Asymptotic high-energy behavior of hadronic total cross sections from lattice QCD

We will show how a universal and Froissart-like (i.e., of the kind "B log^2 s") hadron-hadron total cross section can emerge in QCD asymptotically at high energy, finding indications for this behavior from the lattice. The functional integral approach provides the natural setting for achieving this result, since it encodes the energy dependence of hadronic scattering amplitudes in a single elementary object, i.e., a proper correlation function of two Wilson loops.Comment: Talk given (by E. Meggiolaro) at the "48th Rencontres de Moriond on QCD and High Energy Interactions", La Thuile (Valle d'Aosta, Italy), 9-16 March 2013; 4 pages, 1 tabl

On the rise of proton-proton cross-sections at high energies

The rise of the total, elastic and inelastic hadronic cross sections at high energies is investigated by means of an analytical parametrization, with the exponent of the leading logarithm contribution as a free fit parameter. Using derivative dispersion relations with one subtraction, two different fits to proton-proton and antiproton-proton total cross section and rho parameter data are developed, reproducing well the experimental information in the energy region 5 GeV - 7 TeV. The parametrization for the total cross sections is then extended to fit the elastic (integrated) cross section data in the same energy region, with satisfactory results. From these empirical results we extract the energy dependence of several physical quantities: inelastic cross section, ratios elastic/total, inelastic/total cross sections, ratio total-cross-section/elastic-slope, elastic slope and optical point. All data, fitted and predicted, are quite well described. We find a statistically consistent solution indicating: (1) an increase of the hadronic cross sections with the energy faster than the log-squared bound by Froissart and Martin; (2) asymptotic limits 1/3 and 2/3 for the ratios elastic/total and inelastic/total cross sections, respectively, a result in agreement with unitarity. These indications corroborate recent theoretical arguments by Ya. I. Azimov on the rise of the total cross section.Comment: 35 pages, 12 figures, discussions improved with further clarifications, references added and updated, one note added, results and conclusions unchanged. Version to be published in J. Phys. G: Nucl. Part. Phy