A Measurement of the Transverse Particle Distribution in the Presence of the Beam-Beam Interaction

The beam beam interaction in e+ e- storage rings causes significant beam size enhancement limiting the attainable luminosity. It is important to understand this effect, in particular the resulting particle distribution shape. Measurements at CESR have been made using an ´active´ probe to obtain horizontal beam profiles and detailed information regarding the vertical distribution tail shape. An estimate of the effect of the probe on the beam is given and results are presented.