Title: Flavour Anomalies with advanced particle Identification MEthods
Period: 1. 10. 2020 - 30. 09. 2025
Leading organization: Institut "Jozef Stefan"
Participating organization: University of Ljubljana, Faculty of Mathematics and Physics
The Standard Model of particle physics, formulated nearly half a century ago, describes the fundamental matter particles and their interactions - almost. There are some acknowledged gaps in its description of our universe as well as new theories and experiments that point to potential violations of some of its existing 'laws'. Lepton universality refers to a key assumption underlying the Standard Model, which states that all three of the equally charged leptons (three of the 12 matter particles, with different masses) are believed to interact in the same way with other particles. Thus, they should be created equally in particle transformations or 'decays' when differences in their masses are considered. However, growing evidence suggests that this may not be the case. The EU-funded FAIME project plans to provide a definite demonstration with experiments involving rare decays, exploiting highly sensitive detection technology and sophisticated analyses.
In the proposed research, precision measurements of rare processes involving heavy quarks and leptons will be used to search for new phenomena beyond the Standard Model, popularly known as New Physics. This research at the intensity frontier is complementary to searches at the highest achievable energies carried out at the LHC proton-proton collider. Indications of very interesting discrepancies have recently been observed by three experiments (LHCb, BaBar, and Belle) between their results and predictions of the Standard Model in certain classes of decays of B mesons, which involve leptons in the final state. The proposed project will address these issues by using large event samples collected with the Belle II detector at a new electron-positron collider, SuperKEKB. By investigating a broad range of selected rare decays of B and D, the project will attempt to provide a definite answer on the violation of Lepton Flavour Universality, one of the cornerstones of our current understanding of the interactions among the elementary particles. Based on the results of these studies, the final stages of the project will be devoted to possible explanations and to studies of transitions that would be based on related new physics phenomena.
Within the proposed research programme, novel, highly advanced identification methods for charged particles will also be developed. They will be of crucial importance to suppress backgrounds arising from other, much more abundant decays in measurements of rare processes where the sensitivity to a possible contribution of New Physics is largest. The proposed research will strongly benefit from the fact that the same group that contributed substantially to the physics programme, concept, design, and construction of the detector, will also carry out the development of novel analysis methods, their calibration and optimization for individual reactions.