Phenomenology of multiple parton radiation in semi-inclusive   deep-inelastic scattering
  In the current region of semi-inclusive deep-inelastic scattering, most events are accompanied by intensive radiation of soft and collinear partons which cannot be reliably described at any fixed order of perturbative QCD. In this paper, a resummation formalism that describes such multiple parton radiation is compared to the HERA data on semi-inclusive DIS, including the distributions of energy flow and charged particle multiplicity. We show that the resummation of multiple parton radiation improves the agreement between the theory and the data. We make some suggestions on further experimental study of multiple parton radiation at HERA. 
P.M. Nadolsky, D.R. Stump, C.-P. Yuan