Experimental Test Of Spin-mass Interaction

There are a number of groups experimentally searching for spin-dependent long-range forces. These works are largely motivated to explore the role of spin in gravitation, and to search for a new force in nature. Among these works, there are two categories: one is searching for spin-spin interaction, the other is spin-mass interaction .The latter also offers an exceptional sensitivity to test the Lorentz and CPT violation. The extraordinary sensitivity of the torsion balance instrument has made it a valuable tool to search for new weak macroscopic forces. In this paper, a torsion balance is used to probe the possible mass-spin (monopole-dipole) interaction between a spin polarized body and the Sun. The spin-polarized torsion pendulum is a strong permanent magnet of Sm2Co17 magnetized along radial direction, which is well shielded by magnetic-shielding materials. The equivalent number of spin-polarized electrons is about 1.5×1023. The advantage of this kind of torsion balance is getting more spin-polarized electrons, but it is difficult to be shielded well. A primary result gives a limit on the coupling constant g s g p/h c<1.4×10-31 for λ→∞. The corresponding limit on CPT and Lorenz violating parameter is at the level of 10-17eV. Three pairs of Helmholtz coils are made to compensate the surrounding magnetic field. At the same time, other torsion balance experiments are carried to test the role of magnetic field. At last, some constructive proposals are discussed to improve the experimental precision, and the expectative aim is at a level of 10 ?2 0eV.