Coupling of baryon resonances to the Nω channel

Abstract

We estimate the resonance coupling strength f RN ω and f RN ρ 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 ρ with values obtained from fitting the hadronic decay widths into N ρ. A reasonable agreement is found, but VMD tends to underestimate the coupling constants. In order to confirm consistency with experimental data, we calculate the crosssections for photon-and pion induced reactions within a Breit-Wigner model. Finally, we study how the properties of ω mesons in nuclear matter are affected from the excitation of resonance-hole loops. For an ω at rest, we find a broadening of about 40 MeV, while at higher momenta the effect of resonance excitations is reduced.

The width of the ω meson in the nuclear medium

“…As for the in-medium width of a ω meson at rest, in [33], where the three pion decay mode is explicitly considered, it is found to increase by an order of magnitude at normal nuclear saturation density as compared to the free width, while in a subsequent revision of the model [37] a value of about 40 MeV is reported. A similar result was also reported in [38], while the width was found to be around 60 MeV in [46] and [49]. All these studies point to a considerable increase of the ω width in the medium with respect to its free width.…”

Properties of theωmeson at finite temperature and density

“…There are a wide range of estimates in the literature. Post and Mosel [15] obtain 20 MeV with a resonance model, Lutz, Wolf and Friman [16] find 70 MeV in a coupled channel approach and Mühlich, Falter and Mosel [17] with their adopted Ref ωN quote −35 MeV. A mass shift of much larger magnitude has been found in the chiral approach of Klingl, Waas and Weise [18].…”

Spin effects and baryon resonance dynamics in φ-meson photoproduction at few GeV

“…At high energies (W ≡ √ s 10 GeV) it brings information on the dynamics of the Pomeron exchange [1,2,3,4,5,6,7,8]. At low energies (W ∼ 2 GeV), its observables are sensitive to the resonance channel and can be used to obtain some unique information about the structure of baryon resonances, properties of V NN * -interactions [9,10,11,12,13,14,15,16], and possible manifestation of the so-called "missing resonances" [17,18,19]. Therefore, the study of vector-meson photoproductions is an important component of the experimental programs at the electron and photon facilities like Thomas Jefferson National Accelerator Facility, the LEPS at SPring-8.…”