MadGraph5_aMC@NLO

Electroweak scheme used in Madgraph

Asked by Duong Nguyen

Dear Authors,
What is the default electroweak scheme used in Madgraph to calculate the electroweak parameter? Which scheme in below is equivalent to the default used in Madgraph (described from 2.1 to 2.6)?
http://www.itp.kit.edu/~vbfnloweb/wiki/doku.php?id=documentation:details:ewscheme
Is it posible to change/chose a scheme?
Best regards,
Duong

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi Duong,

Sorry for the late reply, I was in holliday.

In fact, the scheeme is choosed by the model builder not by MadGraph which have no idea of what the scheme is.
So depending of the model author, you can have all the scheme that are used in VBFNLO.

So this answer your last question. How to change/choose the scheme. Just re-define the model and change the relation between the parameter (which ones are read from the cards and which are computed internally).

Now most of the model in MG comes with the same convention which is the scheme 1 (this sounds natural since VBFNLO is MG4 based). Now if you use the complex mass scheme option and if your model is in scheme 1, then the code change automatically the model in order to pass in scheme 3 (which is the one suitable for complex mass scheme).

Cheers,

Olivier

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