The Monument Experiment; Ordinary Muon Capture to probe 0νββ-decay Nuclear Matrix Elements

Extracting particle physics properties from neutrinoless double-beta (0νββ) decay, requires a detailed understanding of the involved nuclear structures. Still, modern calculations of the corresponding nuclear matrix elements (NMEs) differ by factors 2-3. The high momentum transfer of Ordinary Muon Capture (OMC) provides insight into highly excited states similar to those that contribute virtually to 0νββ transitions. The precise study of the γ's following the OMC process, makes this a promising tool to validate NME calculations, and test the quenching of the axial vector coupling gA. The MONUMENT collaboration is performing a series of explorative OMC measurements involving typical ββ-decay daughter isotopes such as 76Se and 136Ba, as well as other benchmark isotopes. In this poster the experiment carried out at the Paul Scherrer Institute and first results from the beam-time in 2021 will be presented. This research is supported by the DFG Grant: 448829699 and RFBR-DFG with project number: 21-52-12040