Single-top-quark production in the $t$-channel at NNLO

TL;DR

This paper provides a detailed NNLO calculation of t-channel single-top-quark production and decay, resolving previous discrepancies and emphasizing the importance of NNLO corrections for precision in Standard Model analyses.

Contribution

The paper introduces a complete NNLO calculation for t-channel single-top-quark production and decay, resolving prior disagreements and proposing optimized scale choices for improved stability.

Findings

NNLO corrections significantly improve cross section predictions.

Double deep inelastic scattering scales enhance perturbative stability.

NNLO effects are crucial for precise top-quark process identification.

Abstract

We present a calculation of t-channel single-top-quark production and decay in the five-flavor scheme at NNLO. Our results resolve a disagreement between two previous calculations of this process that found a difference in the inclusive cross section at the level of the NNLO coefficient itself. We compare in detail with the previous calculations at the inclusive, differential and fiducial level including b-quark tagging at a fixed scale $\mu=m_t$. In addition, we advocate the use of double deep inelastic scattering (DDIS) scales ($\mu^2=Q^2$ for the light-quark line and $\mu^2=Q^2+m_t^2$ for the heavy-quark line) that maximize perturbative stability and allow for robust scale uncertainties. All NNLO and NLO$\,\otimes\,$NLO contributions for production and decay are included in the on-shell and vertex-function approximation. We present fiducial and differential results for a variety of observables used in Standard Model and Beyond Standard Model analyses, and find an important difference between the NLO and NNLO predictions of exclusive $t+n$-jet cross sections. Overall we find that NNLO corrections are crucial for a precise identification of the t-channel process.