Matter’s Origin From the RadioActivity of Trapped and Laser-Oriented Ions (Status and Perspectives)

Summary

The predominance of matter over antimatter in the universe implies a significant violation of charge-parity (CP) symmetry in fundamental particle interactions, a phenomenon not yet fully explained by the Standard Model (SM) of particle physics. Nuclear beta decay has long served as a critical laboratory for probing new interactions, contributing to the development and testing of the SM. The interplay between low-energy experiments—particularly those examining nuclear beta decay—and high-energy collider experiments remains a productive avenue for exploring physics beyond the SM.

The Matter’s Origin from RadioActivity (MORA) experiment focuses on identifying sources of CP violation in the β decay of trapped and polarized radioactive ions. By measuring the D correlation in the β decay spectra of 23Mg+ and 39Ca+ with unprecedented sensitivity, MORA aims at complementing the search for electric dipole moments to look for new interactions that could explain the matter–antimatter imbalance. The experiment is using an innovative polarization technique combining the high efficiency of ion trapping with that of laser orientation. In its initial phase, MORA uses 23Mg+ beams delivered by the Ion Guide Isotope Separator On-Line (IGISOL) facility at the Accelerator Laboratory of the University of Jyväskylä to demonstrate the laser polarization technique and achieve a measurement of D to the ~10–4 level, which will be competitive with the best limit obtained so far on a nonzero D correlation in neutron decay. In a subsequent phase, the DESIR (Désintégration, Excitation et Stockage d’Ions Radioactifs) facility at GANIL (Grand Accélérateur National d’Ions Lourds) offers rich perspectives for MORA, thanks to the intense beams from SPIRAL 1 (Système de Production d'Ions Radioactifs Accélérés en Ligne) and ad hoc instrumentation for beam cooling, bunching, and purification, so that measurements with a sensitivity to the ~10–5 level can be targeted. At this level, the measurement of the D correlation is sensitive to final-state interaction effects, which are radiative corrections arising largely from weak magnetism, and which are compliant with the SM. The D correlation measurement needs to be repeated with enough precision for at least two isotopes in order to disentangle potential new physics from these effects. For MORA, 39Ca is an obvious candidate to complement a measurement with 23Mg.