Nonlinear QCD meets data: A global analysis of lepton-proton scattering with running coupling Balitsky-Kovchegov evolution

By J. Albacete, N. Armesto, J. G. Milhano, C. Salgado. 2009

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We perform a global fit to the structure function F{sub 2} measured in lepton-proton experiments at small values of Bjorken-x, x{<=}0.01, for all experimentally available values of Q{sup 2}, 0.045 GeV{sup 2}{<=}Q{sup 2}{<=}800 GeV{sup 2}. We show that the recent improvements resulting from the inclusion of running coupling corrections allow for a description of data in terms of nonlinear QCD evolution equations. In this approach F{sub 2} is calculated within the dipole model with all Bjorken-x dependence described by the running coupling Balitsky-Kovchegov equation. Two different initial conditions for the evolution are used, both yielding good fits to data with {chi}{sup 2}/d.o.f.<1.1. The proton longitudinal structure function F{sub L}, not included in the fits, is also well described. Our analysis allows to perform a first principle extrapolation of the proton-dipole scattering amplitude once the initial condition has been fitted to presently available data. We provide predictions for F{sub 2} and F{sub L} in the kinematical regions of interest for future colliders and ultra-high energy cosmic rays. A numerical implementation of our results down to x=10{sup -12} is released as a computer code for public use.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/2612654ed302f90f18ae4479620bccca885d9023