New Probes for Extended Gauge Structures at HERA
  Doncheski and Hewett have recently shown that the ratio of neutral current to charged current cross sections, $R={\sigma_{NC}}/{\sigma_{CC}}$, can provide a more sensitive probe for the existence of heavy leptoquarks at HERA than the usual proceedure which makes use of neutral current asymmetries. The apparent reason for this is that the Standard Model expectations for {\it both} of these cross sections are modified by the existence of such particles in a semi-coherent manner. In this paper we apply this technique to extended electroweak models whose spectrum contains both a $W'$ and a $Z'$. We find that measurements of $R$ can, for some models, substantially increase the HERA search range for new gauge bosons beyond that which can be probed using the more conventional asymmetries. 
T.G. Rizzo