4,931 research outputs found
Angular distributions in decays
The differential decay rates of the processes and
close to the threshold are calculated with
the help of the optical potential. The same calculations are made
for the decays of . We use the potential which has been suggested to
fit the cross sections of scattering together with and
six pion production in annihilation close to the
threshold. The invariant mass spectra is in agreement with the
available experimental data. The anisotropy of the angular distributions, which
appears due to the tensor forces in the interaction, is predicted
close to the threshold. This anisotropy is large enough to be
investigated experimentally. Such measurements would allow one to check the
accuracy of the model of interaction.Comment: 10 pages, 8 figure
Natural explanation of recent results on
We show that the recent experimental data on the cross section of the process
near the threshold can be perfectly
explained by the final-state interaction of and . The
enhancement of the cross section is related to the existence of low-energy real
or virtual state in the corresponding potential. We present a simple analytical
formula that fits the experimental data very well.Comment: 2 pages, 1 figur
Near-threshold resonance in process
We discuss the influence of various contributions of the
potential on the energy dependence of the cross
section near the threshold.
New BESIII experimental data on the cross section and electromagnetic form
factors and are taken into account. Our predictions are in good
agreement with experimental data. We predict a bound state of
at energy below the
threshold that may manifest itself in anomalous behavior of light meson
production cross sections in a given energy region.Comment: 5 pages, 1 figur
Bremsstrahlung on noble gases at low energies
A detailed analysis of the bremsstrahlung spectrum at nonrelativistic
electron scattering on argon and xenon is carried out. It is shown that the
approximate formulas widely used for the description of bremsstrahlung spectra
lead to predictions that significantly differ from the exact results. In the
limit when the photon frequency tends to zero, a rigorous proof of the
relationship between the spectrum of the bremsstrahlung with a transport cross
section of electron scattering on an atom is given. This proof does not require
any assumptions about the dependence of the scattering phases on energy. For
electron energies lower than the luminescence threshold, it is shown that the
predictions for a number of radiated photons obtained by the exact formula are
in good agreement with the available experimental data.Comment: 15 pages, 5 figures, new section on the angular distributions is
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Coupled channels and production of near-threshold resonances in annihilation
The effects of final-state interaction of hadrons, produced in
annihilation near the threshold, are discussed. If there is a loosely bound
state or a virtual state in a system of produced hadrons, then the energy
dependence of hadroproduction cross section is very strong. Our approach is
based on the use of the effective potentials accounting for the interaction
between hadrons in the final state. The cases of a few channels with nonzero
transition amplitudes between them are considered. It is shown that these
transitions drastically change the energy dependence of the cross sections. In
particular, a narrow resonance below the threshold in one channel leads to a
broad peak in another channel. We explained the non-trivial energy dependence
of the production cross sections of , , ,
near the thresholds in annihilation and
obtained good agreement between our predictions and the experimental data
available.Comment: 15 pages, 11 figure
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