Natural Split Mechanism for Sfermions: N=2 Supersymmetry in Phenomenology

We suggest a natural split mechanism for sfermions based on $N$=2 supersymmetry (SUSY). $N$=2 SUSY protects a sfermion in an $N$=2 multiplet from gaining weight by SUSY breaking. Therefore, if partly $N$=2 SUSY is effectively obtained, a split spectrum can be realized naturally. As an example of the natural split mechanism, we build a gauge-mediated SUSY breaking-like model assuming $N$=2 SUSY is partly broken in a UV theory. The model explains the Higgs boson mass and the muon anomalous magnetic dipole moment within $1~\sigma$ level with a splitting sfermion spectrum. The model has seven light sparticles described by three free parameters and predicts a new chiral multiplet, sb: the $N$=2 partner of the ${\rm U(1)_Y}$ vector multiplet. The bini, the fermion component of the sb, weighs MeVs. We mention the experimental and the cosmological aspects of the model.