No light shining through a wall : new results from a photoregeneration experiment

Recently, axion-like particle search has received renewed interest. In particular, several groups have started ``light shining through a wall'' experiments based on magnetic field and laser both continuous, which is very demanding in terms of detector background. We present here the 2$\sigma$ limits obtained so far with our novel set-up consisting of a pulsed magnetic field and a pulsed laser. In particular, we have found that the axion-like particle two photons inverse coupling constant $M$ is $> 8\times 10^5$ GeV provided that the particle mass $m_\mathrm{a} \sim$ 1 meV. Our results definitively invalidate the axion interpretation of the original PVLAS optical measurements with a confidence level greater than 99.9%.Comment: Version that will appear in Physical Review Letters, Vol. 99, n. 18, (2 Nov 2007

A summary of the beatwave experiments at Ecole Polytechnique

We present a summary of the beatwave particle acceleration program developed at Ecole Polytechnique. In dedicated experiments, plasma formation, plasma wave generation and saturation, and particle acceleration were successively studied and understood in detail. A maximum energy gain of 1.3 MeV was obtained, which is compatible with an accelerating gradient of 0.7 GV/m.Comment: 3 pages, 4 figure

Effects of self-generated electric and magnetic fields in laser-generated fast electron propagation in solid materials: Electric inhibition and beam pinching

We present some experimental results which demonstrate the presence of electric inhibition in the propagation of relativistic electrons generated by intense laser pulses, depending on target conductivity. The use of transparent targets and shadowgraphic techniques has made it possible to evidence electron jets moving at the speed of light, an indication of the presence of self-generated strong magnetic fields

Experimental Study of electron acceleration by plasma beat-waves with Nd lasers

International audienceWe have observed the acceleration of electrons by a beat-wave generated in a deuterium plasma by two Nd-YAG and Nd-YLF laser wavelengths. Electrons injected at an energy of 3.3 MeV are observed to be accelerated up to 4.7 MeV after the plasma. The energy gain is compatible with a peak electric field of the order of 1.2 GV/m. The experiment has been performed with different injection energies, from 2.5 to 3.3 MeV, with different plasma dimensions, and with different laser intensitie

Fast electron transport and heating in solid-density matter

Two experiments have been performed to investigate heating by high-intensity laser-generated electrons, in the context of studies of the fast ignitor approach to inertial confinement fusion (ICF). A new spectrometer and layered targets have been used to detect Kα emission from aluminum heated by a fast electron beam. Results show that a temperature of about 40 eV is reached in solid density aluminum up to a depth of about 100 μm

Towards the european strategy for particle physics: The briefing book

This document was prepared as part of the briefing material for the Workshop of the CERN Council Strategy Group, held in DESY Zeuthen from 2nd to 6th May 2006. It gives an overview of the physics issues and of the technological challenges that will shape the future of the field, and incorporates material presented and discussed during the Symposium on the European Strategy for Particle Physics, held in Orsay from 30th January to 2nd February 2006, reflecting the various opinions of the European community as recorded in written submissions to the Strategy Group and in the discussions at the Symposium