PAMELA positron excess as a signal from the hidden sector

The recent positron excess observed in the PAMELA satellite experiment strengthens previous experimental findings. We give here an analysis of this excess in the framework of the Stueckelberg extension of the standard model which includes an extra U(1)(X) gauge field and matter in the hidden sector. Such matter can produce the right amount of dark matter consistent with the Wilkinson Microwave Anisotropy Probe (WMAP) constraints. Assuming the hidden sector matter to be Dirac fermions it is shown that their annihilation can produce the positron excess with the right positron energy dependence seen in the HEAT, AMS, and the PAMELA experiments. The predictions of the pp flux ratio also fit the data.