July 2024
Searching for the unknown with ALPs
“I am fascinated by the many puzzles of modern physics, the measurements that the Standard Model of particle physics (SM) cannot fully describe. That's why I work with effective field theories, because they allow us to explore physics beyond the SM at different energy scales, and they even allow us to search for novel, previously unknown particles without detecting them directly. Here I focus on axions and axion-like particles, ALPs for short, which are not included in the Standard Model. ALPs can potentially explain many of the previously unsolved puzzles, including the absence of CP-violating effects in the strong interaction, one of the biggest open questions in particle physics.
©: Angelika Stehle
Basically, I approach the search for ALPs from two sides: directly and indirectly.
In the direct search, the decay of charged kaons into a pion and an ALP is a revealing process that has not yet been observed. Since this process places limits on the couplings of ALPs to the particles we know, it must be understood precisely. That is why I wanted to calculate the so-called one-loop quantum corrections. To my surprise, however, the theory of this decay was not yet fully understood: Important contributions in the operator basis were missing in order to be able to consistently describe the experimental results. My colleagues and I have now worked these out and published them recently.
In the indirect search, we take advantage of the fact that virtual quantum corrections by ALPs can have an impact on the theoretical prediction of measurement results, and a discrepancy between theory and experiment would be an indicator of new physics. One advantage of indirect searches is that, unlike direct searches, they are independent of the exact properties of the ALP, which are unknown to us, and can therefore also be used to constrain ALP couplings.
I do most of my calculations on the computer, but I also do them in the traditional way with pen and paper. I find it particularly exciting how each solved puzzle usually gives rise to a number of new questions and research ideas, which I then try to answer together with my colleagues.”
Anne Galda has been a PhD student in the group of Professor Matthias Neubert and a Fellow of the Mainz Physics Academy of the Cluster of Excellence PRISMA+ since 2021. After completing her bachelor's thesis on the IceCube experiment, she turned to the theoretical side of particle physics. She finds the answers to the puzzles that fascinate her through her calculations.