Unitarized Diffractive Scattering in QCD and Application to Virtual Photon Total Cross Sections

The problem of restoring Froissart bound to the BFKL-Pomeron is studied in an extended leading-log approximation of QCD. We consider parton-parton scattering amplitude and show that the sum of all Feynman-diagram contributions can be written in an eikonal form. In this form dynamics is determined by the phase shift, and subleading-logs of all orders needed to restore the Froissart bound are automatically provided. The main technical difficulty is to find a way to extract these subleading contributions without having to compute each Feynman diagram beyond the leading order. We solve that problem by using nonabelian cut diagrams introduced elsewhere. They can be considered as colour filters used to isolate the multi-Reggeon contributions that supply these subleading-log terms. Illustration of the formalism is given for amplitudes and phase shifts up to three loops. For diffractive scattering, only phase shifts governed by one and two Reggeon exchanges are needed. They can be computed from the leading-log-Reggeon and the BFKL-Pomeron amplitudes. In applications, we argue that the dependence of the energy-growth exponent on virtuality $Q^2$ for $\gamma^*P$ total cross section observed at HERA can be interpreted as the first sign of a slowdown of energy growth towards satisfying the Froissart bound. An attempt to understand these exponents with the present formalism is discussed.Comment: 41 pages in revtex preprint format, with 10 figure

Double-logarithmic behavior of inelastic fermion form factors in QED and QCD

The effective kinematic diagram technique is applied to study inelastic form factors of electron and quark in QED and QCD. The explicit expressions for these form factors in the double-logarithmic approximation are presented. The self-consistency of the results is shown by demonstrating the fulfillment of the Kinoshita-Lee-Nauenberg theorem.Comment: 8 pages, REVTeX. Misprints corrected, references adde

Saturation and Wilson Line Distributions

We introduce a Wilson line distribution function bar{W}_tau(v) to study gluon saturation at small Feynman x_F, or large tau=ln(1/x_F). This new distribution can be obtained from the distribution W_tau(alpha) of the Color Glass Condensate model and the JIMWLK renormalization group equation. bar{W}_tau(v) is physically more relevant, and mathematically simpler to deal with because of unitarity of the Wilson line v. A JIMWLK equation is derived for bar{W}_tau(v); its properties are studied. These properties are used to complete Mueller's derivation of the JIMWLK equation, though for bar{W}_tau(v) and not W_tau(alpha). They are used to derive a generalized Balitsky-Kovchegov equation for higher multipole amplitudes. They are also used to compute the unintegrated gluon distribution at x_F=0, yielding a completely flat spectrum in transverse momentum squared k^2, with a known height. This is similar but not identical to the mean field result at small k^2.Comment: One reference and two short comments added. To appear in Physical Revies

QCD analysis of the diffractive structure function F_2^{D(3)}

The proton diffractive structure function $F_2^{D(3)}$ measured in the H1 and ZEUS experiments at HERA is analyzed in terms of both Regge phenomenology and perturbative QCD evolution. A new method determines the values of the Regge intercepts in ``hard'' diffraction, confirming a higher value of the Pomeron intercept than for soft physics. The data are well described by a QCD analysis in which point-like parton distributions, evolving according to the DGLAP equations, are assigned to the leading and sub-leading Regge exchanges. The gluon distributions are found to be quite different for H1 and ZEUS. A {\it global fit} analysis, where a higher twist component is taken from models, allows us to use data in the whole available range in diffractive mass and gives a stable answer for the leading twist contribution. We give sets of quark and gluon parton distributions for the Pomeron, and predictions for the charm and the longitudinal proton diffractive structure function from the QCD fit. An extrapolation to the Tevatron range is compared with CDF data on single diffraction. Conclusions on factorization breaking depend critically whether H1 (strong violation) or ZEUS (compatibility at low $\beta$) fits are taken into account.Comment: 24 page

Dijet Production at Large Rapidity Intervals

We examine dijet production at large rapidity intervals at Tevatron energies, by using the theory of Lipatov and collaborators which resums the leading powers of the rapidity interval. We analyze the growth of the Mueller-Navelet $K$-factor in this context and find it to be negligible. However, we do find a considerable enhancement of jet production at large transverse momenta. In addition, we show that the correlation in transverse momentum and azimuthal angle of the tagging jets fades away as the rapidity interval is increased.Comment: 12 pages, preprint DESY 93-139, SCIPP 93/3

Vector Meson Photoproduction from the BFKL Equation II: Phenomenology

Diffractive vector meson photoproduction accompanied by proton dissociation is studied for large momentum transfer. The process is described by the non-forward BFKL equation which we use to compare to data collected at the HERA collider.Comment: 39 pages, 29 figure

Large Scale Rapidity Correlations in Heavy Ion Collisions

We discuss particle production mechanisms for heavy ion collisions. We present an argument demonstrating how the fluctuations of the number of produced particles in a series of classical emissions can account for KNO scaling. We predict rapidity correlations in the particle production in the event by event analysis of heavy ion collisions on the rapidity scales of the order of one over the strong coupling constant.Comment: REVTeX, 13 pages, 3 figure

Geometric Scaling in a Symmetric Saturation Model

We illustrate geometric scaling for the photon-proton cross section with a very simple saturation model. We describe the proton structure function F2 at small x in a wide kinematical range with an elementary functional form and a small number of free parameters. We speculate that the symmetry between low and high Q2 recently discovered in the data could be related to a well-known symmetry of the two-gluon- exchange dipole-dipole cross section.Comment: 15 pages, 4 figure

Efficacy and safety of the six-dose regimen of artemether-lumefantrine in pediatrics with uncomplicated Plasmodium falciparum malaria: A pooled analysis of individual patient data

Patient data from eight clinical trials were pooled and analyzed to study the efficacy and safety of the six-dose versus four-dose regimen of artemether-lumefantrine (coartemether; Coartem) in children weighing 5-25 kg. A total of 544 patients with uncomplicated P. falciparum malaria (six-dose: 343; four-dose: 201), matched for demographic and baseline characteristics and individual coartemether doses were included in the analysis. Analysis of day 28 cure rate based on the intention-to-treat and evaluable populations yielded corrected cure rates for the six-dose regimen of 93% and 96% compared with 61% and 76%, respectively, for the four-dose regimen (P \u3c 0.0001 for both comparisons). Similarly high cure rates were achieved with the six-dose regimen in non-immune infants weighing as little as 5 kg. The six- and four-dose regimens were equally well tolerated. The main finding of this analysis is that the six-dose regimen of coartemether is safe and more efficacious than the four-dose regimen in children. Copyright © 2006 by The American Society of Tropical Medicine and Hygiene

The Reggeon →\to 2 Reggeons ++ Particle vertex in the Lipatov effective action formalism

The vertex for gluon emission during the splitting of a reggeized gluon into two is constructed in the framework of Lipatov effective action formalism. Its reduction to a pure transverse form for the diffractive amplitude gives the standard Bartels vertex plus an additional contribution corresponding to the emission from a pointlike splitting vertex. This additional contribution turns out to be given by a longitudinal integral divergent both in the ultraviolet and infrared. A certain specific recipe for this part, including the principal value prescription for the integration, allows to eliminate this unwanted contribution.Comment: 4 figures; misprints corrected; to be published in Eur.Phys.J.