EFT operator sensitivity

Asked by Pim Verschuuren

Dear experts,

Is there an easy way to check which operators of a chosen UFO model, in this case SMEFT@NLO, have any impact on your process?

Kind regards,

Pim

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Olivier Mattelaer (olivier-mattelaer) said :
#1

You can do the following
import model SMEFT@NLO
generate MYPROCESS
output MYDIR

Then you can check in MYPROCESS/MYDIR/Source/model/coupl_write.inc

In that file you will have all the coupling defined within the model that are used for the processes that you generate.
After that the rest of the work is very model specific (and the notion of operator does not exists in the UFO model)
but in general it should be quite simple to track all those coupling to a unique operator via their analytical expression.

Cheers,

Olivier

> On 24 Feb 2021, at 09:11, Pim Verschuuren <email address hidden> wrote:
>
> New question #695722 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/695722
>
> Dear experts,
>
> Is there an easy way to check which operators of a chosen UFO model, in this case SMEFT@NLO, have any impact on your process?
>
> Kind regards,
>
> Pim
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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Pim Verschuuren (pverschu) said :
#2

Hi Olivier,

Thank you for the fast response. Just to make sure I interpret this correct, in coupl_write.inc I found two long lists:

DOUBLE COMPLEX GC_358, GC_360, R2GC_1674_1167, R2GC_1681_1170,
$ R2GC_2226_1574, R2GC_2238_1580, R2GC_2238_1581, R2GC_2239_1582
....more rows

 COMMON/COUPLINGS/ GC_358, GC_360, R2GC_1674_1167, R2GC_1681_1170
$ , R2GC_2226_1574, R2GC_2238_1580, R2GC_2238_1581,
....more rows

These two lists seem to be identical in values so I assume I can take a coupling name from either?

Also, to make the translation to SMEFT@NLO operators, I found the file couplings.py in the model directory MG/models/SMEFT@NLO. Can I make the following inference:

The list in the process dir contains the coupling GC_358
The file couplings.py in the model dir contains

GC_358 = Coupling(name = 'GC_358',
                  value = '(ctG*complex(0,1)*G*vev0)/(Lambda**2*cmath.sqrt(2))',
                  order = {'NP':2,'QCD':1})

which means the coupling depends linearly on the wilson coefficient ctG? Also, how do I interpret lines such as order = {'NP':2. 'QCD':1, 'QED':3}?

Cheers,

Pim

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Olivier Mattelaer (olivier-mattelaer) said :
#3

> These two lists seem to be identical in values so I assume I can take a coupling name from either?

Yes.

> which means the coupling depends linearly on the Wilson coefficient ctG?

yes (as long as vev0 does not depend of Ctg implicitely which is unlikely)

> {'NP':2. 'QCD':1, 'QED':3}?

for your specific question you can ignore those.
Those are used to forbid some Feynman Diagram (like those with double insertion of operator/...)

Cheers,

Olivier

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Pim Verschuuren (pverschu) said :
#4

Thank you very much!