Grant: Subatomic Physics Envelope - Project

The Belle II experiment is located at the SuperKEKB e+e- collider at the KEK laboratory in Tsukuba, Japan. It is a successor to the successful Belle and BaBar experiments, which were cited in the 2008 Physics Nobel Prize. The primary physics goal of Belle II is to search for evidence of new physics. This includes a wide range of measurements that are sensitive to the presence of heavy virtual particles, and that can be precisely predicted in the standard model. These measurements could include CP violation and other asymmetries, rare decays, or forbidden decays. The mass reach of these indirect probes can exceed that of direct searches at the LHC, and is complementary to them. Belle II also has unique sensitivity for search for the production of new, light, particles, such as those predicted by Dark Sector models. Belle II will also continue Belle and BaBar's successful program of exploring and characterizing CP violation and weak force. The Canadian group is leading the R&D effort on polarizing the SuperKEKB electron beam. Upgrading SuperKEKB with polarization would open a unique program to measure weak neutral-current interaction strengths of unprecedented precision separately for multiple flavours. It will give the most precise measurement of a key Standard Model parameter, sin2thetaW, from a single experiment, probe its running, and provide unique sensitive to new physics. This polarization upgrade is included in the KEK Roadmap 2022-2026 and Belle II submission to the Snowmass planning process. The experiment has so far recorded 430 fb-1. The detector is currently installing a new two-layer pixel detector, and will resume data taking in October 2023. SuperKEKB set a world record for instantaneous luminosity of 4.7 x 1034 s-1 cm-2, and has a goal of increasing the instantaneous luminosity to 4 x 1035 s-1 cm-2. The experiment will collect data through the mid-2030's, with a goal of collecting 50 fb-1 of data. The Canadian group is responsible for the calorimeter reconstruction and calibration software, and the related calibration operations. Canadian collaborators are active in physics analysis, with leadership roles in the Semileptonic working group, and developing world-leading dark sector searches. Canadian members have also been holding senior management roles within the collaboration. Computing is essential, with data sets approaching the size of LHC experiments. Canada is providing a CFI-funded data center, and is one of the leading producers of simulated events. The group is requesting funds to support graduate students and postdocs; for travel primarily to KEK, but also for conferences; limited material and supplies; and funds for specialized technical support. It will support the accelerator physics R&D program needed for the polarization upgrade. Note that this project grant reflects the merging of two existing project grants, "The Belle II project", and "SuperKEKB Electron Beam Polarization Upgrade".