Single top quark production at LHC with anomalous Wtb couplings

We investigate single top production in the presence of anomalous Wtb couplings. We explicitly show that, if these couplings arise from gauge invariant effective operators, the only relevant couplings for single top production and decay are the usual gamma(mu) and sigma(mu nu)q(nu) terms, where q is the W boson momentum. This happens even in the single top production processes where the Wtb interaction involves off-shell top and/or bottom quarks. With this parameterisation for the Wtb vertex, we obtain expressions for the dependence on anomalous couplings of the single top cross sections. for (i) the t-channel process, performing a matching between tj and t (b) over barj production, where j is a light jet; (ii) s-channel t (b) over bar production; (iii) associated tW(-) production, including the correction from tW(-)(b) over bar. We use these expressions to estimate, with a fast detector simulation, the simultaneous limits which the measurement of single top cross sections at LHC will set on V-tb and possible anomalous couplings. Finally, a combination with top decay asymmetries and angular distributions is performed, showing how the limits can be improved when the latter are included in a global fit to Wtb couplings. (C) 2008 Elsevier B.V. All rights reserved.