Angular correlations in multi-jet final states from kt-dependent parton   showers
  We investigate parton-branching methods based on transverse-momentum dependent (TMD) parton distributions and matrix elements for the Monte Carlo simulation of multi-particle final states at high-energy colliders. We observe that recently measured angular correlations in ep final states with multiple hadronic jets probe QCD coherence effects in the space-like branching, associated with finite-angle gluon radiation from partons carrying small longitudinal momenta, and not included in standard shower generators. We present Monte Carlo calculations for azimuthal two-jet and three-jet distributions, for jet multiplicities and for correlations in the transverse-momentum imbalance between the leading jets. We discuss comparisons with current experimental multi-jet data, and implications of corrections to collinear-ordered showers for LHC final states. 
F.Hautmann and H.Jung