Definition of drjj parameter in the run card
Dear MadGraph experts,
I am trying to check my own numerical computation of a total cross section for a p p > j j process
against a total cross section from MadGraph.
In MadGraph I generate events for p p > j j process (where j = g u d s c u~ d~ s~ c~) .
I do not use Pythia and 0 = ickkw and drjj = 0.1
Now if I do not impose any cuts on distance between jets in my code I am getting agreement between my code and MadGraph.
(My code just does a numerical Monte-Carlo integration of analytical expression for cross section integrand as a function of y_1, y_2 and pT).
However if impose a cut on a distance between jets in my code deltaR >= 0.1 I am starting to get a disagreement between MadGraph and my calculations.
I define deltaR as
deltaR = sqrt(deltaEta2 + deltaPhi^2)
where deltaE = y1 - y3 and deltaPhi = 2 * ( atan(exp(-y1) - atan(exp(-2) )
last expression for deltaPhi follows from the connection between pseudorapidity and an an angle between particle and a beem pipe y = -ln ( tan(teta / 2)).
Moreover if I set drjj = 3.0 in my code I am getting a zero cross section and in MadGraph I still capable to generate events and calculate a cross section...
I suspect that I do not really understand how drjj is defined in MadGraph ..
So my questions are:
Could you please tell me how drjj is define in MadGraph?
And is there any difference between drjj in case when one switch on showering ?
Is there any difference in the definition of drjj for two jet final state and three (or four) jet final states ?
Is there any difference between definition of drjj, drll, draj and all these parameters in run card?
Thank you very much!
With best regards,
Oleh
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