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Searching for a charged Higgs boson and development of a hardware track trigger with the ATLAS experiment
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. (ATLAS)
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes searches for a heavy charged Higgs boson decaying into a top and bottom quark pair, and the development of a hardware track trigger with theATLAS experiment. The data for the two searches was collected with the ATLAS detector at the Large Hadron Collider(LHC) with pp collision energies of √s = 8 and 13 TeV, and corresponds to an integrated luminosity of 20.3 and 13.2 fb-1 respectively. The main background for this signal is the production of tt̄ pairs with additional heavy flavor radiation. The searches with a single lepton in the final state found no evidence of a charged Higgs boson, and set 95% CLS upper limits on the production times branching ratio for masses ranging between 200-1000 GeV. The preparation of using the final state with two leptons in future searches is discussed. The design of a hardware track trigger based on pattern matching and linear track fitting was studied for the purpose of reducing the high event rates of the High-Luminosity LHC, which is expected to provide pp collisions with a luminosity about five times the nominal value, in the second half of the 2020’s. A simulation framework was developed to emulate the pattern matching and was used to test its ability to filter hits in high pile-up environments. The results of this simulation, together with simulations of the track fitting and latency, show that such a track trigger is a viable option for the ATLAS experiment in the High Luminosity-LHC era.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. , p. 110
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1557
Keywords [en]
High energy physics, charged Higgs boson, Particle tracking
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
URN: urn:nbn:se:uu:diva-329227ISBN: 978-91-513-0069-6 (print)OAI: oai:DiVA.org:uu-329227DiVA, id: diva2:1139995
Public defence
2017-10-27, Häggsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2017-10-04 Created: 2017-09-11 Last updated: 2017-10-18
List of papers
1. The design of a fast level-1 track trigger for the high luminosity upgrade of ATLAS
Open this publication in new window or tab >>The design of a fast level-1 track trigger for the high luminosity upgrade of ATLAS
2016 (English)In: PoS - Proceedings of Science, ISSN 1824-8039, E-ISSN 1824-8039, p. 1-5Article in journal (Other academic) Published
Abstract [en]

The high-luminosity upgrade of the LHC will increase the rate of the proton-proton collisions by approximately a factor of 5 with respect to the initial LHC design. The ATLAS experiment will upgrade consequently, increasing its robustness and selectivity in the expected high radiation environment. In particular, the earliest, hardware based, ATLAS trigger stage ("Level 1") will require higher rejection power, still maintaining efficient selection on many and various physics signatures. The key ingredient is the possibility of extracting tracking information from the brand new full-silicon detector and use it for the decision process. While fascinating, this solution poses a big challenge in the choice of the architecture, due to the reduced latency available at this trigger level (few tens of micro-seconds) and the high expected working rates (order of MHz). In this paper, we review the design possibilities of such a system in a potential new trigger and readout architecture, and present the performance resulting from a detailed simulation of possible hardware-based algorithms, to be implemented in the context of Associative Memories and FPGA technologies, as foreseen by R&D plans on these devices.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-329224 (URN)
Conference
Fourth Annual Large Hadron Collider Physics Conference (LHCP 2016), 13-18 June 2016 Lund, Sweden
Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2017-11-29Bibliographically approved
2. Search for new phenomena in events with at least three photons collected in pp collisions at √s = 8 TeV with the ATLAS detector
Open this publication in new window or tab >>Search for new phenomena in events with at least three photons collected in pp collisions at √s = 8 TeV with the ATLAS detector
Show others...
2016 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 76, no 4, article id 210Article in journal (Refereed) Published
Abstract [en]

Results of a search for new phenomena in events with at least three photons are reported. Data from proton-proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb(-1), were collected with the ATLAS detector at the LHC. The observed data are well described by the Standard Model. Limits at the 95 % confidence level on new phenomena are presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay Z -> 3 gamma, as well as di-photon and tri-photon resonance searches. For a Standard Model Higgs boson decaying to four photons via a pair of intermediate pseudoscalar particles (a), limits are found to be sigma x BR(h -> aa) x BR(a -> gamma gamma)(2) < 10(-3) sigma(SM) for 10 GeV < m(a) < 62 GeV. Limits are also presented for Higgs boson-like scalars (H) for m(H) > 125 GeV, and for a Z' decaying to three photons via Z' -> a + gamma -> 3 gamma. Additionally,the observed limit on the branching ratio of the Z boson decay to three photons is found to be BR (Z -> 3 gamma) < 2.2 x 10(-6), a result five times stronger than the previous result from LEP.

National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-297529 (URN)10.1140/epjc/s10052-016-4034-8 (DOI)000375307600001 ()
Note

ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1140/epjc/s10052-016-4034-8

Funding: We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF, DNSRC and Lundbeck Foundation, Denmark; EPLANET, ERC and NSRF, European Union; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, DFG, HGF, MPG and AvH Foundation, Germany; GSRT and NSRF, Greece; RGC, Hong Kong SAR, China; ISF, MINERVA, GIF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; BRF and RCN, Norway; MNiSW and NCN, Poland; GRICES and FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MSTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SER, SNSF and Cantons of Bern and Geneva, Switzerland; NSC, Taiwan; TAEK, Turkey; STFC, the Royal Society and Leverhulme Trust, United Kingdom; DOE and NSF, United States of America. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN and the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA) and in the Tier-2 facilities worldwide.

Available from: 2016-06-23 Created: 2016-06-23 Last updated: 2017-11-22Bibliographically approved
3. Search for charged Higgs bosons in the H → tb decay channel in pp collisions at s = √13 TeV using the ATLAS detector.
Open this publication in new window or tab >>Search for charged Higgs bosons in the H → tb decay channel in pp collisions at s = √13 TeV using the ATLAS detector.
2016 (English)Conference paper, Published paper (Other academic)
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-329226 (URN)
Conference
38th International Conference on High Energy Physics (ICHEP) 2016
Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2017-09-11
4. Comparison of two hardware-based hit filtering methods inhigh-pileup environments
Open this publication in new window or tab >>Comparison of two hardware-based hit filtering methods inhigh-pileup environments
2017 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221Article in journal (Other academic) Submitted
National Category
Subatomic Physics Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-329225 (URN)
Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2017-09-11

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