NNLL threshold resummation for top-pair and single-top production

TL;DR

Top-quark production at hadron colliders is dominated by soft-gluon emissions near threshold, requiring higher-order resummation for precise total and differential cross sections. The paper applies NNLL threshold resummation in moment space (1PI kinematics) to generate approximate NNLO predictions for ttbar and single-top observables, including detailed differential distributions. It validates the approach by showing excellent agreement with exact NLO and partial NNLO results and with LHC/Tevatron data, and it provides state-of-the-art predictions at 7 and 8 TeV. The work demonstrates robustness of soft-gluon resummation across channels and observables and points toward future NNLO/NNNLO refinements.

Abstract

I discuss threshold resummation at NNLL accuracy in the standard moment-space approach in perturbative QCD for top-pair and single-top production. For top quark pair production I present new approximate NNLO results for the total cross section and for the top quark transverse momentum and rapidity distributions at 8 TeV LHC energy. I discuss the accuracy of the soft-gluon approximation and show that the NLO and NNLO approximate results from resummation are practically indistinguishable from exact NLO and partial NNLO results. For single top production I present new approximate NNLO results for the total cross sections in all three channels at the LHC and also for the top quark transverse momentum distributions in t-channel production and in top-quark associated production with a W boson. For both ttbar and single-top production the agreement of theoretical results with LHC and Tevatron data is excellent.

Figures (6)

• Figure 1: The soft-gluon matrix $S_{LI}$. The eikonal lines connect with color tensors $c_I$ and $c_L$.
• Figure 2: Comparison of exact and approximate NLO results for the total top-pair cross section and top-quark $p_T$ distribution (left); NNLO approximate top-pair total cross section compared with data at the LHC (right).
• Figure 3: NNLO approximate top-quark $p_T$ distributions (left) and related $K$-factors (right) at the LHC.
• Figure 4: NNLO approximate top-quark normalized $p_T$ distribution compared with CMS data (left) and top-quark rapidity distributions (right) at the LHC.
• Figure 5: Total $\sigma(t)+\sigma({\bar{t}})$ approximate NNLO cross sections in all three single-top channels compared with data from the LHC (left); $tW$-channel top-quark $p_T$ distribution at the LHC (right).