HELICITY PRECESSION OF ACCELERATED FERMIONS FROM SPIN ROTATION COUPLING

The spin-rotation and spin-acceleration contributions to the helicity precession of fermions are calculated in the approximation E much-grea ter-than mc2 in the laboratory frame. An application of the results to perfect, circular accelerators indicates that evidence previously add uced for the ''circular Unruh'' effect should be re-interpreted as evi dence in favour of the Mashhoon effect. The acceleration effect exists , but is smaller than the Mashhoon effect at all energies. High energy accelerators may prove useful in the study of these and other aspects of spin-rotation-gravity coupling.