Top quark pair production and decay at hadron colliders

Abstract

In ongoing and upcoming hadron collider experiments, top quark physics will play an important rôle in testing the Standard Model and its possible extensions. In this work we present analytic results for the differential cross sections of top quark pair production in hadronic collisions at next-to-leading order in the QCD coupling, keeping the full dependence on the spins of the top quarks. These results are combined with the corresponding next-to-leading order results for the decay of polarized top quarks into dilepton, lepton plus jets, and all jets final states. As an application we predict double differential angular distributions which are due to the QCD-induced top quark spin correlations in the intermediate state. In addition to the analytic results, we give numerical results in terms of fit functions that can easily be used in an experimental analysis.

Two-loop leading color corrections to heavy-quark pair production in the gluon fusion channel

“…(2.3) arises from the interference of one-loop diagrams with the tree-level amplitude [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. The O(α 2 S ) term A 2 consists of two parts, the interference of two-loop diagrams with the Born amplitude and the interference of one-loop diagrams among themselves: The term A (1×1) 2 was derived in [87][88][89][90].…”

“…Most of the observables related to the top-quark pair production have been calculated up to NLO [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. In several cases, the next-to-leading (NLO) corrections have been supplemented by the resummation of large logarithmic corrections at leading (LL, [25][26][27][28][29][30][31]), next-to-leading (NLL, [32][33][34][35][36][37][38]) and next-to-next-to-leading logarithmic (NNLL, [39][40][41][42][43]) accuracy.…”

Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7 TeVusing the ATLAS detector

“…In the SM, tt pairs are produced essentially unpolarized at hadron colliders [3], as has been tested in recent measurements by the D0 Collaboration [4] and the ATLAS and CMS Collaborations [5,6]. Nonetheless, the correlation of the spin orientation of the top quark and the top antiquark can be studied, and is predicted to be nonzero [3,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

Top quark charge asymmetry: searching for light axigluons in t t ¯ $$ t\overline{t} $$ + jet production at the LHC

“…This absence of a collinear pole in the anti-symmetric tt + jet cross section is again related to the symmetry properties of the corresponding inclusive tt production cross section (see section 2 and footnote 6 at the end of section 2) and a divergent behaviour in the leading order tt + jet cross section is connected with a collinear pole proportional to 1/ in the NLO cross section for the tt cross section (see, e.g., eq. (3.15) in [70]). Since the 2 → 2 Born cross section is invariant under rotations about the beam axis, there is no collinear pole in the ϕ-anti-symmetric part of the NLO tt cross section and correspondingly the incline asymmetry of the tt + jet final state stays finite in the collinear limits.…”