Speaker
Description
The MOLLER Experiment at Jefferson Lab, Virginia, will utilize parity-violating electron scattering to measure the asymmetry in Moller scattering, and extract the weak mixing angle with unprecedented precision. The predicted asymmetry is ~33 parts per billion, with a target uncertainly of 0.8 ppb, corresponding to a 2.4% determination of the electron’s weak charge and a projected precision of δ(sin^2 (θ_W) ) = ±0.00028. This measurement will provide a stringent test of the Standard Model while offering sensitivity to new neutral current interactions at the Multi-TeV scale, making MOLLER a powerful probe of physics beyond the Standard Model.
To support these precision goals, pixel detectors based on High Voltage Monolithic Active Pixel Sensors (HV-MAPS) are being integrated into two key MOLLER subsystems. Each silicon sensor has an active area of ~20 x 20 mm^2. With pixel sizes of ~80 x 80 microns and thicknesses as low as 50 microns, they provide fine spatial resolution with minimal material for unwanted scattering. Operation at high bias voltages enable fast charge collection by drift, allowing high detection rates in high-rate environments like MOLLER.
A family of HV-MAPS (known as MuPix) will be implemented in two detector subsystems for MOLLER. In the Compton Polarimeter, planes of pixel detectors will provide tracking and profile measurements to support precise beam polarization monitoring. For the Main Integrating Detector, the planes are installed behind a subset of the overall Cherenkov detector modules, and operate as profile detectors, measuring the spatial distribution of scattered electrons across the detector array. These measurements provide critical input for alignment, acceptance studies, and control for systematic effects in the asymmetry extraction.
This work demonstrates the implementation of these pixel sensors in both subsystems, including the design and analysis of mounting and cooling structures under projected operating conditions. The talk will also cover the development of the readout architecture, which utilizes the low-power GigaBit Transceiver (lpGBT) and VTRx+ optical transceiver at its core for high-speed communication with these chip arrays. A specialized pick-and-place system is being developed for high precision sensor assembly during detector module construction.
| Keyword-1 | MOLLER |
|---|---|
| Keyword-2 | electron detector |
| Keyword-3 | compton polarimeter |