A Method for Measuring Emittance in $e^+ e^-$ Colliding Beams
  We have developed techniques that allow simultaneous measurement of the spatial size of the luminous colliding beam region and the angular spread of beams in collision using e+e- --> mu+mu- events. These are demonstrated at the CLEO interaction point of the Cornell Electron-Positron Storage Ring, CESR, taking advantage of the small and well understood resolution of the CLEO tracking system. These measurements are then used to extract the horizontal beta, horizontal emittance and the vertical emittance and search for dynamic effects at CESR. 
D. Cinabro, K. Korbiak, M. Billing. N. Mistry, D. Rice and D. Rubin