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, ξ, was inferred from the beam profiles and current, was compared to the tune shift of the coherent beam-beam π mode, and was corroborated by luminosity measurement. Values of ξ up to 0.09 were achieved without significant lifetime reduction