Resolving the Tevatron Top Quark Forward-Backward Asymmetry Puzzle: Fully Differential Next-to-Next-to-Leading-Order Calculation

TL;DR

This paper presents a fully differential NNLO QCD calculation of top quark pair production, resolving discrepancies in the Tevatron forward-backward asymmetry and aligning theoretical predictions with experimental measurements.

Contribution

It provides the first complete fully differential NNLO QCD calculation for a two-to-two scattering process with all colored partons, improving the precision of asymmetry predictions.

Findings

Standard Model asymmetry AFB^{SM} = 0.095 ± 0.007

Agreement with D0 measurement AFB^{D0} = 0.106 ± 0.03

Approximately 1.5 sigma below CDF measurement AFB^{CDF} = 0.164 ± 0.047

Abstract

We determine the dominant missing Standard Model (SM) contribution to the top quark pair forward-backward asymmetry at the Tevatron. Contrary to past expectations, we find a large, around 27%, shift relative to the well-known value of the inclusive asymmetry in next-to-leading order (NLO) QCD. Combining all known Standard Model corrections, we find that AFB^{SM} = 0.095 +- 0.007. This value is in agreement with the latest D0 measurement [V. M. Abazov et al. (D0 Collaboration), Phys. Rev. D 90, 072011 (2014)] AFB^{D0} = 0.106+- 0.03 and about 1.5 sigma below that of CDF [T. Aaltonen et al. (CDF Collaboration), Phys. Rev. D 87, 092002 (2013)] AFB^{CDF} =0.164 +- 0.047. Our result is derived from a fully differential calculation of the next-to-next-to leading order (NNLO) QCD corrections to inclusive top pair production at hadron colliders and includes - without any approximation - all partonic channels contributing to this process. This is the first complete fully differential calculation in NNLO QCD of a two-to-two scattering process with all coloured partons.