I have been trying to generate one-loop diagrams (for a range of different models generated with FeynRules) and output pythia, yet have hit the error:
Traceback (most recent call last):
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/interface/extended_cmd.py", line 1544, in onecmd
return self.onecmd_orig(line, **opt)
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/interface/extended_cmd.py", line 1493, in onecmd_orig
return func(arg, **opt)
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/interface/master_interface.py", line 304, in do_output
self.cmd.do_output(self, line, *args, **opts)
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/interface/madgraph_interface.py", line 8182, in do_output
self.export(nojpeg, main_file_name, group_processes, args)
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/interface/master_interface.py", line 318, in export
return self.cmd.export(self, *args, **opts)
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/interface/madgraph_interface.py", line 8340, in export
exporter = self._curr_exporter.generate_process_directory(\
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/iolibs/export_cpp.py", line 1774, in generate_process_directory
process_exporter_pythia8.generate_process_files()
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/iolibs/export_cpp.py", line 226, in generate_process_files
self.write_process_cc_file(writers.CPPWriter(filename))
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/iolibs/export_cpp.py", line 300, in write_process_cc_file
self.get_process_function_definitions()
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/iolibs/export_cpp.py", line 1105, in get_process_function_definitions
color_amplitudes = [me.get_color_amplitudes() for me in \
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/iolibs/export_cpp.py", line 1105, in <listcomp>
color_amplitudes = [me.get_color_amplitudes() for me in \
File "/home/s4358844/MG5_aMC_v3.1.0/MG5_aMC_v3_1_0/madgraph/loop/loop_helas_objects.py", line 2399, in get_color_amplitudes
raise self.PhysicsObjectError("Usage of get_color_amplitudes is not allowed in a LoopHelasMatrixElement")
madgraph.core.base_objects.PhysicsObject.PhysicsObjectError: Usage of get_color_amplitudes is not allowed in a LoopHelasMatrixElement
I can see that the function get_color_amplitudes() in loop_helas_object.py simply returns this error to prevent usage of this. However, I can also see that below this, there are functions 'get_born_color_amplitudes' and 'get_loop_color_amplitudes'. Is there a choice of settings that will allow Pythia to be output for a loop process, or, is Pythia not capable of handling these at all?
The easiest way to reproduce the error is to just use the loop_sm model:
import model loop_sm
generate g g > h > t t~ g [noborn=QCD]
output pythia8 PythiaLOOP
Any help would be greatly appreciated,
Christopher