zero cross section error

[Amalia Betancur]

Hello,

I am trying to calculate a cross section with a model implemented in SARAH, using MG5_aMC_v2_5_5.

When I run the process p p > ci1 nv1 (where ci1 is a charged fermion and nv2 a majorana fermion) the process seems to work and the cross section is calculated. However, if I try to generate the conjugate process p p > ci1bar nv1, madgraph can not calculate the cross section, however,it does calculate the matrix element (using the standalone output).
I am attaching the debug.log file

What could be the issue?

Thank you very much,

Amalia

[Olivier Mattelaer (olivier-mattelaer)]

Hi,

Can you attach the tarball of the process?
Something weird happens but unfortunately, I do not have enough information to know which one of the detailed log file I need to get an idea of the problem.

It would be even better if you can join the log of both process, such that I can see why the other ones goes trough and see if that run is problematic or not.

Thanks,

Olivier

> On 27 Feb 2018, at 20:50, Amalia Betancur <email address hidden> wrote:
>
> Public bug reported:
>
> Hello,
>
> I am trying to calculate a cross section with a model implemented in
> SARAH, using MG5_aMC_v2_5_5.
>
> When I run the process p p > ci1 nv1 (where ci1 is a charged fermion and nv2 a majorana fermion) the process seems to work and the cross section is calculated. However, if I try to generate the conjugate process p p > ci1bar nv1, madgraph can not calculate the cross section, however,it does calculate the matrix element (using the standalone output).
> I am attaching the debug.log file
>
> What could be the issue?
>
> Thank you very much,
>
> Amalia
>
> ** Affects: mg5amcnlo
> Importance: Undecided
> Status: New
>
> ** Attachment added: "run_01_tag_1_debug.log"
> https://bugs.launchpad.net/bugs/1752158/+attachment/5064703/+files/run_01_tag_1_debug.log
>
> --
> You received this bug notification because you are subscribed to
> MadGraph5_aMC@NLO.
> https://bugs.launchpad.net/bugs/1752158
>
> Title:
> zero cross section error
>
> Status in MadGraph5_aMC@NLO:
> New
>
> Bug description:
> Hello,
>
> I am trying to calculate a cross section with a model implemented in
> SARAH, using MG5_aMC_v2_5_5.
>
> When I run the process p p > ci1 nv1 (where ci1 is a charged fermion and nv2 a majorana fermion) the process seems to work and the cross section is calculated. However, if I try to generate the conjugate process p p > ci1bar nv1, madgraph can not calculate the cross section, however,it does calculate the matrix element (using the standalone output).
> I am attaching the debug.log file
>
> What could be the issue?
>
> Thank you very much,
>
> Amalia
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/mg5amcnlo/+bug/1752158/+subscriptions

[Amalia Betancur (amaliab2)]

Hello,

I am attaching a tarball of the problematic process.

I am not sure what would be the log of a process that runs through, is it the banner.txt located at the events file?

Thank you,

Amalia

[Olivier Mattelaer (olivier-mattelaer)]

Sorry looks like I forget about this thread.
I've just put it back in my todo list. Sorry for that.

Olivier

[Olivier Mattelaer (olivier-mattelaer)]

Hi,

Looks like that the issue was that some of your PDG code was too large to be handle by MG5_aMC.

Here is the diff that fix the problem (just push the limit a bit further.

=== modified file 'Template/LO/Source/rw_events.f'
--- Template/LO/Source/rw_events.f 2016-11-20 14:05:38 +0000
+++ Template/LO/Source/rw_events.f 2018-04-11 20:43:00 +0000
@@ -217,7 +217,7 @@
       write(largeBuff,'(a)') '</event>'
       evt_record=trim(evt_record)//CHAR(13)//CHAR(10)//trim(largeBuff)
       return
- 51 format(i9,5i5,5e19.11,f3.0,f4.0)
+ 51 format(i11,5i5,5e19.11,f3.0,f4.0)
       end

@@ -300,7 +300,7 @@
       enddo
       write(lun,'(a)') '</event>'
       return
- 51 format(i9,5i5,5e19.11,f3.0,f4.0)
+ 51 format(i11,5i5,5e19.11,f3.0,f4.0)
       end

       subroutine write_comments(lun)

[Amalia Betancur (amaliab2)]

Hello,

I don't know where to find: 'Template/LO/Source/rw_events.f'

But I made the pdg code for the BSM particles shorter and it worked!

Thank you very much!