Research On The Spin-dependent Interaction

All particles which are the component of matter in the universe possess the property of spin. An important development of the general relativity is that the spin of the particle is considered as a new source of field. It is well known that the gravitation field is created by the mass and the electromagnetism field produced by the charge. Therefore, the intrinsic spin is likely to produce a torsion field, and this field may interact with other particles with intrinsic spin.This possible effect of spin in gravitation with torsion has attracted a lot of attention. Therefore it is necessary to make concrete predictions about its effects and how to measure them. Hammond developed a theory of gravitation with torsion, in which a dimensionless coupling constant K is introduced to describe the spin-dependent interaction. A particular prediction of the theory is the existence of the spin-spin interaction. According to the experimental result of Chui and Ni, who investigated the interaction of a polarized test mass and a paramagnetic salt, a stringent upper bound of K<2×1014 is obtained.In this thesis, according to the torsion theory developed by Hammond, we calculate the spin-dependent interaction and give a better upper bound of K. Firstly, Based on this theory, the interaction between the intrinsic spin of a particle and the mass source is calculated. It is shown that the spin-dependent interactions in torsion theory are similar to that for macroscopic rotating body in the general relativity without torsion. And this result indicates that, in nature, the microscopic intrinsic spin is similar to the macroscopic rotation. Secondly, in order to give a new upper bound of K, we using the coupling of spin-rotation in a coordinates system on the surface of the earth, according to the recent torsion pendulum experiment with polarized electrons by Heckel et al., we set a new limit on the value of the torsion coupling constant K as K∈[0.53,0.95], which have improved many orders than the constraints from the early spin-spin experiment with K<2×1014.