1. ttbar τ + jets: Update on QCD Estimation
William Edson
SUNY at Albany

2. Chi-squared minimization
Equation:
N(x): total number of events of type x for distribution
n(x)i: number of events in bin of type x
frac(Sig): fraction of N(Remain) expected to be Signal
binfrac(x)i: fraction of events in bin of type x expected from MC or template
σi: uncertainty in bin i

3. Chi-squared minimization cont.
σi determined by adding in quadrature
bin error:
data
signal, MC
QCD template
other backgrounds, MC
statistical error:
data: signal region (times 2)
data: background region
other backgrounds, MC (times 2)
signal and other backgrounds combined, MC: background region

4. Results Run 1: Rescale signal MC in all regions and rerun:
chi-squared: 31.78
signal fraction: /
Rescale signal MC in all regions and rerun:
chi-squared: 30.94
signal fraction: /

5. Highest pT bjet reconstruction
Results for plot:
chi-square: 16.66
p-value:
ndf: 11
chi/ndf: 1.51

6. 2nd highest pT bjet reconstruction
Results for plot:
chi-square: 4.79
p-value:
ndf: 11
chi/ndf: 0.44

7. Dijet reconstruction Results for plot: chi-square: 11.29
p-value:
ndf: 12
chi/ndf: 0.94

8. Closest Top mass reconstruction
Results for plot:
chi-square: 6.88
p-value:
ndf: 8
chi/ndf: 0.86

9. Back-up

10. Chi-squared minimization
Equation:
nx: number of events in bin of type x
sfSig,QCD: scale factor for either Signal or QCD
σi: uncertainty in data bin i
sfSig = ±
sfQCD = ±

11. ABCD Regions Signal Region (A): Background Regions (B, C and D):
BDTScore > 0.7 and Closest Top Mass < 230GeV
Background Regions (B, C and D):
B: BDTScore < 0.7 and Closest Top Mass < 230GeV
C: BDTScore > 0.7 and Closest Top Mass > 230GeV
D: BDTScore < 0.7 and Closest Top Mass > 230GeV

12. Cutflow C0: GRL C1: Trigger C2: Primary vertex with ntracks > 4
C3: Electron/muon overlap, larVeto
C4: Jet cleaning
C5: Lepton Veto
C6: njets >= 4 with eta < 2.5 and |jvf| > 0.75
C7: MET > 60GeV
C8: MT < 70GeV
C9: Sum ET < 500GeV
C10: >= 1 bjet
C11: Tau n ≥ 1, BDTScore > 0.7
C12: Trigger matched tau n ≥ 1 and pT >= 40GeV
C13: MC tau object match