Despite its tremendous success in describing the available high energy physics data to high precision, the standard model (SM) of particle physics is known to be incomplete. The most popular extension of the SM is supersymmetry. It provides elegant solutions to various problems of the SM, e.g. the fact that in the SM the mass of the Higgs boson is sensitive to large radiative corrections driving its mass to the Planck scale. The reported results are based on data samples of proton-antiproton collisions at a center-of-mass energy of (square root)s = 1.96 TeV provided by the Tevatron. The analyzed data is recorded by the D0 detector [1]. All reported limits are calculated at the 95% confidence level (CL) based on the modified frequentist approach [2]. Recent searches by the D0 collaboration for Higgs bosons in extensions of the Standard Model at the Tevatron are reported with emphasis on neutral Higgs bosons in supersymmetry.

The analysis described in this thesis is the search for the Higgs boson, decaying into bb pair, in the associated production with a vector boson, in the extreme Higgs boson transverse momentum region where the Higgs boson is reconstructed using the large-R jet technique. The use of the large-R jets allows to add a part of the phase space unexplored so far, which is particularly sensitive to possible new physics. The analysed data have been collected at LHC by the ATLAS detector between 2015 and 2018 at a centre-of-mass energy of √s = 13 TeV. The same dataset has been used to perform the differential pp → ZH and pp → WH cross-section measurements used to extract the information on the Higgs couplings and to put limits on Beyond the Standard Model effects. Furthermore the analysis has been re-used to perform a cross-section measurement of the diboson ZZ and WZ processes because the diboson and the Higgs processes have a similar topology. For the first time the ZZ(bb) and WZ(bb) cross-sections are measured at √s = 13 TeV and the observed cross-section measurements are consistent with the Standard Model predictions.

The search for the Higgs boson is one of the main goals in High Energy Physics and one of the highest priorities at Run II of the Tevatron. There are many alternative Higgs boson models beyond the SM, including Supersymmetry (SUSY) and Fermiophobic Higgs bosons, which can actively be probed at the Tevatron, and in the absence of an excess constrained. The latest limits for several SUSY searches are presented in Section 2 and for the Fermiophobic Higgs boson searches in Section 3. More information on all these searches, along with the latest results, can be found on the CDF and D0 public results webpages. Results are presented for beyond the Standard Model Higgs boson searches using up to 4.2 fb−1 of data from Run II at the Tevatron. No significant excess is observed in any of the channels so 95% confidence level limits are presented.

This thesis studies collider phenomenology of physics beyond the Standard Model at the Large Hadron Collider (LHC). It also explores in detail advanced topics related to Higgs boson and supersymmetry – one of the most exciting and well-motivated streams in particle physics. In particular, it finds a very large enhancement of multiple Higgs boson production in vector-boson scattering when Higgs couplings to gauge bosons differ from those predicted by the Standard Model. The thesis demonstrates that due to the loss of unitarity, the very large enhancement for triple Higgs boson production takes place. This is a truly novel finding. The thesis also studies the effects of supersymmetric partners of top and bottom quarks on the Higgs production and decay at the LHC, pointing for the first time to non-universal alterations for two main production processes of the Higgs boson at the LHC–vector boson fusion and gluon–gluon fusion. Continuing the exploration of Higgs boson and supersymmetry at the LHC, the thesis extends existing experimental analysis and shows that for a single decay channel the mass of the top quark superpartner below 175 GeV can be completely excluded, which in turn excludes electroweak baryogenesis in the Minimal Supersymmetric Model. This is a major new finding for the HEP community. This thesis is very clearly written and the introduction and conclusions are accessible to a wide spectrum of readers.

Volume 8.

The work presented in this PhD dissertation is the first search at CMS for Higgs bosons produced in association with top quarks (ttH) in a final state consisting of only jets. The results presented in this book uncover a new class of ttH events that will help us elucidate our understanding of the Yukawa sector interactions between the Higgs boson and the top quark. Despite this being the most common decay signature for ttH, a large contamination of SM backgrounds makes it the most challenging for extracting a signal from data. The PhD thesis presents many sophisticated tools and techniques that were developed in order to overcome these challenges. These tools pave the way for future analyses to investigate other standard model and beyond-standard model physics.

The recent observation of the Higgs boson has been hailed as the scientific discovery of the century and led to the 2013 Nobel Prize in physics. This book describes the detailed science behind the decades-long search for this elusive particle at the Large Electron Positron Collider at CERN and at the Tevatron at Fermilab and its subsequent discovery and characterization at the Large Hadron Collider at CERN. Written by physicists who played leading roles in this epic search and discovery, this book is an authoritative and pedagogical exposition of the portrait of the Higgs boson that has emerged from a large number of experimental measurements. As the first of its kind, this book should be of interest to graduate students and researchers in particle physics.