Search for heavy Higgs bosons in top-antitop final states at ATLAS

Despite the many successes of the Standard Model in its predictions of particle interactions, there are still several experimental observations that cannot be described within the framework of the Standard Model. Consequently, the search for New Physics is an important feature of the ATLAS physics program. This talk will discuss searches where the target is the production of a heavy scalar (H) or pseudoscalar (A) Higgs-like particle, through its decay to a top-antitop quark pair (ttbar). Several Beyond Standard Model (BSM) theories predict the existence of new, heavy particles with the addition of a second Higgs doublet to the Standard Model. In the top-associated production, the 4-top final state is distinctive, although it has a small cross section. In gluon-initiated production, the presence of strong interference between the signal process and the dominant background process, the Standard Model ttbar production, distorts the signal shape from a Breit-Wigner resonance peak to a peak-dip structure, the shape of which depends on the specific model parameters. This talk describes the search for heavy Higgs particles produced in association with a ttbar pair and the corresponding upper limits calculated. In addition, the complications from the presence of interference in gluon-initiated production are discussed and the development of a dedicated statistical analysis method to accommodate these significant interference effects is explained.