Four-fermion effective interactions and recent data at HERA

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. (C) 1997 Elsevier Science B.V.