Extra Higgs bosons in tt production at the LHC

The top quark has a large Yukawa coupling with the Higgs boson. In the usual extensions of the standard model the Higgs sector includes extra scalars, which also tend to couple strongly with the top quark. Unlike the Higgs, these fields have a natural mass above 2mt, so they could introduce anomalies in tt production at the LHC. We study their effect on the tt invariant mass distribution at √(s)=7 TeV. We focus on the bosons (H,A) of the minimal supersymmetric model and on the scalar field (r) associated with the new scale f in Little Higgs (LH) models. We show that in all cases the interference with the standard amplitude dominates over the narrow-width contribution. As a consequence, the mass difference between H and A or the contribution of an extra T-quark loop in LH models becomes an important effect in order to determine if these fields are observable there. We find that a 1 fb-1 luminosity could probe the region tanβ≤3 of supersymmetry and v/(√(2)f)≥0.3 in LH models.