How to change MadWidth default options

Asked by Reza Goldouzian on 2021-05-21

Dear Experts,

I would like to change the width of top quark in the presence of tblnu EFT vertex which add t>lnub decay mode.
When I use 'DECAY 6 auto' in parameter card, madgraph uses the default setting of MadWidth for calculating the width of top quark and does not include my new three-body decay mode. I always receive the same top width (1.4669 GeV) independent of the input value of the Wilson coefficient. I even increased the WC to 100 (for Lambda=1TeV) but I find the same width as default.

I see the following massage when running the madgraph
'compute_widths 6 --precision_channel=0.01 --body_decay=4.0025 --path=/Users/rezagol/calc/MG5_aMC_v2_6_6/EFTDecay_tlnub/Cards/param_card.dat --output=/Users/rezagol/calc/MG5_aMC_v2_6_6/EFTDecay_tlnub/Cards/param_card.dat'

When I call the MadWidth from a MadGraph5aMC-@NLO and use the same model (dim6 top) and the same cards but with the following parameter
--body_decay=3

I receive a new width which varies as a function of the WC.

I do not know why 4.0025 (default value for --body_decay parameter) does not include 3 body decays. I also do not know how to change the default value of the --body_decay parameter when I run inside madgraph by adding 'auto' to the parameter card.

Thanks,
Reza

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Olivier Mattelaer (olivier-mattelaer) said :
#1

Hi,

You can not change the option passed with the auto mode.
So you have to call the madwidth command by hand.

Cheers,

Olivier

> On 21 May 2021, at 12:55, Reza Goldouzian <email address hidden> wrote:
>
> New question #697179 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/697179
>
> Dear Experts,
>
> I would like to change the width of top quark in the presence of tblnu EFT vertex which add t>lnub decay mode.
> When I use 'DECAY 6 auto' in parameter card, madgraph uses the default setting of MadWidth for calculating the width of top quark and does not include my new three-body decay mode. I always receive the same top width (1.4669 GeV) independent of the input value of the Wilson coefficient. I even increased the WC to 100 (for Lambda=1TeV) but I find the same width as default.
>
> I see the following massage when running the madgraph
> 'compute_widths 6 --precision_channel=0.01 --body_decay=4.0025 --path=/Users/rezagol/calc/MG5_aMC_v2_6_6/EFTDecay_tlnub/Cards/param_card.dat --output=/Users/rezagol/calc/MG5_aMC_v2_6_6/EFTDecay_tlnub/Cards/param_card.dat'
>
> When I call the MadWidth from a MadGraph5aMC-@NLO and use the same model (dim6 top) and the same cards but with the following parameter
> --body_decay=3
>
> I receive a new width which varies as a function of the WC.
>
> I do not know why 4.0025 (default value for --body_decay parameter) does not include 3 body decays. I also do not know how to change the default value of the --body_decay parameter when I run inside madgraph by adding 'auto' to the parameter card.
>
> Thanks,
> Reza
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Reza Goldouzian (rgoldouz) said :
#2

Hi Olivier,

Thanks a lot for your prompt reply.

I am trying to use weights so I need to update the top width at each weight. So I think calling madwidth command by hand does not work for me. Is it correct?

do you know why --body_decay=4.0025 does not include three body decays of top quark? Is it connected to the 0.0025 precision?
Is there a way to generate a sample with weights for those operators which add a three body decay modes and can change the top width?

Thanks a lot,
Reza

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#3

I guess that you will need to prepare the cards in advance.

> do you know why --body_decay=4.0025 does not include three body decays of top quark? Is it connected to the 0.0025 precision?

If you read the paper this should be clear.
The first estimator is only based on existing 2 body configuration so indeed if you add a four point interaction that can be miss by the auto mode. If you passe to the second estimator this should be included since we do have Feynman Diagram at that stage.

Cheers,

Olivier

> On 21 May 2021, at 13:30, Reza Goldouzian <email address hidden> wrote:
>
> Question #697179 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/697179
>
> Reza Goldouzian posted a new comment:
> Hi Olivier,
>
> Thanks a lot for your prompt reply.
>
> I am trying to use weights so I need to update the top width at each
> weight. So I think calling madwidth command by hand does not work for
> me. Is it correct?
>
> do you know why --body_decay=4.0025 does not include three body decays of top quark? Is it connected to the 0.0025 precision?
> Is there a way to generate a sample with weights for those operators which add a three body decay modes and can change the top width?
>
> Thanks a lot,
> Reza
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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