Motivated by models proposed to explain Standard Model anomalies, and the unprecedented τ+τ- data to be collected by the Belle II experiment during the next years, we study the kinematics of tau pair decays and propose a new method to search for lepton flavor violating processes in tau lepton decays to invisible beyond Standard Model particles, such as τ→ℓα, where ℓ is either an electron or a muon, and α is a massive particle that escapes undetected. The new method improves by one order of magnitude the expected upper limit on the τ→ℓα production in 3×1 prong tau decays and establishes the possibility of performing this search in 1×1 prong tau decays which has not been previously considered.
De La Cruz-Burelo, E., De Yta-Hernandez, A., & Hernandez-Villanueva, M. (2020). New method for beyond the Standard Model invisible particle searches in tau lepton decays. Physical Review D, 102(11), 115001. https://doi.org/10.1103/PhysRevD.102.115001