CP-violation and ππ\pi\pi-interaction in the radiative decays of KLK_L and KSK_S

The phases of terms of amplitude that arise from the $\pi\pi$ interaction are obtained by using a simple realistic model of $\pi\pi$ interaction via virtual $\rho$-meson, instead of the ChPT. It is shown that the standard ChPT approach cannot reproduce the contribution of the $\rho$-meson to the $\pi\pi$ interaction. It is shown that the interference between the terms of amplitude with different CP-parity appears only when the photon is polarized (linearly or circularly). Instead of measuring the linear polarization, the angular correlation between the $\pi^{+}\pi^{-}$ and $e^{+}e^{-}$ planes in $K_{S,L}\to\pi^{+}\pi^{-}e^{+}e^{-}$ decay can be studied.Comment: 6 pages, 7 figures, 1 table, LaTex; moriond.sty included; text corrected. Contribution to the XXXVIIth Rencontres de Moriond, "Electroweak interactions and unified theories", Les Arcs, France, 9-16 Mar 200

Tailored laser pulse chirp to maintain optimum radiation pressure acceleration of ions

Ion beams generated with ultra-intense lasers-plasma accelerators hold promises to provide compact and affordable beams of relativistic ions. One of the most efficient acceleration setups was demonstrated to be direct acceleration by the laser's radiation pressure. Due to plasma instabilities developing in the ultra-thin foils required for radiation pressure acceleration, however, it is challenging to maintain stable acceleration over long distances. Recent studies demonstrated, on the other hand, that specially tailored laser pulses can shorten the required acceleration distance suppressing the onset of plasma instabilities. Here we extend the concept of specific laser pulse shapes to the experimentally accessible parameter of a frequency chirp. We present a novel analysis of how a laser pulse chirp may be used to drive a foil target constantly maintaining optimal radiation pressure acceleration conditions for in dependence on the target's areal density and the laser's local field strength. Our results indicate that an appropriately frequency chirped laser pulse yields a significantly enhanced acceleration to higher energies and over longer distances suppressing the onset of plasma instabilities.Comment: 7 pages, 4 figure

Vacuum polarization and plasma oscillations

We evidence the existence of plasma oscillations of electrons-positron pairs created by the vacuum polarization in an uniform electric field with E < Ec. Our general treatment, encompassing also the traditional, well studied case of E > Ec, shows the existence in both cases of a maximum Lorentz factor acquired by electrons and positrons and allows determination of the a maximal length of oscillation. We quantitatively estimate how plasma oscillations reduce the rate of pair creation and increase the time scale of the pair production. These results are particularly relevant in view of the experimental progress in approaching the field strengths E < Ec.Comment: to appear in Phys. Lett.

Single-Cycle High-Intensity Electromagnetic Pulse Generation in the Interaction of a Plasma Wakefield with Nonlinear Coherent Structures

The interaction of coherent nonlinear structures (such as sub-cycle solitons, electron vortices and wake Langmuir waves) with a strong wake wave in a collisionless plasma can be exploited in order to produce ultra-short electromagnetic pulses. The electromagnetic field of a coherent nonlinear structure is partially reflected by the electron density modulations of the incident wake wave and a single-cycle high-intensity electromagnetic pulse is formed. Due to the Doppler effect the length of this pulse is much shorter than that of the coherent nonlinear structure. This process is illustrated with two-dimensional Particle-in-Cell simulations. The considered laser-plasma interaction regimes can be achieved in present day experiments and can be used for plasma diagnostics.Comment: 11 pages, 11 figures. Submitted to Phys. Rev.