Speaker
Description
The MuSun experiment utilizes a unique cryogenic time projection chamber to extract the $\mu d$ capture rate to better than 1.5% precision via determination of the $10^{-3}$ deviation of the muon lifetime in deuterium gas from the free muon lifetime. This measurement will lead to a benchmark result in calibrating weak interactions in the two nucleon system, relevant for calculating fundamental reactions in neutrino-astrophysics within modern effective field theories. The full statistics required were collected over two beam periods in the $\pi$E1 area of the Paul Scherrer Institute in 2014 and 2015. However, the ambitious precision goal would not be met until a series of subtle systematic uncertainties were under control, leading to a challenging analysis over the subsequent years. In order to understand and correct for these systematic issues, including muon-catalyzed fusion interference, determination of the gas purity to unprecedented levels, and unexpected beam electron backgrounds, several advanced studies and techniques have been developed. The analysis of the first dataset is nearly finished, with all systematic uncertainty contributions close to the design goal. This analysis will be presented in detail together with an outlook for the full MuSun dataset.
