Speaker
Description
Probing the shape of the Higgs potential is a primary objective of the next generation of flagship particle physics experiments, for which measuring $\lambda_\mathrm{hhh}$, the trilinear Higgs self-coupling, will play a crucial role. Despite operating below the di-Higgs production threshold, circular $e^{+}e^{-}$ machines will still have indirect access to $\lambda_\mathrm{hhh}$ via its loop-level contributions to single-Higgs production observables. In this work, we investigate how well $\lambda_\mathrm{hhh}$ can be determined by such indirect effects within a global EFT fit. While most studies to date assume that future measurements will be compatible with SM predictions, here we consider non-SM values of $\lambda_\mathrm{hhh}$, using an inert doublet extension of the SM as an example of a New Physics scenario that could be realised in nature. We find that theory uncertainties related to the truncation of the EFT expansion and to higher-order corrections, which are often neglected, can substantially affect the resulting precision for $\lambda_\mathrm{hhh}$. Moreover, in order to investigate the impact of experimental noise on the fit results, we perform a series of toy studies where we smear the central values for the pseudo-measurements according to their projected experimental uncertainty.