Structure functions from the NMC

The New Muon Collaboration has measured deep inelastic muon scattering on hydrogen and deuterium at incident energies of 90 and 280 GeV. From the measured cross section ratios σd/σp the difference of R, the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, was obtained. Covering a range in x from 0.01 to 0.3 at a typical Q2 of 9 GeV2 the results are compatible with zero. The structure functions F2p and F2d were extracted in a wide kinematic range: 0.006 1 GeV2. Extrapolation to small χ of recent parton distributions are shown to disagree with the NMC results.