Dominant NNLO corrections to four-fermion production near the W-pair production threshold

TL;DR

This paper computes the dominant NNLO corrections to four-fermion production near the W-pair threshold, showing a small impact on W-mass measurements and discussing correction interference effects.

Contribution

It introduces a calculation of the leading NNLO corrections using unstable-particle effective theory for W-pair production near threshold.

Findings

Correction causes a 3 MeV shift in W-mass measurement.

Provides a method to include multiple Coulomb photon effects.

Discusses implementation of realistic experimental cuts.

Abstract

We calculate the parametrically dominant next-to-next-to-leading order corrections to four-fermion production e^- e^+ -> mu^- nubar_mu u dbar + X at centre-of-mass energies near the W-pair production threshold employing the method of unstable-particle effective theory. In total the correction is small, leading to a shift of 3 MeV in the W-mass measurement. We also discuss the implementation of realistic cuts and provide a result for the interference of single-Coulomb and soft radiative corrections that can easily be extended to include an arbitrary number of Coulomb photons.