Production of HHH and HHV(V=γ,Z) at the hadron colliders

We consider the production of two Higgs bosons in association with a gauge boson or another Higgs boson at the hadron colliders. We compute the cross sections and distributions for the processes $ p p \to H H H $ and $H H Z$ within the standard model. In particular, we compute the gluon-gluon fusion one-loop contributions mediated via heavy quarks in the loop. It is the leading order contribution to $ p p \to H H H $ process. To the process $ p p \to H H Z $, it is next-to-next-to-leading-order (NNLO) contribution in QCD coupling. We also compare this contribution to the next-to-leading-order (NLO) QCD contribution to this process. The NNLO contribution can be similar to NLO contribution at the Large Hadron Collider (LHC), and significantly more at higher center-of-mass energy machines. We also study new physics effects in these processes by considering $ttH, HHH, HHHH, HZZ$, and $HHZZ$ interactions as anomalous. The anomalous couplings can enhance the cross sections significantly. The $gg \to HHH$ process is specially sensitive to anomalous trilinear Higgs boson self-coupling. For the $gg \to HHZ$ process, there is some modest dependence on anomalous $HZZ$ couplings.