NEW EXPERIMENTAL LIMIT ON THE SPATIAL ANISOTROPY FOR POLARIZED ELECTRONS

Is our laboratory in an isotropic state for spin states? For example, motion of the earth through the cosmic neutrino background would produ ce a term of the form gsigma . v in the energy of an electron. Certain kinds of vacuum states have this effect on electrons too. TO search f or such a term or a term like g'sigma . n where n is a particular dire ction in the universe, we use a torsion pendulum carrying a transverse ly spin-polarized ferrimagnetic Dy-Fe mass which exhibit orbital compe nsation of the electron intrinsic spin magnetic moments. With this mag netic compensated mass, pure-Fe and mu-metal shields reduced magnetic torques to a good extent. The searched terms would produce a sinusoida l oscillation of the pendulum with a period of one sidereal day. We ha ve not detected such an oscillation. Analysis of our experimental resu lts gives a limit 3.5 x 10(-18) eV for the splitting of the spin state s of an electron at rest on the Earth. Compared to previous results, t his is an improvement of more than a factor of 2.