The Tensor Pomeron and Small-x Deep Inelastic Scattering

We apply the tensor-pomeron model to small-$x$ deep-inelastic lepton-proton scattering and photoproduction. Our model includes a soft and a hard tensor pomeron as well as a reggeon contribution. Data with c.m. energies $6 < \sqrt{s} < 318$ GeV and virtualities $Q^2 < 50 \,\mbox{GeV}^2$ are considered. Our fit gives a very good description of the available data in this kinematic region, including the latest HERA data for $x < 0.01$. In particular, the transition region from low to high $Q^2$ is well described. Within the errors, the hard pomeron is absent in photoproduction. The intercepts of the soft and hard pomeron in the two-tensor-pomeron model are found to be $1.0935\, ({}^{+76}_{-64})$ and $1.3008 \,({}^{+73}_{-84})$, respectively. We argue that a vector pomeron would not give any contribution to photoproduction.