Collisions of resonantly coupled round beams at the Cornell electron-positron storage ring (CESR)

As a first step toward testing the proposed "Mobius" scheme, we used existing CESR elements to collide round, rather than flat, beams. The tune shift parameter, /spl xi/, was inferred from the beam profiles and current, was compared to the tune shift of the coherent beam-beam /spl pi/ mode, and was corroborated by luminosity measurement. Values of /spl xi/ up to 0.09 were achieved without significant lifetime reduction.