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arXiv · hep-ph/0202012

S-Matrix Unitarity, Impact Parameter Profiles, Gluon Saturation and High-Energy Scattering

A. I. Shoshi·F. D. Steffen·H. J. Pirner
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Abstract

A model combining perturbative and non-perturbative QCD is developed to compute high-energy reactions of hadrons and photons and to investigate saturation effects that manifest the S-matrix unitarity. Following a functional integral approach, the S-matrix factorizes into light-cone wave functions and the universal amplitude for the scattering of two color-dipoles which are represented by Wegner-Wilson loops. In the framework of the non-perturbative stochastic vacuum model of QCD supplemented by perturbative gluon exchange, the loop-loop correlation is calculated and related to lattice QCD investigations. With a universal energy dependence motivated by the two-pomeron (soft + hard) picture that respects the unitarity condition in impact parameter space, a unified description of pp, pip, Kp, gamma* p, and gamma gamma reactions is achieved in good agreement with experimental data for cross sections, slope parameters, and structure functions. Impact parameter profiles for pp and longitudinal gamma* p reactions and the gluon distribution of the proton xG(x,Q^2,b) are calculated and found to saturate in accordance with S-matrix unitarity. The c.m. energies and Bjorken x at which saturation sets in are determined.

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A. I. Shoshi, F. D. Steffen, H. J. Pirner. 2002-06-25. S-Matrix Unitarity, Impact Parameter Profiles, Gluon Saturation and High-Energy Scattering. https://doi.org/10.1016/s0375-9474(02)01042-4

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