I am a particle physicist, Royal Society University Research Fellow and member of the ATLAS Collaboration working in the Oxford Particle Physics subdepartment.
My research focuses on searches for ground-breaking physics, the theoretical modelling and simulation of these phenomena, and the operation of the ATLAS experiment.
Research
My group and I look for evidence of new particles and phenomena beyond the well-understood Standard Model of Particle Physics.
I have advanced our modelling and simulation of collider black holes through the development of the CHARYBDIS simulation program, including angular momentum and spin for the first time, and superior production and decay models. I led several searches for such exotic states in ATLAS using data from LHC Run-1.
I was editor of the first ATLAS search paper of Run 2, looking for new phenomena in high-energy LHC events with two jets - particle showers initiated by high-momentum hadrons in the detector. This analysis set very strong limits on dark matter mediator particles. By using new and innovative analysis strategies looking for additional radiation or trigger-level analysis, we extended these searches - providing sensitivities to much lower mass particles.
Current Research: My research focuses on channels using the discovered Higgs boson as a tool to search for new particles and evidence of dark matter.
Recently, I have searched for the mono-Higgs production signature: pair production of dark matter particles, produced in association with a single Higgs boson. Due to the unique nature of the Higgs, interactions between dark matter and it may be stronger and more important than those with other SM particles. I placed world-leading limits on many Higgs-dark matter models, such as the 2hdm+a.
In many of these predictions, there is an additional piece of the puzzle - a heavier Higgs boson which mediates the dark matter interactions and which decays to two of the known Higgs bosons.
I search for this di-Higgs signature in its four b-quark final state - the most common decay, but one where high backgrounds must be well understood. Improving this sensitivity of this signature is critical, with the large volumes of data from the LHC's High Luminosity run, we will be able to measure to the Higgs self-coupling - one of the last unmeasured parameters of the Standard Model. Our analysis of the full ATLAS Run-2 dataset is the first to incorporate VBF production in an integrated manner and set the first ATLAS limits on Effective Field Theory operators from di-Higgs production. I have also worked on combining our result with other signatures of two HIggs bosons, which gives a fuller picture of our understanding of this important aspect of the Higgs self-coupling. The increased luminosity from LHC Run-3 will provide further sensitivity in this important signature.
In many models, dark matter mediators are expected to have enhanced rates to heavy quarks. By searching for decays to bb with initial state radiation jet allowing us to select these events, we can search for these dark matter mediators at lower masses. This channel is also sensitive to boosted bb decays of the Higgs boson, allowing a measurement of the highest momentum HIggs bosons through the Higgs+jet process. Our first result included the first constraints on the production of Higgs bosons with TeV-scale transverse momentum.
Currently, I convene the ATLAS Common Dark Matter subgroup, which oversees and coordinates dark matter interpretations and large-scale combinations across the ATLAS physics programme. Additionally, I am a convenor of the LHC Physics Centre's Dark Matter Working Group (LHCDMWG) with brings together theorists and experimentalists to discuss new dark matter results, guide the community through the publication of white papers with recommended interpretations, model benchmarks, etc. and provide a forum for the exchange of new ideas relating to collider dark matter searches.
Through these efforts, I have set world-leading limits on invisible decays of the Higgs boson, sensitive to a wide variety of possible dark matter models and am working on a similarly powerful combination of our results to illustrate our sensitivity and constraints on the well-motivated 2hdm+a benchmark.
Complementing phyiscs analysis, currently I work on improving our ability to identify the flavour of hadronic jets at colliders and specifically means of calibrating topologies with two close-by b-quark jets. I have also led the jet software group within ATLAS to develop, support and improve the ATLAS jet software. I follow future computing activities through the STFC SwiftHEP programme and the HEP Software Foundation.
I have held a range of operational roles, including responsibilities for ATLAS prompt reconstruction and Data Quality. In 2016, I was elected to be Data Preparation Coordinator, one of the four ATLAS activity area coordinators (the others being physics, trigger and computing), sitting on the Executive board - the main body for the direction of ATLAS. In this critical position from 2016-2018, I led a diverse team of physics, operational and computing experts to process, assess and understand all the data recorded during the highly successful LHC Run 2.