Four-Fermion Effective Interactions and Recent Data at HERA

Abstract

We discuss the possibility of explaining the excess in the cross section at high-Q^2 recently found at HERA in terms of four-fermion effective interactions. To avoid the constraints from low-energy data, we select three special cases in which the contact interaction is a product of vector-vector, axial-axial and vector-axial currents. For these a satisfactory fit of HERA data is possible, while keeping agreement with LEPII and CDF data, for an interaction scale $\Lambda =3.5$ TeV. As the statistics of the experiments improves-and if the effect persists-it will be soon possible to discriminate between such contact terms and the alternative explanation in terms of leptoquark exchange.