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ChrisVer
Gold Member
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I was reading this document from CMS:
https://cds.cern.ch/record/2002036?ln=en
But I have some problems understanding how they calculated the bckg coming from the QCD.
My questions come from Sec.6 Background, so you can jump and have a quick glimpse over it (?).
They used the tight-to-loose ratio by the ABCD method. You have four regions A,B,C,D.
The QCD regions C,D are obtained with applying (tight) or not (loose) isolation criteria on your jets and probably some choice on your discriminant for the analysis variable [itex]p_T^{\tau}/E_T^{miss}[/itex] , I think it should be >1.5 to get the QCD enriched data.
By that it says you can determine the tight-to-loose ratio, which you use as a weight for your signal events at A the QCD template (?) to obtain your background (B).
a) However I don't understand how this method actually works to find the QCD background. What is making the tight-to-loose ratio useful as a weight? I also don't understand what is the QCD template signal.
b) Also why the ratio is called tight-to-loose while in the text they give it as [itex]R_{TTL}= N_C/N_D[/itex] (obviously loose-to-tight).
c) Finally, I don't understand what they are actually trying to say with:
https://cds.cern.ch/record/2002036?ln=en
But I have some problems understanding how they calculated the bckg coming from the QCD.
My questions come from Sec.6 Background, so you can jump and have a quick glimpse over it (?).
They used the tight-to-loose ratio by the ABCD method. You have four regions A,B,C,D.
The QCD regions C,D are obtained with applying (tight) or not (loose) isolation criteria on your jets and probably some choice on your discriminant for the analysis variable [itex]p_T^{\tau}/E_T^{miss}[/itex] , I think it should be >1.5 to get the QCD enriched data.
By that it says you can determine the tight-to-loose ratio, which you use as a weight for your signal events at A the QCD template (?) to obtain your background (B).
a) However I don't understand how this method actually works to find the QCD background. What is making the tight-to-loose ratio useful as a weight? I also don't understand what is the QCD template signal.
b) Also why the ratio is called tight-to-loose while in the text they give it as [itex]R_{TTL}= N_C/N_D[/itex] (obviously loose-to-tight).
c) Finally, I don't understand what they are actually trying to say with:
Any idea what they are trying to point out with those numbers? The only threshold for [itex]p_T/E_T^{miss}[/itex] I saw was that it should be larger than 1.5 for the C,D region (so they varied this number by 0.05 per time)... but there is no upper threshold written anywhere :/The tight-to-loose ratio is calculated using different [itex]p_T^{\tau}/E_T^{miss}[/itex] thresholds of 1.5, 1.55 and 1.6, the upper threshold was varried from 3 to 4, 5 and 20
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