Flipped SU(5) from Z_{12-I} orbifold with Wilson line

Abstract

We construct a three family flipped SU(5) model from $Z_{12-I}$ orbifold with one Wilson line. The gauge group is $\rm SU(5)\times U(1)_X\times U(1)^2\times[SU(2)\times SO(10)]^\prime$. This model does not derive any nonabelian group except SU(5) from $E_8$, which is possible only for two cases, one in ${\bf Z}_{12-I}$ and the other in ${\bf Z}_{12-II}$. We present all possible Yukawa couplings. We place the third family in the twisted sectors and two light families in the untwisted sector. From the Yukawa couplings, the model provides the R-parity, the doublet-triplet splitting, and one pair of Higgs doublets. It is also shown that quark and lepton mixings are possible. In addition, $b-\tau$ unification is achieved, and $\nu_\tau$ mass can be in the sub-eV range. So far we have not encountered a serious phenomenological problem. There exist vectorlike flavor SU(5) exotics (including \Qem=$\pm\frac16$ color exotics and \Qem=$\pm\frac12$ electromagnetic exotics) and SU(5) singlet vectorlike exotics with \Qem=$\pm\frac12$ which can be removed near the GUT scale