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T: Fachverband Teilchenphysik

T 10: QCD (Theorie) I

T 10.5: Vortrag

Mittwoch, 30. März 2011, 17:45–18:00, 30.23: 10-1

Decoupling of the heavy top from the weak neutral current and Γ(Z → hadrons) — •Jörg Rittinger — TTP, KIT, Karlsruhe

The Z decay rate into hadrons is related to the QCD corrections of the imaginary part of the Z propagator via the optical theorem. Because of the SU(2) coupling to left handed fermions both vector and axial vector current appear. Since at high loop (up to 4 loop) only massless propagators or massive tadpoles can be calculated we have to decouple the t quark. The t quark decouples naivly for the vector current, but not for the axial vector current. This procedure and the 4 loop results of the axial vector correlator will be the topic of this talk.