Top Quark Electroweak Dipole Moment at a High Energy Muon Collider

Abstract

We study the sensitivity reach to probe the electroweak dipole operators associated with a top quark at a multi-TeV lepton collider. Studying the electroweak dipole operators is strongly motivated by precision physics. The operators exhibit unique chiral structure and can be enhanced with respect to others in theories beyond the Standard Model. We illustrate this point in a strongly coupled composite Higgs model. We find that a high energy $\mu^+\mu^-$ collider may offer unique opportunity to probe the electroweak dipole operators beyond the coverage by the LHC and future hadron colliders. The significant sensitivity is achieved by the leading channel $\mu^+ \mu^- \to t \bar t$ near the threshold, and substantially improved by the novel channel $\mu^+ \mu^- \to t \bar t h$ at high energies. We may be able to reach a new physics scale well above the collider energy for moderate couplings of the Wilson coefficients. Our main conclusions are applicable to future $e^+e^-$ colliders.