Measurements of parity violation in the scattering of polarized electrons from protons

A new generation of experiments measuring the parity violating interference between the weak and electromagnetic interactions in the scattering of polarized electrons from hydrogen is described. The goal of these experiments is to measure independently each of the four electron-nucleus electro-weak coupling constants. The precision obtainable in terms of the coupling constants will be about an order of magnitude better than the deep inelastic scattering experiment at SLAC. A wide range of beam energies, from 0.6 GeV to 2.0 GeV, will be required. The large duty factor of the proposed accelerator will have important advantages, including simplification of the polarized electron source and lowering of the instantaneous rate of detected events to the level where individual pulses can be counted. For the higher energy data conventional large-acceptance magnetic spectrometers will be appropriate, and for the lower energies special Cherenkov or total absorption counters will be developed. A 30 cm long liquid hydrogen target compatible with a 100 μa beam current will also be required