Light U(1)s in Heterotic String Models
Viraf Mehta (Liverpool U.)
14.11.2013 at 16:15
Although additional low scale U(1)s have been discussed extensively in GUTs and string
models, having a viable light, extra U(1) in worldsheet heterotic string constructions has
proven to be a challenge. Here, we present the construction of heterotic string models
using the free fermionic formulation and focus on how viable U(1)s may arise. We motivate
an example as an appealing proposition to explain the suppression of proton decay
mediating operators. This forbids the undesired operators, and thus they may only arise
after the U(1) is broken. We give details of a left-right symmetric model that may
accommodate such a symmetry and consider constraints on such string-derived U(1)s
focussing on those imposed by gauge coupling unification and proton stability. In two
contrasting cases we show that the gauge data at the electroweak scale necessitate that
the Z' charges are embeddable in E6. We finally discuss how models with the
required properties may be constructed in the free fermionic formulation.
Arnold Sommerfeld Center
Theresienstrasse 37
Room 348/349