays of MSSM charged Higgs bosons 17 June 2004, 9th Nordic LHC Physics Workshop, Copenhagen
Event Production • Used HERWIG for event production and ATLFAST for fast detector simulation • Will show results for one point, tanβ = 10 and mA = 350 GeV, in the Parameter Set A • Events produced: • 106 signal events; gb → H+t, H+ → χχ and t → bqq • 107 background events; gg → tt(other bkg channels will be investigated in the future) • Luminosity: 100 fb-1 was assumed • Cross Section: • Signal; NLO σ = 75fb • Bkg tt; Herwig’s logfile σ = 456200fb • Signal Branching Ratio: • H+ is forced to decay to χχ and t is forced to decay hadronically BRTOT = BR(H+→ χχ)*BR(t→bqq) = 0.77*2/3 = 0.51
Cuts: Tracking Cut • The isolation criteria in previous cut was only based on ATLFASTs calorimeter • Tracking in ATLFAST gives impractically large files • The “true MC particles” was used to see if any particle was too close (ΔR < 0.3) to any of the three leptons • A track efficiency of 0.9 was assumed* *This is probably an underestimation since according to S. Gadomski (ATL-CONF-2000-009) the efficiency of finding muons is 98% for the Inner Detector
Cuts: 2l Mass Cut • χ0j→ 2 same flavor, opposite sign leptons + one (or more if j>2) undetectable particle(s) • Out of the three isolated leptons at least 2 are required to have same flavor and opposite sign • The inv. mass of these two is kinematically constrained. For j=2: • If third lepton has same flavor, the biggest Mll are used for the cut 10 < Mll < 63
Cuts: 2l Mass Cut j = 3 Signal events, gb → H+t j = 2
Cuts: 2l Mass Cut background, gg → tt
Cuts: Jet Cut • This cut will be needed only for susy background with many hard jets • For now the parameters are chosen not to decrease the significance of this analysis with only tt bkg
Not Enough MC • 107 tt background events don't give enough statistics • Usedwhere • The Significant with weights = , w = br*cs*L / (# simulated events)
Scan Other Sets Background Statistics Pure 3l+N Future Work • SweGrid is right NOW producing more tt events • Look at more backgrounds; ttZ, ttγ, tth, χχ, q, g • Herwig; force χχ→3l+N • BR(H+→χχ→3l+N) from diagrams achieved indirectly from ISAJET • Get significance for points in the tanβ vs. mA plane • Explore the 5σ discovery potential • Make 5σ scans for different Parameter Sets