Aleksandr Starostin 
Physics Department, University of California, Los Angeles   

The Fourth Reincarnation of the Crystal Ball and Eta Physics  

The eta meson is the second lightest hadron with unusually long lifetime. The unique 
properties of eta allow to study many fundamental topics of physics including breaking of 
isospin symmetry, pion-pion interactions, search for violation of discrete symmetries of 
nature and for physics beyond the standard model. One of the world largest eta samples is 
collected at the bremsstrahlung photon beam at Mainz Microton (MAMI) in Germany 
using the Crystal Ball spectrometer. This is the fourth cycle of experiments for the 
original Crystal Ball constructed nearly thirty years ago at SLAC. Refurbished and 
equipped with a new fast data acquisition system the nearly full coverage  
electromagnetic calorimeter continues to provide high quality experimental data. I will 
show some recent results obtained with the Crystal Ball at MAMI and discuss possible 
future eta measurements.