New Physics meets the Strong Force

The Standard Model (SM) is the (admittedly dull) name given to one of most profound theoretical achievements of science. It is an overwhelmingly successful description, not just of fundamental particles, but of the forces that govern their interactions. Despite its success, the SM is incomplete and leaves us with deep open questions. One such puzzle is the nature of dark matter. This mysterious material fills our universe, in greater abundance than the well-understood material forming stars and planets. To date it is only understood through its gravitational signature and its relation to standard material is unknown. A second question follows from the well-established fact that every particle has a corresponding anti-particle and that, upon contact, matter and anti-matter annihilate in an explosion of light. Given this remarkable correspondence, it is unknown how matter came to dominate anti-matter, leading to the formation of galaxies, stars and planets.

This proposal will combine advanced theoretical ideas with high-performance computing to investigate these two fundamental issues. The project distinguishes itself from other on-going research in this area by exploring the connections between dark matter, matter/anti-matter imbalance and a specific part of the Standard Model known as the strong force. The strong force binds fundamental particles called quarks and gluons into protons and neutrons, and the energy of these interactions generates nearly all of the mass of everyday matter. It also binds protons and neutrons together into nuclei, giving rise to all known elements.

But the same properties that make the strong-force so rich also make it an incredible challenge for theoretical physicists. The best known methods involve combining powerful theoretical tools with numerical calculations driven by world-class supercomputers. The first aspect of the proposed project will use these methods to understand how strongly-interacting dark matter particles might interact with each other, and investigate the experimental implications. The second part will shed light on exactly how heavy particles produced in collider experiments decay into the lighter particles that are detected and explore the remarkable fact that such decays violate symmetries relating matter and anti-matter. It is currently unknown if new physics is playing a role but, if it is, this could well be related to the mechanism that led to matter dominance in the early universe.

Despite its incredible success in describing a wide variety of phenomena, both in earth-based experiments and astro-physical observations, the Standard Model of particle physics is unambiguously incomplete. This proposal will consider two key gaps in the current understanding: (i) the nature of the dark matter that is known to fill the universe but has escaped direct detection and (ii) the dominance of matter over anti-matter and its apparent contradiction with the approximate symmetries of the microscopic world. The proposed research will address the interplay of these issues with the strong force, an essential sector of the Standard Model. As a result of the theoretically challenging nature of the strong force, theoretical calculations are often either impossible or rely on uncontrolled approximations.

To overcome this, I will lead a team in combining advanced theoretical methods with large scale numerical calculations using a framework called lattice QCD. The proposal requires high-performance computing as well as advanced reconstruction techniques and the development required for the scientific investigation is expected to have consequences reaching well outside of academia. In addition, the fundamental nature of the questions elevate them to a level of interest for anyone with an underlying scientific curiosity.

The software and data analysis techniques, in particular to be developed in the component concerning advanced reconstruction techniques, are expected to have a high impact outside the physics community. The reconstruction of spectral information from data correlations is a ubiquitous problem, appearing, for example, in seismology and medical imagining. The tools we develop will be provided in an open source package and a special effort will be made to disseminate the progress outside the scientific community. Further, the ambitious nature of the calculations considered will require pre-exascale computing and the interplay between the scientific and computational development will serve as a powerful driving force on both sides. In this respect the University of Edinburgh already has a strong track record that the successful proposal will push to a new level.

Finally, this proposal will undoubtedly find resonance with the wider public. The nature of dark matter, a mysterious weakly-interacting background density with a clear gravitational signature, is a mystery so profound and simple that a wider audience can appreciate the intrigue. The same is true for the excess of matter over anti-matter, the contradiction between the nearly symmetric microscopic world and the massive imbalance that defines our daily experience. With this in mind an important output of this proposal will be dedicated public outreach, through public lectures, blog posts and online videos, describing the progress of this work to the general public. One cannot overestimate the long-term positive effect, on society and industry, of funding such fundamental research and presenting the progress in an open and accessible way.