Design and Analysis of Small Angle Monitors for the MOLLER Experiment*

The MOLLER experiment aims to make the most precise measurement to date of the parity-violating asymmetry in electron–electron (Møller) scattering, providing a sensitive determination of the weak mixing angle at low energies. Such precision offers a unique probe of physics beyond the Standard Model, complementing searches at high-energy colliders like the LHC. Achieving this goal requires tight control of systematic uncertainties, where the Small Angle Monitors (SAMs) play a central role. Strategically placed to minimize expected physics asymmetries relative to the main detectors, the SAMs serve as sensitive monitors of false asymmetries. My work has focused on SAM design, calibration, and performance verification. I will present results from photoelectron lightguide testing, single-photon calibrations, and photomultiplier tube (PMT) characterizations, along with more recent contributions including scintillator construction and the development of a self-triggering PMT high-voltage scan system. These efforts demonstrate that the SAM detectors are meeting their stringent performance requirements, thereby ensuring the precision of the MOLLER measurement.