A Z2xZ2 standard model

TL;DR

This paper constructs a string theory model using Z2 x Z2 orbifold compactification that yields the exact chiral MSSM spectrum, preserves gauge coupling unification, and maintains massless gauge bosons with realistic phenomenology.

Contribution

It introduces a novel heterotic string compactification that achieves the MSSM spectrum with exact chiral matter and realistic gauge symmetry breaking without flux in hypercharge.

Findings

Exact chiral MSSM spectrum obtained

Preserves gauge coupling unification

Maintains massless gauge bosons after symmetry breaking

Abstract

We present a Z_2 x Z_2 orbifold compactification of the E_8 x E_8 heterotic string which gives rise to the exact chiral MSSM spectrum. The GUT breaking SU(5) to SU(3)_C x SU(2)_L x U(1)_Y is realized by modding out a freely acting symmetry. This ensures precision gauge coupling unification. Further, it allows us to break the GUT group without switching on flux in hypercharge direction, such that the standard model gauge bosons can remain massless when the orbifold singularities are blown up. The model has vacuum configurations with matter parity, a large top Yukawa coupling and other phenomenologically appealing features.