MadGraph5_aMC@NLO

Need help modifying a 4 flavor model to be 5 flavor instead

Asked by David Overton

As the summary says, we have a 4 flavor W' model file. However, the W' in the model doesn't couple to d or s quarks so we need a b pdf in the proton and therefore a 5 flavor model. Is there any to either modify the model file itself or modify the madgraph cards to achieve this?

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

You can use the trick of the following FAQ to set the b mass to zero at the model level.
Then the "b" will automatically be set as part of the proton/jet definition and all the code will be set in a 5 flavor scheme automatically.

Cheers,

Olivier
FAQ #2312: “FR Model much slower than build-in MG model. Why and how to fix?”.

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David Overton (doverton) said : 		#2

This is what I was planning on doing but I was told that setting the b mass to 0 in a 4FS model would not be the same as using a 5FS model. I'll link the pull request where the discussion is happening for more context.

https://github.com/cms-sw/genproductions/pull/2979

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Olivier Mattelaer (olivier-mattelaer) said : 		#3

If you follow the FAQ, the change is at the model level and then no problem.
Since I'm the "Madgraph author" refer in the other thread. you can be quite confident in the above statement.

Cheers,

Olivier

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David Overton (doverton) said : 		#4

Okay I'll give this a try. Thanks for the help