  Analytical study of the rapidity distribution of the final state particles in
deep inelastic scattering at small x is presented. We separate and analyse
three sources of particle production: fragmentation of the quark-antiquark
pair, accompanying coherent soft gluon radiation due to octet color exchange in
the t-channel, and fragmentation of gluons that form parton distribution
functions. Connection to Catani-Ciafaloni-Fiorani-Marchesini (CCFM) equations
and the role of gluon reggezation are also discussed.
