Extended scalar sectors, effective operators and observed data

Understand

The available data on the 125 GeV scalar $h$ is analysed to explore the room for new physics in the electroweak symmetry breaking sector.

• The first part of the study is model-independent, with $h$ couplings to standard model particles scaled by quantities that are taken to be free parameters.
• At the same time, the additional loop contributions to $h \rightarrow \gamma\gamma$ and $h \rightarrow Z\gamma$, mediated by charged scalar contributions in the extended scalar sector, are treated in terms of gauge-invariant effective operators.
• Having justified this approach for cases where the concerned scalar masses are a little above the $Z$-boson mass, we fit the existing data to obtain marginalized 1$\sigma$ and 2$\sigma$ regions in the space of the coefficients of such effective operators, where the limit on the $h \rightarrow Z\gamma$ branching ratio is used as a constraint.