Influence of CP and CPT on production and decay of Dirac and Majorana fermions

The consequences of CP and CPT invariance for production and subsequent decay of Dirac and Majorana fermions in polarized fermion-antifermion annihilation are analytically studied. We derive general symmetry relations for the production spin density matrix and for the three-particle decay matrices and obtain constraints for the polarization and the spin-spin correlations of Dirac and Majorana fermions. We prove that only for Majorana fermions the energy and opening angle distribution factorizes exactly into contributions from production and decay if CP is conserved. (orig.)Available from TIB Hannover: RA 2999(01-17) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Selectron pair production at e"-e"- colliders and e"+e"- colliders with polarized beams

We investigate selectron pair production and decay in e"-e"- scattering and e"+e"- annihilation with polarized beams taking into account neutralino mixing as well as ISR and beamstrahlung corrections. One of the main advantages of having both modes at disposal is their complementarity concerning the threshold behaviour of selectron pair production. In e"-e"- the cross sections at threshold for e_Re_R and e_Le_L rise proportional to the momentum of the selectron and in e"+e"- that for e_Re_L. Measurements at threshold with polarized beams can be used to determine the selectron masses m_e__L__/__R precisely. Moreover we discuss how polarized electron and positron beams can be used to establish directly the weak quantum numbers of the selectrons. We also use selectron pair production to determine the gaugino mass parameter M_1. This is of particular interest for scenarios with non-universal gaugino masses at a high scale resulting in vertical stroke M_1 vertical stroke >> vertical stroke M_2 vertical stroke at the electroweak scale. Moreover, we consider also the case of a non-vanishing selectron mixing and demonstrate that it leads to a significant change in the phenomenology of selectrons. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(01-173) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman