Top Quark Mass in Exophobic Pati--Salam Heterotic String Model

Understand

We analyse the phenomenology of an exemplary exophobic Pati-Salam heterotic string vacuum, in which no exotic fractionally charged states exist in the massless string spectrum.

• Our model also contains the Higgs representations that are needed to break the gauge symmetry to that of the Standard Model and to generate fermion masses at the electroweak scale.
• We show that the requirement of a leading mass term for the heavy generation, which is not degenerate with the mass terms of the lighter generations, places an additional strong constraint on the viability of the models.
• In many models a top quark Yukawa may not exist at all, whereas in others two or more generations may obtain a mass term at leading order.