Gauge Coupling Running in Minimal SU(3)xSU(2)xU(1) Superstring Unification

TL;DR

This paper investigates how gauge coupling constants evolve in minimal supersymmetric string models, emphasizing the importance of string threshold corrections and modular weights to align theoretical predictions with experimental data.

Contribution

It introduces a framework expressing string threshold corrections in terms of modular weights and moduli, providing constraints for minimal string unification to match observations.

Findings

Threshold corrections are crucial for accurate gauge coupling predictions.

Constraints on modular weights are necessary for agreement with experimental values.

Minimal string unification can be consistent with data under specific conditions.

Abstract

We study the evolution of the gauge coupling constants in string unification schemes in which the light spectrum below the compactification scale is exactly that of the minimal supersymmetric standard model. In the absence of string threshold corrections the predicted values $\sin^2\theta _W=0.218$ and $\alpha _s=0.20$ are in gross conflict with experiment, but these corrections are generically important. One can express the string threshold corrections to $\sin^2\theta _W$ and $\alpha_s$ in terms of certain $modular$ $weights$ of quark, lepton and Higgs superfields as well as the $moduli$ of the string model. We find that in order to get agreement with the experimental measurements within the context of this $minimal$ scheme, certain constraints on the $modular$ $weights$ of the quark, lepton and Higgs superfields should be obeyed. Our analysis indicates that this $minimal$ $string$ $unification$