Abstract
Precision experiments, such as the search for electric dipole moments of charged particles using storage rings, demand for an understanding of the spin dynamics with unprecedented accuracy. The ultimate aim is to measure the electric dipole moments with a sensitivity up to 15 orders in magnitude better than the magnetic dipole moment of the stored particles. This formidable task requires an understanding of the background to the signal of the electric dipole from rotations of the spins in the spurious magnetic fields of a storage ring. One of the observables, especially sensitive to the imperfection magnetic fields in the ring is the angular orientation of stable spin axis. Up to now, the stable spin axis has never been determined experimentally, and in addition, the JEDI collaboration for the first time succeeded to quantify the background signals that stem from false rotations of the magnetic dipole moments in the horizontal and longitudinal imperfection magnetic fields of the storage ring. To this end, we developed a new method based on the spin tune response of a machine to artificially applied longitudinal magnetic fields. This novel technique, called spin tune mapping, emerges as a very powerful tool to probe the spin dynamics in storage rings. The technique was experimentally tested in 2014 using polarized deuterons stored in the cooler synchrotron COSY, and for the first time, the angular orientation of the stable spin axis at two different locations in the ring has been determined to an unprecedented accuracy of better than 2.8 μ rad.8 MoreReceived 6 March 2017DOI:https://doi.org/10.1103/PhysRevAccelBeams.20.072801Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBaryogenesis & leptogenesisBeam code development & simulation techniquesBeam diagnosticsBeam dynamicsBig bang nucleosynthesisElectric momentMagnetic momentNuclear tests of fundamental interactionsPolarization phenomenaAccelerators & Beams
Highlights
Our very existence hinges on the net baryonic content of the Universe
We reported about the first ever attempt for the in situ determination of the spin stable axis of polarized particles in a storage ring
On a purely statistical basis, a sensitivity to the proton and deuteron Electric dipole moments (EDMs) at the level of σjdp;dj < 10−29 ecm looks feasible [43]. Such an upper bound on the CP- and time reversal invariance violating EDM would be 15 orders of magnitude smaller than the magnetic dipole moment, allowed by all symmetries
Summary
Our very existence hinges on the net baryonic content of the Universe. In the big bang paradigm, the baryon asymmetry of the Universe is generated during the offequilibrium expansion of the Universe due to baryon number and CP non-conserving processes [1]. The present study, carried out by the JEDI Collaboration (Jülich Electric Dipole moment Investigations) [13] in September 2014 at COSY, is motivated by ideas on the search for EDMs of protons and deuterons using a storage ring [13,16]. It is part of an extensive world-wide effort to push further the frontiers of precision spin dynamics of polarized particles in storage rings. The Appendices (A, B, C, D, E, and F) are reserved for technical aspects on the statistical and the systematic accuracy of the spin tune determination and on the theoretical background behind the spin tune mapping
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