Polarized electron-nucleon scattering at TESLA

Measurements of polarized electron-nucleon scattering can be realized at th e TESLA linear collider facility with projected luminosities that are about two orders of magnitude higher than those expected of other experiments at comparable energies. Longitudinally polarized electrons, accelerated as a small fraction of the total current in the e(+) arm of TESLA, can be direct ed onto a solid state target that may be either longitudinally or transvers ely polarized. A large variety of polarized parton distribution and fragmen tation functions can be determined with unprecedented accuracy, many of the m for the first time. A main goal of the experiment is the precise measurem ent of the x-and Q(2)-dependence of the unknown transversity distributions that will provide us with the full information on the nucleon's quark spin structure as relevant for high energy processes. Comparing their Q(2)-evolu tion to that of the corresponding helicity distributions constitutes an imp ortant precision test of the predictive power of QCD in the spin sector. Th e additional possibilities of using unpolarized targets and of experiments with a real photon beam turn TESLA-N into a versatile next-generation facil ity at the intersection of particle and nuclear physics.