Geometric scaling in diffractive deep inelastic scattering

The geometric scaling property observed in the HERA data at small x, that the deep inelastic scattering (DIS) total cross-section is a function of only the variable Q^2*x^\lambda, has been argued to be a manifestation of the saturation regime of QCD and of the saturation scale Q^2_s(x) x^{-\lambda}. We show that this implies a similar scaling in the context of diffractive DIS and we observe, for several diffractive observables, that the experimental data from HERA confirm the expectations of this scaling.Comment: 9 pages, 3 figures, references added, version to appear in PL

MILOU : a Monte-Carlo for Deeply Virtual Compton Scattering

In this note, we present a new generator for Deeply Virtual Compton Scattering processes. This generator is based on formalism of Generalized Partons Distributions evolved at Next Leading Order (NLO). In the following we give a brief description of this formalism and we explain the main features of the generator for the elastic reactions, as well as for proton dissociation.Comment: 18 pages, 9 figure

New measurement of charge asymmetry xF3x{F}_3 from HERA

After presenting the recent measurements of neutral current cross section in DIS at HERA, we explain the effect of the $\gamma-Z_0$ interference at the electro-weak scale, visible on these data. Then, the beam charge difference $x{F}_3$ is measured and the interference itself is extracted. Results are discussed in the context of perturbative QCD.Comment: 4 pages, 3 figures, proceedings of the International Workshop on Positrons at Jefferson Lab (March 25-27, 2009), Thomas Jefferson National Accelerator Facility, Newport News, V

Programmed state assignment algorithms for asynchronous sequential machines.

An important step in the synthesis procedure for realizing a normal fundamental mode asynchronous sequential circuit is the internal state assignment. Although systematic methods have been developed to construct minimum-transition-time state assignments, they become long and tedious with hand methods for machines with more than 7 or 8 internal states. To extend the application of these algorithms to larger problems, this paper presents an efficient digital computer program for generating minimum-variable state assignments. An alternate program is also presented which, though shorter, does not guarantee a minimum-variable assignment --Abstract, page ii

Generalised parton distributions at HERA and prospects for COMPASS

We present a model of generalised parton distributions based on a forward ansatz in the DGLAP region. We discuss some aspects of the parametrisations, as the dependence in t, with factorised and non-factorised approaches, where t is the square of the four-momentum exchanged at the hadron vertex. The predictions of this model are then compared with DVCS cross sections from H1 and ZEUS, and a related observable, the skewing factor, defined as the following ratio imaginary amplitudes : R \equiv {Im {\cal A} (\gamma^*+p \to \gamma +p)\lfrestriction{t=0}} / {Im {\cal A} (\gamma^*+p \to \gamma^* +p)\lfrestriction{t=0}}. It is an interesting quantity including both the non-forward kinematics and the non-diagonal effects. Finally, we discuss the beam charge asymmetry, which is certainly the most sensitive observable to the different hypothesis needed in the GPDs parametrisations. We show that the approximations done for the t dependence lead to significant differences for the predictions in the HERMES kinematic domain and prospects are given for COMPASS.Comment: 8 pages, 5 figures, submitted to Phys. Lett.