Mr Martin Spinrath (MPI for Physics)
Group theoretical factors from GUT symmetry breaking can lead to predictions for the ratios of quark and lepton Yukawa couplings at the unification scale. Due to SUSY threshold corrections the viability of such predictions can depend strongly on the SUSY parameters. For three common minimal SUSY breaking scenarios we investigate which GUT scale ratios y_e/y_d, y_\mu/y_s, y_\tau/y_b and y_t/y_b are allowed when phenomenological constraints are taken into account. We derive possible new predictions for the GUT scale mass ratios and compare them with the phenomenologically allowed ranges. We find that new GUT scale predictions such as y_\mu/y_s = 9/2 or 6 and y_\tau/y_b = 3/2 or 2 are often favoured compared to the ubiquitous relations y_\mu/y_s = 3 or y_\tau/y_b =1. We will also give a concrete implementation of these new relations.