Speaker
Description
The Measurement of a Lepton-Lepton Electroweak Reaction (MOLLER) experiment at Jefferson Lab will perform a precision measurement of the parity-violating asymmetry in polarized electron-electron (M{\o}ller) scattering, providing a sensitive determination of the weak charge of the electron and a probe of physics beyond the Standard Model. A tracking system based on large-area Gas Electron Multiplier (GEM) detectors will play an important role in spectrometer calibration, determination of the experimental acceptance, and characterization of backgrounds. The MOLLER tracking system consists of 28 large-area triple-GEM detector modules designed to provide reliable charged-particle tracking while operating within the demanding experimental environment. With detector production largely complete, current efforts are focused on system commissioning and optimization of detector operation, readout, and track reconstruction. Performance studies include measurements of detector efficiency as a function of operating voltage, characterization of hit and cluster properties, and track-based measurements of detector efficiency and spatial resolution. The reconstruction framework is also being developed and validated for multi-layer tracking and for identifying the expected response of individual detector planes. This talk will present the current status of the MOLLER GEM tracking system, results from recent commissioning and performance studies, and ongoing work toward integration and operation of the complete tracking system for the MOLLER experiment.