High-energy cosmic-ray positrons from hidden-gauge-boson dark matter

We provide a scenario in which a hidden U(1) gauge boson constitutes dark matter of the Universe and decays into the standard-model particles through a kinetic mixing with an U(1)B−L gauge boson. Interestingly, our model can naturally account for the steep rise in the positron fraction recently reported by PAMELA. Moreover, we find that due to the charge assignment of U(1)B−L, only a small amount of antiprotons are produced in the decay, which is also consistent with the PAMELA and other observational data.