Karlsruhe 2011 – scientific programme
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T: Fachverband Teilchenphysik
T 19: Beyond the Standard Model (Theorie) IV
T 19.4: Talk
Friday, April 1, 2011, 14:45–15:00, 30.23: 6-1
Precision Gauge Unification from Extra Yukawa Couplings — •Ivan Donkin1 and Arthur Hebecker2 — 1Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 19, D-69120 Heidelberg, Germany — 2Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 19, D-69120 Heidelberg, Germany
We investigate the impact of extra vector-like GUT multiplets on the predicted value of the strong coupling. We find in particular that Yukawa couplings between such extra multiplets and the MSSM Higgs doublets can resolve the familiar two-loop discrepancy between the SUSY GUT prediction and the measured value of alpha_3. Our analysis highlights the advantages of the holomorphic scheme, where the perturbative running of gauge couplings is saturated at one loop and further corrections are conveniently described in terms of wavefunction renormalization factors. If the gauge couplings as well as the extra Yukawas are of O(1) at the unification scale, the relevant two-loop correction can be obtained analytically. However, the effect persists also in the weakly-coupled domain, where possible non-perturbative corrections at the GUT scale are under better control.