Karim El Morabit

The discovery of the Higgs boson in 2012, by the ATLAS and CMS experiments, was a success achieved with only a percent of the entire dataset foreseen for the LHC. It opened a landscape of possibilities in the study of Higgs boson properties, Electroweak Symmetry breaking and the Standard Model in general, as well as new avenues in probing new physics beyond the Standard Model. Six years after the discovery, with a conspicuously larger dataset collected during LHC Run 2 at a 13 TeV centre-of-mass energy, the theory and experimental particle physics communities have started a meticulous exploration of the potential for precision measurements of its properties. This includes studies of Higgs boson production and decays processes, the search for rare decays and production modes, high energy observables, and searches for an extended electroweak symmetry breaking sector. This report summarises the potential reach and opportunities in Higgs physics during the High Luminosity phase of the LHC, with an expected dataset of pp collisions at 14 TeV, corresponding to an integrated luminosity of 3 ab$^{-1}$. These studies are performed in light of the most recent analyses from LHC collaborations and the latest theoretical developments. The potential of an LHC upgrade, colliding protons at a centre-of-mass energy of 27 TeV and producing a dataset corresponding to an integrated luminosity of 15 ab$^{-1}$, is also discussed.

The associated production of a Higgs boson with a top quark-antiquark pair (t tH) or with a single top quark (tH) allows the direct measurement of the top-Higgs Yukawa coupling.In this article, recent searches for t tH and tH production at the CMS experiment are reviewed.The analyses use pp collision data collected at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of up to 77.4 fb -1 .

A measurement of the production of a Higgs boson in association with a top quark-antiquark pair and the subsequent decay of the Higgs boson to a bottom quark-antiquark pair ($\text{t}\bar{\text{t}}\text{H}(\text{H}\rightarrow \text{b}\bar{\text{b}})$) at a center-of-mass energy of $13\,\text{TeV}$ is presented. The measurement focuses on the semileptonic decay channel of the top quark-antiquark pair and is based on proton-proton collision data recorded by the CMS Experiment in the years 2016 and 2017 corresponding to an integrated luminosity of $77.4\,\text{fb}^{-1}$. The cross section for the production of a Higgs boson in association with a top quark-antiquark pair ($\text{t}\bar{\text{t}}\text{H}$) depends on the top-Higgs Yukawa coupling and a measurement of $\text{t}\bar{\text{t}}\text{H}$ production provides direct access to this important property of the standard model of particle physics. To achieve the measurement of this process, candidate $\text{t}\bar{\text{t}}\text{H}(\text{H}\rightarrow \text{b}\bar{\text{b}})$ events are first selected from the analyzed data. Artificial neural networks are then used to construct observables that allow the discrimination between signal and background processes. To extract the signal contribution in data, standard model predictions for these observables are fit to data using a profile likelihood approach. This results in a best-fit value for the signal strength relative to the standard model prediction $\mu = \sigma/\sigma_{\text{SM}}$ of \begin{equation} \hat{\mu} = 1.22^{+0.41}_{-0.37}({\text{tot.}}) \left[{}^{+0.19}_{-0.19}({\text{stat.}}) {}^{+0.36}_{-0.32}({\text{syst.}}) \right]. \end{equation} This result is compatible with the standard model prediction and corresponds to an observed (expected) significance of $3.3$ ($2.7$) standard deviations with respect to the background-only hypothesis. In addition, combined analyses performed by the CMS Collaboration are discussed, in which analyses of various production and decay modes of the Higgs boson were statistically combined. The presented anylsis of $\text{t}\bar{\text{t}}\text{H}(\text{H}\rightarrow \text{b}\bar{\text{b}})$ production in the semileptonic channel was an important contribution to theses combinations, which resulted in the observation of $\text{t}\bar{\text{t}}\text{H}$ production and of the $\text{H}\rightarrow \text{b}\bar{\text{b}}$ decay mode.