SLIDE 28 francesco.spano@cern.ch Top Quark with ATLAS @ LHC LPHNE Seminar -24th March 2011
Di-lepton main backgrounds
- “Fake” leptons from data (matrix method)
- Invert high ET and Z window cuts → control
samples enriched with real and “fake” leptons
- Derive probability for “fake” and real leptons to
be in signal region
- Estimate “fakes” as a function of events in
signal and control samples
28
ee µµ eµ Z/γ∗+jets (DD) 1.2+0.5
−0.6
3.4+1.9
−1.4
0.4+0.4
−0.3
1.2+0.7
−0.6
3.2+1.6
−1.3
Non-Z leptons (DD) 0.8 ± 0.8 0.5 ± 0.6 3.0 ± 2.6 Single top (MC) 0.7 ± 0.1 1.3 ± 0.2 2.5 ± 0.4 Dibosons (MC) 0.5 ± 0.1 0.9 ± 0.2 2.1+0.5
−0.3
Total (non t¯ t) 3.5 ± 1.1 7.3+1.8
−1.5
10.8 ± 3.4 t¯ t (MC) 11.5 ± 1.3 20.1 ± 1.7 47.4 ± 4.0 Total expected events 15.0 ± 1.7 27.4 ± 2.4 58.2 ± 5.2 Observed events 16 31 58 [GeV]
miss T
E 50 100 150 200 Events / 5 GeV
10
10 1 10
2
10
3
10
4
10
5
10 [GeV]
miss T
E 50 100 150 200 Events / 5 GeV
10
10 1 10
2
10
3
10
4
10
5
10 [GeV]
miss T
E 50 100 150 200 Events / 5 GeV
10
10 1 10
2
10
3
10
4
10
5
10 data t t single top DY + jets diboson fake leptons uncertainty
control region µ µ
ATLAS Preliminary
L = 35 pb
∫
Events 10 Events 10 Events 10
ATLAS- CONF-2011- 027
- Z/γ* bkg : scale control region with simulation
- in Z mass window, >=2 jets, ETmiss>30
- NZ/γ (SigReg) = Data(ConReg)-OtherMC(CR)*[ MCZ/γ
(SigReg)/MCZ/γ (ConReg) ]
invariant mass [GeV]
+
e 20 40 60 80 100 120 140 160 180 Events / 10 GeV 1 10
2
10
3
10
4
10 invariant mass [GeV]
+
e 20 40 60 80 100 120 140 160 180 Events / 10 GeV 1 10
2
10
3
10
4
10 invariant mass [GeV]
+
e 20 40 60 80 100 120 140 160 180 Events / 10 GeV 1 10
2
10
3
10
4
10 data t t single top DY + jets diboson fake leptons uncertainty
control region ee
ATLAS Preliminary
L = 35 pb
∫
ATLAS- CONF-2011- 027
in Z window for low ETmiss
