Ben Safdi - Why Axions Could Be the Next Big Discovery in Physics (September 4, 2025)

Axions have emerged as one of the most compelling candidates for new physics beyond the Standard Model. They provide an elegant solution to the strong CP problem of quantum chromodynamics, they naturally arise in many extensions of the Standard Model, including string theory, and they may constitute the dark matter that pervades our universe. I will review these motivations and explain why a broad range of current and planned experiments may be poised to detect axions for the first time, opening a new window onto fundamental physics and cosmology. Uploaded 22-09-25 Michael Tarbutt, Imperial College London Measuring the electron’s electric dipole moment with ultracold YbF molecules I will describe two experiments to measure the electron’s electric dipole moment (eEDM) using laser-cooled YbF molecules. The first uses a highly collimated beam of molecules cooled below 100 uK in the two transverse directions. We measure their spin precession as they fly through a region of large electric field. I will present recent data characterizing the sensitivity of this experiment and our efforts to control the dominant sources of noise and systematic error. The second experiment, still under development, will use molecules trapped in an optical lattice. We decelerate the molecules to low velocity using radiation pressure and deliver them to a magneto-optical trap. I will present our progress on slowing and trapping and our design of the eEDM apparatus. ~ This program supports high-risk and potentially high-return small-scale experimental projects aimed at new, ambitious discoveries beyond the current frontier of fundamental physics. “Small-scale” refers to table-top-size experiments or to ones that could fit in a typical university physics research lab. The meeting is intended to advance the supported science by stimulating discussions and the exchange of ideas, while also helping to build a sense of community amongst program grantees. For more information go here: https://www.simonsfoundation.org/event/table-top-experiments-pi-meeting/