QCD in the Regge limit: From gluon Reggeization to physical amplitudes

This paper is a brief survey of the Balitskii-Fadin-Kuraev-Lipatov (BFKL) approach for the description of hard or semi-hard processes in the so-called Regge limit of perturbative QCD. The starting point is a fundamental property of perturbative QCD, the gluon Reggeization. This property, combined with s-channel unitarity, allows to predict the growth in energy of the amplitude of hard or semi-hard processes with exchange of vacuum quantum numbers in the t-channel. When also the so-called impact factors of the colliding particles are known, then not only the behavior with the energy, but the complete amplitude can be determined. This was recently done, for the first time with next-to-leading order accuracy and for a process with colorless external particles, in the case of the electroproduction of two light vector mesons.