Contact interaction explanation of HERA events and SU(3)C × SU(2)L × U(1)Y invariance

We reexamine the contact interaction hypothesis for excess high-Q2 events seen at HERA in e+p → e+X scattering. We consider the most general structure of contact interactions insisting on SU(3)C × SU(2)L × U(1)Y invariance. Apart from constraints for e+e− → qq̄, Drell-Yan and atomic parity violation experiments, we find stringent constraints from neutrino deep inelastic data, provided one assumes lepton universality. A possible choice of contact terms that escape present bounds is still possible, althought new data from FERMILAB and LEP should further constrain such a possibility.