Pseudoscalar searches with dileptonic tops and jet substructure

The quest for new heavy states is a critical component of the LHC physics program. In this paper, we study the search for pseudoscalar bosons produced in association with a t (t) over bar pair. We consider the final state t (t) over barA -> t (t) over barb (b) over bar with a dileptonic top-pair signature, and reconstruct the boosted A -> b (b) over bar candidate with jet substructure techniques, achieving a remarkable sensitivity over a broad range of pseudoscalar masses and Yukawa couplings. We apply this strategy to a type-I two-Higgs-doublet model (2HDM), demonstrating its ability to probe a realistic, UV-complete extended Higgs sector. In particular, we find that the 13 TeV LHC with 300 fb(-1) of data can constrain the region tan beta > 1.5 at 95% C.L. for a light pseudoscalar with m(A) = 50 GeV. Moreover, the whole mass range 20 GeV < m(A) < 210 GeV can be ruled out for tan beta <= 1. Finally, we show that it is also possible to directly probe the CP-structure of the heavy scalar, and hence to distinguish a CP-odd (A) from a CP-even (H) 2HDM resonance.