Trigger study

1, also check the single lepton trigger used in ttH analysis
2, we can get the scale factor from ttH group and four top full hadronic group.
3, about the lepton pt spectrum in 1tau+1L category, I will try to do "loose lepton veto" as four top 1L analysis did and see whether it will help issue,

to do list&discussion

Object definition
1, we plan to do as ttH analysis
2, they develope their own BDT for prompt electron and muon, we will not repeat this.
3, in their selection, they require no nearby bjet to the leptons, but they do not give the definition of "nearby". How do we define this?
4, actually I already remove the jet close to electron/muon with DeltaR<0.4 in overlap removal. This could be changed.

Background estimation

we first need data/mc comparison.

two types of background 
1, non-fake(prompt) estimated by MC, and scale the cross section(e.g. tt+jets, tt+V). scale factor is from CR(how to define this control region)
2, fake background ( fake tau and fake lepton )

The method is to reverse the lepton/tau ID and derive the fake factor ( which region should be used to derive the fake factor )

we do not need to care about the charge flip background.