Executive Summary : | New physics can accommodate suitable Dark Matter (DM) candidates by extending Standard Models (SM) in various ways, such as adding new non-standard particles to SM. Singlet and one extra doublet extensions (2HDM) of SM have been well studied in the literature. The scope of searching DM candidates in multi Higgs doublet models under various symmetries is still there. The researchers plan to study non-standard members in the electroweak symmetry breaking sector, like the Three Higgs Doublet Model (3HDM) under various symmetry, especially under Z₂ and Z₃ symmetry. They also plan to study the direct detection of the DM candidate in these BSM models using spin-independent cross-sections, which are constrained by direct detection experiments. The gap between the high-energy scale of new physics and the low-energy electroweak scale justifies the necessity of Effective Field Theory (EFT). The total Lagrangian is expressed as a series of higher-dimensional operators with dimensionless coefficients, known as Wilson coefficients. The authors are interested in probing dimension-6 operators and exploring the bounds on Wilson coefficients of 2HDMEFT. A complete set of independent, non-redundant sets of EFT operators, based on 2HDM, is found in literature. The authors are interested in studying the bounds on Wilson coefficients of 2HDMEFT and exploring new vertices and interactions in tree level in 2HDMEFT. Higgs self-interaction plays a crucial role in electroweak symmetry breaking and vacuum stability. |