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Searches for third-generation scalar leptoquarks in √s = 13 TeV pp collisions with the ATLAS detector
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.ORCID iD: 0000-0002-1253-8583
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
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Number of Authors: 28772019 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 6, article id 144Article in journal (Refereed) Published
Abstract [en]

Limits are set on the pair production of scalar leptoquarks, where all possible decays of the leptoquark into a quark (t, b) and a lepton (, ) of the third generation are considered. The limits are presented as a function of the leptoquark mass and the branching ratio into charged leptons for up-type (LQ<sub ) and down-type (/t) leptoquarks. Many results are reinterpretations of previously published ATLAS searches. In all cases, LHC proton-proton collision data at a centre-of-mass energy of = 13 TeV recorded by the ATLAS detector in 2015 and 2016 are used, corresponding to an integrated luminosity of 36.1 fb(-1). Masses below 800 GeV are excluded for both LQu and LQd independently of the branching ratio, with masses below about 1 TeV being excluded for the limiting cases of branching ratios equal to zero or unity.

Place, publisher, year, edition, pages
SPRINGER , 2019. no 6, article id 144
Keywords [en]
Hadron-Hadron scattering (experiments)
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:uu:diva-390809DOI: 10.1007/JHEP06(2019)144ISI: 000473621100001OAI: oai:DiVA.org:uu-390809DiVA, id: diva2:1344786
Note

For complete list of authors see http://dx.doi.org/10.1007/JHEP06(2019)144

Available from: 2019-08-22 Created: 2019-08-22 Last updated: 2019-08-22Bibliographically approved
In thesis
1. 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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Asimakopoulou, Eleni M.Bergeås Kuutmann, ElinBokan, PetarBrenner, RichardEkelöf, TordEllajosyula, VenugopalEllert, MattiasFerrari, ArnaudGradin, P. O. JoakimIsacson, MaxMårtensson, MikaelSales De Bruin, Pedro H.
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