We report a helicity analysis of subthreshold ρ0 production on 2H, 3He, and 12C at low photoproduction energies, The results are indicative of a large longitudinal ρ0 polarization (1=1, m=0) and are consistent with a strong helicity-flip production mechanism. This signature is used to extract in-medium ρ L0 invariant mass distributions for all three nuclei in a manner which is less model dependent than previous measurements. The results are compared to kinematic and phenomenological models of the ρ0 spectral function. The 2H and 3He data distributions support the role of N*(1520) excitation in shaping the in-medium ρL0 invariant mass distribution, while the 12C distributions are consistent with quasi-free ρ L0 production. The data support an in-medium modification of the ρL0 invariant mass distribution.
|Number of pages||7|
|Journal||Physical Review C - Nuclear Physics|
|Publication status||Published - 2003 Dec|
ASJC Scopus subject areas
- Nuclear and High Energy Physics