The mD - bM problem of Dirac gauginos and its solutions

We examine the effective low-energy theory of the adjoint sector of Dirac gaugino models and its UV completions, and identify the main source of tuning. A holomorphic scalar adjoint mass square (the "bM term") is generated at the same order (one-loop) as the Dirac gaugino mass (the "mD term"), leading to the problematic relation bM ~ 16[pi] super(2)m super(2)D, somewhat analogous to the mu - B sub( mu )problem of gauge mediation. We identify the leading operators of the low-energy effective theory contributing to the adjoint sector, and evaluate them in various UV completions, confirming the existence of this problem. We suggest a solution by introducing messenger mixing and tuning the relevant parameters. We also present a novel dynamical model for Dirac gauginos based on a strongly coupled supersymmetric (SUSY) QCD theory, where the additional adjoint M is identified with a confined meson, the U(1) with a baryon number-like symmetry, and the messengers with the confined baryons. We find a SUSY-breaking vacuum with a nonvanishing D term, which after tuning the messenger mixing angles gives rise to a realistic gaugino and squark sector.