Search for the Higgs Boson Produced in Association with Top Quarks with the CMS Detector at the LHC

This thesis studies the interaction between the Higgs boson and the top quark using proton-proton collisions at 13 TeV provided by the LHC at the CMS detector. It focuses on the optimization of the Level-1 (L1) trigger system and the search for the tH and ttH processes with subsequent decays of the Higgs boson to pairs of τ lepton, W bosons or Z bosons. The methods used include machine learning techniques such as multivariant discriminants and the Matrix Element Method (MEM), resulting in the most stringent measurements of the tH and ttH cross sections up to date.

Format: Paperback / softback
Length: 283 pages
Publication date: 10 February 2023
Publisher: Springer Nature Switzerland AG

In this groundbreaking work, researchers delve into the intricate interplay between the Higgs boson and the top quark through proton-proton collisions at an astonishing energy of 13 TeV, facilitated by the LHC's CMS detector at CERN (Geneva). These particles are created through the remarkable process of associate production, where the Higgs boson pairs up with either one or two top quarks. What makes these processes particularly rare is the fact that the top quark and the Higgs boson are the heaviest elementary particles known to science. As a result, identifying them poses a significant experimental challenge. To overcome this obstacle, the CMS detector employs a highly efficient particle selection system, with the Level-1 (L1) trigger system playing a pivotal role. This system filters collision events to retain only those with potential interest for physics analysis. One of the most demanding aspects of the selection is the identification of hadronically decaying τ leptons, which are expected from the Higgs boson decays. However, this task is made even more challenging due to the large background arising from the QCD interactions.

In the first part of this thesis, the authors focus on optimizing the L1 τ algorithm in Run 2 (2016-2018) and Run 3 (2022-2024) of the LHC. This involves the development of a novel trigger concept for the High-Luminosity LHC, a future phase of the LHC that is set to commence in 2027 and deliver a staggering 5 times the current instantaneous luminosity. To achieve this, sophisticated algorithms based on machine learning approaches are employed, leveraging the increasingly modern technology and powerful computation capabilities of the trigger system.

The second part of the work delves into the search for the tH and ttH processes, followed by the subsequent decays of the Higgs boson into pairs of τ lepton, W bosons, or Z bosons. The authors utilize the data recorded during Run 2 to conduct this analysis. By examining the presence of multiple particles in the final state, researchers can gather valuable insights into the behavior of the Higgs boson and the top quark.

This groundbreaking work not only sheds light on the fundamental nature of the universe but also contributes to our understanding of the underlying physics principles. The meticulous analysis and optimization of the L1 τ algorithm and the successful search for rare processes such as tH and ttH processes showcase the remarkable capabilities of the LHC and the dedication of researchers worldwide. As we continue to push the boundaries of scientific knowledge, we can expect even more exciting discoveries in the years to come.

Weight: 462g
Dimension: 235 x 155 (mm)
ISBN-13: 9783030902087
Edition number: 1st ed. 2022