Latest documents http://publikationen.stub.uni-frankfurt.de/index/index/ Fri, 14 Jul 2006 10:41:26 +0200 Fri, 14 Jul 2006 10:41:26 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2379 An alternative theoretical description of axial electron channeling in the multi-GeV region has been developed. We solve a kinetic equation to evaluate an electron distribution function in axially oriented single crystals. Based on the single-string model, the required matrix elements for radiation and scattering by lattice vibrations are calculated employing solutions of the Dirac equation in cylindrical coordinates. Results obtained for 150-GeV electrons propagating along the 〈110〉 axis of germanium are in good agreement with experimental observations. Jürgen Augustin; Andreas Schäfer; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2379 Fri, 14 Jul 2006 10:41:26 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2405 We investigate the possibility that high-energy photons are channeled, when passing through an oriented single crystal, due to Delbrück scattering. For this purpose the exact electron propagator for the single-string model is constructed. Starting from a separation of variables, we solve the Dirac equation for a cylindrical electrostatic potential. The propagator for such external fields is constructed from solutions of the radial Dirac equation. This propagator is applied to a calculation of the S matrix for Delbrück scattering. We specify the conditions under which photon channeling takes place. Unfortunately these conditions are only matched for a very small fraction of those photons being produced by channeled electrons. J. Klenner; Jürgen Augustin; Andreas Schäfer; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2405 Wed, 12 Jul 2006 10:02:26 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2427 The magnetic dipole scattering of neutrinos by the electrostatic potentials of single atoms as well as crystals is investigated. It is shown that scattering by a rigid cubic lattice can amplify the neutrino-atom cross section by a factor of N1/3, N being the number of scatterers. However, comparing the results with typical weak-interaction cross sections, the effect seems to be not observable in experiment. Jürgen Augustin; Berndt Müller; Walter Greiner article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2427 Fri, 07 Jul 2006 12:24:55 +0200