Collective oscillations of a stored deuteron beam close to the quantum limit

We investigated coherent betatron oscillations of a deuteron beam in the storage ring COSY, excited by a detuned radio-frequency Wien filter. These beam oscillations were detected by conventional beam position monitors, read out with lock-in amplifiers. The response of the stored beam to the detuned Wien filter was modelled using the ring lattice and time-dependent 3D field maps of the radio-frequency Wien filter. The influence of uncertain system parameters related to manufacturing tolerances and electronics was investigated using the polynomial chaos expansion. With the currently available apparatus, we show that oscillation amplitudes down to \SI{1}{\micro \meter} can be detected. Future measurements of the electric dipole moment of protons will, however, require control of the relative position of counter-propagating beams in the sub-picometer range. Since the stored beam can be considered as a rarefied gas of uncorrelated particles, we moreover demonstrate that the amplitudes of the zero-point betatron oscillations of individual particles are within a factor of 10 of the Heisenberg uncertainty limit. As a consequence of this, we conclude that quantum mechanics does not preclude the control of the beam centroids to sub-picometer accuracy. The smallest Lorentz force exerted on a single particle that we have been able to determine is \SI{10}{aN}.Comment: 38 pages, 16 figure

Extensive Optimization of a Simulation Model for the Electric Dipole Moment Measurement at the Cooler Synchrotron COSY

The excess of matter in the known part of the universe still poses a puzzle to physics and cannot be explained by the Standard Model of particle physics. Many explanation attempts are based on mechanisms that violate CP symmetry. Such mechanisms exist in the Standard Model but are too weak to explain the observed asymmetry. Therefore, additional theories beyond the Standard Model are needed, which are mostly based on additional CP violating sources. Permanent Electrical Dipole Moments (EDMs) of elementary particles violate CP symmetry and are therefore a promising starting point for investigations of the underlying problem. EDMs of charged particles can be studied using storage rings as particle traps, where the polarization behavior of the beam in electric fields provides information about the size of the EDM. The JEDI (Jülich Electric Dipole moment Investigations) collaboration is specialized in the search for EDMs of hadrons using storage rings. It is engaged in design studies for dedicated storage rings for the investigation of protons and deuterons and uses the magnetic storage ring, the cooler synchrotron, COSY at Forschungszentrum Jülich for the first direct deuteron EDM experiment. In this experiment, an EDM leads to a vertical polarization buildup that is directly proportional to the size of the EDM. However, the vertical polarization component is also influenced by systematic effects such as magnet misalignments. In order to investigate systematic effects individually and to support the data analysis, a realistic simulation model is required. In this thesis the development of such a model based on the Bmad software library is presented. Furthermore, various systematic effects and their impact on the spin motion in COSY are investigated and quantified using tracking simulations. The consideration of measured magnet misalignments and their measurement errors results in a minimum resolvable EDM of d = 1.49 · 10−19 e · cm. For a more realistic description of the experimental situation, algorithms are implemented which fit the simulation model to the real conditions by variation of selected machine parameters. The algorithms are successfully tested by means of simulations and afterwards applied to measurement data. The fit results confirm additional magnetic displacements and lead overall to a significantly increased agreement between simulation model and reality

SIMULATION MODEL IMPROVEMENTS AT THE COOLER SYNCHROTRON COSY USING THE LOCO ALGORITHM

The JEDI (Jülich Electric Dipole moment Investigations) collaboration is searching for Electric Dipol Moments (EDMs) of charged particles in storage rings. In a stepwise approach, a first direct deuteron EDM measurement was performed at the Cooler Synchrotron COSY and design studies for a dedicated proton EDM storage ring are underway. In an experiment with a polarized beam in a storage ring, an EDM leads to a vertical polarization buildup. However, the vertical polarization component is also induced by systematic effects such as magnet misalignments. To investigate systematic effects individually and to support data analysis, a realistic simulation model of the storage ring is needed. In this paper, the development of such a model based on the Bmad software library is presented. Furthermore, various systematic effects and their impact on the spin motion in COSY are investigated and quantified by means of beam and spin tracking simulations

Search for Electric Dipole Moments at COSY in Jülich - Spin-Tracking Simulations using BMAD

The observed matter-antimatter asymmetry in the universe cannot be explained by the StandardModel (SM) of particle physics. In order to resolve the matter dominance an additional CP violatingphenomenon is needed. A candidate for physics beyond the SM is a non-vanishing Electric DipoleMoment (EDM) of subatomic particles. Since permanent EDMs violate parity and time reversalsymmetries, they are also CP violating if the CPT-theorem is assumed.The JEDI (Jülich Electric Dipole moment Investigations) collaboration in Jülich is preparing adirect EDM measurement of protons and deuterons first at the storage ring COSY (COoler SYn-chrotron) and later at a dedicated storage ring.In order to analyse the data and to disentangle the EDM signal from systematic effects spin trackingsimulations are needed. Therefore a model of COSY was implemented using the software libraryBmad. It includes the measured magnet misalignments of the latest survey and a simplifieddescription of the RF-Wien Filter device that is used for the EDM measurement. The modelwas successfully benchmarked using analytical predictions of the spin behavior. A crucial pointregarding the data analysis is the knowledge of the orientation of the invariant spin axis withvanishing EDM at the position of the RF-Wien Filter. Especially its radial component is unknownand spin tracking simulations can be used to determine this missing number. Tracking results aswell as the algorithm to find the invariant spin axis will be presented

Search for Electric Dipole Moments at Cosy in Jülich - Spin-Tracking Simulations Using Bmad

The observed matter-antimatter asymmetry in the universe cannot be explained by the Standard Model (SM) of particle physics. In order to resolve the matter dominance an additional CP violating phenomenon is needed. A candidate for physics beyond the SM is a non-vanishing Electric Dipole Moment (EDM) of subatomic particles. Since permanent EDMs violate parity and time reversal symmetries, they are also CP violating if the CPT -theorem is assumed. The JEDI (Jülich Electric Dipole moment Investigations) collaboration in Jülich is preparing a direct EDM measurement of protons and deuterons first at the storage ring COSY (COoler SYnchrotron) and later at a dedicated storage ring. In order to analyse the data and to disentangle the EDM signal from systematic effects spin tracking simulations are needed. Therefore a model of COSY was implemented using the software library Bmad. It includes the measured magnet misalignments of the latest survey and a simplified description of the RF-Wien Filter device that is used for the EDM measurement. The model was successfully benchmarked using analytical predictions of the spin behavior. A crucial point regarding the data analysis is the knowledge of the orientation of the invariant spin axis with vanishing EDM at the position of the RF-Wien Filter. Especially its radial component is unknown and spin tracking simulations can be used to determine this missing number. Tracking results as well as the algorithm to find the invariant spin axis will be presented

Storage Ring to Search for Electric Dipole Moments of Charged Particles -- Feasibility Study

The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly helium-3) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10$^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY (Cooler Synchrotron, Forschungszentrum J\'ulich) activities that demonstrate technical feasibility. Achievements to date include reduced polarisation measurement errors, long horizontal-plane polarisation lifetimes, and control of the polarisation direction through feedback from the scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally the high precision electric-field storage ring