Phenomenological viability of string inspired multi-Higgs doublet models
  We analyse the phenomenological viability of heterotic $Z_3$ orbifold models with two Wilson lines, which naturally predict three families of matter and Higgs fields. We study the orbifold parameter space, and discuss the compatibility of the predicted Yukawa couplings with current experimental data, thus evaluating the viability of the orbifold configurations. We address the implications of tree-level flavour changing neutral processes in constraining the Higgs sector of the model, finding that viable scenarios can be obtained for a fairly light Higgs spectrum. 
A.M. Teixeira