Double logarithmical corrections to beam asymmetry in polarized electron-proton scattering

The up-down asymmetry in transversally polarized electron proton scattering is induced by the interference between one and two photon exchange amplitudes. Inelastic intermediate hadronic states (different from one-proton state) of the two photon exchange amplitude give rise to contributions containing the square of "large logarithm" (logarithm of the ratio of the transferred momentum to the electron mass). We investigate the presence of such contributions in higher orders of perturbation theory. The relation with the case of zero transfer momentum is explicitly given. The mechanism of cancellation of infrared singularities is discussed.Comment: 9 pages, 8 figure

Radiative decays of pseudoscalar (P) and vector (V) mesons and the process e^+e^- \to \eta' \rho

Radiative decays of pseudoscalar and vector mesons are calculated in the framework of the chiral Nambu-Jona-Lasinio (NJL) model. We use the amplitude for triangle quark loops of anomalous type. In evaluating these loop integrals we use two methods. In the first one, we neglect the dependence of external momenta by reproducing the Wess-Zumino-Witten terms of effective chiral meson Lagrangian. In the second method, we take into account the momentum dependence of loop integrals omitting their imaginary part. This makes it possible to allow for quark confinement. As applied both the methods is in qualitative agreement with each other and with experimental data. The second method allows us to describe the electron-positron annihilation with production of $\eta'$ and $\rho$ mesons in the center of mass energy range from 1.6 to 3.5\GeV. The comparison with the recent experimental data is presented.Comment: 7 pages, 4 figures, 1 tabl

QED radiative corrections to the decay pi^0 to e^+e^-

We reconsider QED radiative corrections (RC) to the $\pi^{0}\to e^{+}e^{-}$ decay width. One kind of RC investigated earlier has a renormalization group origin and can be associated with the final state interaction of electron and positron. It determines the distribution of lepton pair invariant masses in the whole kinematic region. The other type of RC has a double-logarithmic character and is related to almost on-mass-shell behavior of the lepton form factors. The total effect of RC for the $\pi^{0}\to e^{+}e^{-}$ decay is estimated to be 3.2% and for the decay $\eta \to e^{+}e^{-}$ is 4.3%.Comment: 12 pages, 3 figure

Processes e+e−→π0(π0′)γe^+e^-\to\pi^0({\pi^0}')\gamma in the NJL model

The processes of electron-positron annihilation into $\pi^0\gamma$ and into $\pi'(1300)\gamma$ are considered within the NJL model. Intermediate vector mesons $\rho^0$, $\omega$, $\rho'(1450)$, and $\omega'(1420)$ are taken into account. The latter two mesons are treated as the first radial excited states. They are incorporated into the NJL model by means of a polynomial form factor. Numerical predictions for the cross sections of these processes are received for the center-of-mass energies below 2 GeV. Our results for the $\pi^0\gamma$ production are in agreement with experimental data received in the energy region 600 -- 1020 MeV.Comment: 4 pages, 5 figure