Author: Callum KilbyPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A Search for the Standard Model Higgs Boson Produced in Association with Dileptonically Decaying Top Quarks and Decaying Into a Pair of Bottom Quarks with the ATLAS Detector
Higgs Boson Decays into a Pair of Bottom Quarks
Author: Cecilia TosciriPublisher: Springer Nature
ISBN: 3030879380
Category : Science
Languages : en
Pages : 171
Book Description
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.
Search for the Standard Model Higgs Boson Produced in Association with Top Quarks and Decaying Into a B ̄ B Pair in P P Collisions at √ S
Author: Felix BührerSearch for the Production of a Standard Model Higgs Boson in Association with Top-quarks and Decaying Into a Pair of Bottom-quarks with 13 TeV ATLAS Data
Author: Nedaa Alexandra AsbahA Search for the Standard Model Higgs Boson Produced in Association with a Pair of Top Quarks and Decaying to a Pair of Bottom Quarks
Author: Joshuha Thomas-WilskerA Search for the Higgs Boson Decaying to Two B-quarks in Association with a Dileptonically Decaying Top-quark Pair with the ATLAS Detector
Author: Ian ConnellySearch for the Standard Model Higgs Boson Produced in Association with a Vector Boson and Decaying to a B-quark Pair with the ATLAS Detector
Author: Ben Harry SmartSearch for a Standard Model Higgs Boson Produced in Association with a Top-quark Pair and Decaying to Bottom Quarks Using a Matrix Element Method
Author: A Search for the Standard Model Higgs Boson Produced in Association with a W Boson
Author: Martin J. FrankPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
We present a search for a standard model Higgs boson produced in association with a W boson using data collected with the CDF II detector from proton/antiproton collisions at a center of mass energy of 1.96 TeV. The search is performed in the WH channel where the W boson decays leptonically and the Higgs boson decays to a bottom/antibottom quark pair. The two quarks usually fragment into two jets, but sometimes a third jet can be produced via gluon radiation, so we have increased the standard two-jet sample by including events that contain three jets. We reconstruct the Higgs boson using two or three jets depending on the kinematics of the event. We find an improvement in our search sensitivity using the larger sample together with this multijet reconstruction technique. Our data show no evidence of a Higgs boson, so we set 95% confidence level upper limits on the WH production rate. We set limits between 3.36 and 28.7 times the standard model prediction for Higgs boson masses ranging from 100 to 150 GeV/c^2.
Author: Leonid Serkin