On non-factorisable contributions to t-channel single-top production

Christian Brønnum-Hansen,Chen-Yu Wang,Jérémie Quarroz,Kirill Melnikov

doi:10.1007/jhep11(2021)130

Christian Brønnum-Hansen, Chen-Yu Wang + Show 2 more

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https://doi.org/10.1007/jhep11(2021)130

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Abstract

We compute the non-factorisable contribution to the two-loop helicity amplitude for t-channel single-top production, the last missing piece of the two-loop virtual corrections to this process. Our calculation employs analytic reduction to master integrals and the auxiliary mass flow method for their fast numerical evaluation. We study the impact of these corrections on basic observables that are measured experimentally in the single-top production process.

Highlights

Scattering mediated by an exchange of a W boson, ii) the s-channel process that at the partonic level corresponds to q q → W ∗ → t b and, iii) the associated production that involves the g b → W t process
The more recent computations of such corrections presented in refs. [16, 17] are quite sophisticated and incorporate top quark decays and QCD corrections to them in the narrow width approximation, all existing calculations of next-to-next-to-leading order (NNLO) QCD corrections to t-channel single-top production do not account for the so-called non-factorisable contributions
Since at next-to-next-to-leading order two gluons in a colour-singlet state can be exchanged between different fermion lines, non-factorisable diagrams start contributing at that order and, in principle, have to be accounted for

Summary

Introduction

Scattering mediated by an exchange of a W boson, ii) the s-channel process that at the partonic level corresponds to q q → W ∗ → t b and, iii) the associated production that involves the g b → W t process. Studies of single-top production rely on a precise theoretical description of this process that can be obtained in the context of perturbative QCD and collinear factorisation This has been done at next-to-leading order (NLO) in perturbative QCD in refs. The goal of this paper is to make the first step towards a better understanding of non-factorisable corrections to single-top production at the LHC and to calculate their contributions to the two-loop virtual amplitude We do this by expressing all two-loop integrals that appear in non-factorisable diagrams through master integrals keeping exact dependence on the top quark mass and the W mass and by computing these integrals using the auxiliary mass flow method [21,22,23].1. We do this by expressing all two-loop integrals that appear in non-factorisable diagrams through master integrals keeping exact dependence on the top quark mass and the W mass and by computing these integrals using the auxiliary mass flow method [21,22,23].1 As we explain in detail below, this computational set up is similar to the one used previously by two of the present authors [26, 27]

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