Towards a new global QCD analysis: low x DIS data from non-linear evolution

Abstract

A new approach to global QCD analysis is developed. The main ingredients are two QCD-based evolution equations. The first one is the Balitsky-Kovchegov nonlinear equation, which sums higher twists while preserving unitarity. The second equation is linear and it is responsible for the correct short distance behavior of the theory, namely it includes the DGLAP kernel. Our approach allows extrapolation of the parton distributions to very high energies available at the LHC as well as very low photon virtualities, $Q^2\ll 1 {\rm GeV^2}$. All existing low $x$ data on the $F_2$ structure function is reproduced using one fitting parameter. The resulting $χ^2/df=1$. Analyzing the parameter $λ\equiv \partial\ln F_2/\partial(\ln 1/x)$ at very low $x$ and $Q^2$ well below $1 {\rm GeV^2}$ we find $λ\simeq 0.08 - 0.1$. A result which agrees with the "soft pomeron" intercept without involving soft physics.