Gravitational Compensation for a Laboratory-Scale Test of the Equivalence Principle

Certain quantum theories that seek to unify the Standard Model and General Relativity put in to question the validity of the Weak Equivalence Principle (WEP), which states that the laws of relativity hold at every distance scale. Some of these theories require violations of the WEP. To search for these possible violations, the University of Washington's E\"{o}t-Wash group uses a rotating torsion balance that provides the most precise small-scale laboratory measurements of the WEP. Environmental factors surrounding the lab cause the largest systematic effect in this experiment by creating gravitational coupling between environmental field gradients and the multipole moments of the pendulum. Compensators have been constructed to minimize the strength of the q21, q22, and q31 multipole interactions on the pendulum due to these factors. This talk will focus on the development of an external mass distribution that provides improved compensation of the gravitational couplings, thereby allowing for a more precise measurement to be made.