Development of a scintillating-fiber-based beam monitor for the coherent muon-to-electron transition experiment

The coherent muon-to-electron transition (COMET) experiment is a leading experiment for the coherent conversion of \(\mu ^- \textrm{N}\rightarrow e^- \textrm{N}\) using a high-intensity pulsed muon beamline, produced using innovative slow-extraction techniques. Therefore, it is critical to measure the muon beam characteristics. We set up a muon beam monitor (MBM), where scintillating fibers woven in a cross shape were coupled to silicon photomultipliers to measure the spatial profile and timing structure of the extracted muon beam for the COMET. The MBM detector was tested successfully with a proton beamline at the China Spallation Neutron Source and took data with good performance in the commissioning run. The development of the MBM, including its mechanical structure, electronic readout, and beam measurement results, are discussed