No abstract

A new approach to global QCD analysis is developed. The main ingredients are two QCD-based evolution equations. The first one is the Balitsky-Kovchegov nonlinear equation, which sums higher twists while preserving unitarity. The second equation is linear and it is responsible for the correct short distance behavior of the theory, namely it includes the DGLAP kernel. Our approach allows extrapolation of the parton distributions to very high energies available at the LHC as well as very low photon virtualities, Q 2 ≪ 1 GeV 2 .All existing low x data on the F 2 structure function is reproduced using one fitting parameter. The resulting χ 2 /df = 1.Analyzing the parameter λ ≡ ∂ ln F 2 /∂(ln 1/x) at very low x and Q 2 well below 1 GeV 2 we find λ ≃ 0.08 − 0.1. A result which agrees with the "soft pomeron" intercept without involving soft physics.

In this paper we develop an approach to soft scattering processes at high energies, which is based on two mechanisms: Good-Walker mechanism for low mass diffraction and multi-Pomeron interactions for high mass diffraction. The pricipal idea, that allows us to specify the theory for Pomeron interactions, is that the so called soft processes occur at rather short distances (r 2 ∝ 1/ < p t > 2 ∝ α ′ IP ≈ 0.01 GeV −2 ), where perturbative QCD is valid. The value of the Pomeron slope α ′ IP was obtained from the fit to experimental data. Using this theoretical approach we suggest a model that fits all soft data in the ISR-Tevatron energy range, the total, elastic, single and double diffractive cross sections, including t dependence of the differential elastic cross section, and the mass dependence of single diffraction. In this model we calculate the survival probability of diffractive Higgs production, and obtained a value for this observable, which is smaller than 1% at the LHC energy range.

Abstract:The values and energy dependence for the survival probability <| S | 2 > of large rapidity gaps (LRG) are calculated in a three channel model. This model includes single and double diffractive production, as well as elastic rescattering. It is shown that <| S | 2 > decreases with increasing energy, in line with recent results for LRG dijet production at the Tevatron. This is in spite of the weak dependence on energy of the ratio (σ el + σ SD )/σ tot .

We show that eikonal corrections imposed on diffraction dissociation processes calculated in the triple Regge limit, produce a radical change in the energy dependence of the predicted cross section. The induced correction is shown to be in general agreement with the recent Tevatron experimental data.