Decays in v2.3.3 and v2.4.3

Hi Matthew,

Can you check in the beta version of 2.5.0?
available on this link:
https://launchpad.net/mg5amcnlo

I think that it should fix that problem.

Cheers,

Olivier

> On Sep 21, 2016, at 16:02, Matthew Low <email address hidden> wrote:
>
> New question #401831 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/401831
>
> Dear Madgraph team,
>
> I am simulating a process with a new particle, X+, in the s-channel decaying to W+ and a photon. I am finding that in v2.3.3 both:
>
> A) p p > X+ > W+ a
> B) p p > X+, X+ > W+a
>
> work fine (X+ is relatively narrow). However, in v2.4.3 A) still works but B) does not work (i.e. Survey return zero cross section.)
>
> Looking briefly at some of the process files I notice that in SubProcesses/P1_.../G1/run1_app.log there is an "smin" parameter set to zero (for the case that does not work) while it is set to a non-zero number for the case that does work. I don't see a similar line in the same file for v2.3.3. On the other hand "p p > w+, w+ > j j" works fine so maybe it is due to the presence of the new X+?
>
> Thanks!
> - Matthew
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

I tried the 2.5.0 beta but it still doesn't work unfortunately. I've just emailed you the model files in case my model is doing something strange.

Thanks!
- Matthew

Hi,

Sorry for the delay but I did not manage to find time to investigate on this before now.
Here is the proper fix. Thanks a lot for the report and for your patience.

Cheers,

Olivier

=== modified file 'Template/LO/SubProcesses/myamp.f'
--- Template/LO/SubProcesses/myamp.f 2016-06-16 15:03:59 +0000
+++ Template/LO/SubProcesses/myamp.f 2016-09-29 18:27:44 +0000
@@ -212,7 +212,8 @@
 c
             onshell = (abs(xmass - prmass(i,iconfig)) .lt.
      $ bwcutoff*prwidth(i,iconfig).and.
- $ prwidth(i,iconfig)/prmass(i,iconfig).lt.0.1d0)
+ $ (prwidth(i,iconfig)/prmass(i,iconfig).lt.0.1d0.and.
+ $ gForceBW(i,iconfig).eq.1))
             if(onshell)then
 c Remove on-shell forbidden s-channels (gForceBW=2) (JA 2/10/11)
               if(gForceBW(i,iconfig).eq.2) then

> On Sep 26, 2016, at 21:02, Valentin Hirschi <email address hidden> wrote:
>
> Question #401831 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/401831
>
> Assignee: None => Olivier Mattelaer
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

No problem! Thanks for the help!

With the added lines it still doesn't work for me. Is it possible it should be?

+ $ (prwidth(i,iconfig)/prmass(i,iconfig).lt.0.1d0.or.

where I swapped the "and" or an "or". This does seem to work for me with the cross-sections from the p p > X > .... vs. p p > X , X > ... agreeing within 5%.

Thanks again!
- Matthew

Hi Matthew,

Yes you are right.

Thanks so much,

Olivier