141 research outputs found
Different approaches to calculate the decay width
The rare decay, currently under analysis by the
NA48/2 Collaboration, is considered. We have performed two theoretical
approaches to calculate the differential decay width -- in the kaon rest frame,
where we use Cabibbo-Maksimovicz variables, and in the center-of-mass system of
the lepton pair. The latter essentially simplifies the computations. A
comparison between the two approaches has been performed. We have also found
the dependencies of the differential decay rate as a function of the virtual
photon and dipion system massesComment: 10 pages,5 figure
New Perturbation Theory for Nonstationary Anharmonic Oscillator
The new perturbation theory for the problem of nonstationary anharmonic
oscillator with polynomial nonstationary perturbation is proposed. As a zero
order approximation the exact wave function of harmonic oscillator with
variable frequency in external field is used. Based on some intrinsic
properties of unperturbed wave function the variational-iterational method is
proposed, that make it possible to correct both the amplitude and the phase of
wave function. As an application the first order correction are proposed both
for wave function and S-matrix elements for asymmetric perturbation potential
of type The transition amplitude
''ground state - ground state'' is analyzed in detail
depending on perturbation parameter (including strong coupling
region ) and one-dimensional refraction coefficient .Comment: LaTeX, 13 page
Enhancement of low-mass dileptons in ultraperipheral collisions
It is shown that production of low-mass -pairs in ultraperipheral
nuclear collisions is enhanced due to the Sommerfeld-Gamow-Sakharov (SGS)
factor. This effect is especially strong near the threshold of creation of
unbound -pairs with low masses in the two-photon fusion. Coulomb
attraction of the non-relativistic components of such pairs may lead to the
increased intensity of 511 keV photons. It can be recorded at the NICA collider
and has some astrophysical implications. The analogous effect can be observed
at LHC in dilepton production.Comment: 10 p., 3 Fig
Process 3 -> 3 and crossing symmetry violation
Using the Sudakov technique we sum the perturbation series for the process
and obtain the compact analytical expression for the amplitude of this
process, which takes into account all possible Coulomb interactions between
colliding particles. Compare it with the amplitude of the lepton pair
production in heavy ion collision i.e. in the process , we show that
crossing symmetry between this processes holds only if one neglects the
interaction of produced pair with ions (i.e. in the approximation
).Comment: LaTeX2e, 10 pages, 5 eps figure
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