Selectron pair production at e- e- 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 initial state radiation and beamstrahlung corrections. One of the main advantages of having both modes at disposal is their complementarity concerning the threshold behavior of selectron pair production. In e(-)e(-) the cross sections at threshold for (e) over tilde (R) (e) over tilde (R) and (e) over tilde (L)(e) over tilde (L) increase proportional to the momentum of the selectron and in e(+)e(-) that for <(e)overtilde>(R)<(e)overtilde>(R). Measurements at threshold with polarized beams can be used to determine the selectron masses m (e) over tilde (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 \M-1\ much greater than \M-2\ at the electroweak scale. Moreover, we consider also the case of non-vanishing selectron mixing and demonstrate that it leads to a significant change in the phenomenology of selectrons.