Predicitions for high-energy real and virtual photon-photon scattering from color dipole BFKL-Regge factorization

High-energy virtual photon-virtual photon scattering can be viewed as interaction of small size color dipoles from the beam and target photons, which makes $\gamma^{*}\gamma^{*}, \gamma^{*}\gamma$ scattering at high energies (LEP, LEP200 & NLC) an indispensable probe of short distance properties of the QCD pomeron exchange. Based on the color dipole representation, we investigate consequences for the $\gamma^{*}\gamma^{*},\gamma^{*}\gamma$ scattering of the incorporation of asymptotic freedom into the BFKL equation which makes the QCD pomeron a series of isolated poles in the angular momentum plane. The emerging color dipole BFKL-Regge factorization allows us to relate in a model-independent way the contributions of each BFKL pole to $\gamma^{*}\gamma^{*},\gamma^{*} \gamma$ scattering and DIS off protons. Numerical predictions based on our early works on color dipole BFKL phenomenology of DIS on protons are in a good agreement with the experimental data on the photon structure function $F_{2\gamma}$ and most recent data on the $\gamma^*\gamma^*$ cross section $\sigma^{\gamma^*\gamma^*}(Y)$ from OPAL and L3 experiments at LEP200. We discuss the role of non-perturbative dynamics and predict pronounced effect of the Regge-factorization breaking due to large unfactorizable non-perturbative corrections to the perturbative vacuum exchange. We comment on the salient features of the BFKL-Regge expansion for $\gamma^{*}\gamma^{*},\gamma^{*}\gamma$ scattering including the issue of decoupling of subleading BFKL poles and the soft plus rightmost hard BFKL pole dominance .Comment: 16 pages, 10 figures; treatment of the soft component is modified, one more figure with the description of the recent data from OPAL is added. The version to appear in Eur. Phys. J.

Incoherent Eta Photoproduction from the Deuteron near Threshold

Very recent data for the reaction gamma+d ->eta np, namely total cross sections, angular and momentum spectra, are analyzed within a model that includes contributions from the impulse approximation and next order corrections due to the np and eta-N interactions in the final state. Comparison between the calculations and the new data indicate sizable contributions from the np and eta-N final state interactions. Some systematic discrepancies between the calculations and the data are also found

A microscopic investigation of the transition form factor in the region of collective multipole excitations of stable and unstable nuclei

We have used a self-consistent Skyrme-Hartree-Fock plus Continuum-RPA model to study the low-multipole response of stable and neutron/proton-rich Ni and Sn isotopes. We focus on the momentum-transfer dependence of the strength distribution, as it provides information on the structure of excited nuclear states and in particular on the variations of the transition form factor (TFF) with the energy. Our results show, among other things, that the TFF may show significant energy dependence in the region of the isoscalar giant monopole resonance and that the TFF corresponding to the threshold strength in the case of neutron-rich nuclei is different compared to the one corresponding to the respective giant resonance. Perspectives are given for more detailed future investigations.Comment: 13 pages, incl. 9 figures; to appear in J.Phys.G, http://www.iop.org/EJ/jphys