Multiplicity of (mini-)jets at small x

We derive closed expressions for the mean and variance of the (mini-)jet multiplicity distribution in hard scattering processes at low x. Here (mini-)jets are defined as those due to initial-state radiation of gluons with transverse momenta greater than some resolution scale mR, where Λ2 << mR2 << Q2, Λ being the intrinsic QCD scale and Q the momentum transfer scale of the hard scattering. Our results are valid to leading order in log(1/x) but include all sub-leading logarithms of Q2/mR2. As an illustration, we predict the mini-jet multiplicity in Higgs boson production at the Large Hadron Collider. (author)