Interplay of hard and soft physics in small x deep inelastic processes

1994

Citations per year

19911998200520122019024681012
Abstract:
Coherence phenomena, the increase with energy of coherence length and the nonuniversality of parton structure of the effective pomeron are explained. New hard phenomena directly calculable in QCD such as diffractive electroproduction of states with M 2Q 2M~2\ll Q~2 and the color transparency phenomenon as well as new options to measure the light-cone wave functions of various hadrons are considered. An analogue of Bjorken scaling is predicted for the diffractive electroproduction of ρ\rho mesons at large momentum transfers and for the production of large rapidity gap events, as observed at HERA. A phenomenological QCD evolution equation is suggested to calculate the basic characteristics of the large rapidity gap events. The increase of parton densities at small xx as well as new means to disentangle experimentally soft and hard physics are considered. We discuss constraints on the increase of deep inelastic amplitudes with Q 2Q~2 derived from the inconsistency of QCD predictions for inclusive and exclusive processes and from unitarity of the S matrix for collisions of wave packets. New ways to probe QCD physics of hard processes at large longitudinal distances and to answer the long standing problems on the origin of the pomeron are suggested. Unresolved problems and perspectives of small xx physics are also outlined.
  • lepton nucleon: deep inelastic scattering
  • deep inelastic scattering: lepton nucleon
  • structure function: small-x
  • hard scattering
  • diffraction: coherence
  • quantum chromodynamics
  • electron nucleon: exclusive reaction
  • photon nucleon: exclusive reaction
  • vector meson: electroproduction
  • electroproduction: vector meson