Pair Production of Neutral Higgs Particles in Gluon--Gluon Collisions
  Pair production processes of neutral Higgs particles will allow us to study the trilinear Higgs couplings at future high--energy colliders. Several mechanisms give rise to multi--Higgs final states in hadron interactions. In the present paper we investigate Higgs pair production in gluon--gluon collisions. After recapitulating pair production in the Standard Model, the analysis of the cross sections is carried out in detail for the neutral Higgs particles in the minimal supersymmetric extension. 
T. Plehn, M. Spira and P.M. Zerwas