Evaluating ME using standalone MG code

Hello,

I am trying to produce and use standalone code for ME computation using MadGraph. For this I use the prescription from here: https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-4 , from the secion labelled 'Full library of process in python for version 2.6.0 and 2.7.0 ' to have a single python library for the full set of matrix-element with different final states 4mu, 4e, 2mu2e and 2e2mu. Note that I use MG v2.7.3 for this computation.

First, I generate the process as such:

import model SMEFTatNLO-cpG_ctp_cpt (cpG_ctp_cpt is just a custom restrict_card that I create in the SMEFTatNLO model)
generate g g > l+ l- l+ l- /g QCD=4 QED=4 NP^2==4
output standalone gg4l_OpgSquared_standalone --prefix=int

This should produce the tree-level ggH process available with the dim-6 operators of SMEFTatNLO.

Then I do 'make allmatrix2py.so' and use the library for ME computations as such for a rough example:

import allmatrix2py
allmatrix2py.initialise('../Cards/param_card.dat')

def invert_momenta(p):
        """ fortran/C-python do not order table in the same order"""
        new_p = []
        for i in range(len(p[0])): new_p.append([0]*len(p))
        for i, onep in enumerate(p):
            for j, x in enumerate(onep):
                new_p[j][i] = x
        return new_p
p =[[ 0.5000000E+03, 0.0000000E+00, 0.0000000E+00, 0.5000000E+03],
    [0.5000000E+03, 0.0000000E+00, 0.0000000E+00, -0.5000000E+03],
    [ 0.8855133E+02, -0.2210069E+02, 0.4008035E+02, -0.7580543E+02],
    [ 0.3283294E+03, -0.1038496E+03, -0.3019338E+03, 0.7649492E+02],
    [ 0.1523581E+03, -0.1058810E+03, -0.9770964E+02, 0.4954839E+02],
    [ 0.4307611E+03, 0.2318313E+03, 0.3595630E+03, -0.5023788E+02]
    ]

p =invert_momenta(p)
nhel = -1 # means sum over all helicity
pdgs = [21,21,11,-11,13,-13] #which pdg is requested
scale2 = 0.0 #only used for loop matrix element. should be set to 0 for tree-level
alphas=0.13

ans = allmatrix2py.smatrixhel(pdgs,p,alphas,scale2,nhel)
print ans

Now, no matter the four momenta, the answer always seems to be 0.0.

Note that for the simple example of 'generate p p > t t~' I do get a decent answer. Also, this issue seems to only arise when trying to have a single python library for the full set of matrix-element. It works okay for each of the SubProcesses/P_xx_xxxx using the prescription in the same webpage.

Is there a way to resolve this issue? We would prefer to have the code for the full set of SubProcesses if possible.

Thanks,
Jay Sandesara