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ATLAS discovery potential for the Charged Higgs Boson in H+  decays
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. (ATLAS)
2007 (English)In: CDSArticle in journal (Refereed) Published
Abstract [en]

The \textsc{Atlas} discovery potential for the hadronic decay of a heavy charged Higgs boson, H , is presented. A new matched production algorithm for the processes ggtbH and gbtH is used allowing to span the investigated mass range from mHmt up to mHmt with a consistent treatment of the transition region. For the considered charged Higgs boson masses from 165 to 600 GeV, H is the most relevant decay channel together with Htb . Whereas the latter suffers from large irreducible backgrounds, the decay channel offers a decisively cleaner signature. This is the first \textsc{Atlas} Full Simulation study of the H channel. For the background, \textsc{Atlas} Fast Simulation is used for the investigation of a greater variety of channels than in previous studies, emphasizing the need for new selection cuts with additional discriminating power between signal and background. Such cuts are introduced and it is shown that current limits from direct charged Higgs boson searches can be substantially extended already with a few years of LHC data.

Place, publisher, year, edition, pages
Keyword [en]
ATLAS Charged Higgs
URN: urn:nbn:se:uu:diva-110659OAI: oai:DiVA.org:uu-110659DiVA: diva2:277889
Available from: 2009-11-21 Created: 2009-11-21 Last updated: 2011-03-04Bibliographically approved
In thesis
1. Looking for the Charged Higgs Boson: Simulation Studies for the ATLAS Experiment
Open this publication in new window or tab >>Looking for the Charged Higgs Boson: Simulation Studies for the ATLAS Experiment
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The discovery of a charged Higgs boson (H+) would be an unambiguous sign of physics beyond the Standard Model. This thesis describes preparations for the H+ search with the ATLAS experiment at the Large Hadron Collider at CERN. The H+ discovery potential is evaluated, and tools for H+ searches are developed and refined.

The H+→τν decay mode has been known as the most promising H+ discovery channel. Within this thesis, first studies of this channel with realistic detector simulation, trigger simulation and consideration of all dominant systematic uncertainties have been performed. Although, as shown by these studies, the discovery sensitivity is significantly degraded compared to studies using a parametrized detector simulation, this channel remains the most powerful ATLAS H+ discovery mode. Future searches will rely on multivariate analysis techniques like the Iterative Discriminant Analysis (IDA) method. First studies indicate that a significant sensitivity increase can be achieved compared to studies based on sequential cuts. The largest uncertainty in H+ searches is the expected $t\bar{t}$ background contribution. It is shown that numbers obtained from simulated events could be off by a factor of two, decreasing the discovery sensitivity dramatically. In this thesis, the Embedding Method for data-driven background estimation is presented. By replacing the muon signature in $t\bar{t}$ events with a simulated τ, events which allow an estimation of the background contribution at the 10% level are obtained.

The ATLAS τ identification focuses on comparably clean environments like Z and W decays. To optimize the performance in high-multiplicity events like H+→τν, tau leptons are studied in $t\bar{t}$ and pile-up events. Variables which do not show discrimination power in high-multiplicity events are identified, and in some cases similar, more powerful variables are found. This allows to recover some of the performance loss and to increase the robustness of the τ identification.

For the analysis of large amounts of data produced by the ATLAS detector, seamless interoperability of the various Grid flavors is required. This thesis introduces translators to overcome differences in the information system between a number of Grid projects,and highlights important areas for future standardization.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. VI+50 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 696
charged Higgs, tau, ATLAS, HEP, CERN, LHC, Particle Physics, Grid
National Category
Physical Sciences
Research subject
High Energy Physics
urn:nbn:se:uu:diva-110882 (URN)978-91-554-7676-2 (ISBN)
Public defence
2010-01-15, Polhemsalen, Ångström Laboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Available from: 2009-12-22 Created: 2009-11-30 Last updated: 2009-12-22Bibliographically approved

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