Higher-order power corrections in a transverse-momentum cut for colour-singlet production at NLO

Leandro Cieri,Marco Rocco,Carlo Oleari

doi:10.1140/epjc/s10052-019-7361-8

Leandro Cieri, Marco Rocco + Show 1 more

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https://doi.org/10.1140/epjc/s10052-019-7361-8

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Abstract

We consider the production of a colourless system at next-to-leading order in the strong coupling constant alpha _{{displaystyle } {scriptstyle } {scriptscriptstyle } {scriptscriptstyle } mathrm{S}}. We impose a transverse-momentum cutoff, q_{{displaystyle } {scriptstyle } {scriptscriptstyle } {scriptscriptstyle } mathrm{T}}^{{displaystyle } {scriptstyle } {scriptscriptstyle } {scriptscriptstyle } mathrm{cut}}, on the colourless final state and we compute the power corrections for the inclusive cross section in the cutoff, up to the fourth power. The study of the dependence of the cross section on q_{{displaystyle } {scriptstyle } {scriptscriptstyle } {scriptscriptstyle } mathrm{T}}^{{displaystyle } {scriptstyle } {scriptscriptstyle } {scriptscriptstyle } mathrm{cut}} allows for an understanding of its behaviour at the boundaries of the phase space, giving hints on the structure at all orders in alpha _{{displaystyle } {scriptstyle } {scriptscriptstyle } {scriptscriptstyle } mathrm{S}} and on the identification of universal patterns. The knowledge of such power corrections is also a required ingredient in order to reduce the dependence on the transverse-momentum cutoff of the QCD cross sections at higher orders, when the q_{mathrm{T}}-subtraction method is applied. We present analytic results for both Drell–Yan vector boson and Higgs boson production in gluon fusion and we illustrate a process-independent procedure for the calculation of the all-order power corrections in the cutoff. In order to show the impact of the power-correction terms, we present selected numerical results and discuss how the residual dependence on q_{{displaystyle } {scriptstyle } {scriptscriptstyle } {scriptscriptstyle } mathrm{T}}^{{displaystyle } {scriptstyle } {scriptscriptstyle } {scriptscriptstyle } mathrm{cut}} affects the total cross section for Drell–Yan Z production and Higgs boson production via gluon fusion at the LHC.

Highlights

The current precision-physics program at the Large Hadron Collider (LHC) requires Standard Model (SM) theoretical predictions at the highest accuracy
In order to show the impact of the power-correction terms, we present selected numerical results and discuss how the residual dependence on qTcut affects the total cross section for Drell–Yan Z production and Higgs boson production via gluon fusion at the LHC
We do not expect this to be true in general when cuts are applied to the final state

Summary

Introduction

The current precision-physics program at the Large Hadron Collider (LHC) requires Standard Model (SM) theoretical predictions at the highest accuracy. Data belonging to “benchmark” processes, which are measured with the utmost precision at the LHC, need to be tested against theoretical results at the same level of accuracy. This is important for the extraction of SM parameters per se, and for searches of signals of new physics, that can appear as small deviations in kinematic distributions with respect to the SM predictions. Until a few years ago, the standard for such calculations was next-to-leading order (NLO) accuracy. For several “standard candles” processes, the first steps towards the calculation of differential cross sections at N3LO have been taken (see e.g. [1,2])

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