On the NNLO QCD corrections to single-top production at the LHC

Mathias Brucherseifer,Fabrizio Caola,Kirill Melnikov

doi:10.1016/j.physletb.2014.06.075

Mathias Brucherseifer, Fabrizio Caola + Show 1 more

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https://doi.org/10.1016/j.physletb.2014.06.075

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Abstract

We present a fully-differential calculation of the NNLO QCD corrections to the t-channel mechanism for producing single top quarks at the LHC. We work in the structure function approximation, computing QCD corrections to the light- and heavy-quark lines separately and neglecting the dynamical cross-talk between the two. The neglected contribution, which appears at NNLO for the first time, is color-suppressed and is expected to be sub-dominant. Within this approximation, we find that, for the total cross section, NNLO QCD corrections are in the few percent range and, therefore, are comparable to NLO QCD corrections. We also find that the scale independence of the theoretical prediction for single-top production improves significantly once NNLO QCD corrections are included. Furthermore, we show how these results change if a cut on the transverse momentum of the top quark is applied and derive the NNLO QCD prediction for the ratio of single top and single anti-top production cross sections at the 8 TeV LHC.

Highlights

Studies of top quarks produced in hadron collisions are important for understanding many properties of these heavy particles, including their masses, their couplings to electroweak gauge bosons, their Cabbibo–Kobayashi–Maskawa matrix element V tb etc
In this paper we described the calculation of NNLO QCD corrections to t-channel single-top production cross section at the LHC
We found that the NNLO QCD corrections are small, of the order of a few percent

Summary

Introduction

Studies of top quarks produced in hadron collisions are important for understanding many properties of these heavy particles, including their masses, their couplings to electroweak gauge bosons, their Cabbibo–Kobayashi–Maskawa matrix element V tb etc. There are two main mechanisms for producing top quarks in hadron collisions Both at the Tevatron and the LHC, the dominant one occurs due to strong interactions and, through such processes as qq → ttor gg → tt, leads to the production of ttpairs. The main background for observing singletop production at a hadron collider is the direct production of W bosons in association with jets in general and with b-jets in particular. The severity of this background and the relative smallness O(1 pb) of the single-top production cross section made detailed studies of this process at the Tevatron very difficult. Since the single-top production cross section is proportional to the electroweak coupling of a top quark to a W -boson, an O(20%) measurement of the production cross section can be interpreted as an O(10%) measurement of the CKM matrix element |Vtb| or an O(20%) measurement of the top quark width

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