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T: Fachverband Teilchenphysik
T 14: QCD (Theorie) 4
T 14.2: Talk
Friday, March 2, 2012, 09:45–10:00, VG 3.103
NNLL top-antitop production close to threshold — Andre Hoang1, Pedro Ruiz-Femenia2, and •Maximilian Stahlhofen1 — 1University of Vienna, Austria — 2IFIC, Valencia
We use the effective field theory framework vNRQCD to describe the resonance line-shape of top-antitop-quark production in electron-positron collisions. The process is governed by three different scales: the mass of the top quarks m, their 3-momentom ∼ mv and their kinetic energy ∼ mv2, where v is the relative velocity of the quarks. Close to the production threshold this velocity is very small (v≪ 1) and leads to large terms ∼ (αs/v )n and large logarithms of the ratios of the physical scales in quantum corrections to the total cross section. The effective theory vNRQCD allows for a systematic resummation of these terms employing a Schrödinger equation and a renormalization group with a “subtraction velocity” as scaling parameter, respectively. We will discuss recent improvements in the theoretical prediction of the top-antitop resonance cross section and present the latest result at NNLL.