The Belle II experiment is at the forefront of modern science in high energy physics. The data obtained will verify the predictions of the Standard Model for the probabilities of rare decays of the B and D mesons and the t lepton, improve the accuracy of measuring the parameters of symmetry breaking between matter and antimatter, and possibly detect manifestations of new physics.
The experiment is being conducted at the Japanese KEK High-Energy Research Organization, on the SuperKEKV collider. Researchers working on the experiment are from the NSU Laboratory for Researching Physics of B- and D-Mesons Physics (LRBDM) and Laboratory for Researching the Properties of b- and c-Quarks in e + e- Annihilation (LRPQA) that are based at the Physics Department Interdisciplinary Center of Elementary Particle Physics and Astrophysics that was created in 2014. These researchers are joined by colleagues from the Budker Institute of Nuclear Physics (INP). INP and KEK have been collaborating since 1993 and have been engaged in the Belle I and Belle II research.
The scientists are modernizing the calorimeter of the Belle II detector, a system for recording and measuring the energy and direction of photons and electrons and identifying charged particles. The calorimeter includes nine thousand counters based on CsI (Tl) scintillation crystals. Russian physicists developed the calorimeter electronics and are now providing support and calibrating the counters.
The NSU laboratories are developing and maintaining a calorimeter data collection system, software for reading recorded data at high speed. In addition, they have developed a module that allows you to quickly measure the luminosity of the collider, highlighting the events of elastic electron-positron scattering and measuring their frequency. The data from this module is used to configure the collider and to determine the number of useful events recorded in the experiment.
Alexander Kuzmin, Head of LRBDM, talked about the results of this research,
The Standard Model presents the interaction of elementary particles in modern theory. The results of many experiments are in excellent agreement with this theory. However, at very small distances, manifestations of new, unknown interactions are possible. The Belle II experiment aimed at finding manifestations of new physics. In experiments conducted at CERN at the Large Hadron Collider, the energy of interacting particles increases, which makes it possible to bring these particles closer together and reveal manifestations of new interactions. In our experiment, we operate at lower energies, but we measure with very high accuracy. This allows us to detect manifestations of interactions that occur deep inside the interacting particles.
From April to June 2019, a statistics collection session was held at the KEK Belle II installation. This was the first data set with all working detector subsystems. Scientists tested the performance of all Belle II subsystems and data collection systems, and recorded experimental data that are currently being processed. According to Kuzmin, the SuperKEKB collider obtained a luminosity of 1034cm-2s-1 during the session, a comparable to the luminosity of the previous KEKB setup. This is a significant achievement, but in the future, luminosity has to be increased 80 times.
Kuzmin continued,
To detect rare decays, it is necessary to investigate a large number of decays of B and D mesons and t leptons. The frequency of production of these particles is determined by the luminosity of the setup, a value characterizing the frequency of interaction of electrons and positrons in the collider. Luminosity depends on the intensity of electron-positron beams and their size. Creating a collider that ensures the effective interaction of dense, intense beams is a complex task for accelerator physics. SuperKEKB will have the highest luminosity in the world.
Novosibirsk scientists continue to oversee the operations and further improvement of the calorimeter and Belle II luminosity measurement system. During the last data set session, calibrations were conducted, as well as verification and adjustment of the calorimeter data acquisition system, and the Belle II experiment is just getting started.
