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2 nd lepton veto, in the one-lepton SUSY analysis

2 nd lepton veto, in the one-lepton SUSY analysis

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2 nd lepton veto, in the one-lepton SUSY analysis

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  1. 2nd lepton veto, in the one-lepton SUSY analysis Till Eifert

  2. One-lepton analysis • ‘good’ leptons : pT > 20 GeV, isolated: etcone20 < 10 GeV, overlap removal, medium el, combined mu, etc. • Require one ‘good’ lepton • Veto events with a 2nd ‘good’ lepton with a lowered cut on pT > 10 GeV • After transverse mass cut, dominant background : full-leptonic ttbar • -> can we improve the 2nd lepton veto cut ?

  3. Use MC truth • T1 sample (semi- & full-leptonic ttbar decays), ca. 2 million events (but with negative event weight) • Sqrt(s) = 10 TeV • Run one-lepton SUSY event selection, apart from mT cut • Use MC truth to classify events

  4. Look at semi-leptonic ttbar decays • mT edge: el / mu (better resolution) • Tau -> el/mu : no mT edge (part of momentum goes into extra neutrino) • Very few hadronic taus -> one-lepton selection !

  5. Look at full-leptonic ttbar decays • Left: about same number of (el/mu)+(el/mu) as (el/mu)+(tau->had) • Right: mostly el+el or el+mu that pass the 2nd lepton veto cut • Can try to reduce (el/mu)+(el/mu) and (el/mu)+(tau->el/mu) background in mT > 100 GeV . • (el/mu) + tau->had difficult to tackle (I think, because of high tau-rate in SUSY).

  6. Some numbers Component mT < 100 GeV mT > 100 GeV #------------------------------------------------------------- semilep: el 2794 85 semilep: mu 3413 91 semilep: lep.tau 1069 6 semilep: had.tau 43 4 fulllep: 2 el/mu 200 177 fulllep: el/mu + lep.tau 95 66 fulllep: el/mu + had.tau 227 232 fulllep: 2 tau (any) 43 12 #------------------------------------------------------------- sum : 7884 673 Try to reduce by changing the lepton veto cut

  7. Look for reason why 2nd lep was not found Use full-leptonic ttbar decays, match truth to reco, save object selection information Leptons in MC truth 2x(el) 2x(mu) el+mu #------------------------------------------------------------- total evts : 127 59 192 failed pT cut : 9 10 failed eta cut : 1 4 failed etcone20 : 6 8 failed author : 5 0 failed etacrack : 6 --- failed Medium : 40 --- failed Mu bestMatch : --- 8 failed Mu combinedMu : --- 8 failed Mu chi2 : --- 0 failed overlapRemoval : 16 14 no matching reco el/mu: 56 20 truth out of eta acc. : 6 6 truth muon |eta|<0.1 : --- 13 el failed truth match : --- --- 48 mu failed truth match : --- --- 4 good El, no good mu : --- --- 57 no good El, good mu : --- --- 135 other cases : --- --- 0 Object selection can fail for more than one reason Mostly the electrons that are not selected!

  8. Un-associated truth el Note: events with an el in |eta| ~1.4 crack are rejected! (maybe should remove this CSC cut) As expected, most un-associated muons in |eta| < 0.1 region Un-associated truth mu

  9. Next steps • Improve S/B in signal region (mT > 100 GeV) • Lower electron isEM medium requirement • Change : veto events with isolated track that is not associated to primary el/mu • Run on SU3 & T1, compare S/B • Other ideas ?