Next-to-Leading Order Corrections to Single Top Quark Production and Decay at the Tevatron: 1. s-channel Process

TL;DR

The paper delivers a comprehensive NLO QCD analysis of s-channel single top quark production at the Tevatron, including corrections to both production and decay while maintaining top-spin information via a modified narrow width approach. It quantifies the sizable impact of O(αs) corrections on the inclusive rate, acceptance under realistic cuts, and a broad set of kinematic and spin observables, with particular attention to three-jet events and top reconstruction. The study reveals that initial-state corrections dominate and that the decay corrections, though smaller, significantly shape several distributions and spin-related observables. It also demonstrates the relevance of these results for Higgs searches, where s-channel single top acts as a background to WH with H → bb, underscoring the need to incorporate NLO effects for reliable background predictions. Overall, the work provides a detailed framework and benchmarks for comparing NLO predictions to experimental analyses of single top processes and spin correlations at hadron colliders.

Abstract

We present a study of s-channel single top quark production at the upgraded Tevatron $p\bar{p}$ collider, including the next-to-leading order (NLO) QCD corrections to the production and the decay of the top quark. The "modified" narrow width approximation was adopted to preserve the spin of the top quark in its production and decay. We discuss the effect of the different $O(α_s)$ contributions on the inclusive cross section as well as various kinematic distributions after imposing the relevant cuts to select s-channel single top signal events. In particular the $O(α_s)$ decay contribution, while small in size, has a significant impact on several distributions. With the help of the best-jet algorithm to reconstruct the top quark we demonstrate that it is possible to study kinematical and spin correlations in s-channel single top events. We furthermore compare top quark spin measurements in two different basis and show how NLO corrections have to be taken into consideration in searches for the Higgs boson through $W^{\pm}H$ associated production at the Tevatron.

Figures (20)

• Figure 1: The theoretical cutoff $s_{min}$ dependence of the inclusive s-channel single top quark cross section at the Tevatron with $\mu_{R}=\mu_{F}=m_{t}$ for $m_{t}=178\,{\rm GeV}$. The decay branching ratio $t\rightarrow bW^{+}(\rightarrow e^{+}\nu)$ has been included.
• Figure 2: Top quark mass as well as renormalization and factorization scale dependence of the inclusive s-channel single top quark cross section at Tevatron. The decay branching ratio of $t\to bW^{+}(\to e^{+}\nu)$ has been included.
• Figure 3: Inclusive s-channel single top quark cross section at Tevatron for $m_t=178$ GeV, versus the ratio of the factorization scale $\mu_F$ to its typical value $\mu_0$, where $\mu_0=m_t$ and $\mu_0=\sqrt{\hat{s}}$, respectively. The decay branching ratio of $t\to bW^{+}(\to e^{+}\nu)$ has been included.
• Figure 4: Cross section and fraction of 3-jet events at NLO for varying jet $E_{T}$ cuts, requiring only that $n_{jets}\geq2$, and not making any cuts on the electron or neutrino. The left-hand figure shows the total cross section for events with 2 or 3 jets as a function of the jet $E_{T}$ cut for three different jet pseudo-rapidity cuts. The right-hand figure shows the fraction of 3-jet events as a function of the jet $E_{T}$ for different jet pseudo-rapidity cuts. The lowest threshold considered is 15 GeV.
• Figure 5: The transverse momentum $p_{T}$ (left) and pseudo-rapidity $\eta$ (middle) distributions of the electron and the missing transverse energy $\not\!\! E_{T}$ (right) after selection cuts, comparing Born level to $O(\alpha_{s})$ and full NLO.