Based on the ${\mathbf{Z}}_{12-I}$ orbifold compactification of heterotic string theory, we construct a flipped-SU(5) model with three families of standard model matter and ingredients for dynamical supersymmetry breaking through the hidden sector matter ${\overline{\mathbf{10}}}^{\prime }$ and ${\mathbf{5}}^{\prime }$ of $\mathrm{SU}(5{)}^{\prime }$, which are neutral under the visible sector flipped-SU(5). The appearance of one chiral set ${\overline{\mathbf{10}}}^{\prime }$ and ${\mathbf{5}}^{\prime }$ is the new feature of the present flipped-SU(5) string model with ${sin}^2{\theta }_W^0=\frac{3}{8}$. As required, all the exotic states are shown to decouple from low energy physics. Above the compactification scale, the flipped-SU(5) gauge symmetry is enhanced to SO(10) gauge symmetry by including the Kaluza-Klein modes. The threshold correction is calculated by counting Kaluza-Klein modes, and we show that the model allows a very wide range for the hidden-sector confining scale (${10}^{11}\mathrm{GeV}–{10}^{16}\mathrm{GeV}$).

• Received 22 June 2009

DOI:https://doi.org/10.1103/PhysRevD.80.115012