Measurement of azimuthal asymmetries in neutral current deep inelastic scattering at HERA

The distribution of the azimuthal angle of charged and neutral hadrons relative to the lepton plane has been studied for neutral currentdeep inelastic ep scattering using an integrated luminosity of 45 pb-1 taken with the ZEUS detector. The kinematic range is 100 energy-flowmethod, which allows the measurement to be made over a larger range of pseudorapiditycompared to previous results. The dependence of the moments of the azimuthal distributions on the pseudorapidityand minimum transverse energy of the final-state hadrons are presented. Although the predictions from next-to-leading-order QCD describe the data better than do the Monte Carlo models incorporating leading-logarithm parton showers, they still fail to describe the magnitude of the asymmetries. This suggests that higher-order calculations may be necessary to describe these data.