RG-improved single-particle inclusive cross sections and forward-backward asymmetry in $ t\bar{t} $ production at hadron colliders

Abstract

We use techniques from soft-collinear effective theory (SCET) to derive renormalization-group improved predictions for single-particle inclusive (1PI) observables in topquark pair production at hadron colliders. In particular, we study the top-quark transverse-momentum and rapidity distributions, the forward-backward asymmetry at the Tevatron, and the total cross section at NLO+NNLL order in resummed perturbation theory and at approximate NNLO in fixed order. We also perform a detailed analysis of power corrections to the leading terms in the threshold expansion of the partonic hard-scattering kernels. We conclude that, although the threshold expansion in 1PI kinematics is susceptible to numerically significant power corrections, its predictions for the total cross section are in good agreement with those obtained by integrating the toppair invariant-mass distribution in pair invariant-mass kinematics, as long as a certain set of subleading terms appearing naturally within the SCET formalism is included.

NNLO QCD predictions for fully-differential top-quark pair production at the Tevatron

“…The values shown here differ from figure 11 of ref. [5]; they correspond to the original calculations [120,121] and have been provided to us by the authors of refs. [120,121] for the purpose of this comparison.…”

“…The result of ref. [120] is NLO+NNLL in momentum space, uses default scale µ = 2m t and is shown here with its normalisation not rescaled to exact NNLO. The result of ref.…”

Associated production of a top pair and a Higgs boson beyond NLO

“…We obtain the approximate NNLO corrections from the perturbative information contained in a soft-gluon resummation formula valid to next-to-next-to-leading logarithmic (NNLL) accuracy. The derivation of this formula is based on the soft-collinear effective theory (SCET) methods 1 used to study differential top-quark pair production (tt) cross sections at NNLL in [15,17,18] (see [19][20][21][22] for SCET-based studies of the total tt cross section). In fact, since both tt and ttH production contain four colored partons, the study of soft-gluon corrections to these processes is conceptually identical and differs only because of the underlying kinematics.…”

NNLO corrections to top-pair production at hadron colliders: the all-fermionic scattering channels

“…Alternatively, in refs. [9][10][11] the resummed NNLL (and, by truncation, the approximate NNLO) total inclusive cross-section was derived from the resummed differential one.…”

“…A number of phenomenological studies have been presented in the literature [9][10][11][12][13][14][15][16][17]. Critical comparisons of the various approaches can be found in refs.…”