Rho Meson Broadening in Hot and Dense Hadronic Matter

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The modification of the width of rho mesons due to in-medium decays and collisions is evaluated. The decay width is calculated from the imaginary part of the one-loop self-energy at finite temperature. The collision width is related to the cross sections of the ρ + pion and the ρ + nucleon reactions. A calculation based on an effective Lagrangian shows the importance of including the direct ρπ→ρπ scattering which is dominated by the a₁ exchange. A large broadening of the spectral function is found, accompanied by a strength suppression at the pole.