Results of numerical simulations for unstable-particles pair production in modified perturbation theory in NNLO

Abstract

We consider pair production and decay of fundamental unstable particles in the framework of a modified perturbation theory (MPT), which treats resonant contributions of unstable particles in the sense of distributions. The cross-sections for the top-quark pair production and for the $W$-boson pair production in $e^{+}e^{-}$ annihilation are calculated within the NNLO in models that admit exact solutions. In both cases an excellent convergence of the MPT is detected at the energies close to and above the maximum of the cross section. In the case of $W$-boson pair production a precision of the description at the ILC energies is ensured at the level of one per-mille or higher.