SuperKEKB

SuperKEKB is a particle accelerator located at KEK (High Energy Accelerator Research Organisation) in Tsukuba, Ibaraki Prefecture, Japan. SuperKEKB will collide electrons with positrons at the centre-of-momentum energy close to the mass of the Υ(4S) resonance making it a second-generation B-factory for the Belle II experiment. The accelerator is an upgrade to the KEKB accelerator, providing approximately 40 times higher luminosity, due mostly to superconducting quadrupole focusing magnets. The accelerator achieved "first turns" (first circulation of electron and positron beams) in February 2016. First collisions are expected in early 2018.

The SuperKEKB design reuses many components from KEKB. Under normal operation, SuperKEKB will collide electrons at 7 GeV with positrons at 4 GeV (compared to KEKB at 8 GeV and 3.5 GeV respectively). The centre-of-momentum energy of the collisions will therefore be slightly above the Υ(4S) mass (10.57 GeV/c²). The accelerator will also perform short runs at energies of other Υ resonances, in order to obtain samples of other B mesons and baryons. The asymmetry in the beam energy provides a relativistic Lorenz boost to the B meson particles produced in the collision. The direction of the higher-energy beam determines the 'forward' direction, and the affects the design of much of the Belle II detector.

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