A new understanding of fermion masses from the unified theory of spins   and charges
  In this letter we try to answer those of the open questions of the Standard model which concern the appearance of families, mass protection mechanism and the Yukawa couplings - by using the approach (proposed by one of us), which suggests a new way beyond the Standard model. The approach has in the starting action for fermions, which carry in d(=1 +13)-dimensional space only the spin (two kinds of the spin) and interact with only spin connection and vielbein fields, the term manifesting as a mass term in d=1+3. (After making several approximations and assumptions) we connect free parameters of the approach with the experimental data and investigate a possibility that the fourth family appears at low enough energies to be observable in the new generation of accelerators. 
A. Borstnik Bracic, M. Breskvar, D. Lukman, N.S. Mankoc Borstnik