16 research outputs found
Spin decoherence and off-resonance behavior of radiofrequency-driven spin rotations in storage rings
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.Comment: 31 pages, 10 figures, 5 table
Pilot bunch and co-magnetometry of polarized particles stored in a ring
In polarization experiments at storage rings, one of the challenges is to
maintain the spin-resonance condition of a radio-frequency spin rotator with
the spin-precessions of the orbiting particles. Time-dependent variations of
the magnetic fields of ring elements lead to unwanted variations of the spin
precession frequency. We report here on a solution to this problem by shielding
(or masking) one of the bunches stored in the ring from the high-frequency
fields of the spin rotator, so that the masked pilot bunch acts as a
co-magnetometer for the other signal bunch, tracking fluctuations in the ring
on a time scale of about one second. While the new method was developed
primarily for searches of electric dipole moments of charged particles, it may
have far-reaching implications for future spin physics facilities, such as the
EIC and NICA.Comment: 5 pages, 3 figures + references + supplemental material (6 pages, 2
figures, 6 tables + references
First Search for Axionlike Particles in a Storage Ring Using a Polarized Deuteron Beam
Based on the notion that the local dark-matter field of axions or axionlike particles (ALPs) in our Galaxy induces oscillating couplings to the spins of nucleons and nuclei (via the electric dipole moment of the latter and/or the paramagnetic axion-wind effect), we establish the feasibility of a new method to search for ALPs in storage rings. Based on previous work that allows us to maintain the in-plane polarization of a stored deuteron beam for a few hundred seconds, we perform a first proof-of-principle experiment at the Cooler Synchrotron (COSY) to scan momenta near 970 MeV/c. This entails a scan of the spin-precession frequency. At resonance between the spin-precession frequency of deuterons and the ALP-induced electric dipole moment (EDM) oscillation frequency, there is an accumulation of the polarization component out of the ring plane. Since the axion frequency is unknown, the momentum of the beam and, consequently, the spin-precession frequency are ramped to search for a vertical polarization change that occurs when the resonance is crossed. At COSY, four beam bunches with different polarization directions are used to make sure that no resonance is missed because of the unknown relative phase between the polarization precession and the axion or ALP field. A frequency window of 1.5 kHz width around the spin-precession frequency of 121 kHz is scanned. We describe the experimental procedure and a test of the methodology with the help of a radio-frequency Wien filter located on the COSY ring. No ALP resonance is observed. As a consequence, an upper limit of the oscillating EDM component of the deuteron as well as its axion coupling constants are provided