Quark and lepton masses in 5D SO(10)

We construct a five dimensional supersymmetric SO(10) x D3 grand unified model with an S1/(Z2 x Z'2) orbifold as the extra dimension. The orbifold breaks half of the supersymmetry and breaks the SO(10) gauge symmetry down to SU(4)C x SU(2)L x SU(2)R. The Higgs mechanism is used to break the remaining gauge symmetry the rest of the way to the Standard Model. We place matter fields variously in the bulk and on the orbifold fixed points and the resulting massless fields are mixtures between these brane and bulk fields. A chiral adjoint field in the bulk gets a U(1)X vacuum expectation value, resulting in an X-dependent localization of the bulk matter fields and the Standard Model Higgs field. This Higgs field localization allows us to simultaneously explain the hierarchies mu> mb. The model uses 11 parameters to fit the 13 independent low energy observables of the quark and charged lepton Yukawa matrices. The model predicts the values of two quark mass combinations, mu/mc and mdmsmb, each of which are predicted to be approximately 1σ above their experimental values. The remaining observables are successfully fit at the 5% level. We note that this 5D theory, as formulated, has problems retaining the Pati-Salam Yukawa symmetry relations. A simple 6D fix, which preserves the 5D results, solves this problem