Spin decoherence and off-resonance behavior of radiofrequency-driven spin rotations in storage rings

TL;DR

This paper provides an analytic framework for understanding how detuning and decoherence affect radiofrequency-driven spin rotations in storage rings, crucial for precision polarization experiments like electric dipole moment measurements.

Contribution

It introduces a detailed formalism accounting for detuning and decoherence effects on spin dynamics, aiding interpretation of experimental data in storage ring polarization control.

Findings

Analytic description of detuning effects on spin precession components

Application of formalism to pilot bunch approach in COSY experiment

Identification of phase of horizontal polarization envelope as stability indicator

Abstract

Radiofrequency-driven resonant spin rotators are routinely used as standard instruments in polarization experiments in particle and nuclear physics. Maintaining the continuous exact parametric spin-resonance condition of the equality of the spin rotator and the spin precession frequency during operation constitutes one of the challenges. We present a detailed analytic description of the impact of detuning the exact spin resonance on the vertical and the in-plane precessing components of the polarization. An important part of the formalism presented here is the consideration of experimentally relevant spin-decoherence effects. We discuss applications of the developed formalism to the interpretation of the experimental data on the novel pilot bunch approach to control the spin-resonance condition during the operation of the radiofrequency-driven Wien filter that is used as a spin rotator in the first direct deuteron electric dipole moment measurement at COSY. We emphasize the potential importance of the hitherto unexplored phase of the envelope of the horizontal polarization as an indicator of the stability of the radiofrequency-driven spin rotations in storage rings. The work presented here serves as a satellite publication to the work published concurrently on the proof of principle experiment about the so-called pilot bunch approach that was developed to provide co-magnetometry for the deuteron electric dipole moment experiment at COSY.