[en] We study jet physics in the high energy regime of QCD. Based on the NLO BFKL equation, we construct a vertex for the production of a jet at central rapidity in k_T-factorization. A jet algorithm is introduced, and we take special care of the separation of multi-Regge and quasi-multi-Regge kinematics. The connection with the energy scale of the evolution is investigated in detail. The result is discussed for two situations: scattering of highly virtual photons, which requires a symmetric energy scale to separate the impact factors from the gluon Green's function, and hadron-hadron collisions, where a non-symmetric scale choice is needed. For the second case we are able to de ne a NLO unintegrated gluon density, valid in the small-x regime, and give the evolution equation for this density as well. In the second part, we examine the angular decorrelation of Mueller- Navelet jets. Using an operator formalism in the space of anomalous dimension and conformal spin, we implement the NLO BFKL Green's function to study the rapidity dependence of angular decorrelations. We incorporate the necessary summation of collinearly enhanced corrections beyond NLO accuracy. We compare our results with data from the Tevatron p anti p-collider and provide predictions for the LHC as well. We also extend our study to the angular decorrelation between a forward jets and the electron in deep inelastic ep scattering. The angular decorrelation has not been measured in DIS so far, but we give theoretical results for this observable which already implement the experimental cuts. (orig.)

[en] We derive analytic expressions for high energy 2 → 2 off-shell scattering amplitudes of weak vector bosons. They are obtained from six fermion final states in processes of the type e⁺e^- → anti ν_e + (WW) + ν_e → anti ν_e + (lν)(lν) + anti ν_e. As an application we reconsider the unitarity bounds on the Higgs mass. Particular attention is given to the role of the photon exchange which has not been considered in earlier investigations; we find that the photon weakens the bound of the Higgs mass. (orig.)

[en] We derive analytic expressions for high energy 2→2 off-shell scattering amplitudes of weak vector bosons. They are obtained from six-fermion final states in processes of the type e⁺e^-→ν_e+(WW)+ν_e→ν_e+(lν)(lν)+ν_e. As an application we reconsider the unitarity bounds on the Higgs mass. Particular attention is given to the role of the photon exchange which has not been considered in earlier investigations; we find that the photon weakens the bound of the Higgs mass

[en] In the framework of a toy model which possesses the main features of QCD in the high-energy limit, we conduct a numerical study of scattering amplitudes constructed from parton splittings and projectile-target multiple interactions, in a way that unitarizes the amplitudes without however explicit saturation in the wave function of the incoming states. This calculation is performed in two different ways. One of these formulations, the closest to field theory, involves the numerical resummation of a factorially divergent series, for which we develop appropriate numerical tools. We accurately compare the properties of the resulting amplitudes with what would be expected if saturation were explicitly included in the evolution of the states. We observe that the amplitudes have similar properties in a small but finite range of rapidity in the beginning of the evolution, as expected. Some of the features of reaction-diffusion processes are already present in that range, even when wave function saturation is left out of the model.

[en] We calculate and analyze Z and W^± production in association with quark-antiquark pair in k_T-factorization. Numerical calculations are performed using the Monte Carlo generator CASCADE for proton proton collisions at LHC energy. We compare total and differential cross sections calculated in k_T-factorization approach with total differential cross sections obtained in LO and NLO calculations in collinear factorization approach. We provide strong evidence that some of the effects of the NLO and even higher order collinear calculation are already included in the LO k_T-factorization calculation. (orig.)

[en] We study the decorrelation in azimuthal angle of Mueller-Navelet jets at hadron colliders within the BFKL formalism. We introduce NLO terms in the evolution kernel and present a collinearly-improved version of it for all conformal spins. We show how this further resummation has good convergence properties and is closer to the Tevatron data than a simple LO treatment. However, we are still far from a good fit. We offer estimates of these decorrelations for larger rapidity differences which should favor the onset of BFKL effects and encourage experimental studies of this observable at the LHC. (orig.)

[en] We study the azimuthal angle decorrelation of forward jets in Deep Inelastic Scattering. We make predictions for this observable at HERA describing the high energy limit of the relevant scattering amplitudes with quasi-multi-Regge kinematics together with a collinearly improved evolution kernel for multiparton emissions. (orig.)

[en] The inclusive production of jets in the central region of rapidity is studied in k_T-factorization at next-to-leading order (NLO) in QCD perturbation theory. Calculations are performed in the Regge limit making use of the NLO BFKL results. A jet cone definition is introduced and a proper phase-space seperation into multi-Regge and quasi-multi-Regge kinematic regions is carried out. Two situations are discussed: scattering of highly virtual photons, which requires a symmetric energy scale to separate impact factors from the gluon Green's function, and hadron-hadron collisions, where a non-symmetric scale choice is needed. (orig.)

[en] In this contribution we discuss the production of two pion pairs in high energy photon collisions as they can be produced in ultraperipheral collisions at hadron colliders such as the Tevatron, RHIC or LHC. We find that charge asymmetries may reveal the existence of the perturbative Odderon.

[en] The experimental evidence for Odderon exchange processes is still weak. In this talk, we will show that the Odderon could be observed by interference effects with the Pomeron in charge asymmetries in the production of two pion pairs. After discussing the theoretical framework for our calculation based on high energy factorization and the necessary phenomenological input, the calculation of the charge asymmetry and its result will be presented. We will conclude with a discussion of experimental rates to be expected in ultra-peripheral collisions at the LHC. (author)