Medium Modifications of Light Vector Mesons in Nuclei Original Research Article

There is tremendous interest both experimentally and theoretically in possible modification of the properties of vector mesons, such as a shift in their masses and/or broadening of their widths in dense nuclear matter. These effects can be related to partial restoration of chiral symmetry at high density or temperature. The light vector mesons (ρ, ω, and ϕ) were photo-produced on 2H, C, Ti, Fe, and Pb targets at the Thomas Jefferson National Laboratory using the CEBAF Large Acceptance Spectrometer (CLAS). The properties of the ρ vector meson at normal nuclear densities and zero temperature were investigated via their rare leptonic decay to e+e−. The rho meson mass distributions were extracted for each of the targets. With respect to the ρ-meson mass, we obtain a small shift compatible with zero. Also, we measure widths consistent with standard nuclear many-body effects such as collisional broadening and Fermi motion.