Prompt photon, Drell-Yan and Bethe-Heitler processes in hard photoproduction

We present prospects and requirements for the study at HERA of hard photon processes which generate high $p_T$ photons in the final state, and processes which generate Drell-Yan lepton pairs.Comment: 6 pages, 3 embedded figures. To appear in the proceedings of the workshop "Future physics at HERA

Dissipation of Quantum Turbulence in the Zero Temperature Limit

Turbulence, produced by an impulsive spin-down from angular velocity Omega to rest of a cube-shaped container, is investigated in superfluid 4He at temperatures 0.08 K - 1.6 K. The density of quantized vortex lines L is measured by scattering negative ions. Homogeneous turbulence develops after time t of approximately 20 \Omega and decays as L proportional to t^(-3/2). The corresponding energy flux epsilon = nu' (kappa L)^2, which is proportional to t^(-3), is characteristic of quasi-classical turbulence at high Re with a saturated energy-containing length. The effective kinematic viscosity in the T=0 limit is nu' = 0.003 kappa, where kappa=10^(-3) cm^2 / s is the circulation quantum.Comment: 4 pages, 5 figures. Updated following referees comment

Spatial beam self-cleaning and supercontinuum generation with Yb-doped multimode graded-index fiber taper based on accelerating self-imaging and dissipative landscape

We experimentally demonstrate spatial beam self-cleaning and supercontinuum generation in a tapered Ytterbium-doped multimode optical fiber with parabolic core refractive index profile when 1064 nm pulsed beams propagate from wider (122 µm) into smaller (37 µm) diameter. In the passive mode, increasing the input beam peak power above 20 kW leads to a bell-shaped output beam profile. In the active configuration, gain from the pump laser diode permits to combine beam self-cleaning with supercontinuum generation between 520-2600 nm. By taper cut-back, we observed that the dissipative landscape, i.e., a non-monotonic variation of the average beam power along the MMF, leads to modal transitions of self-cleaned beams along the taper length

The structure effects in polarization and cross section in inelastic A(p,p')X reaction with the 40Ca and 12C nuclei at 1 GeV

The polarization of the secondary protons in inelastic (p,p') reaction on the 40Ca and 12C nuclei at the initial proton energy 1 GeV was measured in the wide range of the scattered proton momenta at a laboratory angle 21 degree. The cross section of the reactions were measured as well. The outgoing protons from the reaction were detected using a magnetic spectrometer equipped with a multiwire-proportional chambers polarimeter. A structure in the polarization and cross section data, related probably to scattering of the nucleon correlation in the nuclei, was observed.Comment: 13 pages, 5 figures, 7 table