Novel Method of Measuring Electron Positron Colliding Beam Parameters
  Through the simultaneous measurement of the transverse size as a function of longitudinal position, and the longitudinal distribution of luminosity, we are able to measure the $\beta_y^\ast$ (vertical envelope function at the collision point), vertical emittance, and bunch length of colliding beams at the Cornell Electron-positron Storage Ring (CESR). This measurement is possible due to the significant ``hourglass'' effect at CESR and the excellent tracking resolution of the CLEO detector. 
D. Cinabro, K. Korbiak, R. Ehrlich, S. Henderson, N. Mistry