Constraints on Electron-quark Contact Interactions and Implications to models of leptoquarks and Extra Z Bosons

We update the global constraint on four-fermion $ee q q$ contact interactions. In this update, we included the published data of H1 and ZEUS for the 94--96 run in the $e^+ p$ mode and the newly published data of H1 for the 1999 run in the $e^- p$ mode. Other major changes are the new LEPII data on hadronic cross sections above 189 GeV, and the atomic parity violation measurement on Cesium because of a new and improved atomic calculation, which drives the data within $1\sigma$ of the standard model value. The global data do not show any evidence for contact interactions, and we obtain 95% C.L. limits on the compositeness scale. A limit of $\Lambda^{eu}_{LL+(-)} > 23 (12.5)$ TeV is obtained. Implications to models of leptoquarks and extra Z bosons are examined.