Top-quark couplings to TeV resonances at future lepton colliders

Abstract

We study the processes $W_L W_L \to t \bar t$ and $W_L Z_L \to t\bar b (\bar t b)$ at future lepton colliders as probes of the couplings of the top quark to resonances at the TeV scale. We consider the cases in which the dominant low energy feature of a strongly interacting electroweak symmetry breaking sector is either a scalar or a vector resonance with mass near 1 TeV. We find that future lepton colliders with high energy and high luminosity have great potential to sensitively probe these physics scenarios. In particular, at a 1.5 TeV linear collider with an integrated luminosity of 200 fb$^{-1}$, we expect about 120 events for either a scalar or a vector to decay to $t\bar t, t \bar b$. Their leading partial decay widths, which characterize the coupling strengths, can be statistically determined to about 10% level.