U-boson and the HyperCP exotic events

We show that the very light spin-1 gauge U-boson of the extra U(1)′ gauge model in the framework of the supersymmetric Standard Model extension can be a good candidate of the new light particle suggested by the HyperCP experiment. We demonstrate that the flavor changing neutral currents (FCNCs) for the HyperCP events in the decay of Σ+→pμ+μ− can be generated at both tree and loop levels. In particular, we find that the loop induced s→dU transition due to the tensor-type interaction with the dimension-5 electric dipole operator plays a very important role on the FCNCs. Our explanation of the HyperCP data with the spin-1 U-boson is different from that based on a light pseudoscalar Higgs boson or sgoldstino in the literature. In particular, the U-boson involves a rich phenomenology in particle physics as well as cosmology.