Search For The Standard Model Higgs Boson In The Dimuon Decay Channel With The Atlas Detector
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Search for the Standard Model Higgs Boson Decay to [mu]+[mu]- with the ATLAS Detector
Author | : |
Publisher | : |
Total Pages | : 19 |
Release | : 2014 |
Genre | : |
ISBN | : |
In this study, a search is reported for Higgs boson decay to ?+?- using data with an integrated luminosity of 24.8 fb-1 collected with the ATLAS detector in pp collisions at √s = 7 and 8 TeV at the CERN Large Hadron Collider. The observed dimuon invariant mass distribution is consistent with the Standard Model background-only hypothesis in the 120–150 GeV search range. For a Higgs boson with a mass of 125.5 GeV, the observed (expected) upper limit at the 95% confidence level is 7.0 (7.2) times the Standard Model expectation. This corresponds to an upper limit on the branching ratio BR(H→?+?-) of 1.5×10-3.
Discovery and Measurement of the Higgs Boson in the WW Decay Channel
Author | : David Hall |
Publisher | : Springer |
Total Pages | : 175 |
Release | : 2015-06-15 |
Genre | : Science |
ISBN | : 3319199897 |
This thesis describes the stand-alone discovery and measurement of the Higgs boson in its decays to two W bosons using the Run-I ATLAS dataset. This is the most precise measurement of gluon-fusion Higgs boson production and is among the most significant results attained at the LHC. The thesis provides an exceptionally clear exposition on a complicated analysis performed by a large team of researchers. Aspects of the analysis performed by the author are explained in detail; these include new methods for evaluating uncertainties on the jet binning used in the analysis and for estimating the background due to associated production of a W boson and an off-shell photon. The thesis also describes a measurement of the WW cross section, an essential background to Higgs boson production. The primary motivation of the LHC was to prove or disprove the existence of the Higgs boson. In 2012, CERN announced this discovery and the resultant ATLAS publication contained three decay channels: gg, ZZ, and WW.
Search for Higgs Boson Pair Production in the bb̅ τ+ τ- Decay Channel
Author | : Luca Cadamuro |
Publisher | : Springer |
Total Pages | : 273 |
Release | : 2018-12-06 |
Genre | : Science |
ISBN | : 3030040550 |
This thesis presents innovative contributions to the CMS experiment in the new trigger system for the restart of the LHC collisions in Run II, as well as original analysis methods and important results that led to official publications of the Collaboration. The author's novel reconstruction algorithms, deployed on the Field-Programmable Gate Arrays of the new CMS trigger architecture, have brought a gain of over a factor 2 in efficiency for the identification of tau leptons, with a very significant impact on important H boson measurements, such as its decays to tau lepton pairs and the search for H boson pair production. He also describes a novel analysis of HH → bb tautau, a high priority physics topic in a difficult channel. The original strategy, optimisation of event categories, and the control of the background have made the result one of the most sensitive concerning the self-coupling of the Higgs boson among all possible channels at the LHC.
Search for the Standard Model Higgs Boson in the Dimuon Final State in Proton-proton Collisions at a Center-of-mass Energy of 13tev with the Cms Detector
Author | : Elizabeth Michelle Goens Kennedy |
Publisher | : |
Total Pages | : 141 |
Release | : 2017 |
Genre | : Cathodes |
ISBN | : 9780355471915 |
This dissertation presents a search for the 125 GeV Standard Model Higgs boson in the opposite-sign dimuon decay channel. The search is performed in 35.92 fb-1 of proton-proton collision data taken at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. Results are found by combining several topological categories. The resulting 95% confidence level upper limit on [sigma]/[sigma] subcript [SM H→ [mu]+[mu]-] is 2.41 × SM expected and 2.79 × SM observed.
Search for the Higgs Boson in the Vector Boson Fusion Channel at the ATLAS Detector
Author | : Eric Ouellette |
Publisher | : Springer |
Total Pages | : 114 |
Release | : 2015-01-20 |
Genre | : Science |
ISBN | : 3319135996 |
This Thesis describes the first measurement of, and constraints on, Higgs boson production in the vector boson fusion mode, where the Higgs decays to b quarks (the most common decay channel), at the LHC. The vector boson fusion mode, in which the Higgs is produced simultaneously with a pair of quark jets, provides an unparalleled opportunity to study the detailed properties of the Higgs, including the possibility of parity and CP violation, as well as its couplings and mass. It thus opens up this new field of study for precision investigation as the LHC increases in energy and intensity, leading the way to this new and exciting arena of precision Higgs research.
Standard Model Higgs Boson Searches in the Weak Boson Decay Channels with the ATLAS Detector
Author | : German David Carrillo Montoya |
Publisher | : |
Total Pages | : 252 |
Release | : 2012 |
Genre | : |
ISBN | : |
Higgs Boson Decays into a Pair of Bottom Quarks
Author | : Cecilia Tosciri |
Publisher | : Springer Nature |
Total Pages | : 171 |
Release | : 2021-10-22 |
Genre | : Science |
ISBN | : 3030879380 |
The discovery in 2012 of the Higgs boson at the Large Hadron Collider (LHC) represents a milestone for the Standard Model (SM) of particle physics. Most of the SM Higgs production and decay rates have been measured at the LHC with increased precision. However, despite its experimental success, the SM is known to be only an effective manifestation of a more fundamental description of nature. The scientific research at the LHC is strongly focused on extending the SM by searching, directly or indirectly, for indications of New Physics. The extensive physics program requires increasingly advanced computational and algorithmic techniques. In the last decades, Machine Learning (ML) methods have made a prominent appearance in the field of particle physics, and promise to address many challenges faced by the LHC. This thesis presents the analysis that led to the observation of the SM Higgs boson decay into pairs of bottom quarks. The analysis exploits the production of a Higgs boson associated with a vector boson whose signatures enable efficient triggering and powerful background reduction. The main strategy to maximise the signal sensitivity is based on a multivariate approach. The analysis is performed on a dataset corresponding to a luminosity of 79.8/fb collected by the ATLAS experiment during Run-2 at a centre-of-mass energy of 13 TeV. An excess of events over the expected background is found with an observed (expected) significance of 4.9 (4.3) standard deviation. A combination with results from other \Hbb searches provides an observed (expected) significance of 5.4 (5.5). The corresponding ratio between the signal yield and the SM expectation is 1.01 +- 0.12 (stat.)+ 0.16-0.15(syst.). The 'observation' analysis was further extended to provide a finer interpretation of the V H(H → bb) signal measurement. The cross sections for the VH production times the H → bb branching ratio have been measured in exclusive regions of phase space. These measurements are used to search for possible deviations from the SM with an effective field theory approach, based on anomalous couplings of the Higgs boson. The results of the cross-section measurements, as well as the constraining of the operators that affect the couplings of the Higgs boson to the vector boson and the bottom quarks, have been documented and discussed in this thesis. This thesis also describes a novel technique for the fast simulation of the forward calorimeter response, based on similarity search methods. Such techniques constitute a branch of ML and include clustering and indexing methods that enable quick and efficient searches for vectors similar to each other. The new simulation approach provides optimal results in terms of detector resolution response and reduces the computational requirements of a standard particles simulation.