zerowidth_tchannel vs set width auto

Asked by Richard Ruiz

Dear Team,

I have an order-of-operations question. :)

Suppose I have the w+ w+ > e+ e+ process via a heavy, t-channel Majorana N and no other diagram. In theory, N has a width. However, the zerowidth_tchannel = true option ensures that this is set to zero for the WW > ee process.

My understanding is that zerowidth_tchannel is implemented by common_run_interface.py at the time of "output process". Therefore, if at runtime I do "set width auto", will this overwrite the width with a nonzero value? Subsequently, will my cross section then be evaluated assuming a non-zero t-channel width?

Thank you for looking into this question!

best
richard

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Richard Ruiz
Solved:
Last query:
Last reply:
Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#1

Hi,

> Therefore, if at runtime I do "set width auto", will this overwrite the width with a nonzero value? Subsequently, will my cross section then be evaluated assuming a non-zero t-channel width?

No the width of all T-channel will be zero ignoring whatever value you set in the param_card (auto is not different).

Cheers,

Olivier

> On 2 May 2022, at 09:20, Richard Ruiz <email address hidden> wrote:
>
> New question #701623 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/701623
>
> Dear Team,
>
> I have an order-of-operations question. :)
>
> Suppose I have the w+ w+ > e+ e+ process via a heavy, t-channel Majorana N and no other diagram. In theory, N has a width. However, the zerowidth_tchannel = true option ensures that this is set to zero for the WW > ee process.
>
> My understanding is that zerowidth_tchannel is implemented by common_run_interface.py at the time of "output process". Therefore, if at runtime I do "set width auto", will this overwrite the width with a nonzero value? Subsequently, will my cross section then be evaluated assuming a non-zero t-channel width?
>
> Thank you for looking into this question!
>
> best
> richard
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Richard Ruiz (rruiz) said :
#2

Thanks for the quick response Olivier!

best