Search

We consider as an example the two-pion decay of the ρ meson, the 3 S1 q $$ \bar q $$ state of the constituent quarks—the decay being determined by the transition q $$ \bar q $$ → ππ contains information about confinement interactions. One can specify in this decay two types of transitions: (i) the bremsstrahlung radiation of a pion q → q + π (or $$ \bar q $$ → $$ \bar q $$ + π) with a subsequent fusion q $$ \bar q $$ → π, and (ii) the direct transition q $$ \bar q $$ → ππ. We demonstrate how in the amplitudes of the corresponding transitions the quark singularities have to disappear, i.e., what is the way the quark confinement at relatively short distances can be realized. We calculate and estimate the contributions of processes with bremsstrahlung radiation of the pion and of the direct transition q $$ \bar q $$ → ππ. The estimates demonstrate that the processes involving the direct transition q $$ \bar q $$ → ππ are necessary, but they cannot be determined unambiguously by the decay ρ(775) → ππ. We conclude that for the determination of the q $$ \bar q $$ → ππ transition more complete data on the resonance decays into the ππ channels are needed than those available at the moment. [ABSTRACT FROM AUTHOR]

It is shown that, as in the case of light mesons, heavy-quarkonium states lie, to a high precision, on Regge trajectories in the ( n, M 2) and ( M 2, J) planes with a universal slope. Specifically, $$c\bar c$$ states are described to a high precision by linear trajectories. For $$b\bar b$$ states, there is no such linearity but, as in the other cases, there is a universal quantum-number dependence of the trajectory. [ABSTRACT FROM AUTHOR]

The transverse-momentum spectra of direct J/psi; arid psi;' mesonis in pp interactions at the Tevatron collider energy of √ 8 = 1.8 TeV are calculated on the basis of nonrelativistic QCD, the fragmentation model, the kT-factorization approach, arid the standard parton model. The contribution of gluon fragmentation is shown to exceed the contribution of c-quark fragmentation both within the parton model arid within the kT-factorization approach. Experimental data of the CDF Collaboration agree with the assumption that gluon fragmentation plays a dominant role in the QQ [³3 S1, 8] octet state, with the nonperturbative matrix element taking approximately equal values in the parton model arid in the kT- factorization approach. [ABSTRACT FROM AUTHOR]

Weak radiative decay &lgr; → ne[SUP+]e[SUP-] depends in general on four independent electromagnetic transition form factors. These form factors can be fixed in an extended model of dominance of vector mesons, where the asymptotic behavior of form factors is in agreement with quark counting rules. The dependence of the branching ratio of the &lgr; → ne[SUP+]e[SUP-] decay on the relative weight of four electromagnetic form factors is investigated. [ABSTRACT FROM AUTHOR]