A polarized electron-nucleon scattering experiment at TESLA

Longitudinally polarized electrons, accelerated as a small fraction of the total current in the ef arm of the TESLA collider, can be directed onto a solid state target that may be either longitudinally or transversely polarized. In this way, polarized electron-nucleon scattering measurements can be realized with projected luminosities that are about two orders of magnitude higher than those of comparable experiments. This will allow the measurement of a large variety of polarized parton distribution and fragmentation functions with unprecedented accuracy, many of them for the first time. A main result will be the precise measurement of the x- and Q(2)-dependence of the as yet experimentally totally unknown transverse quark spin distributions.