MadGraph5_aMC@NLO

Problem getting decay width at masses greater than 80 GeV

Asked by Kevin Alberto Urquía Calderón

I am using the model SM_HeavyN_NLO and SM_HeavyN_Gen3Mass_NLO, and I'm trying to calculate the decay width of a heavy neutrino into three fermions. Basically:

generate n1 > ff ff ff

Where I defined ff as all fermions. I have also added "set mn1 scan:range(20,120,2)" to scan the mass range that I want, but every time I get to 80 GeV, the value of the decay width skyrockets, there a less than ten events generated and I have an uncertainty ridiculously big.

I was working earlier with other decays, specifically n1 > e- mu+ vm and I did not have the same problem.

How can I fix this?

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

Please update to the latest version, this is likely to fix that issue.

Cheers,

Olivier

> On 6 Jun 2021, at 18:15, Kevin Alberto Urquía Calderón <email address hidden> wrote:
>
> New question #697427 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/697427
>
> I am using the model SM_HeavyN_NLO and SM_HeavyN_Gen3Mass_NLO, and I'm trying to calculate the decay width of a heavy neutrino into three fermions. Basically:
>
> generate n1 > ff ff ff
>
> Where I defined ff as all fermions. I have also added "set mn1 scan:range(20,120,2)" to scan the mass range that I want, but every time I get to 80 GeV, the value of the decay width skyrockets, there a less than ten events generated and I have an uncertainty ridiculously big.
>
> I was working earlier with other decays, specifically n1 > e- mu+ vm and I did not have the same problem.
>
> How can I fix this?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Kevin Alberto Urquía Calderón (kurquia) said : 		#2

Thanks! It's working now! But I had a problem updating MadGraph. After I write "install update" in the console, I get the following message:

Command "install update" interrupted with error:
TypeError : cannot use a string pattern on a bytes-like object
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in 'MG5_debug'.
Please attach this file to your report

I'm not sure how can I attach the file, I pasted what contained it here:
https://pastebin.com/RE8PjgpH

I had to manually download it again. I just want to update it this way so I don't have to download all the files I had again.