Development of a trigger scintillator for the MOLLER experiment

The measurement of lepton-lepton electroweak reaction (MOLLER) experiment will measure the weak charge of the electron to a fractional accuracy of 2.4% at an average Q² of 0.0056 (Gev/c)². A set of Trigger Scintillators, positioned upstream and downstream ends of the four-gas electron multiplier (GEM) detectors are an integral part of the tracking detector system. These scintillators track individual electrons in calibration runs to measure the detailed shapes of all particle trajectories which helps to calibrate the detectors and understand the kinematics of the MOLLER apparatus. Trigger scintillators serve as the primary trigger of the tracking detector system, help in spectrometer calibration, determining electron momentum distribution, and understanding background measurements. This tracking detector system is instrumental in ensuring that the rate distribution measured at low beam currents by the full tracking system closely aligns with that observed at full luminosity.

At Louisiana Tech University, we are building Trigger scintillators using an organic scintillator embedded with wavelength shifting (WLS) fibers. Using WLS fiber instead of a light guide leads to the collecting and guiding of light photons toward photo-multiplier tube (PMT) efficiently. We have constructed and tested the initial prototype where we achieved a cosmic muon efficiency above 98%. Currently, the final prototype is under construction. The progress, current status of the final prototype testing, and plans for final detector constructions will be given.