Constraining the t →u flavor changing neutral Higgs coupling at the LHC

We study the constraints on t→u flavor changing neutral Higgs coupling and how it may be explored further at the LHC. In the general two Higgs doublet model, such transitions can be induced by a nonzero ρtu Yukawa coupling. We show that such couplings can be constrained by existing searches at the LHC for mH, mA, and mH+ in the sub-TeV range, where H, A, and H+ are the exotic CP-even, CP-odd, and charged scalars. We find that a dedicated ug→tH/tA→tt? search can probe the available parameter space of ρtu down to a few percent level for 200 GeV?mH, mA?600 GeV, with discovery possible at high luminosity. Effects of how other extra top Yukawa couplings, such as ρtc and ρtt, dilute the sensitivity of the ρtu probe are discussed. ? 2020 authors. Published by the American Physical Society.