Neutrinos: understanding why the universe is made of matter and not antimatter.

Dr Patrick Dunne, UKRI Future Leaders Fellow (Advanced Research Fellow), Faculty of Natural Sciences, Department of Physics, Imperial College London

One of the big questions in physics is why the Universe around us is dominated by matter with almost no antimatter present. The only known differences between the behaviour of matter and antimatter, are orders of magnitude smaller than would be needed to explain this cosmic imbalance. One of the last places in our theory of particle physics where these differences could be is in a process called neutrino oscillations, where particles called neutrinos change as they travel. Measurements of this phenomenon with the required precision to see these differences have only recently become experimentally possible.

The T2K experiment in Japan fires a beam of neutrinos 300km from one side of Japan to the other and has over the last few years released the first indications that neutrino oscillations have large amounts of matter-antimatter difference (published on the cover of Nature in April 2020). This talk will describe the discovery of the neutrino, neutrino oscillations, the hundreds of km long experiments that are used to measure them, and the experimental effort to take our indications to a definitive discovery and precision measurement of the phenomenon.