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 Try to reduce by changing the lepton veto cut
Component mT < 100 GeV mT > 100 GeV # semilep: el semilep: mu semilep: lep.tau semilep: had.tau 43 4 fulllep: 2 el/mu fulllep: el/mu + lep.tau fulllep: el/mu + had.tau fulllep: 2 tau (any) sum :
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 : failed pT cut : 9 10 failed eta cut : 1 4 failed etcone20 : 6 8 failed author : 5 0 failed etacrack : failed Medium : failed Mu bestMatch : failed Mu combinedMu : failed Mu chi2 : failed overlapRemoval : no matching reco el/mu: truth out of eta acc. : 6 6 truth muon |eta|<0.1 : el failed truth match : mu failed truth match : good El, no good mu : no good El, good mu : other cases :
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 ?