Pair production of fundamental unstable particles in modified perturbation theory in NNLO

TL;DR

This paper develops a modified perturbation theory approach to accurately calculate the pair production and decay of unstable particles at NNLO, showing excellent convergence near and above the cross-section peak.

Contribution

It introduces a modified perturbation theory framework for NNLO calculations of unstable particle pair production, including resonant contributions as distributions.

Findings

MPT provides excellent convergence near and above the cross-section maximum.

The method accurately reproduces exact solutions in a model with resonant particles.

Universal massless-particles contributions are effectively incorporated.

Abstract

We consider pair production and decay of fundamental unstable particles in the framework of a modified perturbation theory (MPT) treating resonant contributions in the sense of distributions. The cross-section of the process is calculated within the NNLO of the MPT in a model that admits exact solution. Universal massless-particles contributions are taken into consideration. A comparison of the outcomes with the exact solution demonstrates excellent convergence of the MPT series at the energies near and above the maximum of the cross-section.