MadGraph5_aMC@NLO

Using MadGraph to model neutrino interactions

Asked by Dale Adam Julson

Hi, I am looking to model the interactions between electrons and high energy neutrinos. What I am finding however is that when I reduce the overall energy of the electron, MadGraph throws an error. Here are the MadGraph commands I am using:

>import model sm-full
>generate e+ vl > all all
>output
>launch

At this point, everything runs correctly. The default values for the electron beam is 500 GeV and the neutrino beam 1000 GeV. When I reduce the electron beam to be 1 GeV and the neutrino beam to be 1000 GeV, MadGraph throws an error with the following associated debug.log file:

generate_events run_02
Traceback (most recent call last):
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/interface/extended_cmd.py", line 1541, in onecmd
    return self.onecmd_orig(line, **opt)
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/interface/extended_cmd.py", line 1490, in onecmd_orig
    return func(arg, **opt)
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/interface/madevent_interface.py", line 2474, in do_generate_eve\
nts
    self.run_generate_events(switch_mode, args)
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/interface/common_run_interface.py", line 7126, in new_fct
    original_fct(obj, *args, **opts)
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/interface/madevent_interface.py", line 2513, in run_generate_ev\
ents
    self.exec_cmd('survey %s %s' % (self.run_name,' '.join(args)),
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/interface/extended_cmd.py", line 1570, in exec_cmd
    stop = Cmd.onecmd_orig(current_interface, line, **opt)
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/interface/extended_cmd.py", line 1490, in onecmd_orig
    return func(arg, **opt)
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/interface/madevent_interface.py", line 3371, in do_survey
    jobs, P_zero_result = ajobcreator.get_helicity()
  File "/Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/madgraph/madevent/gen_ximprove.py", line 187, in get_helicity
    raise Exception(pjoin(self.me_dir,'error'))
Exception: /Users/dalejulson/Desktop/Vanderbilt/MG5_aMC_v2_9_16/bin/PROC_sm-full_2/error

I have found a few other very similar MadGraph questions/answers [1,2], however I have been unable to get any of those suggested fixes to work here. Is there anything that can be done to model such interactions with lower energy electrons?

Thanks!

[1] https://answers.launchpad.net/mg5amcnlo/+question/678937
[2] https://answers.launchpad.net/mg5amcnlo/+question/244150

Question information

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Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
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Solved by:
Olivier Mattelaer
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Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

Sorry for the late answer, I was only notified today.

I have run the following code on the LTS version and it worked but not with 3.5.2 version.
The reason is that some of the feynman diagram that you generate does not have any -phase space since the mass of the final state is higher than the initial energy that you put in the system and looks like depending of the version, MG5aMC just ignore the issue (and just raise a warning or fail to handle it and crash).

The simplest solution is to only ask for the process which are kinematically possible at the energy that you are looking for.

Cheers,

Olivier

Revision history for this message
Dale Adam Julson (djulson) said : 		#2

Thanks Olivier Mattelaer, that solved my question.