el laboratory for dark matter, neutrino, and new electroweak phenomena

Particle physics is concerned with the study of matter (the building blocks of everything in our Universe) and how this matter interacts to produce everything we see around us. The matter we know on a day-to-day basis is made up of just three types of particles: electrons, protons and neutrons. Protons and neutrons themselves are built from combinations of just two sub-atomic particles, known as the up and down quarks. Other less obvious phenomena, such as why we have mass, or what causes radioactivity, require additional fundamental particles to be added to our models. In total, to explain all the phenomena we have tested, two groups (known as quarks and leptons) of six fundamental particles, four "force-carrying" particles ("gauge bosons"), and the Higgs boson are needed. This set of particles and their interactions are described in a mathematical theory called the Standard Model (SM) of Particle Physics.

The SM is the most successful scientific theory we have: predicting the answer to every test we can throw at it, including tests at the highest energy particle collider ever built, the Large Hadron Collider (LHC) at the CERN laboratory in Switzerland. It seems we understand the sub-atomic world quite well, but there are some unsolved mysteries. Even though the SM works well at describing what we now know, there are some phenomena that are simply not addressed by the SM -- it has no answer. These include what is dark matter, the mysterious substance which makes up 26.8% of the known Universe, and why neutrinos have an incredibly small but non-zero mass unlike any other particle -- what makes them special?

Dedicated experiments exist to try and understand these questions, but so far the puzzles remain. We desperately need new ways of studying these phenomena, and my research presents a new opportunity to do so. Observations tell us that both neutrinos and dark matter should interact via the electroweak force. The most powerful tool we have at our disposal to study electroweak particle interactions is the LHC. Proton-proton collisions at the LHC dominantly result in interactions via the strong force. My research has focused on novel ways to isolate the extremely rare pure-electroweak particle interactions from the huge jumble of strong interactions, and measure these for the first time.

Using these techniques, I will effectively turn the LHC from a proton-proton collider into an electroweak boson collider, and by studying the particles emitted from the high-energy collision of two electroweak bosons I will be able to study rare and previously-hidden electroweak phenomena, using the ATLAS detector. I have identified two particle signatures that I will study. One will give a unique ability to search for dark matter, the other will allow me to study the mechanisms behind what gives neutrinos mass. As well as being more sensitive than any other technique used currently at the LHC, this method also fills in the gaps in sensitivity where other dedicated non-LHC neutrino and dark matter experiments cannot probe, but where these phenomena might be found. Without this approach we may miss what we are looking for.

We are not limited to just studying these two specific phenomena: the electroweak boson collider can also reveal to us things we never expected! Beyond its novelty and sensitivity, this technique has a strength in that we can observe anything out-of-the-ordinary that has rare electroweak-only interactions, and can exploit the wide-ranging particle detection capabilities of ATLAS to find out what these newly-discovered phenomena really are.