Search

The two-photon decay widths of scalar mesons σ(600), f0(980), and a0(980) are calculated in the framework of the local Nambu-Jona-Lasinio model. The contributions of the quark loops (Hartree-Fock approximation) and the meson loops (next 1/ N c approximation, where N c is the number of colors) are taken into account. These contributions, as we show, are the values of the same order of magnitude. For the f0 decay the K-loop contribution turns out to play the dominant role. The results are in satisfactory agreement with modern experimental data. [ABSTRACT FROM AUTHOR]

The inclusive production of heavy quarks and quarkonia in photon-photon collisions at the LEP2 collider is considered within the semihard ( k T-factorization) QCD approach. The dependence of the total and differential cross sections for the production of heavy ( c and b) quarks and D* and J/ψ mesons on the choice of unintegrated gluon distribution is studied. The transition of a $$c\bar c$$ charmed pair to observed J/ψ mesons is described on the basis of the color-singlet model. The results of the calculations are compared with currently available experimental data obtained by the L3, OPAL, ALEPH, and DELPHI Collaborations. It is shown that the polarization properties of J/ψ mesons at the LEP2 collider are sensitive to the behavior of unintegrated gluon distributions. This means that experimental investigations of the polarization properties of quarkonia in photon-photon collisions may provide a direct test of the dynamics of gluon distributions in the photon. [ABSTRACT FROM AUTHOR]

The process γ[sup *]γ → σ is investigated in the framework of the SU(2) × SU(2) chiral NJL model. The form factor of the process is derived for arbitrary virtuality of γ[sup *] in the Euclidean kinematic domain. The asymptotic behavior of this form factor resembles the asymptotic behavior of the γ[sup *]γ → π form factor.© 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]