Interference Effects in $t{\bar t}$ Production at the LHC as a Window on New Physics

Many extensions of the Standard Model contain (pseudo)scalar bosons with masses in the TeV range. At hadron colliders, such particles would predominantly be produced in gluon fusion and would decay into top quark pair final sates, a signal that interferes with the large QCD background $gg \to t\bar t$. This phenomenon is of interest for searches for by the LHC experiments. Here, we consider the signal and background interference in this process and study it in various benchmark scenarios, including models with extra singlet (pseudo)scalar resonances, two-Higgs doublet models, and the minimal supersymmetric extension of the SM with parameters chosen to obtain the measured light Higgs mass (the hMSSM). We allow for the possible exchanges of beyond the SM vector-like particles as well as scalar quarks. We calculate the possible interference effects including realistic estimates of the attainable detection efficiency and mass resolution. Studies of our benchmark scenarios indicate that searches with an LHC detector could permit the observation of the $t\bar t$ final states or constrain significantly large regions of the parameter spaces of the benchmark scenarios.