Next-to-leading order corrections to Wt production and decay

TL;DR

This work delivers a next-to-leading order QCD calculation for $Wt$ production, including full leptonic decays of the $W$ and top quarks and radiation in the top decay. A $b$-quark PDF framework combined with a $p_T$ veto on extra $b$-jets separates the $Wt$ signal from doubly-resonant $t\bar{t}$ contributions, while real and virtual corrections are handled with a dipole subtraction scheme for massive quarks. At the LHC, inclusive NLO corrections are mild (around 10%), with smaller scale dependence when the veto is applied; in Higgs searches targeting $H\rightarrow WW^*$, NLO effects appreciably reshape key distributions and can reduce the $Wt$ background by substantial factors. The results enhance background modeling for Higgs analyses and provide a more precise baseline for single-top production, though they rely on approximations such as massless $b$ quarks, on-shell top quarks, and parton-level treatment without hadronization.

Abstract

We present the results of a next-to-leading order calculation of Wt production, including the decays of both the top quark and the W boson. The effects of radiation in the decay of the top quark are also included. The separation of diagrams which appear in the real corrections, into singly- and doubly-resonant contributions, is performed using a b-jet veto which is motivated by the use of the bottom quark distribution function. We find that, for a choice of scale which is suitable for this approach, the QCD corrections are very mild and only change the cross section by up to 10% at the LHC, depending on the severity of the b-jet veto. When further cuts are applied, applicable for a Higgs boson search in the H->WW channel, we find that the radiative effects greatly decrease the number of background events expected from this process. In addition, the shapes of relevant distributions can be significantly changed at next-to-leading order.

Figures (12)

• Figure 1: The two tree level diagrams for the $Wt$ process.
• Figure 2: One loop diagrams representing virtual corrections in the production stage.
• Figure 3: One loop diagrams contributing to the calculation of virtual radiation in the decay stage.
• Figure 4: Diagrams representing the emission of real radiation in the production stage. In the calculation, the additional gluon must also be crossed into the initial state and diagrams containing two quark lines (not shown) are also included.
• Figure 5: Diagrams contributing to real radiation in the decay of the top quark.