Global analysis of the higgs effective field theory

Das, Sreejit (2025) Global analysis of the higgs effective field theory. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Sreejit Das (20MS117)) 20MS117_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

Effective field theories have become the standard language to parameterize deviations from the Standard Model in Higgs and electroweak physics. The effective field theory lagrangian most commonly utilized for this purpose— the Standard Model Effective Field Theory (SMEFT)—comes with many implicit assumptions. The most general parametrization is in fact provided by the so called Higgs Effective Field Theory (HEFT) lagrangian. Many popular models beyond the Standard Model, such as models with additional singlets and doublets, in fact map to the HEFT and not the SMEFT at low energies. The main objective of this thesis is to develop the framework to carry out global HEFT fit taking into account LEP Z-pole data and data from diboson and Higgs processes at the LHC. To this end, we present a complete basis of HEFT operators to parametrize the processes and find expressions for these observables in terms of the HEFT Wilson coefficients. We then carry out a global fit to obtain the projected sensitivity of the HL-LHC to probe these operators. As the SMEFT is a special case of the HEFT we demonstrate how our results can be translated to projected bounds on SMEFT operators by taking the appropriate limit.

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