A proposal for a test of Weak Equivalence Principle with improved accuracy using a cryogenic differential accelerometer installed on a pendulum

We present here the concept for a new experimental test of the Weak Equivalence Principle (WEP) carried out in the gravity field of the Sun. In this experiment, two test masses of different materials are the central elements of a differential accelerometer with zero baseline. The differential accelerometer is placed on a pendulum, in such a way as to make the common center of mass of the two test masses coincident with the center of mass of the pendulum. Exploiting a very precise centering, such a system should provide a high degree of attenuation of the local seismic noise; this, together with an integration time of the order of tens of days, would allow a verification of the WEP with an accuracy improved by at least an order of magnitude with respect to the state of the art. One of the strengths of this experiment is the know-how acquired from a previous study and technology development (GREAT: General Relativity Accuracy Test) that involved a test of the WEP in the gravity field of the Earth, in free fall inside a co-moving capsule released from a stratospheric balloon.