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Searches for Higgs bosons with hadronically decaying τ-leptons: Using Grid and Cloud computing techniques
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. ATLAS Collaboration. (ATLAS)ORCID iD: 0000-0003-0407-0957
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes a measurement of the Standard Model Higgs boson coupling to fermions in decays to two τ-leptons, a search for charged Higgs bosons in decays to a τ-lepton and a neutrino, as well as the reconstruction, identification and triggering of hadronically decaying τ-leptons. The data considered are collected by the ATLAS experiment at the Large Hadron Collider.

The reconstruction and identification of hadronically decaying τ-leptons in the ATLAS experiment during Run 2 of the Large Hadron Collider are described, and the performance of the τ trigger is measured in events with top–antitop-quark pairs using data from 13 TeV proton–proton collisions, corresponding to an integrated luminosity of 3.2 fb-1, collected in 2015, and 11.5 fb-1, collected in 2016.

Hadronically decaying τ-leptons are of importance to many physical processes involving Higgs bosons. The coupling of the Standard Model Higgs boson to fermions is measured in decays to two τ-leptons using 7 TeV data corresponding to an integrated luminosity of 4.5 fb-1, collected in 2011, and 8 TeV data corresponding to an integrated luminosity of 20.3 fb-1, collected in 2012. The signal strength is measured to be μ = 1.4, corresponding to an excess over the background-only model of 4.5σ.

Charged Higgs bosons are searched for in decays to a τ-lepton and a neutrino, where the τ-lepton decays hadronically. 13 TeV data corresponding to an integrated luminosity of 14.7 fb-1, collected in 2015 and 2016, are used. No excess over the Standard Model background is observed, and the 95 % confidence-level exclusion limits on σ(pp → [b]tH+) × (H+ → τν) are set to 2.0 pb–8 fb in the range 200–2000 GeV.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. , 111 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1434
Keyword [en]
LHC, ATLAS, Higgs, Charged Higgs, Tau lepton, 2HDM, MSSM
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
URN: urn:nbn:se:uu:diva-304291ISBN: 978-91-554-9706-4OAI: oai:DiVA.org:uu-304291DiVA: diva2:1015018
Public defence
2016-11-21, Polhemsalen, 10134, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2016-10-31 Created: 2016-10-03 Last updated: 2016-11-17
List of papers
1. Using Puppet to contextualize computing resources for ATLAS analysis on Google Compute Engine
Open this publication in new window or tab >>Using Puppet to contextualize computing resources for ATLAS analysis on Google Compute Engine
2014 (English)In: 20th International Conference on Computing in High Energy and Nuclear Physics (CHEP2013), Parts 1-6, 2014, Vol. 513, 032073- p.Conference paper (Refereed)
Abstract [en]

With the advent of commercial as well as institutional and national clouds, new opportunities for on-demand computing resources for the HEP community become available. The new cloud technologies also come with new challenges, and one such is the contextualization of computing resources with regard to requirements of the user and his experiment. In particular on Google's new cloud platform Google Compute Engine (GCE) upload of user's virtual machine images is not possible. This precludes application of ready to use technologies like CernVM and forces users to build and contextualize their own VM images from scratch. We investigate the use of Puppet to facilitate contextualization of cloud resources on GCE, with particular regard to ease of configuration and dynamic resource scaling.

Series
, Journal of Physics Conference Series, ISSN 1742-6588 ; 513
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-235859 (URN)10.1088/1742-6596/513/3/032073 (DOI)000342287200154 ()
Conference
20th International Conference on Computing in High Energy and Nuclear Physics (CHEP), OCT 14-18, 2013, Amsterdam, NETHERLANDS
Note

Group Author(s): ATLAS Collaboration

Available from: 2014-11-12 Created: 2014-11-11 Last updated: 2016-10-03Bibliographically approved
2. Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector
Open this publication in new window or tab >>Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector
Show others...
2015 (English)In: Journal of High Energy Physics (JHEP), ISSN 1029-8479, E-ISSN 1126-6708, no 4, 117Article in journal (Refereed) Published
Abstract [en]

Results of a search for H -> tau tau decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb(-1) and 20.3 fb(-1) at centre-of-mass energies of root s = 7TeV and root s = 8 TeV respectively. All combinations of leptonic (tau -> l nu(nu) over bar with l = e, mu) and hadronic (tau -> hadrons nu) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of mu = 1.43(-0.37)(+0.43) is consistent with the predicted Yukawa coupling strength in the Standard Model.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-255002 (URN)10.1007/JHEP04(2015)117 (DOI)000353557400001 ()
Note

ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1103/PhysRevLett.114.161801

Available from: 2015-06-12 Created: 2015-06-12 Last updated: 2016-10-06Bibliographically approved
3. Commissioning of the reconstruction of hadronic tau lepton decays in ATLAS using pp collisions at √= 13 TeV
Open this publication in new window or tab >>Commissioning of the reconstruction of hadronic tau lepton decays in ATLAS using pp collisions at √= 13 TeV
2015 (English)Report (Refereed)
Keyword
tau, ATLAS, LHC, trigger
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
urn:nbn:se:uu:diva-304620 (URN)
Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2016-10-06
4. Search for charged Higgs bosons produced in association with a top quark and decaying via H± → τν using pp collision data recorded at √s = 13 TeV by the ATLAS detector
Open this publication in new window or tab >>Search for charged Higgs bosons produced in association with a top quark and decaying via H± → τν using pp collision data recorded at √s = 13 TeV by the ATLAS detector
2016 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 759Article in journal (Refereed) Published
Abstract [en]

Charged Higgs bosons produced in association with a single top quark and decaying via H ± → τ ν are searched for with the \{ATLAS\} experiment at the LHC, using proton–proton collision data at s = 13   TeV corresponding to an integrated luminosity of 3.2   fb − 1 . The final state is characterised by the presence of a hadronic τ decay and missing transverse momentum, as well as a hadronically decaying top quark, resulting in the absence of high-transverse-momentum electrons and muons. The data are found to be consistent with the expected background from Standard Model processes. A statistical analysis leads to 95% confidence-level upper limits on the production cross section times branching fraction, σ ( p p → [ b ] t H ± ) × \{BR\} ( H ± → τ ν ) , between 1.9 pb and 15 fb, for charged Higgs boson masses ranging from 200 to 2000 GeV. The exclusion limits for this search surpass those obtained with the proton–proton collision data recorded at s = 8   TeV. 

Keyword
Higgs, charged higgs, atlas, tau, mssm, 2hdm
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
urn:nbn:se:uu:diva-304285 (URN)10.1016/j.physletb.2016.06.017 (DOI)
Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2016-10-06
5. Charged Higgs boson searches in ATLAS and CMS
Open this publication in new window or tab >>Charged Higgs boson searches in ATLAS and CMS
2016 (English)In: Charged Higgs searches from ATLAS and CMS, 2016, Vol. LHCP2016, 085Conference paper (Other academic)
Abstract [en]

Results from searches for charged Higgs bosons in ATLAS and CMS are presented. The searches cover singly charged Higgs boson decays in the $H^+ \rightarrow \tau\nu$, $H^+ \rightarrow t\bar{b}$, $H^+ \rightarrow c\bar{s}$, and $H^+ \rightarrow W^+Z$ modes, and doubly charged Higgs boson decays in the $\Phi^{++}\Phi^{--} \rightarrow 4l$ and $\Phi^{++}\Phi^{-} \rightarrow 3l$ modes, with \SI{7}{TeV} and \SI{8}{TeV} data from the Run 1 of the LHC. The first search for charged Higgs bosons with \SI{13}{TeV} data in the $H^{+} \rightarrow \tau\nu$ decay mode with ATLAS is also presented. The results are interpreted in various theoretical models.

Results from searches for charged Higgs bosons in ATLAS and CMS are presented. The searches cover singly charged Higgs boson decays in the H+→τνH+→τν, H+→tb¯H+→tb¯, H+→cs¯H+→cs¯, and H+→W+ZH+→W+Z modes, and doubly charged Higgs boson decays in the Φ++Φ−−→4lΦ++Φ−−→4l and Φ++Φ−→3lΦ++Φ−→3l modes, with 7 TeV and 8 TeV data from the Run 1 of the LHC. The first search for charged Higgs bosons with 13 TeV data in the H+→τνH+→τν decay mode with ATLAS is also presented. The results are interpreted in various theoretical models.

Series
, Proceedings, Fourth Annual Large Hadron Collider Physics (LHCP2016): Lund, Sweden, June 13-18, 2016, 085
Keyword
higgs, charged higgs, mssm, 2hdm, susy, supersymmetry
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
urn:nbn:se:uu:diva-304286 (URN)
Conference
Fourth Annual Large Hadron Collider Physics
Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2016-10-06
6. Reconstruction and identification of hadronically decaying tau leptons with the ATLAS experiment
Open this publication in new window or tab >>Reconstruction and identification of hadronically decaying tau leptons with the ATLAS experiment
2016 (English)In: Reconstruction and identification of hadronically decaying tau leptons with the ATLAS experiment, 2016, Vol. LHCP2016, 211Conference paper (Other academic)
Abstract [en]

Tau leptons are important to many physical processes in high-energy physics. They are used for measurements of Standard Model processes, and searches for new physics beyond the Standard Model. With their high mass, tau leptons are prime signatures for e.g. Higgs boson decays to fermions. In these proceedings, the reconstruction and identification algorithms for hadronically decaying tau leptons in Run-2 of the LHC are presented, along with the identification performance in \SI{13}{TeV} data collected in 2015.

Series
, Proceedings, Fourth Annual Large Hadron Collider Physics (LHCP2016): Lund, Sweden, June 13-18, 2016, 211
Keyword
tau, tau lepton, hadronic decay, atlas
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
urn:nbn:se:uu:diva-304287 (URN)
Conference
Fourth Annual Large Hadron Collider Physics
Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2016-10-06
7. Search for charged Higgs bosons in the τ+jets final state using 14.7 fb-1 of pp collision data recorded at √s = 13 TeV with the ATLAS experiment
Open this publication in new window or tab >>Search for charged Higgs bosons in the τ+jets final state using 14.7 fb-1 of pp collision data recorded at √s = 13 TeV with the ATLAS experiment
2016 (English)Conference paper (Refereed)
Abstract [en]

The experimental observation of charged Higgs bosons, H±, which are predicted by several models with an extended Higgs sector, would indicate physics beyond the Standard Model. This note presents the results of a search for charged Higgs bosons in 14.7 fb−1 of pp collision data at √ s = 13 TeV recorded by the ATLAS detector at the LHC. The search targets the τ+jets channel in top-quark-associated H ± production with a hadronically decaying W boson and τ lepton in the final state. No evidence of a charged Higgs boson is found. For the mass range of mH± = 200 − 2000 GeV, upper limits are set on the production cross section of the charged Higgs boson with the subsequent decay H± → τν in a range of 2.0 − 0.008 pb.

Keyword
higgs, charged higgs, atlas, lhc, tau, mssm, 2hdm
National Category
Subatomic Physics
Research subject
Physics with specialization in Elementary Particle Physics
Identifiers
urn:nbn:se:uu:diva-304284 (URN)
Conference
38th International Conference on High Energy Physics, Chicago, IL, USA, 03 - 10 Aug 2016
Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2016-10-06

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