Searches for new physics using missing energy at ATLAS
Lead Research Organisation:
University College London
Department Name: Physics and Astronomy
Abstract
The project will build on previous work using the VH signature at ATLAS to search for signatures of new physics involving missing energy, as well as relevant Standard Model measurements.
Organisations
People |
ORCID iD |
| Gavin Hesketh (Primary Supervisor) | |
| Alice Morris (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| ST/N50449X/1 | 01/10/2015 | 31/03/2021 | |||
| 1813138 | Studentship | ST/N50449X/1 | 01/10/2016 | 30/06/2020 | Alice Morris |
| Description | Long-lived particles (LLPs) occur in many extensions to the Standard Model and may elude searches for new promptly-decaying particles. The work funded through this award contributed to a search for neutral LLPs decaying into hadronic states in the calorimeter of the ATLAS detector at the LHC, using data collected in 2016 at a centre-of-mass energy of 13 TeV. Machine learning techniques were employed to identify candidate events containing displaced jets. Compared with the previous iteration of this search, this analysis extended and improved the limits on the production cross-section times branching ratio as a function of LLP proper decay length, most notably for models with high-mass mediators. The results from this displaced jets search were also combined with those from an ATLAS search for displaced jets in the muon spectrometer (MS). These combinations provide a useful summary of the overall ATLAS sensitivity to models with pair-produced, hadronically-decaying, neutral LLPs across the full range of decay lengths accessible to the ATLAS experiment. As the time required to double the luminosity collected by LHC experiments increases to years, the importance of reliable and easy-to-use tools for reinterpretations is growing. In the case of LLP searches, the RECAST framework is critical as no other tool allows for high fidelity reinterpretations of published results. For a small fraction of the effort necessary to resurrect a published result, let alone to perform a new search, the RECAST framework was used to improve the scope and depth of the ATLAS search program. The preservation and subsequent reinterpretation of the calorimeter displaced jets search using the RECAST framework resulted in an accurate and efficient reinterpretation of the published result in terms of three new physics models not considered in the original search. In all three cases, the existing limits from the dedicated searches were extended to shorter decay lengths. |
| Exploitation Route | This work has already influenced the next ATLAS calorimeter displaced jets search strategy which will consider the full Run 2 dataset and has indicated that there is the potential for the search to be sensitive to a wider range of signatures than previously thought. This successful reinterpretation using the RECAST framework has been an example for other LLP searches to follow in future, encouraging more sharing of signal models and greater collaboration between similar analyses, thereby allowing the data recorded by the ATLAS experiment to remain useful for as long as possible. |
| Sectors | Other |