### Abstract

We construct a relativistic and unitary approach to 'high' energy pion- and photon-nucleon reactions taking the πN, πΔ, ρN, ωN, ηN, K Λ, K ∑ 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.

Original language | English |
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Pages (from-to) | 431-496 |

Number of pages | 66 |

Journal | Nuclear Physics A |

Volume | 706 |

Issue number | 3-4 |

DOIs | |

Publication status | Published - Aug 12 2002 |

### Keywords

- Meson-nucleon scattering
- Vector mesons in matter

### ASJC Scopus subject areas

- Nuclear and High Energy Physics

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## Cite this

*Nuclear Physics A*,

*706*(3-4), 431-496. https://doi.org/10.1016/S0375-9474(02)00868-0