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

TL;DR

This paper constructs a three-family flipped SU(5) string model from heterotic string theory on a Z_{12-I} orbifold with Wilson line, addressing gauge symmetry, Yukawa couplings, and phenomenological features.

Contribution

It presents a novel string-derived flipped SU(5) model with detailed gauge structure, Yukawa couplings, and phenomenological implications, including mechanisms for quark-lepton mixing and exotic particle removal.

Findings

The model achieves three families with realistic Yukawa couplings.

It provides solutions for doublet-triplet splitting and R-parity.

Exotic particles can be decoupled near the GUT scale.

Abstract

We construct a three family flipped SU(5) model from the heterotic string theory compactified on the $\Z_{12-I}$ orbifold with one Wilson line. The gauge group is $\rm SU(5)\times U(1)_X\times U(1)^2\times[SU(2)\times SO(10)\times U(1)^2]^\prime$. This model does not derive any nonabelian group except SU(5) from $E_8$, which is possible only for two cases in case of one shift $V$, one in ${\bf Z}_{12-I}$ and the other in ${\bf Z}_{12-II}$. We present all possible Yukawa couplings. We place the third quark family in the twisted sectors and two light quark 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. 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) vectorlike singlet exotics with \Qem=$\pm\frac12$ which can be removed near the GUT scale. In this model, ${\rm sin}^2\theta_W^0={3/8}$ at the full unification scale.