Generating events with QED loop

Asked by Maheyer J Shroff on 2020-11-24

Hello MadGraph experts,

I am new to MadGraph and I am interested in calculating the EWK loop contribution of a p p > W Z process.

Since aMC@NLO v2.8 doesn't support QED at NLO accuracy, I understand (and I would appreciate it if you could verify this) that I could generate loop-induced processes using the [noborn=QED] tag.

My setup is as follows:

set complex_mass_scheme
import model loop_qcd_qed_sm_Gmu
generate p p > w+ z QCD=0 [noborn=QED]

The diagrams are mostly what I am after (except those for the Goldstone bosons and the ghost particles)

When I ``launch`` the output is pasted as below:
Generating 10000 events with run name run_01
survey run_01
INFO: compile directory
initMadLoop -r -f
Initializing MadLoop loop-induced matrix elements (this can take some time)...
MadLoop initialization finished.
compile Source Directory
Using random number seed offset = 21
INFO: Running Survey
Creating Jobs
Working on SubProcesses
INFO: P0_qq_wpz
INFO: Idle: 8, Running: 4, Completed: 0 [ current time: 10h02 ]
INFO: Idle: 7, Running: 4, Completed: 1 [ 15.3s ]
INFO: Idle: 5, Running: 4, Completed: 5 [ 33.8s ]
Note: The following floating-point exceptions are signalling: IEEE_UNDERFLOW_FLAG IEEE_DENORMAL
INFO: Idle: 4, Running: 4, Completed: 7 [ 44.1s ]
Note: The following floating-point exceptions are signalling: IEEE_UNDERFLOW_FLAG IEEE_DENORMAL
INFO: Idle: 3, Running: 4, Completed: 9 [ 59.6s ]
WARNING: name 'file' is not defined

After this, the process stalls and when I manually quit, I get the error:
Command "generate_events run_01" interrupted with error:
NameError : name 'file' is not defined
Please report this bug on
More information is found in '/MG5_aMC_v2_8_0/question/run_01_tag_1_debug.log'.
Please attach this file to your report.

I was hoping if you could shed light on this problem, and would appreciate your advice if this is the direction to take if one wants to calculate the QED/EWK loop effects and generate events of such a process.

Thanks a lot for the help!

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The [noborn=QED] is bypassing any check that you do not have born.
and goes directly to loop-induce mode.
However, in your case you do have a born and therefore it is unlikely that the loop computation that you are performing is finite.
This should be part of the problem that you face.
Then you also face a python3 compatibility issue which is already fixed in the development version.



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