ROTATABLE-TORSION-BALANCE EQUIVALENCE PRINCIPLE EXPERIMENT FOR THE SPIN-POLARIZED HoFe3

Abstract

We use a rotatable torsion balance to perform an equivalence principle test on a magnetically shielded spin-polarized body of HoFe 3. With a rotation period of one hour, the period of possible signal is reduced from one solar day by 24 times, and hence the 1/f noise is greatly reduced. Our present experimental results give a limit of (-0.68 ± 0.90) × 10-9 on the Eötvös parameter [Formula: see text] and a limit of (1.8 ± 5.3) × 10-9 on the Eötvös parameter [Formula: see text] of equivalence of the polarized body compared with unpolarized aluminum–brass cylinders in the solar gravitational field, and a limit (-0.24 ± 0.55) × 10-9 on the Eötvös parameter [Formula: see text] in the earth gravitational field. This improves the previous limit on the Eötvös parameter [Formula: see text] for polarized electrons in the solar gravitational field by one order of magnitude.