Searches for Higgs pair production with the ATLAS Experiment at the LHC.
Supervisors: Dr Carl Gwilliam (Liverpool), Dr Katharina Behr (DESY)
Open until filled
Following the momentous discovery of the Higgs boson by the ATLAS and CMS collaborations in 2012, substantial progress has been made in measuring its properties, including mass, spin and couplings to other particles. However, the ultimate test of electroweak symmetry breaking (ESWB) can only be obtained by reconstructing the characteristic Mexican-hat-shaped potential. Measurement of the Higgs self-coupling via production of Higgs boson pairs provides a unique direct probe of this potential, giving a key handle on many of the open questions in the Standard Model.
The PhD position will be conducted jointly between the University of Liverpool and the DESY laboratory in Germany. Both groups made key contributions to the observation of the Higgs boson and play leading roles in precision measurements of its properties and in searches for rare phenomena such as Higgs-pair production. They have also contributed significantly to the reconstruction of charged particles and the identification of tau leptons and b-quark jets (b-jets)
Given the di-Higgs cross-section is more than 1000 times smaller than that of single Higgs production, the upcoming LHC Run 3 dataset coupled with state-of-the art machine learning (ML) techniques will be crucial. The successful applicant will search for Higgs pair production using the LHC Run 2 + Run 3 data collected by the ATLAS experiment, focusing on one of the main hadronic decay channels. In doing so, the student will play a major role in commissioning and improving the identification of tau leptons or b-jets with the new data and will optimise ML methods, for example to discriminate Higgs boson pairs from background processes. They will also contribute to the combination of the results from the various di-Higgs channels and preparations for a potential ATLAS + CMS combination.
The PhD will be awarded by the University of Liverpool but will be co-supervised by both Liverpool and DESY staff. During the first year of the PhD, the student will be based in Liverpool, undertaking postgraduate training in particle physics in addition to starting the Higgs-pair research project. The student will then spend 18 months to 2 years based at DESY focusing on the Higgs-pair analysis and the object identification studies outlined above. In the final year, the student will return to Liverpool to finalise the result for publication and write up their thesis. Throughout the PhD there will be opportunities for short trips to CERN. There is also funding available for attending at least one relevant training school and at least one international conference.
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