Scattering of vector mesons off nucleons

By M. Lutz, G. Wolf, B. Friman. 2001

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Abstract We construct a relativistic and unitary approach to ‘high’ energy pion– and photon–nucleon reactions taking the πN , πΔ , ρN , ωN , ηN , KΛ , KΣ final states into account. Our scheme dynamically generates the s - and d -wave nucleon resonances N (1535), N (1650) and N (1520) and isobar resonances Δ (1620) and Δ (1700) in terms of quasi-local interaction vertices. The description of photon-induced processes is based on a generalized vector-meson dominance assumption which directly relates the electromagnetic quasi-local four-point interaction vertices to the corresponding vertices involving the ρ and ω fields. We obtain a satisfactory description of the elastic and inelastic pion– and photon–nucleon scattering data in the channels considered. The resulting s -wave ρ – and ω –nucleon scattering amplitudes are presented. Using these amplitudes we compute the leading density modification of the ρ and ω energy distributions in nuclear matter. We find a repulsive energy shift for the ω meson at small nuclear density but predict considerable strength in resonance–hole like ω -meson modes. Compared to previous calculations our result for the ρ -meson spectral function shows a significantly smaller in-medium effect. This reflects a fairly small coupling strength of the N (1520) resonance to the ρN channel.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/afb9d5ab81a4fec4c1e3ff7751ba2f4153ffc2c1