Searches for multi-Higgs final states allow to constrain parameters of the SM (or extensions thereof) that directly relate to the mechanism of electroweak symmetry breaking. Multi-Higgs production cross sections, however, are small and the phenomenologically accessible final states are challenging to isolate in the busy multi-jet hadron collider environment of the LHC run 2 and HL-LHC. This makes the necessity to extend the list of potentially observable production mechanisms obvious. Most of the phenomenological analyses in the past have focused on gg→. hh+. jets; in this paper we study pp→tt-hh at the HL-LHC and find that this channel for h→bb- and semi-leptonic and hadronic top decays has the potential to provide an additional handle to constrain the Higgs trilinear coupling in a global fit at the end of the high luminosity phase.
Englert, C., Krauss, F., Spannowsky, M., & Thompson, J. M. (2015). Di-Higgs phenomenology in tt-hh: The forgotten channel. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 743, 93–97. https://doi.org/10.1016/j.physletb.2015.02.041