Dissertation: Why is there something instead of nothing? Laser-polarised ions test why matter exists
What did you study?
Shortly after the Big Bang, equal amounts of matter an antimatter should have been produced, which would have then annihilated each other. For the universe to be the way it is, the laws of nature must contain asymmetries, but the ones we know of today are too small to account for it. Matter’s origin from the radioactivity of trapped and polarised ions (MORA) searches for a new asymmetry in the weak interaction, which governs radioactive decay.
In MORA, radioactive 23Mg ions produced at the University of Jyväskylä's Accelerator Laboratory are captured in a trap, and a laser aligns their nuclear spins in one direction. When an ion decays, it emits a beta particle, and the remaining nucleus gets a recoil momentum. In a perfectly symmetric universe, the directions of these two particles in the perpendicular plane to the spin would show no preferred pattern. A small deviation would reveal new physics.
What were the main results?
The dissertation achieved the very first spin polarisation measurement of trapped 23Mg, crucial for the asymmetry measurement. To attain this, two challenges were overcome: First, the beam contained x1000 more Na ions than 23Mg, but it was cut down to a manageable x2-x10 more Na than 23Mg. Second, the trap efficiency was improved from 10% to consistently 40%, thanks to improving the stability of a HV switch and other electronics improvements.
How can the results be applied?
Now MORA has sufficient radioactive 23Mg for a first asymmetry measurement: tens of thousands of ions trapped per cycle. This paves the way for measuring the asymmetry with unprecedent sensitivity. In the longer term, MORA will move to the new DESIR facility in Caen, France, where the precision will improve ten-fold.
Matter’s origin from radioactivity: First experiment analysis will be defended on Friday 23.10.2026 at 17:00 (16:00 France) in GANIL, Maison d’Hôtes, Caen, France. The opponent is Dr. Bertram Blank and the custos is Tommi Eronen. The language of the dissertation is English.
The dissertation is available in the JYX publication archive.
