Speaker
Description
Chiral model calculations, assuming a partial restoration of chiral symmetry in a nuclear medium, predict modifications of meson properties within nuclei. This motivated a still ongoing widespread experimental campaign starting in the 1990’s to measure the properties of mesons in photon-, pion-, and proton-induced reactions on nuclei and in relativistic and ultra-relativistic heavy-ion collisions. Meson properties can be extracted from studying their decay or their production in the medium. The first approach is basically only applicable for the short-lived ρ-meson (τ≈1.4 fm/c) which mostly decays in the nuclear medium in spite of its recoil momentum. The in-medium properties of longer-lived mesons, decaying to a large extent outside of the nuclear medium can be extracted from their near-threshold yields and momentum distributions by comparing to reactions on the free nucleon and in comparison to model calculations. An overview will be given on experimentally determined in-medium mass shifts and broadening of all light mesons (K+, K0, K-, η, η’, ρ, ω, ϕ), allowing for the extraction of the real and imaginary part of the meson-nucleus potential. Based on the potential parameters, the chances for observing meson-nucleus bound states will be discussed. The most promising candidates appear to be the K-,η and η’ meson.
