Group of William Shepherd

(Since September 2018 at Sam Houston State University, Texas, US).

We direct our research efforts toward ensuring that no stone is left unturned in the search for new physics. Our focus is on three major avenues of investigation.

First, it is important to ensure that all of the data we already have, from the LHC but also from lower-energy, high-precision measurements like those made at LEP, is exploited fully. The data which we have already taken provides important guidelines on what is and isn't likely to be found in newer experiments, and ensuring that these constraints are consistently included in the evaluation of potential new physics is one important thrust of our research. In the interest of such consistency, it is important to consider the measurements in as model-independent a way as possible. To that end, we investigate the Standard Model as an Effective Field Theory, positing that there is a mass gap between the known particles and those responsible for new physics effects and utilizing the tools which have worked very well in understanding QCD and flavour phenomena to parameterize the effects of new physics. This allows us to be completely agnostic about the nature of the new heavy particles and nonetheless learn about their potential influence on the measurements we have already made.

Second, while many specific models have been proposed to solve particular theoretical or experimental challenges to the Standard Model, we haven't yet discovered evidence for any new particles at the LHC. Given this, it becomes more important to ensure that we are collecting every scrap of information we can from the searches performed. We work to identify new phenomena which are currently neglected in the searches performed at the LHC and recommend new techniques to include these novel possibilities.

Finally, our group also focuses on the most salient experimental challenge to the Standard Model, the problem of dark matter. It is well known that there is additional mass in the universe which is not made up of ordinary matter and which is crucial to the formation of galaxies and clusters as we have observed them. This source of additional mass is totally unknown. While it is possible that this new matter interacts only gravitationally, that would leave its origins a great mystery. There are multiple models in particle physics which predict, instead, that particles which interact rarely (but more strongly than through gravity) with ordinary matter can naturally have an abundance in the universe which comports with our measurements.

This is another place where many different experiments at wildly different energy levels have important input to our full understanding. Direct and indirect detection of dark matter provide important insight into the dark matter which already exists in our universe, while collider or other experiments hope to produce new dark matter particles and measure their properties in that way. Linking these various experiments together to fully understand what is known about dark matter and where is most promising to look next is an important focus of our research.