We present a calculation of O(alpha_s) contributions to the process of t-channel single-top production and decay, which include virtual and real corrections arising from interference of the production and decay subprocesses. The calculation is organi
zed as a simultaneous expansion of the matrix elements in the couplings alpha_{ew},alpha_s and the virtuality of the intermediate top quark, (p_t^2-m_t^2)/m_t^2 ~ Gamma_t/m_t, and extends earlier results beyond the narrow-width approximation.
We present a method to compute off-shell effects for processes involving resonant particles at hadron colliders with the possibility to include realistic cuts on the decay products. The method is based on an effective theory approach to unstable part
icle production and, as an example, is applied to t-channel single top production at the LHC.