2,349 research outputs found
Asymptotic behavior of nucleon electromagnetic form factors in time-like region
We study the asymptotic behavior of the ratio of Pauli and Dirac
electromagnetic nucleon form factors, , in time-like region for
different parametrizations built for the space-like region. We investigate how
fast the ratio approaches the asymptotic limits according to the
Phragm\`en-Lindel\"of theorem. We show that the QCD-inspired logarithmic
behavior of this ratio results in very far asymptotics, experimentally
unachievable. This is also confirmed by the normal component of the nucleon
polarization, , in (in collisions of unpolarized
leptons), which is a very interesting observable, with respect to this theorem.
Finally we observe that the 1/Q parametrization of contradicts this
theorem.Comment: 9 pages, 1 figur
Polarization observables in lepton-deuteron elastic scattering including the lepton mass
Expressions for the unpolarized differential cross section and for various
polarization observables in the lepton-deuteron elastic scattering, , , , , have been obtained in one-photon-exchange
approximation, taking into account the lepton mass. Polarization effects have
been investigated for the case of a polarized lepton beam and polarized
deuteron target which can have vector or tensor polarization. Numerical
estimations of the lepton mass effects have been done for the unpolarized
differential cross section and for some polarization observables and applied to
the case of low energy muon deuteron elastic scattering.Comment: 29 pages, 6 figur
Model independent study of massive lepton elastic scattering on the proton, beyond the Born approximation
Model independent expressions for all polarization observables in elastic scattering are obtained, taking into account the lepton mass and
including the two-photon exchange contribution. The spin structure of the
matrix element is parametrized in terms of six independent complex amplitudes,
functions of two independent kinematical variables. General statements about
the influence of the two--photon--exchange terms on the differential cross
section and on polarization observables are given. Polarization effects have
been investigated for the case of a longitudinally polarized lepton beam and
polarized nucleon in the final state.Comment: 28 pages, 3 figure
Neutron electric form factor at large momentum transfer
Based on the recent, high precision data for elastic electron scattering from
protons and deuterons, at relatively large momentum transfer , we
determine the neutron electric form factor up to GeV. The values
obtained from the data (in the framework of the nonrelativistic impulse
approximation) are larger than commonly assumed and are in good agreement with
the Gari-Kr\"umpelmann parametrization of the nucleon electromagnetic form
factors.Comment: 11 pages 2 figure
Radiative corrections for electron proton elastic scattering taking into account high orders and hard photon emission
We investigate the effect of high order radiative corrections in unpolarized
electron proton elastic scattering and compare with the calculations at lowest
order, which are usually applied to experimental data. Particular attention is
devoted to the dependence of radiative corrections, which is
directly related to the electric proton form factor. We consider in particular
the effects of the interference terms for soft and hard photon emission. Both
quadratic amplitude describing the collinear emission along the scattered
electron as well as the interference with the amplitudes of emission from the
initial electron and the emission from protons are important in leading and
next to leading approximation and they may compensate in particular kinematical
conditions.Comment: 16 pages, 11 figures, 1 tabl
Experimental constraint on the meson form factors in the time--like region
The annihilation reaction is considered.
The constraint on time-like -meson form factors from the measurement done
by the BaBar collaboration at GeV is analyzed.Comment: 10 pages 3 figure
Survival probability in Generalized Rosenzweig-Porter random matrix ensemble
We study analytically and numerically the dynamics of the generalized
Rosenzweig-Porter model, which is known to possess three distinct phases:
ergodic, multifractal and localized phases. Our focus is on the survival
probability , the probability of finding the initial state after time
. In particular, if the system is initially prepared in a highly-excited
non-stationary state (wave packet) confined in space and containing a fixed
fraction of all eigenstates, we show that can be used as a dynamical
indicator to distinguish these three phases. Three main aspects are identified
in different phases. The ergodic phase is characterized by the standard
power-law decay of with periodic oscillations in time, surviving in the
thermodynamic limit, with frequency equals to the energy bandwidth of the wave
packet. In multifractal extended phase the survival probability shows an
exponential decay but the decay rate vanishes in the thermodynamic limit in a
non-trivial manner determined by the fractal dimension of wave functions.
Localized phase is characterized by the saturation value of ,
finite in the thermodynamic limit , which approaches
in this limit.Comment: 21 pages, 12 figures, 61 reference
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