Rho meson propagation and dilepton enhancement in hot hadronic matter

Abstract

A realistic model for the free rho meson with coupling to two-pion states is employed to calculate the rho propagator in a hot and dense hadron gas. The medium modifications are based on hadronic rescattering processes: intermediate two-pion states are renormalized through interactions with surrounding nucleons and deltas, and rho meson scattering is considered off nucleons, deltas, pions and kaons. Constraints from gauge invariance as well as the full off-shell dynamics of the interactions are accounted for. Within the vector dominance model we apply the resulting in-medium rho spectral function to compute e + e − production rates from π + π − annihilation. The calculation of corresponding e + e − spectra as recently measured in central collisions of heavy-ions at CERN/SpS energies gives reasonable agreement with the experimental data. 25.75.+r, 12.40.Vv, 21.65.+f

Momentum dependence of the pion cloud for ϱ-mesons in nuclear matter

“…(3.6) and (3.7) for the Nh and ∆h polarization. Assuming the momentum | p| of the hole to be small compared to the pion momentum | k|, one obtains 12) where…”

“…Alternatively, however, the CERES dilepton spectra could also be explained by a strong broadening of the ρ meson in hot and dense matter [11,12].…”

“…Therefore it was assumed in ref. [12] that this part of the selfenergy does only depend on the invariant mass M of the ρ meson, but not on its 3-momentum q. For the resonance contributions the q-dependence was taken into account.…”

The impact of chirally odd condensates on the rho meson

“…Such a broadening can be obtained in hadronic many-body approaches, e.g., [10][11][12][13][14], which at first sight are not related directly to chiral restoration in the above spirit. Pion dynamics and resonance formation, both fixed to vacuum data, provide the important input for such many-body calculations.…”

“…Additional non-scalar condensates come into play, in particular for in-medium situations. In (10,11), only the twisttwo non-scalar condensates [27] are displayed,…”