Probing ttγ and ttZ couplings at the LHeC

We study the deep inelastic scattering and photo-production modes of (tt) over bar pairs at the proposed LHeC and its potential to probe the electromagnetic and weak dipole moments (MDM and EDM for tt gamma) of the top quark. A framework of eight independent gauge-invariant dimension-six operators involving the top quark and the electroweak gauge bosons is used. Four of these operators modify the charged tbW coupling which can be probed through the single (anti)top production mode, as reported in the literature. One generates tt gamma(Z) as well as tbW couplings, while the other two do not generate tbW but only tt gamma(Z). Our focus is on the MDM and EDM of the top quark for which the photo-production mode of t (t) over bar can be an excellent probe. At the proposed electron energies of E-e = 60 and 140 GeV the LHeC could set constraints stronger than the indirect limits from b -> s gamma and the potential limits of the LHC through (tt) over bar production.