Low x saturation at HERA ?

We compare the predictions of two distinct dipole models for inclusive and exclusive diffractive processes. While only one of these dipole models contains perturbative saturation dynamics, we show that the predictions of both models are fully consistent with the available HERA data, indicating no compelling evidence for saturation at present HERA energies.Comment: 8 pages, 4 figures, presented at the 26th Montreal-Rochester-Syracuse-Toronto (MRST) conference held at Concordia University, Montreal, Canada, 12th-14th May 2004. To appear in the proceeding

THE STRUCTURE FUNCTION F_2^{\gamma}(x,Q^2) AT LEP2

The unique nature of the photon can be investigated in hitherto unexplored kinematic regions at LEP2. We discuss the theoretical significance of deep inelastic measurements and present a prescription that allows a theoretically and experimentally sensible separation of the so-called `anomalous' and `hadronic' components of the target photon. We perform preliminary studies regarding the ability to reconstruct the $\gamma^* \gamma$ CM energy (and hence $x$) and the usefulness of the easier to measure electron structure function.Comment: 6 pages Latex + 5 figures in a uuencoded fil

Breakdown of QCD coherence ?

We reconsider the calculation of a non-global QCD observable and find the possible breakdown of QCD coherence. This breakdown arises as a result of wide angle soft gluon emission developing a sensitivity to emission at small angles and it leads to the appearance of super-leading logarithms. We use the `gaps between jets' cross-section as a concrete example and illustrate that the new logarithms are intimately connected with the presence of Coulomb gluon contributions. Numerical estimates of their potential phenomenological significance are presented.Comment: 7 pages, 3 figures; proceedings of Workshop on Diffraction in High-Energy Physics - DIFFRACTION 2006, Sep. 5-10 2006, Adamantas, Milos island, Greec

Multiparton Interactions in Photoproduction at HERA

The high energy photoproduction of jets is being observed at the ep collider, HERA. It may be that the HERA centre-of-mass energy is sufficiently large that the production of more than one pair of jets per ep collision becomes possible, owing to the large number density of the probed gluons. We construct a Monte Carlo model of such multiparton interactions and study their effects on a wide range of physical observables. The conclusion is that multiple interactions could have very significant effects upon the photoproduction final state and that this would for example make extractions of the gluon density in the photon rather difficult. Total rates for the production of many (i.e. > 2) jets could provide direct evidence for the presence of multiple interactions, although parton showering and hadronization significantly affect low transverse energy jets.Comment: 21 pages, 8 figures include

The self-care for people initiative: the outcome evaluation.

To determine the effects of a community-based training programme in self-care on the lay population

Further analysis of the BFKL equation with momentum cutoffs

In this paper we investigate the effect of introducing transverse momentum cutoffs on the BFKL equation. We present solutions in moment space for various models of the BFKL kernel for different combinations of these cutoffs. We improve on previous calculations by using the full BFKL kernel (rather than simplified analytic approximations). The significance of the next-to-leading or ``higher twist'' terms in the kernel are assessed. We find that, while these terms are negligible in the absence of cutoffs, introducing an infra-red cutoff markedly enhances their significance.Comment: 27 pages, latex, 6 figure

Extracting the rho meson wavefunction from HERA data

We extract the light-cone wavefunctions of the rho meson using the HERA data on diffractive rho photoproduction. We find good agreement with predictions for the distribution amplitude based on QCD sum rules and from the lattice. We also find that the data prefer a transverse wavefunction with enhanced end-point contributions.Comment: 13 pages, 7 figures, significant improvements over the original version with a new section on distribution amplitudes adde

Extracting the Distribution Amplitudes of the rho meson from the Color Glass Condensate

We extract the leading twist-2 and subleading twist-3 Distribution Amplitudes (DAs) of the rho meson using the HERA data on diffractive rho photoproduction. We do so using several Colour Glass Condensate (CGC) inspired and a Regge inspired dipole models. We find that our extracted twist-2 DA is not much model dependent and is consistent with QCD Sum Rules and lattice predictions. The extracted twist-3 DA is more model dependent but is still consistent with the Sum Rules prediction.Comment: 21 pages, 10 figures, 3 tables. Section 6 revised, figures 8 and 9 and table 3 updated. Conclusions essentially unchange

Scattering of shock waves in QCD

The cross section of heavy-ion collisions is represented as a double functional integral with the saddle point being the classical solution of the Yang-Mills equations with boundary conditions/sources in the form of two shock waves corresponding to the two colliding ions. I develop the expansion of this classical solution in powers of the commutator of the Wilson lines describing the colliding particles and calculate the first two terms of the expansion.Comment: 23 pages, 13 figure