Checkpoint: this macros will allow one to reproduce the plots 45-48 from the note as well as tables 13-15 from the note
We estimate QCD background using ABCD method in order to improve our systematic uncertainty on the background estimation. ABCD method is very simple.
1) choose 2 variables: assume two variables are independent
2) assume the fraction should be same if there is no correlation: N_A / N_B = N_C / N_D
3) In our study, use two variables: sign of muon pair, muon isolation
4) QCD fraction in each region has a dependence. We produce the correction factor for each region: B, C, D
5) Produce N_B, N_C, N_D from data sample, and estimate N_A from them at the end (applying the correction factors)
QCDFrac.C: to produce correction factors for each region
ABCD2vari.C: to produce the ABCD results. The correction factors from the QCDFrac.C are plugged in this macro as an input.
ttbar data driven background estimation