Light by Light Scattering at High Energy: a Tool to Reveal New Particles

We point out a few remarkable properties of the $\gamma\gamma\to\gamma\gamma$ process at high energy. They should allow to search for effects of new particles and interactions. We give illustrations with threshold effects due to pairs of new charged particles (charginos, charged Higgses, sfermions), resonance effects due to s-channel production of neutral scalars (standard or supersymmetric Higgs particles, technipions) and unitarity saturating amplitudes due to a strongly interacting sector. The use of polarized photon beams is also briefly discussed.Comment: 8 pages and 3 figures, typos corrected. e-mail: [email protected]

Application of the Faddeev-Jackiw formalism to the gauged WZW model

The two-flavor Wess-Zumino model coupled to electromagnetism is treated as a constraint system using the Faddeev-Jackiw method. Expanding into series of powers of the pion fields and keeping terms up to second and third order we obtain Coulomb- gauge Lagrangeans containing non-local terms.Comment: 10 pages, LaTe

The ionization of H, He and Ne atoms using neutrinos or antineutrinos at keV energies

We calculate the ionization cross sections for H, He or Ne atoms using $\nu_e$ and $\bar \nu_e$ scattering at keV energies. Such cross sections are useful for e.g. $\bar \nu_e$-oscillation experiments using a tritium source. Using realistic atomic wave functions, we find that for E_\nu \lsim 10 ~\rm keV the atomic ionization cross sections, normalized to one electron per unit volume, are smaller than the corresponding free electron ones, and that they approach it from below as energies of 20 keV are reached.Comment: 13 pages, 5 figures: Realistic atomic wave functions are used inducing numerical changes in the results. e-mail: [email protected]