4,847 research outputs found
Radiative Losses in Plasma Accelerators
We investigate the dynamics of a relativistic electron in a strongly
nonlinear plasma wave in terms of classical mechanics by taking into account
the action of the radiative reaction force. The two limiting cases are
considered. In the first case where the energy of the accelerated electrons is
low, the electron makes many betatron oscillations during the acceleration. In
the second case where the energy of the accelerated electrons is high, the
betatron oscillation period is longer than the electron residence time in the
accelerating phase. We show that the force of radiative friction can severely
limit the rate of electron acceleration in a plasma accelerator.Comment: 17 pages, 5 figure
A short review of "DGP Specteroscopy"
In this paper we provide a short review of the main results developed in
hep-th/0604086. We focus on linearised vacuum perturbations about the
self-accelerating branch of solutions in the DGP model. These are shown to
contain a ghost in the spectrum for any value of the brane tension. We also
comment on hep-th/0607099, where some counter arguments have been presented.Comment: Minor typos correcte
The Lorentz Integral Transform (LIT) method and its applications to perturbation induced reactions
The LIT method has allowed ab initio calculations of electroweak cross
sections in light nuclear systems. This review presents a description of the
method from both a general and a more technical point of view, as well as a
summary of the results obtained by its application. The remarkable features of
the LIT approach, which make it particularly efficient in dealing with a
general reaction involving continuum states, are underlined. Emphasis is given
on the results obtained for electroweak cross sections of few--nucleon systems.
Their implications for the present understanding of microscopic nuclear
dynamics are discussed.Comment: 83 pages, 31 figures. Topical review. Corrected typo
Rolling in the Higgs Model and Elliptic Functions
Asymptotic methods in nonlinear dynamics are used to improve perturbation
theory results in the oscillations regime. However, for some problems of
nonlinear dynamics, particularly in the case of Higgs (Duffing) equation and
the Friedmann cosmological equations, not only small oscillations regime is of
interest but also the regime of rolling (climbing), more precisely the rolling
from a top (climbing to a top). In the Friedman cosmology, where the slow
rolling regime is often used, the rolling from a top (not necessary slow) is of
interest too.
In the present work a method for approximate solution to the Higgs equation
in the rolling regime is presented. It is shown that in order to improve
perturbation theory in the rolling regime turns out to be effective not to use
an expansion in trigonometric functions as it is done in case of small
oscillations but use expansions in hyperbolic functions instead. This regime is
investigated using the representation of the solution in terms of elliptic
functions. An accuracy of the corresponding approximation is estimated.Comment: Latex, 36 Pages, 8 figures, typos correcte
Proposal to Search for Heavy Neutral Leptons at the SPS
A new fixed-target experiment at the CERN SPS accelerator is proposed that
will use decays of charm mesons to search for Heavy Neutral Leptons (HNLs),
which are right-handed partners of the Standard Model neutrinos. The existence
of such particles is strongly motivated by theory, as they can simultaneously
explain the baryon asymmetry of the Universe, account for the pattern of
neutrino masses and oscillations and provide a Dark Matter candidate.
Cosmological constraints on the properties of HNLs now indicate that the
majority of the interesting parameter space for such particles was beyond the
reach of the previous searches at the PS191, BEBC, CHARM, CCFR and NuTeV
experiments. For HNLs with mass below 2 GeV, the proposed experiment will
improve on the sensitivity of previous searches by four orders of magnitude and
will cover a major fraction of the parameter space favoured by theoretical
models.
The experiment requires a 400 GeV proton beam from the SPS with a total of
2x10^20 protons on target, achievable within five years of data taking. The
proposed detector will reconstruct exclusive HNL decays and measure the HNL
mass. The apparatus is based on existing technologies and consists of a target,
a hadron absorber, a muon shield, a decay volume and two magnetic
spectrometers, each of which has a 0.5 Tm magnet, a calorimeter and a muon
detector. The detector has a total length of about 100 m with a 5 m diameter.
The complete experimental set-up could be accommodated in CERN's North Area.
The discovery of a HNL would have a great impact on our understanding of
nature and open a new area for future research
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