Flavor structure in $SO(32)$ heterotic string theory
  We study the flavor structure in $SO(32)$ heterotic string theory on six-dimensional torus with magnetic fluxes. In particular, we focus on models with the flavor symmetries $SU(3)_f$ and $\Delta(27)$. In both models, we can realize the realistic quark masses and mixing angles. 
Hiroyuki Abe, Tatsuo Kobayashi, Hajime Otsuka, Yasufumi Takano, Takuya   H. Tatsuishi
hep-ph hep-th