Direct Messenger-Matter Interactions in Gauge-Mediated Supersymmetry   Breaking Models
  We categorize general messenger and matter interactions in gauge-mediated SUSY breaking models by an R-parity for the messengers and study their phenomenological consequences. The new interactions may induce baryon- and lepton-number violating processes as well as flavor-changing neutral currents. Bounds on the couplings from low-energy data are generally weak due to the large messenger mass suppression, except for the constraint from proton decay. The soft masses for the scalar particles receive negative corrections from the new interactions. Consequently, in certain region of SUSY parameter space the \mu-parameter is greatly reduced. The pattern of radiative electroweak symmetry breaking, SUSY particle mass spectrum and decay channels are also affected, leading to observable experimental signature at the current and future colliders. 
Tao Han and Ren-Jie Zhang (UW-Madison and UC-Davis)