Multi-top quark production is a staple program at the LHC. Single-top and tt¯ productions are studied extensively, while current efforts are zooming in on four-top search, where the Standard Model (SM) cross section is at O(10) fb. In contrast, only at the fb level in SM, triple-top production has not been targeted for study so far. But such a small cross section makes it a unique probe for New Physics. Without the usual discrete Z2 symmetry, the general two Higgs doublet model (g2HDM) can naturally raise the triple-top production to pb level. We illustrate how certain signal regions of four-top search can be utilized to constrain triple-top production, but urge a dedicated search. As an aside, we note that the CMS study at 13 TeV of scalar tt¯ resonance interfering with QCD production background indicate some activity at 400 GeV. We comment that this could be explained in principle in g2HDM via the extra top Yukawa coupling.
Hou, W. S., Kohda, M., & Modak, T. (2019). Implications of four-top and top-pair studies on triple-top production. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 798. https://doi.org/10.1016/j.physletb.2019.134953