Sensitivity to effective electroweak couplings in single top production at the LHC

We study the mechanism of single top production at the LHC in the framework of an effective electroweak lagrangian, analyzing the sensitivity of different observables to the magnitude of the effective couplings of the top. The analysis is carried out using the effective $W$ approximation, whose validity in the present case is discussed. To be able to distinguish between left and right effective couplings one must necessarily measure the polarization of the top and this can only be achieved indirectly by measuring the angular distribution of top decay products. We show that a unique spin basis (in the top rest frame) exists that allows one to connect the top decay products angular distribution with the single top polarized production cross section.