Naturalness constraints on gauge-mediated supersymmetry breaking models
  The question of naturalness is addressed in the context of gauge-mediated supersymmetry breaking models. Requiring that $M_Z$ arises naturally imposes upper limits on the right-handed selectron mass in these models that are stronger than in the Minimal Supersymmetric Standard Model and are interesting from the point of view of searches at the current and future colliders. 
Gautam Bhattacharyya and Andrea Romanino