Vortex String Picture and Large pT Reactions

Abstract

The deviation of the observed behavior, ρ∼pT−n (n∼8) of the single particle inclusive cross section from the QCD prediction of ρ∼pT−4 may suggest that we have not yet reached the asymptotically perturbative region of QCD but nonperturbative effects of confinement remain in the hard subprocess of strong interactions. On the basis of the vortex string model as a realization of confinement, a possibility is examined to attribute the above deviation from the pT−4 rule to the radial density distribution of the vortex flux along the transverse extension l⊥, if the hard subprocess takes place only when two vortex strings overlap with each other. In a simplified treatment of scattering of two parallel vortices, the magnetic flux distribution of the Nielsen-Olesen model gives ρ∼pT−12, and the two-dimensional Yukawa type distribution gives the pT-8 behavior. When the overlap through crossover of two vortex strings is the basic interaction and has the form ̃χ(k)∼k−2 for the transferred momentum k, ρ∼pT−8 and various power behaviors are explained in accord with the quark-junction power counting rule proposed earlier. A relation of the vortex crossover to quantization of the vortex flux is discussed. Since photons and leptons interact with neither strings nor the junctions but only with quarks, the possibility proposed here allows the ordinary parton interpretation of the lepton-hadron reactions. The observed kT∼1GeV, the averaged transverse momentum of quarks, may be related to l⊥.