KEKB beam collision stability at the picosecond timing and micron position resolution as observed with the Belle detector

Abstract

Using the Belle detector we study the characteristics of beam collisions at the KEKB 3.5 GeV e+ on 8 GeV e− asymmetric energy collider. We investigate the collision timing tIP and its z-coordinate along the beam axis zIP as a function of the position of the colliding bunch in a beam train. The various tIP and zIP behaviors observed by Belle are attributed to beam loading effects in the radio frequency cavities that accelerate the beams with a beam abort gap. We report these results in detail and discuss the prospects for the SuperKEKB collider.