Experimental Study of Electroweak Parameters at PETRA Energies (12<~Ec.m.<~36.7GeV)

We have performed a high-statistics measurement of Bhabha scattering and of the production of hadrons in electron-positron annihilation at PETRA energies ($12 \mathrm{GeV}<~\sqrt{s}<~36.7 \mathrm{GeV}$). Combining the results with measurements of ${\mu }^{+}{\mu }^{-}$ and ${\tau }^{+}{\tau }^{-}$ production enables us to compare our results with electroweak theory. We find ${{sin}^2\theta }_w=0.27\mathrm{}\pm 0.08$. This is in good agreement with the value obtained from neutrino experiments which were carried out in entirely different kinematic regions.