Speaker
Description
PIONEER is a rare pion decay experiment that will run at the Paul Scherrer Institute (PSI) in Switzerland. In its initial phase, the primary objective is to improve the measurement of the $\pi\rightarrow e \nu$ branching ratio: $R_{e/\mu}=\mathcal{B}(\pi\rightarrow e \nu (\gamma)) / \mathcal{B}(\pi\rightarrow \mu \nu (\gamma))$. PIONEER aims to improve on, by more than an order of magnitude, the precision of the best measurement to date, performed by the PIENU experiment at TRIUMF. This would align the measurement of $R_{e/\mu}$ with the $10^{-4}$ precision level of the Standard Model calculations, providing a stringent test of lepton flavour universality. In order to achieve this ambitious goal, PIONEER will be using the world's most intense pion beam at PSI, an active silicon strip LGAD (Low Gain Avalanche Detectors) target and an optimized calorimeter geometry. This talk will focus on the development of a liquid xenon scintillation calorimeter, one of the two designs being considered for the large acceptance, 19-radiation length calorimeter. In addition to the measurement of $R_{e/\mu}$, PIONEER is being developed to include additional physics goals, such as searching for sterile neutrinos and testing CKM quark mixing matrix unitarity.
