Event shapes in deep inelastic scattering at HERA

Mean values and differential distributions of event-shape variables have been studied in neutral current deep inelastic scattering using an integrated luminosity of 82.2 pb(-1) collected with the ZEUS detector at HERA. The kinematic range is 80 < Q(2) < 20480 GeV2 and 0.0024 < x < 0.6, where Q(2) is the virtuality of the exchanged boson and x is the Bjorken variable. The data are compared with a model based oil a combination of next-to-leading-order QCD calculations with next-to-leading-logarithm corrections and the Dokshitzer-Webber non-perturbative power corrections. The power-correction method provides a reasonable description of the data for all event-shape variables studied. Nevertheless, the lack of consistency of the determination of alpha(s), and of the non-perturbative parameter of the model, (alpha(0)) over bar, suggests the importance of higher-order processes that are not yet included in the model. (C) 2006 Elsevier B.V. All rights reserved.