Since the prediction of its existence in 1968 by Sheldon Glashow, Steven Weinberg, and Abdus Salam, the W boson has been one of the most important areas of particle physics research for several reasons. First, the decays of the W boson are a great test for lepton flavour universality through its decays to lepton-antineutrino pairs (or antilepton-neutrino pairs). Another area of investigation around the W boson is linked to its hadronic decays, as these are dependent on both the strong coupling constant and the top two rows of the CKM matrix. More recently, the measurement of the W boson mass made by the CDF collaboration has caused a great deal more interest in this area as the measurement of 80,433 9 MeV lies far outside the current accepted world average from PDG of 80,379 12 MeV. With a deviation of over 7 from the world average it is clear to see the importance of obtaining further measurements of the W mass to determine if this value from CDF is credible, which, if it were the case, would allude to, and be concrete evidence for, effects from beyond standard model physics. As such, this investigation will take advantage of the latest data from RUN 3 of the LHC at s = 13.6 TeV using the ATLAS detector to conduct a precision measurement of the W boson mass.

Plankton in the ocean, microscopic plants (phytoplankton) and tiny animals (zooplankton) that eat the plants, are vital to marine life and to Earth's climate. They form the base of food chains that support ocean ecosystems, and remove carbon from the atmosphere and bury it in (or export it to) the ocean depths. It is currently thought that plankton are responsible for removing 6 billion tonnes of carbon from the atmosphere each year; fossil fuel burning releases about 10 billion tonnes of carbon into the atmosphere annually. Without this export of carbon in the ocean, atmospheric CO2 would be twice the current concentration. The importance of plankton to food chains and carbon export depends on the species of plankton. Larger phytoplankton are better at supporting food chains and at exporting carbon because (1) larger phytoplankton sink quicker, removing carbon away from the sea surface and contact with the atmosphere, and (2) larger phytoplankton support larger zooplankton, which are eaten by fish and which also excrete large, fast-sinking faecal pellets which quickly transfer carbon away from the atmosphere. We have discovered a new link between which types of plankton can grow and the tides flowing over a mid-ocean ridge. The ocean is layered, with warmer, less dense layers at the surface and colder, denser layers deeper in the ocean. When tidal currents flow up and down the flanks of a mid-ocean ridge, these layers are pushed up and down, causing waves on the layers called "internal tidal waves". These internal tidal waves reach up to the sun-lit upper ocean, where photosynthesis by the phytoplankton takes place. We think these waves have two important effects. (1) The waves cause mixing between the layers of ocean, bringing nutrients from deep in the ocean up to the phytoplankton; this will help extra phytoplankton growth, but crucially it is also known that extra nutrient supplies allow larger species of phytoplankton to grow. (2) The waves move the phytoplankton up and down; this provides more light to the phytoplankton, because as they are moved upward they get closer to the light at the sea surface and are able to grow more. Thus, we think that the internal tidal waves create more growth of larger plankton over a mid-ocean ridge, which means better food for marine food chains and more carbon exported away from the atmosphere. This new link may explain why ridges support such diverse ecosystems, and it also means that the ocean over ridges is far better at exporting carbon than we previously thought. We have calculated that, for the whole Atlantic Ocean, including the tidal effect of the mid-Atlantic ridge adds about 50% to current estimates of how much carbon the plankton export. This means that current understanding of the ocean's role in Earth's climate, which ignores the ridge-tide effect, significantly underestimates how much CO2 plankton remove from the atmosphere. We need to fix this because our predictions of our future climate depend on having correct descriptions of the processes that govern atmospheric CO2. We will conduct an expedition to the mid-ocean ridge in the S. Atlantic. We will measure the internal tidal waves and the upward mixing of nutrients, and the effect the waves have on light received by phytoplankton. We will measure how fast the phytoplankton and zooplankton grow in response to these waves, how the species of plankton change over the ridge, and how much carbon is exported downward over the ridge compared to the adjacent ocean basin. This will be the first time that internal tidal waves are linked to patterns of carbon export in the ocean: internal tidal waves occur wherever there are ridges or seamounts in the ocean and our results will have important global implications for our understanding of ocean food webs and Earth's climate.

Few problems in fundamental physics are as clearly motivated or as important as discovering the nature of the elusive dark matter that accounts for most of the mass of the universe. Direct detection experiments located deep underground are searching for the rare interactions of these well-motivated, relic particles in very sensitive detectors. Liquid xenon (LXe) technology has led these searches for over a decade. Recently, the top international collaborations in the field have come together in the XLZD consortium to build the definitive experiment: one able to discover or rule out electroweak-scale particle dark matter in the accessible parameter space remaining above the very challenging neutrino background. Exciting opportunities exist also in neutrino physics, including establishing the existence of neutrinoless double-beta decay; this is another paradigm-shifting discovery which may be accessible to such an experiment, which could explain the matter-antimatter asymmetry in the universe. This proposed 'rare event observatory' will deploy a LXe detector with up to 80 tonnes of 'active' mass in an ultra-low-background experiment to address these and other questions, at least two of which could entail Nobel-Prize worthy discoveries. This Pre-Construction project prepares the UK contribution to the XLZD experiment and builds the case to bring this ambitious international experiment to the UK. STFC is developing a major new underground laboratory at the Boulby mine, and XLZD would be the centrepiece of the new state-of-the-art facility. A future construction project must be carefully prepared, and this development work is delivered through this Pre-Construction project. The proposed UK contribution to XLZD includes major experimental hardware systems, especially those most naturally suited to the host nation; these will be designed and prepared in this phase. In addition, we will deliver with key industrial partners bold programmes for clean manufacture underground, for engineering and skills development, and for environmental sustainability. These programmes relate to challenges that must be addressed, but which we deliberately develop into opportunities: to provide return to UK industry and wider economic impact, to develop capabilities that support future STFC and UKRI projects, and to be a pathfinder in how Big Science moves towards Net Zero.

Background and relevance: In many tropical coastal systems, nutrients and sediments from the land are removed by mangrove and seagrass ecosystems before they reach coral reefs. Increasing anthropogenic land-based sources (LBS) of nutrients can reduce the ability of mangroves and seagrass to mediate excessive nutrients and sediments. Maintaining the health of these systems is vital, as they are important global blue carbon stores and provide numerous other ecosystem services. The study site, Almirante Bay, Bocas del Toro, Panama, is a biodiverse estuary impacted by anthropogenic nutrient inputs from land, which is likely the driver of annual hypoxia. Objectives: This project will examine how nutrient and sediment discharge from rivers along the coast of Almirante Bay with different characteristics (urbanised, peat-rich and clean mountain rivers) impact the adjacent seagrass health, sediment accumulation, sediment provenance, and water quality. The student will relate key attributes of seagrasses (e.g., stem and shoot density, species composition, growth rates) to water-quality and sediment parameters at the sampling sites and adjacent rivers. Seagrass will be surveyed during the wet and dry seasons to assess short-term responses. Eutrophication and other measures of water quality, sediment traps and shallow cores will record sedimentation to assess short to medium term impacts of land-use change on the coastal community. Novelty: There has been no systematic research linking LBS of nutrients and sediments to marine ecosystems' health along continental sites on the Caribbean coast. Timeliness: Reduction of LBS of marine pollution have been identified as an important in the Regional Nutrient Pollution Reduction Strategy and Action Plan for the Wider Caribbean Region and the CBD post-2020 Global Biodiversity Framework. The data provided by this project could be timely contributions to Panama's Nationally Determined Contribution for blue carbon. Links will also be sought with the UK National Capability project CHAMFER https://www.tobymarthews.com/chamfer.html about coastal hazards.

Optimizing the Exhaust Performance via Magnetic Geometry in Advanced Divertors