Techniques for the treatment of IR divergences in decay processes at NLO and application to the top-quark decay

TL;DR

This paper extends two algorithms for handling infrared divergences in decay processes at NLO, applying them to top-quark decay to improve precision in theoretical predictions and facilitate future event generator development.

Contribution

It generalizes the dipole subtraction and slicing methods for decay kinematics with massive and massless particles, enabling more accurate NLO calculations for top-quark decay.

Findings

Calculated NLO QCD and electroweak corrections to top-quark decay width.

Extended algorithms handle complex decay kinematics with multiple charged particles.

Results serve as a foundation for NLO top-quark decay event generators.

Abstract

We present the extension of two general algorithms for the treatment of infrared singularities arising in electroweak corrections to decay processes at next-to-leading order: the dipole subtraction formalism and the one-cutoff slicing method. The former is extended to the case of decay kinematics which has not been considered in the literature so far. The latter is generalized to production and decay processes with more than two charged particles, where new "surface" terms arise. Arbitrary patterns of massive and massless external particles are considered, including the treatment of infrared singularities in dimensional or mass regularization. As an application of the two techniques we present the calculation of the next-to-leading-order QCD and electroweak corrections to the top-quark decay width including all off-shell and decay effects of intermediate W bosons. The result, e.g., represents a building block of a future calculation of NLO electroweak effects to off-shell top-quark pair (WWbb) production. Moreover, this calculation can serve as the first step towards an event generator for top-quark decays at next-to-leading order accuracy, which can be used to attach top-quark decays to complicated many-particle top-quark processes, such as for tt+H or tt+jets.