Dear Florian,

I met 2 problems when working on UFO with MadGraph or HERWIG.
First, how can I generate VBF with MadGraph? the default model files of MadGraph do not include the Higgs couplings to the SM fermions. Therefore, we can invoke "generate p p > h j j $$ w+ w- z". However, UFO generated by SARAH contains both Higgs couplings to SM fermions and the effective the couplings to gluon. We use the command "p p > h1 j j $$ wm wmc z / g" to exclude the gluon, but this command does not exclude the gluon at all. I try to comment the Higgs couplings to SM fermion in the model file, it returns error
Command "generate p p > h1 j j $$ wm wmc z / g" interrupted with error:
NoDiagramException : No amplitudes generated from process Process: g/u1/u2/d1/d2/u1bar/u2bar/d1bar/d2bar g/u1/u2/d1/d2/u1bar/u2bar/d1bar/d2bar > h1 g/u1/u2/d1/d2/u1bar/u2bar/d1bar/d2bar g/u1/u2/d1/d2/u1bar/u2bar/d1bar/d2bar $$ wm wmc z / g BSM=1 HIG=1 HIW=1 WEIGHTED=4 @1. Please enter a valid process

Why this UFO model file cannot generate the vector boson fusion channels? I have made sure the vertices Higgs-W-W exist in file vertices.py.

The 2nd problem: I try to use HERWIG to convert this UFO file and work in CONTUR, it gives error

ufo2herwig MSSM/
Warning: Unknown colour structure f(-1,1,4)*f(-1,2,3) f(-1,1,3)*f(-1,2,4) f(-1,1,2)*f(-1,3,4) ( g g g g ) in V_3195.
Warning: unsupported VVVV ( Wmc A A Wm ) Lorentz structure in V_3196:
Metric(1,3)*Metric(2,4)
Warning: unsupported VVVV ( Wmc A Wm Z ) Lorentz structure in V_3197:
Metric(1,3)*Metric(2,4)
Warning: unsupported VVVV ( Wmc Wmc Wm Wm ) Lorentz structure in V_3198:
Metric(1,3)*Metric(2,4)
Warning: unsupported VVVV ( Wmc Wm Z Z ) Lorentz structure in V_3199:
Metric(1,3)*Metric(2,4)
Traceback (most recent call last):
File "/home/kepingx/share/herwig/bin/ufo2herwig", line 449, in <module>
tc = VVSCouplings(vertex,coupling,prefactors,L,lorentztag)
File "/home/kepingx/share/herwig/lib/Herwig/python/ufo2peg/helpers.py", line 718, in VVSCouplings
couplings[itype]+=eval(reminder, {'cmath':cmath} )
File "<string>", line 1, in <module>
NameError: name 'P' is not defined

My ufo2herwig works for the MadGraph default models files, such as 2HDM, MSSM_SLHA2, even works for the UFO file generated by FeynRules. But this problem of "name P is not defined" exist for all the UFO files generated by SARAH. So, what is the difference of UFO files generated by SARAH and FeynRules.

Best regards,
Keping

Hi,

1) I'm sorry, but I'm not an expert of MG. Maybe, it's better to ask the authors of MG how to single out the channels you want to have.

2) That sounds strange, because "P" is standard in the UFO format to label all particles. I must admit, I never tried the parcer of Herwig for UFO files. Since the files are accepted by MG (aren't they?!), they fulfill the UFO conventions. Therefore, it might be also easier to ask the authors of Herwig if they have an idea why there might be problems.

Cheers,
Florian