Higgs self-coupling measurements with the CMS detector at the LHC and at future colliders in the HH → ZZ(4l)bb decay channel

Abstract

This thesis presents the perspectives on the Higgs boson pair production (HH) measurements in the four-lepton plus two b jets decay channel: HH→ZZ(4l)bb. The HH production gives a direct access to the Higgs boson trilinear self-coupling, providing confirmation to the standard model (SM) predictions and sensitivity to possible physics processes beyond the standard model (BSM). This study has been performed in different scenarios in terms of center-of-mass energy, integrated luminosity and detector layouts. Starting from proton-proton collision data collected at a center-of-mass energy of 13 TeV with the CMS detector at the CERN LHC during 2018, the search has been extended to future experimental scenarios obtained with the upgrade layout of the CMS detector for the High Luminosity (HL-LHC) and the possible subsequent High Energy (HE-LHC) phases of the LHC accelera- tor. The analysis has been repeated with a very high energy hadronic Future Circular Collider (FCC-hh), resulting in a unique overview of the capabilities, exploiting this channel, to confirm or disprove the SM predictions. Finally, since future upgrades of existing detectors and even future accelerator projects have been a consistent part of the work described, this thesis presents also the studies performed on innovative micropattern gaseous detectors (MPGD) called μ-RWELL, that could be suitable for these future experiments. Longevity studies exploiting a gamma source irradiating a μ-RWELL prototype have been conducted to understand the detector behavior in a high radiation environment, foreseen for future implementations in high energy physics experiments. In addition, a homogeneity test on a large area μ-RWELL prototype, to verify the feasibility and robustness of large surface detectors realized with this technology, without compromising the excellent performances, is described.