Narrow Results

Differential and total cross sections are presented for π^-- and K^--induced reactions on a proton target leading to all-neutral final states. Also shown are rates for rare and upper limits for forbidden eta-meson decays to test Chiral Perturbation Theory, the π⁰π⁰ interactions and C and CP invariance.

The physics program of the Crystal Ball spectrometer at MAMI-C began in early 2007. Experiments utilize the upgraded electron accelerator that provides high intensity beams of circularly and linearly polarized real photons with maximum energy of 1.5 GeV. The highly segmented nearly 4π acceptance detection system consists of the Crystal Ball, particle identification detector and versatile endcap TAPS. A wide range of physics topics is under study including the production and decay of η, ω, and η' mesons, the investigation of coherent meson photoproduction on nuclei, measurements of polarization and double polarization observables in meson photoproduction on proton and neutron. The current status of the experiment and some preliminary results are reported.