= Higgs pair production =

This page contains the codes for different models of the Higgs pair production at LHC through gluon fusion.

== SM ==

In this model we calculated the Higgs pair production at LO for a top quark circulating in the loops (exact form factors at LO for the triangle loop and the box from arxiv:9603205v1 [hep-ph]).

The output of MG5 in that case can be downloaded here : [attachment:SM.tar.gz SM]   

== BSM : tthh coupling ==

Here we have implemented a new coupling tthh which has been described in terms of a new parameter c2 (see arxiv:1205.5444v2 [hep-ph]). You can modify its value in the block bsminputs of the paramcard. So by setting c2 to 0 you will recover the above SM result. 

The output of MG5 in that case can be downloaded here : [attachment:tthh.tar.gz tthh] 

== BSM : Additional heavy scalar resonance ==

Finally in this case we have considered the possibility of having a heavy scalar H (called hh in the MG files) as an intermediate state (so that we have the additional process p p > hh > h h that is taken into account). For this model in the paramcard you have the freedom of modifying a wide range of parameters :
* the top yukawa coupling (via the parameter cy) 
* the SM-Higgs trilinear coupling (ctr)
* the H coupling to the top (cyH)
* the H coupling to 2 SM-Higgs (ctrH)
The parameters cy and ctr are just factors that multiply the SM couplings. The parameters cyH and ctrH are similarly used but for the new heavy Higgs. Finally you can also modify :
* the H mass (MHH)
* the H decay width (WHH)

The output of MG5 in that case can be downloaded here : [attachment:HeavyScalar.tar.gz HeavyScalar] 

-- ''Main.!Hespel Benoît - 12 Dec 2013''