A New Gauge Mediation Theory

We propose a class of models with gauge mediation of supersymmetry breaking, inspired by simple brane constructions, where R-symmetry is very weakly broken. The gauge sector has an extended N = 2 supersymmetry and the two electroweak Higgses form an N = 2 hy-permultiplet, while quarks and leptons remain in N = 1 chiral multiplets. Supersymmetry is broken via the D-term expectation value of a secluded U(1) and it is transmitted to the Standard Model via gauge interactions of messengers in N = 2 hypermultiplets: gauginos thus receive Dirac masses. The model has several distinct experimental signatures with respect to ordinary models of gauge or gravity mediation realizations of the Minimal Su-persymmetric Standard Model (MSSM). First, it predicts extra states as a third chargino that can be observed at collider experiments. Second, the absence of a D-flat direction in the Higgs sector implies a lightest Higgs behaving exactly as the Standard Model one and thus a reduction of the 'little' fine-tuning in the low tan β region. This breaking of supersymmetry can be easily implemented in string theory models.