  An excess of events at large Q2 with a positron in the final state has been
observed at HERA which, if confirmed, would be a signal of new physics. It is
not clear at present if a signal of comparable rate is also seen in the charged
current channel (with an antineutrino in the final state). In this note we
analyse the implications of the presence of such a signal in models of new
physics based on contact terms, leptoquarks and squarks with R-violating
decays. We find that in all cases the most likely possibility is that the
charged current signal is absent. As a consequence if this signal is present
the resulting indications are very selective. In particular for squarks only
charged current events with multi-quark final states are possible with quite
definite predictions on the spectrum of supersymmetric particles.
