Construction status and performance evaluation of the Straw-Tube Tracker for the COMET experiment

The COMET experiment at J-PARC aims to search for muon-to-electron conversion in aluminium with a target sensitivity of 10⁻¹⁷. To measure 105 MeV/c signal electrons with a momentum resolution better than 200 keV/c, COMET employs a low-mass Straw-Tube Tracker consisting of five stations read out by dedicated electronics. Three stations have been constructed, and the first station has been commissioned with the COMET beamline, successfully recording the first signals. A full-scale prototype previously demonstrated a spatial resolution of ~110 μm, exceeding the required performance of better than 200 μm. For the first station, baseline noise was resolved through improvements to the grounding and cabling, reducing the noise by 90%. Spatial-resolution studies with the improved setup are now in progress.