The paper titled "Measured and projected beam backgrounds in the Belle II experiment at the SuperKEKB collider" was published in Nuclear Instruments and Methods in Physics Research Section A. Kazuki Kojima, Associate Prof. Kodai Matsuoka, and former Associate Prof. Keisuke Yoshihara authored and contributed to this paper.

The SuperKEKB/Belle II experiment aims to collect an unprecedented data set of 50 ab^-1 of electron-positron collisions in order to perform precise measurements for test of the Standard Model (SM) and search for physics beyond the SM. The SuperKEKB accelerator has achieved the world’s highest luminosity of 4.7×10³⁴ cm^-2s^-1 in 2022. The target luminosity is 6×10³⁵ cm^-2s^-1, which is about 30 times higher than the previous KEKB accelerator, by increasing the beam current and squeezing the beam size at the collision point. However, this leads to increases in backgrounds induced by beam particles, which could damage the detector components and degrade the detector performance. Therefore, it is crucial to understand and control those backgrounds in order to ensure detector performance and maintain adequate reconstruction efficiency. This paper summarizes measurements of beam-induced backgrounds at each sub-detector in the Belle II detector. Future background levels are also estimated based on the measurements. Additionally, the expected degradation in detector performance and acceptable background levels are discussed. In this paper, Mr. Kojima made a major contribution to the evaluation of beam-induced backgrounds in the Time-Of-Propagation counter for particle identification at the Belle II experiement.

Paper information:
A. Natochii, et al., "Measured and projected beam backgrounds in the Belle II experiment at the SuperKEKB collider"
[Nucl. Instrum. Methods Phys. Res. A, 1055, 168550 (2023). DOI:10.1016/j.nima.2023.168550]