In the early moments of the universe, matter and antimatter particles were formed, including protons, neutrons, electrons, and their antimatter counterparts. As the universe expanded and cooled, most of these particles annihilated each other, leaving behind only photons or light.
However, if the universe were perfectly symmetrical with equal amounts of matter and antimatter, there would be no matter left, only light. The fact that there is matter and we exist suggests that there was an imbalance in favor of matter. This leftover matter eventually formed atoms, stars, galaxies, and eventually led to the emergence of life.
Scientists have developed mathematical theories and equations to explain the universe, which rely on the principle of symmetry. To understand the origin of this asymmetry, experimental physicists have been conducting research on fundamental particles like electrons, searching for signs of asymmetry.
A group of scientists at JILA, led by NIST/JILA Fellow Eric Cornell, has made a groundbreaking measurement of electrons to narrow down the search for this asymmetry. They focused on the electron’s electric dipole moment (eEDM), which indicates the evenness of the electron’s negative charge distribution. Any nonzero measurement of eEDM would confirm the presence of asymmetry.
The JILA group achieved a record-breaking precision measurement of eEDM, improving upon previous measurements by a factor of 2.4. To achieve this level of precision, they employed a clever technique using molecules of hafnium fluoride. By applying a strong electric field to the molecules and observing their behavior, they could determine if the electrons were asymmetrical.
Their experiment, which involved stripping electrons off molecules and measuring the energy levels of the resulting ions, showed that the electrons did not exhibit asymmetry within the limits of their measurement. In other words, the electrons appeared to be round and symmetric.
While there is no guarantee that a nonzero measurement of eEDM will be found, this achievement in precision measurement using a tabletop experiment is significant. It demonstrates that costly particle accelerators are not the only means to explore fundamental questions about the universe. The result obtained by the JILA group will contribute to the ongoing search for answers regarding the asymmetry of the early universe.
The researchers emphasize the importance of collaborative efforts among scientists worldwide, exploring different options and continuously measuring the truth. They remain optimistic that, eventually, someone will uncover the evidence needed to fully understand the origin of the universe’s asymmetry.