Scaled Momentum Spectra in Deep Inelastic Scattering

Charged particle production has been studied in deep inelastic scattering (DIS) using an integrated luminosity of about 0.44 fb−1 taken with the ZEUS detector at HERA. The fragmentation properties of the struck quark in deep inelastic scattering have been investigated in the current fragmentation region of the Breit frame as a function of the exchanged boson virtuality Q. The measured evolution of scaled momentum distributions are compared to next-to-leading order calculations convoluted with the fragmentation functions obtained from e+e− experiments. Scaling violations are observed. The scaled momentum spectra are also compared to predictions based on a modified leading-logarithmic QCD approximation and Monte Carlo event generators.