A bottom-up approach to fermion mass hierarchy: a case with vector-like fermions. (28th April 2020)

• Record Type: Journal Article
• Authors: Kawamura, Yoshiharu
• Is Part Of: Progress of theoretical and experimental physics. Volume 2020:Number 4(2020)
• Publication Date: 2020-04-28
• Subjects: B40 -- B55; Physics -- Periodicals; Mathematical physics -- Periodicals; 530.05
• DOI: 10.1093/ptep/ptaa046
• Languages: English
• ISSNs: 2050-3911

Abstract

Abstract: We propose a bottom-up approach in which a structure of high-energy physics is explored by accumulating existence proofs and/or no-go theorems in the standard model or its extension. As an illustration, we study fermion mass hierarchies based on an extension of the standard model with vector-like fermions. It is shown that the magnitude of elements of Yukawa coupling matrices can become $O(1)$ and a Yukawa coupling unification can be realized in a theory beyond the extended model, if vector-like fermions mix with three families. In this case, small Yukawa couplings in the standard model can be highly sensitive to a small variation of matrix elements, and it seems that the mass hierarchy occurs as a result of fine tuning.