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T: Fachverband Teilchenphysik

T 14: QCD (Theorie) 4

T 14.2: Vortrag

Freitag, 2. März 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 ∼ (α_s/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.