A New Approach to the Yukawa Puzzle
  We do a systematic analysis of the question of calculability of CKM matrix elements in terms of quark mass ratios, within the framework of the hypothesis of universality of strength for Yukawa couplings (USY), where all Yukawa couplings have equal moduli, and the flavor dependence is only in their phases. We use the fact that the limit $m_u=m_d=0$ is specially simple in USY, to construct the various ans\"atze. It is shown that the experimentally observed CKM matrix can be obtained within USY ans\"atze corresponding to simple relations among phases of Yukawa couplings. Within USY, one finds a natural explanation why Cabibbo mixing is significantly larger than the other CKM mixings. In the most successful of the USY ans\"atze, one obtains in leading order: $|V_{us}|=\sqrt{m_d/{m_s}}$ ; $ |V_{cb}|=\sqrt{2}(m_s/m_b)$ $ |V_{ub}|= (1/\sqrt{2})\sqrt{m_dm_s/m_b^2}$ ; $|V_{td}|= 3|V_{ub}|$. We study the behavior of this USY ansatz under the renormalization group. 
G.C. Branco, D. Emmanuel-Costa and J.I. Silva-Marcos (CFIF/IST)