Intrinsic transverse momentum and parton correlations from   nonperturbative short-range interactions
  We summarize recent progress in understanding the effects of nonperturbative short-range interactions in QCD on the nucleon's partonic structure at a low scale: (a) Sea quarks have intrinsic transverse momenta up to the chiral symmetry-breaking scale rho^{-1} ~ 0.6 GeV, much larger than those of valence quarks. (b) Sea quarks in the nucleon light-cone wave function exist partly in correlated in pairs of transverse size rho with sigma and pi-like quantum numbers and a distinctive spin structure (L = 1 components). The effects are demonstrated in an effective model of the low-energy dynamics resulting from chiral symmetry breaking in QCD. They have numerous implications for the P_T distribution of hadrons in semi-inclusive DIS and multiparton processes in high-energy pp collisions. 
P. Schweitzer, M. Strikman, C. Weiss
hep-ph