  In the model of hidden sector proposed recently, protons and neutrons scatter
differently on cold-dark-matter particles. First, we summarize briefly our
model based on a mechanism of "photonic portal" between hidden and
Standard-Model sectors of the Universe. Then, we calculate in an elementary way
the differential cross-sections for scattering of protons and neutrons on
sterile Dirac fermions ("sterinos") playing the role of cold-dark-matter
particles. They interact with nucleons through the photonic portal in a
somewhat involved but natural manner. Due to this portal, the differential
cross-section for protons displays a Coulomb-like forward singularity.
