Orateur
Description
Everything we observe in the universe is thanks to interactions of particles and antiparticles, from subatomic processes to the formation of galaxies since the Big Bang. But regardless of where we look, we do not see macroscopic quantities of antimatter in nature, only in quantum interactions or produced by us in laboratories. With our current understanding of physics, when matter originated right after the Big Bang the same amount of antimatter should have been created. The universe as we know would be greatly different.
Sakharov [1] proposed 3 conditions that would create an asymmetry during baryogenesis for matter and antimatter. Processes outside of thermal equilibrium, violation of baryonic number and charge-parity (CP) violation. The MORA experiment aims to measure a CP violation to help explain the matter-antimatter asymmetry. CPV has been observed in the standard model (SM) [2-3] but this contribution is not enough to explain the amount of matter in the universe. Instead of looking in the SM we aim to find CPV in new physics with the D correlation of beta decay [4].
D is a triple correlation between the spin orientation of the parent nucleus, the beta and neutrino momentum. It is non-zero for T reversal violation, and can be calculated by measuring the angle of coincidence between the recoil ions from the decay and beta emission with a polarised (aligned) parent nucleus. In order to precisely measure D (expected to be non-zero at the 10^{-4}/10^{-5} level) we use 23Mg ions in a state of the art ion trap setup , with an octagonal array of detectors to measure the coincidences between recoil ions (MCPs) and betas (double scintillators), a laser to laser-polarise the ion cloud inside of the Paul Trap and annular Si detectors in the axis of the polarisation to measure the polarisation degree (how many trapped ions are polarised).
In 2022 the online commissioning started, then in 2024 we were able to measure a non-zero polarisation degree for the first time, and in 2025 we improved the signal to background ratio and efficiencies to get more statistics. Now, in May of 2026, our week-long measurement will attempt to measure the polarisation degree and the D correlation for the first time, inject clean 23Mg bunches into the trap, and achieve 10^4 trapped Mg ions inside the trap. In this talk I will explain the consequences of a non-zero D correlation, the experimental setup of MORA and IGISOL, and the latest experimental results.
[1] A. D. Sakharov Violation of CP invariance, C asymmetry, and baryon
asymmetry of the universe, Sov. Phys. Usp. (1991)
[2] NA48Collaboration A new measurement of direct CP violastion in two
pion decays of the neutral kaon, Physics Letters B, Volume 465 Issues 1–4
335-348 (1999)
[3] BABAR Collaboration Measurement of CP-Violating Asymmetries in B0
Decays to CP Eigenstates, Phys. Rev. Lett. 86 2515 (2001)
[4] J.D. Jackson and S.B. Treiman and H.W. Wyld Coulomb corrections in
allowed beta transitions, Nucl. Phys. 4 206-212 (1957)