Studying Medium Modifications of Mesons in Elementary Reactions

Experimental searches for medium-modifications of vector mesons in photon and proton induced nuclear reactions are reviewed. Results on ρ, ω and φ mesons are presented. At normal nuclear matter density, the ω and φ meson are found to be lowered in mass by 9-14% and 3.5%, respectively. Compared to the free particle properties increases in widths by factors of about 16 and 3.6, respectively, are observed. For the ρ meson conflicting results on in-medium mass shifts and broadening have been reported. (author)