Using neutrinos to unravel the mysteries of the universe

Neutrinos are the least understood particles we know of. They have extremely small mass and they rarely interact, yet they are extremely abundant and are critical for the evolution of our universe. Neutrinos come in three flavours (electron, muon and tau neutrinos), and since the 1990s we have known that a neutrino can change its flavour as it travels. There are still two big questions left to address about neutrinos. The first is that, surprisingly, we do not yet know which is the lightest neutrino. Finding that the third neutrino is heavier than the other two would give evidence for many Grand Unified Theories that seek to explain particle interactions as different manifestations of a single force. If that is not the case, the way we think about the natural forces in the universe will be completely changed. The second question is whether neutrinos and antineutrinos oscillate in the same way. Answering this question might solve one of the biggest mysteries about the origin of the universe: the Big Bang should have created equal amounts of matter and antimatter, but today, everything around us, from the smallest microorganism to the largest stellar object, is made almost entirely by matter. If neutrinos and antineutrinos oscillate following different rules, they might be the reason why the universe evolved to be dominated by matter rather than antimatter, hence allowing the existence of stars, planets and even us.

This award will allow me to use a coherent strategy to solve these two mysteries, following the ambitious programme of the two experiments best equipped to answer them: NOvA and DUNE. NOvA is a world leading long baseline neutrino experiment: an intense beam of muon neutrinos is produced at the Fermi National Accelerator Laboratory (FNAL), near Chicago, and directed 800 km away towards Minnesota. NOvA uses a near and a far detector to measure the flavour of the neutrinos produced at FNAL, and the flavour of the neutrinos that arrive in Minnesota. DUNE is the future world flagship experiment for neutrino oscillation measurements, fully funded, approved by the US Department of Energy, and currently in the construction phase. DUNE will use the intense muon neutrino beam from FNAL and direct it 1300 km away towards South Dakota. DUNE will use a more powerful beam, a much bigger far detector, and better detector technology than NOvA.

As neutrinos can only be detected when they interact with the matter in the detector and produce other particles, currently theoretical neutrino interaction models are the cause of the largest systematic uncertainties in neutrino oscillation analyses. High precision cross-section measurements of (anti)neutrino interactions and their products are essential for the precision measurements of neutrino oscillation parameters. My strategy is to perform such measurements using the high statistics accumulated by the NOvA near detector, and a prototype of the DUNE near detector. These results will directly impact both the NOvA and DUNE neutrino oscillation analyses. Additionally, I will lead the NOvA-T2K joint neutrino oscillation analysis. The main challenge of this analysis is presented by the very different neutrino interaction models that the two experiments use. Having made major contributions to neutrino cross section and oscillation analyses during my time on T2K, and currently leading the NOvA Beam simulation and data group, and also the NOvA near detector cross section group, I am uniquely qualified to lead and ensure the success of this joint analysis. This will be the most important neutrino physics measurement before the next generation experiments turn on. The experience and reputation gained during the NOvA years by my group at Bristol will ensure our leadership in the DUNE oscillation analysis too.

This fellowship will allow me to establish and lead the neutrino group at the University of Bristol to be at the forefront of two extraordinary discoveries in neutrino physics.

The UKRI FLF will allow me to pursue a cohesive effort to build new networks, contacts and experiences to create a fluent and agile programme with ground-breaking impact for the fields of Science Technology Engineering and Maths (STEM), the UK economy and society as a whole.

Better understanding the nature of neutrinos will have a great impact on neutrino, dark matter, cosmology and astroparticle physics experiments and theory. All stages of this research will be presented in national and international conferences and seminars, which I am invited to speak at regularly. This will ensure maximum collaboration with our colleagues, quick feedback from STEM the community, and a greater impact of our results. Having worked in astroparticle physics experiments for many years, I have established strong relationships and collaborations with my astrophysics colleagues, which I intend to maintain and build by building a global exchange network of experts, within the UK and worldwide.

All STEM fields will find this proposal beneficial: I will ensure the maximum impact of this proposal with a coherent effort in public engagement activities. Through these events, I not only promote greater understanding of the value of the university and its role in research, but also provide career inspiration to diverse audiences. I believe that only by widening participation and encouraging minorities and under-represented groups to pursue a career in STEM we can ensure the best quality of research.

The health care sector will also be impacted by this research: reconstruction algorithms used for particle tracking may be used for medical imaging advancement; cancer treatment techniques, like radiotherapy and proton beam therapy, are enhanced by particle physics research. The defence industry will also find this research impactful: neutrino detectors can provide a way to monitor compliance with non-proliferation treaties by detecting the few MeV antineutrinos produced by operating nuclear reactors in other countries.

Finally, a strong collaboration with the industry sector is already in place through the Fermi National Accelerator Laboratory (FNAL) Proton Improvement Plan-II (PIP-II) upgrade and the University of Bristol's Centre for Doctoral Training (CDT) in Data Intensive Science and the CDT in Interactive Artificial Intelligence. The FNAL PIP-II upgrade is essential for the success of DUNE: the UKRI Science and Technology Facility Council National Laboratories established a partnership with The Welding Institute (TWI) and Nuclear Advanced Manufacturing Research Centre (NAMRC) to combine academic and industry experts, and to form a prototype of the linear accelerator superconductive radio frequency technology. Having been leading the NOvA beam group since 2017, I am keen to join this effort and collaborate with our industry partners. Additionally, the University of Bristol CDTs offer unique opportunities for specialist training in data intensive techniques addressing particle physics science questions, and include collaborations with partner organisations in the commercial, industrial and private sectors, including the Alan Turing Institute, Facebook, Microsoft, and many others. Being based at University of Bristol, I will have access to PhD students within these CDTs, allowing this research proposal to exploit cutting edge algorithms developed with the collaboration of computer science and industry experts. At the same time, our industry partners will have access to cutting edge techniques developed in the research domain. Starting collaborations with industry partners now will also ensure a continuous open dialogue with the industry, and will help us keep these partnerships strong in the future too. Training highly skilled individuals in machine learning techniques will address the current society need of machine learning experts and contribute to the UK economic growth.