Accelerator design at SuperKEKB

TLDR

The target luminosity of 8 × 10^35 cm⁻² s⁻¹ is 40 times higher than that of the KEKB B‑factory, which operated for 11 years until 2010. The SuperKEKB project aims to build a positron–electron collider that reaches this 8 × 10^35 cm⁻² s⁻¹ peak luminosity. SuperKEKB is a double‑ring, asymmetric‑energy collider with 4 GeV positrons and 7 GeV electrons, employing a nano‑beam scheme that uses a very small beta function (β* = 1/20), low emittance, a large horizontal crossing angle, and a bunch length longer than β*, while keeping beam–beam parameters similar to KEKB and doubling the beam currents. This design yields a 40‑fold increase in luminosity compared to KEKB.

Abstract

The SuperKEKB project requires a positron and electron collider with a peak luminosity of 8 × 1035 cm−2 s−1. This luminosity is 40 times that of the KEKB B-factory, which operated for 11 years up to 2010. SuperKEKB is an asymmetry-energy and double-ring collider; the beam energy of the positron (LER) is 4 GeV and that of the electron (HER) is 7 GeV. An extremely small beta function at the interaction point (IP) and a low emittance are necessary. In addition, in order to achieve the target luminosity, a large horizontal crossing angle between two colliding beams is adopted, as is a bunch length much longer than the beta function at the IP. This method is called the "nano-beam scheme". The beam–beam parameter is assumed to be similar to KEKB, the beta function at the IP is 1/20, and the beam currents are twice those of KEKB in the nano-beam scheme. Consequently, the luminosity gain of 40 with respect to KEKB can be obtained.