Program to Identify Secondary Background Sources in the MOLLER Experiment

The MOLLER project is a proposed experiment at Jefferson Lab aiming to measure the parity-violating asymmetry in electron-electron scattering. Electrons accelerated to 11 GeV are incident on a liquid hydrogen target. Those which scatter off of atomic electrons (electrons of interest) are directed by a magnetic spectrometer to a background-free region. However, the incident beam causes other high energy particles to scatter from this target in various directions. These particles could collide with other surfaces within the experimental chamber, consequently creating an additional, undesired source of secondary particles (so-called one-bounce backgrounds). The spectrometer collimation system has been carefully designed, aided by a program called "two-bounce" which checks to see if any of these one-bounce background sources are visible to the detector. We have developed "Two-bounce 3D" to model these sources in three dimensions to explore new potential pathways that may not be covered by analyzing the apparatus in two dimensions (r, z). Borrowing techniques from computer graphics, it employs a bounding-box R-tree to efficiently organize the geometry, allowing for significantly faster intersection computations. Additionally, it utilizes parallel computing to better optimize the usage of computational resources and increase the output resolution. This work will help optimize the experimental design and minimize the risk of unknown new sources of background in the final measurement.