MadGraph5_aMC@NLO

sm-ckm model

Asked by Simona Salvini

Hello,
I have to evaluate the cross section for a process involving W+. I exploited the sm-ckm model in order to generate the matrix elements (C++ output) but I cannot understand if they contain the proper Cabibbo-Kobayashi-Maskawa matrix element or not.
Thanks for any help,
Simona

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Olivier Mattelaer
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Best Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi Simona,

In the param_card, you will find the followings:
###################################
## INFORMATION FOR WOLFENSTEIN
###################################
Block wolfenstein
    1 2.253000e-01 # lamWS
    2 8.080000e-01 # AWS
    3 1.320000e-01 # rhoWS
    4 3.410000e-01 # etaWS

Which is the Wolfenstein parametrization of the CKM matrix:
http://en.wikipedia.org/wiki/Cabibbo%E2%80%93Kobayashi%E2%80%93Maskawa_matrix#Wolfenstein_parameters

When you run the standalone output, you will also see the value of the CKM matrix:
             CKM1x1 = (9.746200e-01,0.000000e+00)
             CKM1x2 = (2.253000e-01,0.000000e+00)
             CKM1x3 = (1.219744e-03,-3.151007e-03)
             CKM2x1 = (-2.253000e-01,0.000000e+00)
             CKM2x2 = (9.746200e-01,0.000000e+00)
             CKM2x3 = (4.101415e-02,0.000000e+00)
             CKM3x1 = (8.020744e-03,-3.151007e-03)
             CKM3x2 = (-4.101415e-02,0.000000e+00)
             CKM3x3 = 1.000000e+00

Is this answer your question?

Cheers,

Olivier

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Simona Salvini (simona-salvini) said : 		#2

Thank you. I read the param_card but I was not sure that every parameter in it was used.

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Olivier Mattelaer (olivier-mattelaer) said : 		#3

Sure they are,

if you use the model
import model sm
you will see that the wolfenstein part of the param_card will not be present.
(and the generation should normally fail if this part is present in the param_card)

Cheers,

Olivier

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Simona Salvini (simona-salvini) said : 		#4

Thank you again.