Explicit Model Realizing Parton-Hadron Duality

We present a model that realizes both resonance-Regge (Veneziano) and parton-hadron (Bloom-Gilman) duality. We first review the features of the Veneziano model and we discuss how parton-hadron duality appears in the Bloom-Gilman model. Then we review limitations of the Veneziano model, namely that the zero-width resonances in the Veneziano model violate unitarity and Mandelstam analyticity. We discuss how such problems are alleviated in models that construct dual amplitudes with Mandelstam analyticity (so-called DAMA models). We then introduce a modified DAMA model, and we discuss its properties. We present a pedagogical model for dual amplitudes and we construct the nucleon structure function F2(x,Q2). We explicitly show that the resulting structure function realizes both Veneziano and Bloom-Gilman duality.Comment: 11 pages, 8 figure

Off mass shell dual amplitude with Mandelstam analyticity

A model for the $Q^2$-dependent dual amplitude with Mandelstam analyticity (DAMA) is proposed. The modified DAMA (M-DAMA) preserves all the attractive properties of DAMA, such as its pole structure and Regge asymptotics, and leads to a generalized dual amplitude $A(s,t,Q^2)$. This generalized amplitude can be checked in the known kinematical limits, i.e. it should reduce to the ordinary dual amplitude on mass shell, and to the nuclear structure function when $t=0$. In such a way we complete a unified "two-dimensionally dual" picture of strong interaction. By comparing the structure function $F_2$, resulting from M-DAMA, with phenomenological parameterizations, we fix the $Q^2$-dependence in M-DAMA. In all studied regions, i.e. in the large and low $x$ limits as well as in the resonance region, the results of M-DAMA are in qualitative agreement with the experiment.Comment: 20 pages, 3 figures; to appear in Phys.Atom.Nuc