Complete off-shell effects in top quark pair hadroproduction with leptonic decay at next-to-leading order

TL;DR

This paper presents the first complete NLO QCD calculations for top quark pair production and decay with off-shell effects, including non-resonant contributions, providing more accurate predictions for collider experiments.

Contribution

It introduces a comprehensive NLO QCD framework incorporating off-shell effects and non-resonant contributions in top pair production and decay, surpassing previous narrow width approximation methods.

Findings

Positive NLO corrections: 2.3% at TeVatron, 47% at LHC.

Forward-backward asymmetry at TeVatron: 0.051 +/- 0.0013.

Residual theoretical uncertainty: 8% (TeVatron), 9% (LHC).

Abstract

Results for next-to-leading order QCD corrections to the pp(p\bar{p}) -> t \bar{t} -> W^+W^- b\bar{b} -> e^{+} \nu_{e} \mu^{-} \bar{\nu}_{\mu} b \bar{b} +X processes with complete off-shell effects are presented for the first time. Double-, single- and non-resonant top contributions of the order {\cal{O}}(\alpha_{s}^3 \alpha^4) are consistently taken into account, which requires the introduction of a complex-mass scheme for unstable top quarks. Moreover, the intermediate W bosons are treated off-shell. Comparison to the narrow width approximation for top quarks, where non-factorizable corrections are not accounted for is performed. Besides the total cross section and its scale dependence, several differential distributions at the TeVatron run II and the LHC are given. In case of the TeVatron the forward-backward asymmetry of the top is recalculated afresh. With inclusive selection cuts, the forward-backward asymmetry amounts to A^{t}_{FB} = 0.051 +/- 0.0013. Furthermore, the corrections with respect to leading order are positive and of the order 2.3% for the TeVatron and 47% for the LHC. A study of the scale dependence of our NLO predictions indicates that the residual theoretical uncertainty due to higher order corrections is 8% for the TeVatron and 9% for the LHC.