Thesis

Exploring the electroweak vacuum with di-Higgs production at the LHC ATLAS experiment

• Call:

  PT-CERN Call 2021/1

• Academic Year:

  2021

• Domain:

  Astroparticle Physics

• Supervisor:

  Ricardo Gonçalo

• Co-Supervisor:

  Konstantinos Nikolopoulos

• Institution:

  Universidade de Coimbra

• Host Institution:

  Laboratório de Instrumentação e Física Experimental de Partículas

• Abstract:

  Since its discovery, the Higgs boson became a prime tool to search for physics beyond the Standard Model (SM). At the current level of precision, the Higgs boson is compatible with SM expectations. A number of open questions indicate the existence of new physics that could be unveiled as we explore the LHC data. A wealth of experimental results from the ATLAS and CMS experiments, probe the region around the minimum of the Higgs potential, or vacuum. But the shape of this potential is not constrained experimentally. This shape is intimately connected to the breaking of the electroweak gauge symmetry, which resulted in the fundamental forces we experience today. To experimentally constrain this shape we must measure the Higgs boson self-coupling, which is accessible at the LHC through the simultaneous production of two Higgs bosons. This is an extremely rare process that has not yet been observed, and has an expected production rate approximately 1000 times smaller than that for the production of a single Higgs boson. Possible production modes for Higgs boson pairs, HH, at the LHC are gluon-gluon fusion (ggF), vector boson fusion (VBF) and associated production with vector bosons or top quarks.Modifications of the EWSB potential are predicted by several beyond the SM (BSM) theories. Some BSM anomalies on the Higgs boson couplings and interactions could enhance the production rate of Higgs boson pairs by more than one order of magnitude. In some cases, the Higgs boson pair production could be observed even with the current LHC luminosity. In this project, I expect to contribute to enhancing our current knowledge in this important area, which will become one of the most important measurements of LHC experiments. The main goal is to search for the production of Higgs boson pairs, focusing on the VBF production channel. The search will utilize data from Run 3 of the LHC and is expected to result in an important publication of the ATLAS collaboration.