Experimental Particle Physics Consolidated Grant 2019-2022

Particle physics, the quest to understand matter, forces and mass generation at the most fundamental level, is never far from the news, particularly the CERN Large Hadron Collider (LHC) and its discovery of the Higgs boson. By the start of this funding period, the LHC will be preparing for its third long run at the highest intensity and energy yet. There will also be a large data sample from previous runs under analysis. Our group has a balanced programme, exploiting the full reach of the LHC in energy and precision, as well as other aspects of the unique capabilities of the CERN accelerator complex. Our largest activity is in the ATLAS Experiment, exploring a wide range of topics at the energy frontier including the properties of the Higgs boson and searches for physics beyond our current knowledge. We are strong on all aspects of Higgs physics and on the properties of the even more massive top quark. We will also perform measurements that test our understanding of the electroweak and strong forces. Around a billion collisions take place per second in ATLAS, whereas only a tiny fraction can be permanently recorded. Our group built, maintains and operates a major part (`L1Calo') of the custom electronics (trigger) that have to select the most interesting, reducing the data rate by a factor of 500 within two millionths of a second of collisions. As part of this funding proposal, we will commission and operate our upgraded L1Calo trigger system. The LHC will operate for a further two decades as the world's premier energy frontier facility. An ambitious programme is underway to upgrade the accelerator in the mid-2020s, giving another huge increase in the collision rate and enabling still more sensitive searches for new phenomena. In order to cope with the event rates and radiation environments, very large-scale upgrades to the detector and its associated electronics are required. We are taking major roles in two of these. In an upgrade to the innermost charged particle tracking detector, we will be constructing intricate `silicon strip' detector modules in our `BILPA' suite of clean rooms, requiring around 8000 ultrasonic wire bonds per day. We will also be designing and constructing modules for a further upgrade to the L1Calo trigger. Beyond ATLAS, we are an expert group on rare decays of heavy quarks. At the LHCb experiment, we are investigating the complex properties and decays of beauty quarks. Among many analysis targets, one of our specialities is the search for differences between decay rates of beauty particles involving electrons and muons, which has led to a tantalising and much-discussed apparent deviation from expectations. In the funding period, we will be studying new data and decay modes to find out whether this is a new effect or merely a very unlikely statistical fluctuation. We will also play a major role in the commissioning and operation of an important upgrade to the detector (the "RICH"), and will provide highly specialised software. Our NA62 group studies the decays of strange particles, produced at the SPS accelerator, into ultra-rare decay modes, also to search for new physics, . Ours is one of the largest groups in the collaboration and the leading one in the UK. In the funding period, we will be busy analysing the first major NA62 data sample and contributing widely to the running of the detector, including the vital `KTAG' component that we built. The future of particle physics also includes high statistics long baseline neutrino experiments. In the funding period, we will be applying our extensive electronics expertise to produce part of the data acquisition system for the next generation `DUNE' facility, as well as preparing for data taking. Finally, we will continue our leadership in future plans and directions for the field and will use the BILPA for R&D into detector technologies, both for future experiments and for technology transfer, for example into Medical Physics.