DATA: 11122019
SEZIONE DI FIRENZE Pomeron was introduced in 1958 in the framework of phe nomenological Regge theory. It is supposed to govern the highenergy asymp totics of various
hadronic processes and control dependence of the total cross section on the energy. There are phenomenological and QCD based Pomerons in the literature. The
bestknown QCD contribution to Pomeron comes from the BFKL equation which resums Leading Logarithmic (LL) contributions, i.e. the singlelogarithmic
contributions multiplied by the overall factor s (or 1/x for the inclusive processes). The highenergy asymptotics of this resum mation is known as the BFKL
Pomeron.
In contrast, a contribution to Pomeron obtained in the DoubleLogarithmic Approximation (DLA) does not involve such factor. By this reason it looks
negligibly small and as a result such DL contributions were ignored by the HEP society.
Using the $gamma^* gamma^*$scattering amplitude as an example, we demonstrate that the DL contribution to Pomeron is of the same value as the BFKL
contribution. We also show that the higher accuracy of calculation the lower is the Pomeron intercept. We fix the applicability region for Pomeron (for
example, the asymptotics of $A_{gammagamma}$ can be used at x < 10^{ˆ’6}). The use of Pomerons outside its
proper applicability region leads to misconceptions such as introducing phenomenological €hard€ Pomerons for both unpolarized and spindependent processes. (Boris Ermolaev)
