Linking theory with experiment: searches for new light particles

Despite its numerous spectacular successes, the standard model of particle physics, which underpins our description of the Universe at its most fundamental level, is far from complete. One of its most dramatic failings is its inability to account for dark matter. Dark matter is a new form of matter that is necessary to explain astrophysical and cosmological observations, but which has never been directly detected, despite accounting for five times as much of the Universe's mass as ordinary matter does. In this fellowship I will resolve challenging open theoretical questions that are crucial for the experimental search for dark matter, and I will form a new research group that acts as a bridge from theory to a concurrent major UK and international experimental programme. Doing so will maximise the physics returns from experimental efforts and investment. It will also provide vital input that will feed into the development of new instruments, substantially increasing the probability of a revolutionary experimental discovery.

One of the foremost candidates to comprise dark matter is a new light particle, since such particles naturally appear in many theoretical models; are automatically produced in the early universe and can explain other mysteries of the standard model. To behave as dark matter new light particles must couple to the visible sector extremely weakly, which makes their discovery challenging. Nevertheless, recent technological advances, for example in quantum amplifiers, mean that these new light particles can now be searched for. Consequently, there is a growing experimental effort aimed at their detection, both in the UK and internationally. However, such searches face numerous challenges: for example, a new light particle could have a mass anywhere in a range that spans more than twenty orders of magnitude, whereas any one instrument can only target a very limited set of masses.

By studying the dynamics of new light particles in the early universe I will make predictions for the dark matter mass. This will dramatically aid the experimental effort by providing sharp mass predictions that instruments can be developed to target. I will also calculate complementary constraints on such particles from observations of stars, to ensure that the experiments are designed to be sensitive to parts of parameter space that are not already ruled out. Further, I will investigate potential new routes to detection by understanding the way that such particles interact with ordinary matter, and complementary signals including in searches for gravitational waves.

My research will benefit theoretical physics as well as the experimental effort. By understanding the properties of new light particles, constraints from experiments can be used to conclusively rule out theoretical models. In the most exciting scenario of a discovery, such work will prove invaluable in determining what has been found and what this means for our understanding of the Universe. For example, a discovery in a specific mass range could tell us about the Universe's evolution at extremely early times, when it was at an energy higher than any we could ever directly study.

A unique aspect of my proposed work is the planned direct links to researchers developing a new UK based experimental facility searching for dark matter. My proposed work will strengthen and further motivate these efforts, and it will lead to connections all the way from theoretical physics to the design and production of quantum devices. In doing so it has the potential to both revolutionise our understanding of fundamental nature of the Universe, and to substantially strengthen a programme that will lead to significant technological development and spinoff applications.