Subjet distributions in deep inelastic scattering at HERA
  Subjet distributions were measured in neutral current deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb-1. Jets were identified using the kT cluster algorithm in the laboratory frame. Subjets were defined as jet-like substructures identified by a reapplication of the cluster algorithm at a smaller value of the resolution parameter ycut. Measurements of subjet distributions for jets with exactly two subjets for ycut=0.05 are presented as functions of observables sensitive to the pattern of parton radiation and to the colour coherence between the initial and final states. Perturbative QCD predictions give an adequate description of the data. 
ZEUS Collaboration: S. Chekanov, et al