'''Authors''': Cen Zhang, Diogo Buarque Franzosi, Eleni Vryonidou

'''Reference''': arXiv:1707.06760

'''Abstract''': The model allows the computation of (pseudo-)scalar resonance production in top-antitop quarks final state at NLO in QCD accuracy, including interference effects.

'''Information''': 
To use the model in MadGraph_aMC@NLO you need to follow these instructions:
 
1 - Comment line self['loop_diagrams']=newloopselection in madgraph/loop/loop_diagram_generation.py inside your distribution ;

2 - Generate the output with [[BR]]
> import model AHttbar >define p = 21 2 4 1 3 -2 -4 -1 -3 5 -5 [[BR]]
>define j = p [[BR]]
>set complex_mass_scheme [[BR]]
>generate p p > t t~ QCD=2 QED=1 EFT=1 [QCD] [[BR]]
>output PROC_pp-tt 

3 - Go into the generated directory (e.g. PROC_pp-tt) and comment the following lines in SubProcesses/montecarlocounter.fc [[BR]]
write(*,*)'Error #4 in set_matrices' [[BR]]
c write(*,*)isspecial0,nglu,nsngl [[BR]]
c stop [[BR]]
c write(*,*)'Error #6 in check_mc_matrices', [[BR]]
c # notagluon,ntot,max_bcol [[BR]]
c stop 

4 - Modify cards according to your needs and generate events using standard commands. SM QCD background, signal and interference will be generated on the same sample.

5 - In the parameter card, the lambda, yht, yht5, ctg, cphig, cphig5 correspond to the coefficients in eq.3.12; yhf and yhf5 are not used by the model; muprime and muyukawa are the (MSbar) scales at which the operator coefficients and the yht/yht5 are defined respectively; creal + i*cimag is the adhoc phase we had to add to all operators for reweighting purpose; cc is an overall coefficient that is multiplied to all operators (so that you can set cc=+x and cc=-x and subtract the two samples to get the pure interference.)