Vector Mesons and Baryon Resonances in Nuclear Matter

We calculate the effect of many-body interactions in nuclear matter on the spectral function of $\rho$ and $\omega$ meson. In particular, we focus on the role played by baryon resonances in this context.Comment: 4 pages, 4 figures, to be published in proceedings of the Third International Conference on Perspectives on Hadronic Physics, 7 - 11 May 2001, Miramare-Trieste, Ital

Vector Meson Decay of Baryon Resonances

We investigate the coupling of vector mesons with nucleons to nucleon resonances in an isospin-selective VMD approach and explore the in-medium properties of vector mesons.Comment: 8 pages, 2tables, 4 figures, invited talk at NSTAR 2001, Workshop on the Physics of Excited Nucleons, University of Mainz, Germany, March 7-10, 2001. To be published in World Scientifi

Coupling of Baryon Resonances to the NωN \omega channel

We estimate the resonance coupling strength $f_{RN\omega}$ and $f_{RN\rho}$ from a Vector Meson Dominance (VMD) analysis. The isoscalar and isovector part of the photon coupling are obtained separately from helicity amplitudes. The reliability of this approach is tested by comparing VMD predictions for $f_{RN\rho}$ with values obtained from fitting the hadronic decay widths into $N \rho$. A reasonable agreement is found, but VMD tends to underestimate the coupling constants. In order to confirm consistency with experimental data, we calculate the cross-sections for photon-and pion induced reactions within a {\it Breit-Wigner} model. Finally, we study how the properties of $\omega$ mesons in nuclear matter are affected from the excitation of resonance-hole loops. For an $\omega$ at rest, we find a broadening of about 40 MeV, while at higher momenta the effect of resonance excitations is reduced.Comment: 21 pages, 5 ps figures, misprints corrected, discussion added, improved calculation of gamma N -> omega N, revised version to be published in Nuclear Physics

In-medium Properties of Hadrons -- Observables

We first briefly review the theoretical basis for calculations of changes of hadronic properties in dense nuclear matter. These changes have usually been investigated by means of relativistic heavy-ion reactions. Here we discuss that observable consequences of such changes can also be seen in more elementary reactions on nuclei. Particular emphasis is put on a discussion of actual observables in photonuclear reactions; we discuss in detail $\eta$- and vector-meson production. We show that photoproduction of $\eta$'s can yield essential information on in-medium properties of the $S_{11}(1535)$ resonance while the $\phi$ meson properties will probably not be accessible through the $K^+K^-$ decay channel. However, for $\omega$ mesons the $\pi^0\gamma$ decay channel, due to its reduced final state interaction, looks more promising in this respect. Completely free of final state interactions is dilepton production in the few GeV range. We show that the sensitivity of this decay channel to changes of hadronic properties in medium in photonuclear reactions on nuclei is as large as in ultrarelativistic heavy ion collisions. Finally we discuss that hadron production in nuclei at 10 -- 20 GeV photon energies can give important information on the hadronization process.Comment: Invited Lecture by U. Mosel at Erice International School on Nuclear Physics 200

General Relativistic Contributions in Transformation Optics

One potentially realistic specification for devices designed with transformation optics is that they operate with high precision in curved space-time, such as Earth orbit. This raises the question of what, if any, role does space-time curvature play in determining transformation media? Transformation optics has been based on a three-vector representation of Maxwell's equations in flat Minkowski space-time. I discuss a completely covariant, manifestly four-dimensional approach that enables transformations in arbitrary space-times, and demonstrate this approach for stable circular orbits in the spherically symmetric Schwarzschild geometry. Finally, I estimate the magnitude of curvature induced contributions to satellite-borne transformation media in Earth orbit and comment on the level of precision required for metamaterial fabrication before such contributions become important.Comment: 14 pages, 3 figures. Latest version has expanded analysis, corresponds to published versio