EDM search and nucleon-nucleon scattering study at COSY Jülich

Author: Mirian Tabidze
Co-authors: Nodar Lomidze, Zara Bagdasaryan, Andro Kacharava, Gogi Macharashvili, David Mchedlishvil, Mikheil Nioradze, David Chiladze
Keywords: Spin, EDM, nucleon, deuteron, elastic scattering
Annotation:

There is an increasing interest towards the measurement of Electric Dipole Moment (EDM) of fundamental particles. Its non-zero value would directly prove CP-violation, which is one of the necessary conditions of baryon-antibaryon asymmetry. Although Standard Model (SM) allows CP-violation, it’s too weak to explain the expected baryogenesis rate. Hence relatively stronger source of CP violation has to be found. For this purpose a study has been initiated with the Cooler Synchrotron (COSY) at the Forschungszentrum Jülich, Germany. Some results of the precursor experiments are discussed in the following. In order to reach 10^{-29} e.cm. order of precision in Deuteron EDM measurements, it is necessary to use High Voltage (17 MV/m) radial electric field and spin coherence time (SCT) should be not less than 1000 seconds. Parameters that affect SCT were studied at the existing COSY facility. It was determined that sextupole magnets should be used in the non-linear parts of the accelerator, while the beam should be bunched. Studies were performed with the radio frequency (RF)-solenoid, which worked at one of the resonance frequencies. So far, SCT of 400 seconds was achieved, which is considered to be a significant progress. Studies continue. Concerning nucleon–nucleon (NN) interaction – it is fundamental to the whole of nuclear physics and hence to the composition of matter as we know it. Apart from their intrinsic importance for the study of nuclear forces and in general strong interaction, NN data are necessary ingredients in the modelling of meson production and other nuclear reactions at intermediate energies. The complete investigation of the NN interaction needs precise elastic scattering data as input to a phase–shift analysis (PSA), from which the scattering amplitudes at fixed angles can then be reconstructed. A full data set involves experiments with both beam and target particles polarized in the initial state, as well as the determination of the polarization of one of the final state nucleons. In presentation preliminary results of differential cross section and analyzing power measurements for single polarized pp elastic scattering at ANKE/COSY for different beam energies mare presented. This precision measurements can have a great impact on NN phase shifts.

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