Leptoquark process involving b and b~ quarks
Greetings,
I would like to ask you a couple of questions involving one particular process I would like to study. The process I am trying to study is the t-channel of the following process: b b~ > mu- mu+ with the leptoquark serving as the mediator of the reaction.
I am using the following leptoquark models: https:/
I import these models in the MadGraph following the standard procedure. When I try to generate the process p p > mu- mu+, what I get is the following message:
Survey return zero cross section.
Typical reasons are the following:
1) A massive s-channel particle has a width set to zero.
2) The pdf are zero for at least one of the initial state particles
or you are using maxjetflavor=4 for initial state b:s.
3) The cuts are too strong.
Please check/correct your param_card and/or your run_card.
I have tried to find hints and possible solutions to this problem on the launchpad, and I found out that the potential problem could be the width of the b quark, which is, if I am correct, by default set to zero in MadGraph. I think this could be one of the reasons why the mentioned process cannot be executed.
I have also tried altering the NP parameter upon generating the process in MadGraph. I tried altering NP to 1 and 2, but the same error appeared. The main motivation for setting NP to 2 was because the t-channel of the leptoquark process contains 2 vertices, so I thought that 2 would be the appropriate value. I am, of course, not at all sure about any of this.
When it comes to cuts, I am not sure which cuts should be altered and what values should be assigned to the cuts.
So all in all, I have many things involving this process I am not sure about at all. I also tried to compare different .py files from the sm model and from the leptoquark models, but although I managed to find some differences, that didn't lead to the right solution.
I would like to thank you in advance for your helpful hints and insights. Since I am still learning the basics of MadGraph, I am aware that I am definitely missing something important involving this process.
Thank you once again in advance.
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