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Profile picture of Leif Lönnblad. Photo.

Leif Lönnblad

Professor of Theoretical Physics

Profile picture of Leif Lönnblad. Photo.

Energy conservation and saturation in small-x evolution


  • Emil Avsar
  • Gösta Gustafson
  • Leif Lönnblad

Summary, in English

Important corrections to BFKL evolution are obtained from non-leading contributions and from non-linear effects due to unitarisation or saturation. It has been diffcult to estimate the relative importance of these effects, as NLO effects are most easily accounted for in momentum space while unitarisation and saturation are easier in transverse coordinate space. An essential component of the NLO contributions is due to energy conservation effects, and in this paper we present a model for implementing such effects together with saturation in Mueller's dipole evolution formalism. We find that energy conservation severely dampens the small-x rise of the gluon density and, as a consequence, the onset of saturation is delayed. Using a simple model for the proton we obtain a reasonable qualitative description of the x-dependence of F-2 at low Q(2) as measured at HERA even without saturation effects. We also give qualitative descriptions of the energy dependence of the cross section for gamma*gamma* and gamma*-nucleus scattering.


  • Theoretical Particle Physics

Publishing year





Journal of High Energy Physics



Document type

Journal article




  • Subatomic Physics


  • phenomenological models
  • jets
  • QCD
  • parton model




  • ISSN: 1029-8479