Accelerator physicists at the SuperKEKB electron–positron accelerator in Tsukuba, Japan, are celebrating their December 2024 world-record luminosity of 5.1 × 1034 cm−2 s−1. At the same time, they are scratching their heads about how to reach their target luminosity, which is roughly an order of magnitude higher. Success has implications both for Belle II, the onsite experiment that studies B mesons and other particles, and for future electron–positron colliders.
The researchers’ two-pronged approach to increasing luminosity is conceptually simple: “First, we put in more particles, and then we squeeze the beam,” says Mika Masuzawa, a leading accelerator physicist at SuperKEKB. In practice, though, it’s anything but, she notes. The aim is to use powerful magnets to squeeze the beams to about 50 nm in the vertical dimension and create a so-called nanobeam. So far, they’ve gotten down to 260 nm. For comparison, conventional beam sizes are...
