Signal to background interference in pp →tH- →tW-b b at the LHC Run II

We investigate in the Large Hadron Collider (LHC) environment the possibility that sizeable interference effects between a heavy charged Higgs boson signal produced via bg→tH- (+c.c.) scattering and decaying via H-→W-A→W-bb (+c.c.) and the irreducible background given by bg→tW-bb topologies could spoil current search approaches where the former and latter channels are treated separately. The rationale for this comes from the fact that a heavy charged Higgs state can have a large width, which can also happen for the CP-odd neutral Higgs state emerging in the ensuing decays, which in turn enables such interferences. We conclude that effects are very significant, both at the inclusive and exclusive level (i.e., both before and after H± selection cuts are enforced, respectively) and typically of a destructive nature. This, therefore, implies that currently established LHC reaches for heavy charged Higgs bosons require some level of rescaling. However, this is possible a posteriori, as the aforementioned H± selection cuts shape the interference contributions at the differential level in a way similar to that of the isolated H± signal, so there is no need to reassess the efficiency of the individual cuts. We show such effects quantitatively by borrowing benchmark points from different Yukawa types of a 2-Higgs doublet model parameter space for H± values starting from around 200 GeV.