The Belle II detector records and analyses particle collisions produced by SuperKEKB.

The Belle II detector records and analyses particle collisions produced by SuperKEKB. (Photo: Shota Takahashi/KEK)

Search for antimatter: SuperKEKB accelerator kicks into new gear

Following an eight year conversion period, the SuperKEKB particle accelerator in Japan is almost ready to restart: soon, electrons and positrons will be brought to collision in the completely modernized accelerator ring. In future, the Belle II detector, also modernized, will record and evaluate these events with unprecedented precision.

With the Belle II experiment, scientists aim to investigate a rare violation of symmetry – and clarify the question of why barely any antimatter exists in the today's universe. The decay of B-mesons plays a decisive role here. These particles are formed when electrons and positrons collide.

The new SuperKEKB accelerator produces 40x more collision events than its predecessor – and consequently substantially more data. To allow this data to be analyzed, the Belle detector is also undergoing modernization. In all, about 100 research establishments from 25 countries are working on Belle II. The Max Planck Institute (MPI) for Physics is involved in building the innermost detector.

"The decay point of the B mesons can be observed with the utmost precision using this pixel vertex detector", explains Hans-Günther Moser of the Max Planck Institute for Physics. "This information is critical for identifying possible deviations in particle decay."

On 21 March 2018, an electron beam was successfully introduced into the accelerator ring. It will be followed by a positron beam in early April. In parallel to this, the final preparations are under way for the first particle collision to take place in a few months' time.

A tandem in the search for new physics

The SuperKEKB accelerator and the Belle II detector form a tandem that scientists use to search for new physical processes beyond the standard model. They hope to find evidence of them in rare decays of elementary particles, such as b mesons, c quarks and tau leptons.

The SuperKEKB sets a new record with this modernization, achieving the greatest luminosity compared to other accelerators. This refers to the number of collisions per second and defined area. SuperKEKB also clearly outperforms its predecessor: 1,000 B/anti-B meson pairs are created per second, whereas KEKB achieved 25.


Dr. Hans-Günther Moser
Max Planck Institute for Physics
Chair Institutional Board Belle II
+49 89 32354-248