Scale Anomaly in Supersymmetric Quantum Electrodynamics: Ward Identities, Supersymmetry Breaking, and Decoupling

We study the breaking of the scale symmetry both within classical and quantum frameworks in the supersymmetric quantum electrodynamics (SQED) by applying a four-dimensional regularization that preserves supersymmetry. At the classical level, scale symmetry is shown to be broken by mass terms. At the quantum level, it is demonstrated to be broken by a term proportional to the SQED beta function in the massless limit. It is also shown how this anomaly manifests itself in the low- and high-energy limits and how the Appelquist-Carazzone theorem reproduces the usual quantum electrodynamics result in the limit of heavy selectrons.