Soft and hard Pomeron in the structure function of the proton at low $x$ and low $Q^2$

U. D'Alesio; A. Metz; H.J. Pirner

doi:doi:10.1007/s100520050561

EPJ

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2023 Impact factor 4.2

Particles and Fields

Eur. Phys. J. C 9, 601-609
DOI 10.1007/s100529900096

Soft and hard Pomeron in the structure function of the proton at low x and low Q²

U. D'Alesio - A. Metz - H.J. Pirner

Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 19, D-69120 Heidelberg, Germany

Received: 6 December 1998 / Revised version: 19 April 1999 / Published online: 18 June 1999

Abstract
We study inclusive electroproduction on the proton at low x and low Q² using a soft and a hard Pomeron. The contribution of the soft Pomeron is based on the Stochastic Vacuum Model, in which a nonperturbative dipole-dipole cross section can be calculated by means of a gauge invariant gluon field strength correlator. To model the hard Pomeron exchange we phenomenologically extend the leading order evolution of a power-behaved structure function, $F_2 \propto x^{- \lambda}$ , proposed by López and Ynduráin. This extension allows to consider both the case Q² = 0 and the region of higher Q² on the basis of the same parametrization. A good simultaneous fit to the data on F₂ and on the cross section $\sigma_{\gamma p}$ of real photoproduction is obtained for $\lambda=0.37$ .With four parameters we achieve a $\chi^2/\textrm{d.o.f.} = 0.98$ for 222 data points. In addition, we use our model of the inclusive $\gamma^{\ast} p$ interaction to compute the longitudinal structure function F_L.