Narrow Results

Differential distributions in the π₀π₀γ system created in the annihilation channel of an electron–positron collision are considered. The energy fractions of the pions (Dalitz-plot) distribution are presented in a general form and in approximation of intermediate vector mesons (excited and ordinary ones). It is pointed out that in relevant experiments the generalized polarizability of the neutral pion can be measured. Numerical illustrations are presented.

The first radial excitations of axial-vector mesons are considered in the framework of the extended U(3) × U(3) Nambu–Jona-Lasinio model. We calculate the mass spectrum of a₁, f₁ and also strange axial-vector mesons. For description of radially excited states, we used the form factors of polynomial type of the second order in transverse quark momentum. For the ground- and excited-state mesons consisting of light quarks we have calculated the widths of a number of strong and radiative decays. We got satisfactory agreement with experimental data for the ground states. A set of predictions for the excited states of mesons is given.

The decay widths of ${\rho }^{\prime }\to \pi \pi ,\omega \pi ,\rho \eta$, ${\omega }^{\prime }\to \rho \pi ,\omega \eta$ and ${\pi }^{\prime }\to \rho \pi$ are recalculated within the extended Nambu–Jona-Lasinio (NJL) quark model. It is shown that the mass of ${\rho }^{\prime }(1450)$ meson derived in the NJL model agrees with the one given in Particle Data Group tables but significantly deviates from the recent result of CMD-3 collaboration. Comparisons with earlier theoretical results are presented.