1,654 research outputs found

### Charge asymmetry for electron (positron)-proton elastic scattering at large angle

Charge asymmetry in electron (positron) scattering arises from the
interference of the Born amplitude and the box-type amplitude corresponding to
two virtual photons exchange. It can be extracted from electron proton and
positron proton scattering experiments, in the same kinematical conditions.
Considering the virtual photon Compton scattering tensor, which contributes to
the box-type amplitude, we separate proton and inelastic contributions in the
intermediate state and parametrize the proton form-factors as the sum of a pure
QED term and a strong interaction term. Arguments based on analyticity are
given in favor of cancellation of contributions from proton strong interaction
form factors and of inelastic intermediate states in the box type amplitudes.
In frame of this model, with a realistic expression for nucleon form-factors,
numerical estimations are given for moderately high energies.Comment: 14 pages, 4 figure

### How to reconcile the Rosenbluth and the polarization transfer method in the measurement of the proton form factors

The apparent discrepancy between the Rosenbluth and the polarization transfer
method for the ratio of the electric to magnetic proton form factors can be
explained by a two-photon exchange correction which does not destroy the
linearity of the Rosenbluth plot. Though intrinsically small, of the order of a
few percent of the cross section, this correction is kinematically enhanced in
the Rosenbluth method while it is small for the polarization transfer method,
at least in the range of (Q^2) where it has been used until now.Comment: 4 pages, 4 figures. Version accepted for publication in Phys. Rev.
Let

### Polarization effects in the reaction $e^++e^-\to \rho^+ +\rho^-$ and determination of the $\rho -$ meson form factors in the time--like region

The electron positron annihilation reaction into four pion production has
been studied, through the channel $e^++e^-\to \bar \rho+\rho$. The
differential (and total) cross sections and various polarization observables
for this reaction have been calculated in terms of the electromagnetic form
factors of the corresponding $\gamma^*\rho\rho$ current. The elements of the
spin--density matrix of the $\rho -$meson were also calculated. Numerical
estimations have been done, with the help of phenomenological form factors
obtained in the space--like region of the momentum transfer squared and
analytically extended to the time-like region.Comment: 19 pages, 2 figures, to appear in Phys Rev

### Excitation of two-dimensional plasma wakefields by trains of equidistant particle bunches

Nonlinear effects responsible for elongation of the plasma wave period are
numerically studied with the emphasis on two-dimensionality of the wave. The
limitation on the wakefield amplitude imposed by detuning of the wave and the
driver is found.Comment: 4 pages, 4 figure

### Second quantization method in the presence of bound states of particles

We develop an approximate second quantization method for describing the
many-particle systems in the presence of bound states of particles at low
energies (the kinetic energy of particles is small in comparison to the binding
energy of compound particles). In this approximation the compound and
elementary particles are considered on an equal basis. This means that creation
and annihilation operators of compound particles can be introduced. The
Hamiltonians, which specify the interactions between compound and elementary
particles and between compound particles themselves are found in terms of the
interaction amplitudes for elementary particles. The nonrelativistic quantum
electrodynamics is developed for systems containing both elementary and
compound particles. Some applications of this theory are considered.Comment: 35 page

### Phenomenological insight into JLab proton polarization data puzzle by deuteron impulse approximation

The non-relativistic impulse approximation of deuteron electromagnetic form
factors is used to investigate the space-like region behavior of the proton
electric form factor in regard of the two contradictory experimental results
extracted either from Rosenbluth separation method or from recoil proton JLab
polarization data.Comment: Revtex, 6 pages, 7 figure

### Search for evidence of two photon contribution in elastic electron proton data

We reanalyze the most recent data on elastic electron proton scattering. We
look for a deviation from linearity of the Rosenbluth fit to the differential
cross section, which would be the signature of the presence of two photon
exchange. The two photon contribution is parametrized by a one parameter
formula, based on symmetry arguments. The present data do not show evidence for
such deviation.Comment: 15 pages 3 figures More details on the fitting procedure, more
explicit explanation

### Stability of nonlinear one-dimensional laser pulse solitons in a plasma

In a recent one-dimensional numerical fluid simulation study [Saxena et al.,
Phys. Plasmas 13,032309 (2006)], it was found that an instability is associated
with a special class of one-dimensional nonlinear solutions for modulated light
pulses coupled to electron plasma waves in a relativistic cold plasma model. It
is shown here that the instability can be understood on the basis of the
stimulated Raman scattering phenomenon and the occurrence of density bursts in
the trailing edge of the modulated structures are a manifestation of an
explosive instability arising from a nonlinear phase mixing mechanism.Comment: 17 pages, 7 figures, Published in Phys. Plasma

### Random matrices, non-backtracking walks, and orthogonal polynomials

Several well-known results from the random matrix theory, such as Wigner's
law and the Marchenko--Pastur law, can be interpreted (and proved) in terms of
non-backtracking walks on a certain graph. Orthogonal polynomials with respect
to the limiting spectral measure play a role in this approach.Comment: (more) minor change

### Global analysis of proton elastic form factor data with two-photon exchange corrections

We use the world's data on elastic electron--proton scattering and
calculations of two-photon exchange effects to extract corrected values of the
proton's electric and magnetic form factors over the full Q^2 range of the
existing data. Our analysis combines the corrected Rosenbluth cross section and
polarization transfer data, and is the first extraction of G_Ep and G_Mp
including explicit two-photon exchange corrections and their associated
uncertainties. In addition, we examine the angular dependence of the corrected
cross sections, and discuss the possible nonlinearities of the cross section as
a function of epsilon.Comment: 13 pages, 3 figures, 4 tables, to be submitted to Phys. Rev.

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