Observation of Vertical Betatron Sideband due to Electron Clouds in the   KEKB LER
  The effects of electron clouds on positively-charged beams have been an active area of research in recent years at particle accelerators around the world. Transverse beam-size blow-up due to electron clouds has been observed in some machines, and is considered to be a major limiting factor in the development of higher-current, higher-luminosity electron-positron colliders. The leading proposed mechanism for beam blow-up is the excitation of a fast head-tail instability due to short-range wakes within the electron cloud. We present here observations of betatron oscillation sidebands in bunch-by-bunch spectra that may provide direct evidence of such head-tail motion in a positron beam. 
J. W. Flanagan (1), K. Ohmi (1), H. Fukuma (1), S. Hiramatsu (1), M.   Tobiyama (1), E. Perevedentsev (2) ((1) High Energy A...