5D SUSY orbifold SU(6) GUT and pseudo-Goldstone Higgs doublets

We construct a 5D SUSY SU(6) GUT on an S(1)/Z2×Z2′ orbifold. The first stage of gauge symmetry breaking occurs through compactification and a specific selection of boundary conditions. Additional symmetries play a crucial role for the generation of μ and Bμ terms of appropriate values: with a SU(2)cus custodial symmetry the Higgs doublets naturally emerge as massless pseudo-Goldstone bosons in the unbroken SUSY limit. After SUSY breaking they get masses of the order of the weak scale. If instead of SU(2)cus a discrete Z5 symmetry is applied the Higgs doubletʹs masses are still adequately suppressed, but they are not pseudo-Goldstones. The Z5 discrete symmetry also can be very important for GUT scale generation and an all order hierarchy. Fermion masses are naturally generated and nicely blend with additional symmetries. In the considered scenario unification of the three gauge couplings occurs near 1016 GeV.