Asked by Yizhou Cai on 2021-03-03

Dear experts,

I am generating some samples like generate p p > h2 > t t~, and then use MadSpin to define the decay of top quark. I use a param_card, whice has set the width of h2 and t, in MadEvent. And MadSpin caculate another parem_card because the previous one did not contain the branch of t, and in this card the width of h2 is difference with the previous one. I am not sure which width is used.

I would appreciate your help. Thank you!

Yizhou

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Yizhou Cai
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2021-03-04
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2021-03-04
2021-03-04
 Olivier Mattelaer (olivier-mattelaer) said on 2021-03-03: #1

So the one used is the one computed by MadSpin, since it needs to be consistent with the BR information.
If that one does not match your previous one, you will get a warning (as you have observe I guess).
To avoid that, you have to specify not only the full-width but also the BR information in the original param_card and madspin will then use that information.

Cheers,

Olivier

> On 3 Mar 2021, at 15:05, Yizhou Cai <email address hidden> wrote:
>
> New question #695837 on MadGraph5_aMC@NLO:
>
> Dear experts,
>
> I am generating some samples like generate p p > h2 > t t~, and then use MadSpin to define the decay of top quark. I use a param_card, whice has set the width of h2 and t, in MadEvent. And MadSpin caculate another parem_card because the previous one did not contain the branch of t, and in this card the width of h2 is difference with the previous one. I am not sure which width is used.
>
> I would appreciate your help. Thank you!
>
> Yizhou
>
> --

 Yizhou Cai (yzcai) said on 2021-03-04: #2

I just got the following lines of output:

INFO: We need to recalculate the branching fractions for t~,w-,w+,t
INFO: using the FeynRules formula present in the model (arXiv:1402.1178)

So h2 > t t~ process use the latter card, even if the process was not defined in MadSpin?

 Olivier Mattelaer (olivier-mattelaer) said on 2021-03-04: #3

decay A
and that in the param_card has not the BR for particle A
then all particle with "decay" have their width re-computed.

Cheers,

Olivier

> On 4 Mar 2021, at 03:05, Yizhou Cai <email address hidden> wrote:
>
> Question #695837 on MadGraph5_aMC@NLO changed:
>
> Yizhou Cai posted a new comment:
> I just got the following lines of output:
>
> INFO: We need to recalculate the branching fractions for t~,w-,w+,t
> INFO: using the FeynRules formula present in the model (arXiv:1402.1178)
>
> So h2 > t t~ process use the latter card, even if the process was not
>
> --

 Yizhou Cai (yzcai) said on 2021-03-04: #4

No, I don't have this line. There is just decay t and w in Madspin card.

Cheers,
Yizhou

 Olivier Mattelaer (olivier-mattelaer) said on 2021-03-04: #5

So in that case, your width for h2 is not recomputed and should have the same value for the two cards.

> On 4 Mar 2021, at 08:30, Yizhou Cai <email address hidden> wrote:
>
> Question #695837 on MadGraph5_aMC@NLO changed:
>
> Yizhou Cai posted a new comment:
> No, I don't have this line. There is just decay t and w in Madspin card.
>
> Cheers,
> Yizhou
>
> --