The $\pi \rho$ Cloud Contribution to the $\omega$ Width in Nuclear Matter

Abstract

The width of the $\omega$ meson in cold nuclear matter is computed in a hadronic many-body approach, focusing on a detailed treatment of the medium modifications of intermediate $\pi \rho$ states. The $\pi$ and $\rho$ propagators are dressed by their selfenergies in nuclear matter taken from previously constrained many-body calculations. The pion selfenergy includes $Nh$ and $\Delta h$ excitations with short-range correlations, while the $\rho$ selfenergy incorporates the same dressing of its $2\pi$ cloud with a full 3-momentum dependence and vertex corrections, as well as direct resonance-hole excitations; both contributions were quantitatively fit to total photo-absorption spectra and $\pi N\to \rho N$ scattering. Our calculations account for in-medium decays of type $\omega N\to \pi N^{(\ast )},\pi \pi N(\Delta )$, and 2-body absorptions $\omega NN\to N{N}^{(\ast )},\pi NN$. This causes deviations of the in-medium $\omega$ width from a linear behavior in density, with important contributions from spacelike $\rho$ propagators. The $\omega$ width from the $\rho \pi$ cloud may reach up to 200 MeV at normal nuclear matter density, with a moderate 3-momentum dependence. This largely resolves the discrepancy of linear $T$-$\varrho$ approximations with the values deduced from nuclear photoproduction measurements.

7 pages, 4 eps figures; v2: includes 3-mom dependence of width and additional discussion

References in corpus (10)

• phi photo-production from Li, C, Al, and Cu nuclei at Egamma=1.5 - 2.4 GeV
• Modification of the $\omega$-Meson Lifetime in Nuclear Matter
• Absorption of the $\omega$ and $\varphi$ Mesons in Nuclei
• Inclusive $\omega$ photoproduction from nuclei and $\omega$ in the nuclear medium
• Thermal Dileptons from Hot and Dense Strongly Interacting Matter
• The spectral function of the omega meson in nuclear matter from a coupled-channel resonance model
• The STAR Dilepton Physics Program
• The omega rho pi coupling in the VMD model revisited
• Hadrons in Medium -- Theory confronts experiment
• Analysis of $\omega$ self-energy at finite temperature and density in the real-time formalism

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• Momentum dependence of the imaginary part of the $\omega$- and ${\eta }^{\prime }$-nucleus optical potential
• Interactions of $\omega$-Mesons in Nuclear Matter and with Nuclei
• Velocity dependence of the mass modifications of $\rho$ and $\omega$ mesons in 12 GeV $p+A$ reactions