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To catch a long-lived particle: hit selection towards a regional hardware track trigger implementation
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. (ATLAS)ORCID iD: 0000-0002-7288-3610
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.ORCID iD: 0000-0003-1630-6664
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2019 (English)In: Article in journal (Refereed) Submitted
Place, publisher, year, edition, pages
2019.
National Category
Accelerator Physics and Instrumentation
Identifiers
URN: urn:nbn:se:uu:diva-389892OAI: oai:DiVA.org:uu-389892DiVA, id: diva2:1339733
Available from: 2019-07-31 Created: 2019-07-31 Last updated: 2019-08-08
In thesis
1. Exploration of extended Higgs sectors, development of a displaced track trigger, and improvements in GRID middleware
Open this publication in new window or tab >>Exploration of extended Higgs sectors, development of a displaced track trigger, and improvements in GRID middleware
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Two possible solutions to the Standard Model (SM) fine-tuning problem are presented in this thesis, MSSM and Compositeness. The Higgs sector of the MSSM can be tested by searching for charged Higgs bosons. Two direct searches for charged Higgs bosons decaying into a top- and bottom-quark are performed using 13.2 and 36.1 fb¹ respectively of pp collision data collected at √s = 13 TeV with the ATLAS detector. No significant excess over the SM background is observed and upper limits on σ(pp→tbH+B(H+→tb) between 0.07 and 2.9 pb are set at a 95% confidence level in the charged Higgs boson mass range 200–2000 GeV using the CLs method. The phenomenology of a vector-like top-partner decaying into a BSM (pseudo-) scalar is explored and interpreted in 2HDM and Compositeness models. The experimental reach is evaluated using γγ and Zγ final states, and the LHC is determined to be sensitive to top-partner and (pseudo-) scalar masses in the 1–2 TeV range both in the Run 2 and expected Run 3 datasets. Two hardware based hit collection methods targeting long-lived particles are studied for a regional track trigger in anticipation of the HL-LHC upgrade. The efficiency is estimated to be ~20% for a wide range of track parameters for tracks originating from a displaced vertex. The prospect of using GPU-computing on the LHC GRID is considered. Extensions of the ARC middleware Information Providers integrating local GPU information are demonstrated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 95
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1829
Keywords
BSM, Supersymmetry, Standard Model, Higgs, 2HDM, Charged Higgs, Compositeness, Pattern Matching, GRID
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
urn:nbn:se:uu:diva-389896 (URN)978-91-513-0700-8 (ISBN)
Public defence
2019-09-20, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2019-08-28 Created: 2019-07-31 Last updated: 2019-09-17
2. A search for leptoquarks with the ATLAS detector and hardware tracking at the High-Luminosity LHC
Open this publication in new window or tab >>A search for leptoquarks with the ATLAS detector and hardware tracking at the High-Luminosity LHC
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents a search for pair-production of scalar leptoquarks, decaying into third-generation particles, using proton-proton collisions delivered by the Large Hadron Collider (LHC) and recorded by the ATLAS detector. It also presents the development of a hardware track trigger for the Phase-II upgrade of the ATLAS experiment.

The search for pair-production of leptoquarks is performed using data collected by the ATLAS detector in 2015 and 2016 at a center-of-mass energy of 13 TeV. The total integrated luminosity of this data set amounts to 36.1 fb−1 . The search sensitivity is optimized for up-type leptoquarks where both leptoquarks decay to a b-quark and a τ -lepton. However, it also proves sensitive to down-type leptoquarks where both leptoquarks decay to a top-quark and a τ -lepton. The data is found to be compatible with the Standard Model, so exclusion limits are set on the leptoquark mass.

After the High Luminosity upgrade of the LHC, the ATLAS detector faces a 5–7 times increase in the number of simultaneous proton-proton collisions. To benefit from this increase in luminosity, the ATLAS detector has to maintain low trigger thresholds while keeping manageable trigger rates. A crucial part of the solution is the development of Hardware Tracking for the Trigger (HTT). The HTT first selects hit clusters in the inner tracking detector using associative memories and uses the selected clusters to perform linearized track-fits. This thesis presents the HTT system with focus on using the Hough transform as an alternative to associative memories to select clusters in the inner detector. The performance of the Hough transform is studied and a hardware implementation is discussed.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 123
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1833
Keywords
Leptoquarks, Hough transform, LHC, ATLAS, HL-LHC, Particle physics, Particle tracking, Cluster finding, Trigger
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
urn:nbn:se:uu:diva-390352 (URN)978-91-513-0707-7 (ISBN)
Public defence
2019-09-27, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2019-09-04 Created: 2019-08-08 Last updated: 2019-09-17

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