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Jefferson Lab's experiment E04-005, the largest integrated luminosity real photon CLAS experiment to date, provided a large sample of leptonic data; allowing for studies of the ρ-ω interference in the dileptonic decay channel, as well as charge radius and comparative branching ratio studies of the η and η′ through the Dalitz decay channel. An experimental study of the ρ-ω provides valuable input for theoretical models and calculations in addition to establishing a comparative basis for medium modification studies of vector mesons off of heavier targets. The total statistics collected for the η dalitz exceed the world's published statistics by an order of magnitude, while the η′ Daltiz decay is observed and measured for the first time.

Theoretical calculations predict the modification of 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. Photoproduction of vector mesons off nuclei were performed at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). The data were taken with a beam of tagged photons with energies up to 4 GeV on various nuclear targets. The properties of the ρ vector mesons were investigated via their rare leptonic decay to e+e−. This decay channel is preferred over hadronic modes in order to eliminate final state interactions in the nuclear matter. The combinatorial background in the mass spectrum was removed by a self‐normalizing mixed‐event technique. The ρ meson mass distributions were extracted for each of the targets. Statistically significant results regarding medium modification of the rho meson in the nuclear medium rule out lar...

The isoscalar spin‐transfer signature Syd has been used in inelastic scattering of 400 MeV polarized deuterons to search for ΔS=1 ΔT=0 strength in 40Ca and 12C. In 40Ca, spin excitations were found in the 9 MeV region and over a broad range in the continuum with a cluster strength around 15 MeV. In 12C, a previously unknown ΔS=1 ΔT=0 level was observed at 20.5 MeV; ΔS=1 ΔT=0 resonances were also found at 20 MeV and 30 MeV. Microscopic DWIA calculations agree nicely with 12C data.