Investigation of a Beam Spin-Decoherence with a Nonadiabatic Stable Spin Axis Orientation Change

Abstract

A new experiment to measure electric dipole moments (EDMs) of elementary particles, based on measuring the polarized beam’s spin precession frequency, has been proposed for implementation at the NICA facility (JINR, Russia). Polarized beam experiments in general require long spin-coherence times at around 1000 seconds. The proposed method involves a further complication (enhancing the measurement precision by several orders of magnitude): a switching of the accelerator guide-field polarity as part of its CW−CCW injection procedure. For the realization of this latter procedure a calibration process is necessary, during which the beam polarization axis changes its orientation from the radial (used for the measurement) into the vertical (used for the calibration) direction. In case this change occurs adiabatically, the beam particles’ spin-vectors follow the direction of the polarization axis, which negatively affects the calibration accuracy; however, the violation of the adiabiticity condition raises the question as to the conservation of the beam’s spin-coherence. We address this question in the present investigation.