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Göttingen 2012 – scientific programme

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T: Fachverband Teilchenphysik

T 13: QCD (Theorie) 3

T 13.8: Talk

Thursday, March 1, 2012, 18:30–18:45, VG 3.103

Decay Rate of the Z-boson into hadrons at Os4) — •Pavel Baikov2, Konstantin Chetyrkin1, Johann Kühn1, and Jörg Rittinger11Institut für theoretische Teilchenphysik, KIT, Karlsruhe — 2Institute of Nuclear Physics, Moscow State University, Moscow

To calculate the decay rate of the Z-boson into hadrons (ΓZ), one has to do two steps. First the heavy top quark has to be decoupled, which leads to an effective massless 5-flavour QCD. Second the imaginary part of the Z-propagator, which is related to ΓZ due to the optical theorem, has to be calculated in this effective theory. This was done up to Os4), including the calculation of 5-loop propagators.

Since ΓZ is related to one of the most precise determinations of αs, our calculation will improve the existing 3 loop fit, resulting in a small shift in αs and a reduction of the theory uncertainty.

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