z cross-section with simultaneous fit luca lista for: annapaola de cosa, michele de gruttola,...
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Z cross-sectionwith simultaneous fitZ cross-sectionwith simultaneous fit
Luca Lista for:Annapaola De Cosa, Michele De Gruttola, Salvatore Di Guida, Francesco Fabozzi,
Pasquale Noli, Davide Piccolo (LNF)
Luca Lista, Gr-I 2008 2
Analysis strategyAnalysis strategy
•Zµµ two global muons, both matched to HLT primitive•Zµµ two global muons, one matched to HLT primitive•Zµsa 1 global + 1 stand-alone muons, global mu matched to HLT•Zµtk 1 global muon + 1 track, muon matched to HLT•Zµµ non-iso two global muons, at least one non-isolated, at least one matched to HLT
• Define five independent samples:
Luca Lista, Gr-I 2008 3
Data-driven di-muon mass PDFData-driven di-muon mass PDF
Luca Lista, Gr-I 2008 4
MC SamplesMC Samples
Luca Lista, Gr-I 2008 5
Global fit approachGlobal fit approach
• Negligible background on Zµµ sample• Assume identical di-muon peak shape for other
samples– Fully data-diven model (no MC input!)
– Except Zµsa, fitted with a gaussian, due to poorer resolution
Luca Lista, Gr-I 2008 6
Global fit resultsGlobal fit results
Nµµ = 3818 ± 64
Parameter Fit (%) Mc truth(%)
ε HLT Fit = < ε HLT * ε sa>/ < ε sa >
Low statisticsat 10 pb-1 !
Luca Lista, Gr-I 2008 7
Different luminosity scenariosDifferent luminosity scenarios
Luca Lista, Gr-I 2008 8
Cross section stabilityCross section stability
Cross section estimateuncorrected for kinematic efficiency
Luca Lista, Gr-I 2008 9
iso 1
2 ET
Ecal 1
2 ET
Hcal
1 pT
α = 0.75α = 0.75
Relevant calorimeters Relevant calorimeters contributioncontribution
Optimization of isolation selectionOptimization of isolation selection
Luca Lista, Gr-I 2008 10
iso 1
2 ET
Ecal 1
2 ET
Hcal
1 pT
β = -0.75β = -0.75
Hcal more relevant Hcal more relevant than Ecal than Ecal
Optimization of isolation selectionOptimization of isolation selection
Luca Lista, Gr-I 2008 11
First look at real dataFirst look at real data
(Cosmics, of course…)
Luca Lista, Gr-I 2008 12
Ongoing improvementsOngoing improvements
• Apply optimized isolation– Background reduction of ~30 50 %– Reduced statistical error on by ~6%
• Extract peak shape for Zsa from data– Use Z, suppress track on one leg
• Use Extended Unbinned Max. Likelihood fit on low statistics sample
• Validate fit performances using a Toy MC
• Prepare abstract for winter conferences!