Measurement of parity violation in the elastic scattering of polarized electrons fromC12

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ nuclei. Our result is ${\mathit{A}}_{\mathrm{expt}}$=0.60±0.14±0.02 ppm, where the first error is statistical and the second is systematic. With a beam polarization of 0.37, we compute the isoscalar vector hadronic coupling constant γ̃ to be 0.136±0.032±0.009. The standard model predicts γ̃=0.155 at the tree level, in agreement with our data.