Systematic way to do jet-matching to study the effect of ISR and FSR

Asked by Siew Yan HOH on 2014-10-15

Hi, I am new to madgraph, pyhtia and particle physics. I am assigned to a project to study the double counting effect on the multi-jet process, I have simulated chichi+j and chichi+j, chichi+jj in madgraph and i wish to hadronize them in pythia_6 and pythia_8. I did jet matching before on pythia_6, it involve the inspection of the DJR plot and varied the Qcut (Qcut > qcut) in order to achieve a pleateu in matched cross section vs Qcut. Despite of that, I still unclear how does the jet matching study perform in a more systematic way.
My questions are:

1.) how to carry out jet matching study in a more systematic way?

2.) Beside DJR plot (which i having problem understanding) and the cross section vs qcut plot, is there any quantities that i can look at to justify the right pair of (xqcut, Qcut) ?

3.) I have tested on pythia_8, but there isn't any DJR plot nor the matched cross section value, how to obtain infomation from pyhtia_8 to study the jet matching?

4.) I like to inspect the spectrum of the signal jet pt after being hadronized, how can I carry out such analysis in pyhtia ? (Usually I analyze the LHE file in madgraph with root, I read about the Hep and lhe file after pythia which is not suitable for analyze)

Thanks and I am sorry for such a long questions.

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