990 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
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