The E158 Experiment

We have carried out a precision of the parity-violating asymmetry A{sub PV} in the scattering of longitudinally polarized electrons off electrons in a liquid hydrogen target. The measurement was performed with the 50 GeV beam line at SLAC. The final result with the full data set collected in three production runs is A{sub PV} = -131 {+-}14 (stat) {+-} 10 (syst) parts per billion. The result leads to new limits on possible contact interactions at the TeV scale. We discuss future prospects for more precise measurements