Discrete R-symmetry anomalies in heterotic orbifold models

TL;DR

This paper investigates anomalies of discrete R-symmetries in heterotic orbifold models, demonstrating their cancellation via the Green-Schwarz mechanism and exploring their implications for supersymmetry and R-parity.

Contribution

It establishes a universal relation between R-symmetry anomalies and beta-function coefficients, and analyzes the potential unbroken R-symmetries relevant for supersymmetry breaking.

Findings

Anomalies satisfy the Green-Schwarz cancellation condition.

Discrete R-symmetries can remain unbroken down to the supersymmetry breaking scale.

A $Z_2$ subgroup may explain R-parity in the MSSM.

Abstract

Anomalies of discrete R-symmetries appearing in heterotic orbifold models are studied. We find that the mixed anomalies for different gauge groups satisfy the universal Green-Schwarz (GS) condition, indicating that these anomalies are canceled by the GS mechanism. An exact relation between the anomaly coefficients of the discrete R-symmetries and one-loop beta-function coefficients is obtained. We also find that the discrete R-symmetries have a good chance to be unbroken down to the supersymmetry breaking scale. Even below this scale a $Z_2$ subgroup is unbroken, which may be an origin of the R-parity of the minimal supersymmetric standard model. Relations between the R-symmetry anomalies and T-duality anomalies are also investigated.