Probing the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>ρ</mml:mi></mml:math>spectral function in hot and dense nuclear matter by dileptons

Abstract

We present a dynamical study of ${e}^{+}{e}^{\ensuremath{-}}$ and ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ production in proton-nucleus and nucleus-nucleus collisions at CERN-SPS energies on the basis of the covariant transport approach HSD employing a momentum-dependent $\ensuremath{\rho}$-meson spectral function that includes the pion modifications in the nuclear medium as well as the polarization of the $\ensuremath{\rho}$ meson due to resonant $\ensuremath{\rho}\ensuremath{-}N$ scattering. We find that the experimental data from the CERES and HELIOS-3 Collaborations can be described equally well as within the dropping $\ensuremath{\rho}$-mass scenario. Whereas corresponding dilepton ${q}_{T}$ spectra are found to be very similar, the inclusive dilepton yield in the invariant mass range $0.85&lt;~M&lt;~1.0$ GeV should allow us to disentangle the two scenarios experimentally.