2,522 research outputs found
The First Year of the Large Hadron Collider: A Brief Review
The first year of LHC data taking provided an integrated luminosity of about
35/pb in proton-proton collisions at sqrt(s)=7 TeV. The accelerator and the
experiments have demonstrated an excellent performance. The experiments have
obtained important physics results in many areas, ranging from tests of the
Standard Model to searches for new particles. Among other results the physics
highlights have been the measurements of the W-, Z-boson and t t-bar production
cross-sections, improved limits on supersymmetric and other hypothetical
particles and the observation of jet-quenching, elliptical flow and J/Psi
suppression in lead-lead collisions at sqrt(sNN) = 2.76 TeV.Comment: 11 pages, 9 figures, invited brief review for Mod. Phys. Lett.
On the Theory of Relativistic Strong Plasma Waves
The influence of motion of ions and electron temperature on nonlinear
one-dimensional plasma waves with velocity close to the speed of light in
vacuum is investigated. It is shown that although the wavebreaking field weakly
depends on mass of ions, the nonlinear relativistic wavelength essentially
changes. The nonlinearity leads to the increase of the strong plasma
wavelength, while the motion of ions leads to the decrease of the wavelength.
Both hydrodynamic approach and kinetic one, based on Vlasov-Poisson equations,
are used to investigate the relativistic strong plasma waves in a warm plasma.
The existence of relativistic solitons in a thermal plasma is predicted.Comment: 13 pages, 8 figure
Ponderomotive scattering of an electron-bunch before injection into a laser wakefield
For the purpose of laser wakefield acceleration, it turned out that also the
injection of electron bunches longer than a plasma wavelength can generate
accelerated femtosecond bunches with relatively low energy spread. This is of
high interest because such injecting bunches can be provided, e.g., by
state-of-the-art photo cathode RF guns. Here we point out that when an e-bunch
is injected in the wakefield it is important to take into account the
ponderomotive scattering of the injecting bunch by the laser pulse in the
vacuum region located in front of the plasma. At low energies of the injected
bunch this scattering results in a significant drop of the collection
efficiency. Larger collection efficiency can by reached with lower intensity
laser pulses and relatively high injection energies. We also estimate the
minimum trapping energy for the injected electrons and the length of the
trapped bunch.Comment: 12 pages, 5 figures, submitted to Phys. Rev.
Magnetic Field of Relativistic Nonlinear Plasma Wave
Longitudinal and transverse behavior of magnetic field of relativistic
nonlinear three-dimensional plasma wave is investigated. It is shown that the
magnetic field of the wave is different from zero and performs higher frequency
oscillations compared to the plasma electron frequency. An increase in the
nonlinearity leads to strengthening of magnetic field. The oscillations of
magnetic field in transverse direction arise, that caused by the phase front
curving of nonlinear plasma wave. The numerical results well conform with
predictions of the analytical consideration of weakly-nonlinear case.Comment: 6 pages, 3 figure
Forward-Backward Correlations and Event Shapes as probes of Minimum-Bias Event Properties
Measurements of inclusive observables, such as particle multiplicities and
momentum spectra, have already delivered important information on
soft-inclusive ("minimum-bias") physics at the Large Hadron Collider. In order
to gain a more complete understanding, however, it is necessary to include also
observables that probe the structure of the studied events. We argue that
forward-backward (FB) correlations and event-shape observables may be
particulary useful first steps in this respect. We study the sensitivity of
several different types of FB correlations and two event shape variables -
transverse thrust and transverse thrust minor - to various sources of
theoretical uncertainty: multiple parton interactions, parton showers, colour
(re)connections, and hadronization. The power of each observable to furnish
constraints on Monte Carlo models is illustrated by including comparisons
between several recent, and qualitatively different, PYTHIA 6 tunes, for pp
collisions at sqrt(s) = 900 GeV.Comment: 13 page
Excitation of nonlinear two-dimensional wake waves in radially-nonuniform plasma
It is shown that an undesirable curvature of the wave front of
two-dimensional nonlinear wake wave excited in uniform plasma by a relativistic
charged bunch or laser pulse may be compensated by radial change of the
equilibrium plasma density.Comment: 6 pages, 4 figure
Electromagnetic radiation from a laser wakefield accelerator
Coherent and incoherent electromagnetic radiation emitted from a laser
wakefield accelerator is calculated based on Lienard-Wiechert potentials. It is
found that at wavelengths longer than the bunch length, the radiation is
coherent. The coherent radiation, which typically lies in the infrared range,
shows features that reveal details of the acceleration process and properties
of the electron bunch, such as its duration, charge, energy, and offset with
respect to the wakefield axis. The incoherent range of the spectrum, which
extends to the X-ray frequency range, consists of rather broad peaks, which are
caused by the acceleration.Comment: 14 pages, incl. 6 figures, submitted for publicatio
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