SEMINAR     SEMINAR   Wednesday, July 16th, 2003 - h. 14.30  Aula Fisica del Nucleo         Simonetta Liuti University of Virginia, Charlottesville, Virginia 22901         Perturbative QCD Interpretation of Parton-Hadron Duality             Abstract A large fraction of the world data on both polarized and unpolarized ep scattering at large Bjorken x lie in the resonance region. A correspondence known as parton-hadron duality was observed between the proton structure function in the resonance region and in deep inelastic scatterign. More recent analyses using high precision data from Jefferson Lab, show that parton-hadron duality is broken for low values of the final state invariant mass, W*2=Q*2(1-x)/x+M*2<2.4 GeV*2. This trend is also seen in recent HERMES data on polarized scattering in the resonance region. We interpret the pattern of violations of parton-hadron duality observed in the data as a dominance of contributions from non partonic degrees of freedom in a pre-hadronic stage