Eur. Phys. J. C (2011) 71: 1705
https://doi.org/10.1140/epjc/s10052-011-1705-3

Regular Article - Theoretical Physics

AAMQS: A non-linear QCD analysis of new HERA data at small-x including heavy quarks

¹ Institut de Physique Théorique, CEA/Saclay, URA 2306, Unité de Recherche Associée au CNRS, 91191, Gif-sur-Yvette cedex, France
² Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15706, Santiago de Compostela, Spain
³ CENTRA, Instituto Superior Técnico (IST), Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
⁴ Physics Department, Theory Unit, CERN, 1211, Genève 23, Switzerland
⁵ LPTHE, UPMC Univ. Paris 6 and CNRS UMR7589, Paris, France

^* e-mail: nestor.armesto@usc.es

Received: 4 April 2011
Revised: 8 June 2011
Published online: 26 July 2011

Abstract

We present a global analysis of available data on inclusive structure functions and reduced cross sections measured in electron–proton scattering at small values of Bjorken-x, x<0.01, including the latest data from HERA on reduced cross sections. Our approach relies on the dipole formulation of DIS together with the use of the non-linear running coupling Balitsky–Kovchegov equation for the description of the small-x dynamics. We improve our previous studies by including the heavy quark (charm and beauty) contribution to the reduced cross sections, and also by considering a variable flavor scheme for the running of the coupling. We obtain a good description of the data, with the fit parameters remaining stable with respect to our previous analyses where only light quarks were considered. The inclusion of the heavy quark contributions resulted in a good description of available experimental data for the charm component of the structure function and reduced cross section provided the initial transverse distribution of heavy quarks was allowed to differ from (more specifically, to have a smaller radius than) that of the light flavors.