Measurement of the eta->pi+pi-e+e- decay branching ratio
  The reaction pd->3He eta at threshold was used to provide a clean source of eta mesons for decay studies with the WASA detector at CELSIUS. The branching ratio of the decay eta->pi+pi-e+e- is measured to be (4.3+/-1.3+/-0.4)x10^-4. 
CELSIUS-WASA Collaboration: Chr. Bargholtz, M. Bashkanov, D.   Bogoslawsky, H. Cal\'en, F. Capellaro, H. Clement, L. Demir\"...