Supersymmetry David Kolchmeyer Advisor Alberto Graziano Overview Brief description of analysis and method Background prediction in SS mumu channel Background prediction in OS mumu ID: 791924
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Slide1
Measuring the Fake Lepton Background in a Search for Supersymmetry
David KolchmeyerAdvisor: Alberto Graziano
Slide2OverviewBrief description of analysis and method
Background prediction in SS mumu channelBackground prediction in OS mumu
channelThings to do for the future
Slide3Analysis and Method
Searching for same sign dileptons from pair produced stopsControl region MT2 < 80Estimate background from one real and one fake lepton from data
Define ‘loose’ electron, measure ratio of fake tight to fake loose leptons in QCD sampleLook for loose-loose events in dilepton data, weight events to get predicted fake tight-tight background
Slide4Event Weighting
Tight-Loose
Tight-TightLoose-LooseLoose-TightTTLL
TLLT
ε
=
η
=
Tight/loose for fake leptons
loose/tight for real leptons
Error propagation implemented in code
p
≈ 1 (good
approx
for
muons
, not electrons)
Slide5QCD sample
Combining T_HLT_Mu8_v16 and T_HLT_Mu17_v3 triggersWeight muons by 1/(luminosity of trigger path) to combine the triggers
Overlap of 51/154368 eventsVeto events with Z candidate or low mass resonanceRequire MET < 20 GeV and MT < 15 to reduce EWK contributionsRequire an away jet of DeltaR > 1 between the jet and all loose electrons/muons in eventFake rate error given from binomial formulaerr(FR) = sqrt(FR(1-FR)/Loose)
Slide6QCD sample plots
Away jet distributionFake rates in different binsMET vs MT2ll in data and Zjets,
Wjets
Slide7SS Plots- Bkg Yield
Slide8SS Plots- Distributions
Missing some MC processes….
SS region should be dominated by fake processesLow statistics
Slide9Compare Muon Isolation in QCD and SS Data
Slide10OS Plots- Bkg Yield
Slide11OS Plots- Distributions
Prediction somewhat agrees with MC for the fake backgrounds…
Slide12Compare Isolation in QCD and OS Data sample
The distributions don’t agree because we are comparing prompt and fake leptons to fake leptons only. Hence data will have more prompt leptons with tighter Iso
Slide13Bias in QCD sampleWe only ask for single lepton triggers, but there was a
dilepton requirement when trees were madeSecond lepton probably is looser, has greater isolation
Slide14For the FutureDo EWK removal
Obtain an unbiased single lepton sampleFind a control region with more statistics (verify with RelIso distribution)Do this for electrons!Do this with 20
ifb
Slide15Thank you!