An SU(5) heterotic standard model

We introduce a new heterotic Standard Model which has precisely the spectrum of the Minimal Supersymmetric Standard Model (MSSM), with no exotic matter. The observable sector has gauge group SU(3)C×SU(2)L×U(1)Y. Our model is obtained from a compactification of heterotic strings on a Calabi-Yau threefold with Z2 fundamental group, coupled with an invariant SU(5) bundle. Depending on the region of moduli space in which the model lies, we obtain a spectrum consisting of the three generations of the Standard Model, augmented by 0, 1 or 2 Higgs doublet conjugate pairs. In particular, we get the first compactification involving a heterotic string vacuum (i.e., a stable bundle) yielding precisely the MSSM with a single pair of Higgs.