991 research outputs found
Unstable-particles pair production in MPTapproach in NNLO
We consider pair production and decay of fundamental unstable particles in
the framework of a modified perturbation theory treating resonant contributions
in the sense of distributions. Outcomes of a numerical simulation up to the
NNLO with taking into account universal massless-particles contributions are
presented.Comment: 3 pages, 1 figure, Talk given at 14th Lomonosov Conference on
Elementary Particle Physics, Moscow, August 19-25, 200
Charge-exchange reactions from the standpoint of the parton model
Using simple arguments, we show that charge-exchange reactions at high
energies go through the hard scattering of fast quarks. On this basis we
describe and , , in a combined approach which defines hard contributions in the parton
model and soft ones in Regge phenomenology. The disappearance of a dip
according to recent GAMS-4 data in the differential cross-section at 0.4--0.5 (GeV/c) at transition to
relatively high momenta, is explained as a manifestation of a mode change of
summation of hard contributions from coherent to incoherent. Other
manifestations of the mentioned mode change are discussed. Constraints on the
-- mixing and gluonium admixture in are obtained.Comment: 18 pages, 8 figures; version to appear in EPJ
Non-coherent contributions in charge-exchange reactions and -- mixing
We analyse on the basis of the fit of
data in a wide region of energies, and at the
energies of GAMS-4. We show that disagreements between the data and the
predictions of Regge theory may be explained by the mode change of summation of
intermediate contributions at increasing energy, from coherent to non-coherent.
A method of experimental measurement of the non-coherent contributions is
proposed. On the basis of available data on the charge-exchange reactions the
-- mixing is estimated.Comment: 18 pages, 4 figures; version to appear in EPJ
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