  Cross sections for e^-p neutral current deep inelastic scattering have been
measured at a centre-of-mass energy of 318 GeV using an integrated luminosity
of 15.9 pb^-1 collected with the ZEUS detector at HERA. Results on the
double-differential cross-section d^2s/dxdQ^2 in the range 185 < Q^2 < 50000
GeV^2 and 0.0037 < x < 0.75, as well as the single-differential cross-sections
ds/dQ^2, ds/dx and ds/dy for Q^2 > 200 GeV^2, are presented. To study the
effect of Z-boson exchange, ds/dx has also been measured for Q^2 > 10000 GeV^2.
The structure function xF_3 has been extracted by combining the e^-p results
presented here with the recent ZEUS measurements of e^+p neutral current deep
inelastic scattering. All results agree well with the predictions of the
Standard Model.
