919 research outputs found
CP-violation and -interaction in the radiative decays of and
The phases of terms of amplitude that arise from the interaction are
obtained by using a simple realistic model of interaction via virtual
-meson, instead of the ChPT. It is shown that the standard ChPT approach
cannot reproduce the contribution of the -meson to the
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 and planes in
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
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.
Helium-3 and Helium-4 acceleration by high power laser pulses for hadron therapy
The laser driven acceleration of ions is considered a promising candidate for
an ion source for hadron therapy of oncological diseases. Though proton and
carbon ion sources are conventionally used for therapy, other light ions can
also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the
same penetration depth as 250 MeV protons, helium ions require only 250 MeV per
nucleon, which is the lowest energy per nucleon among the light ions. This fact
along with the larger biological damage to cancer cells achieved by helium
ions, than that by protons, makes this species an interesting candidate for the
laser driven ion source. Two mechanisms (Magnetic Vortex Acceleration and
hole-boring Radiation Pressure Acceleration) of PW-class laser driven ion
acceleration from liquid and gaseous helium targets are studied with the goal
of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy
requirements. We show that He3 ions, having almost the same penetration depth
as He4 with the same energy per nucleon, require less laser power to be
accelerated to the required energy for the hadron therapy.Comment: 8 pages, 3 figures, 1 tabl
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