Strange quark as a probe for new physics in the Higgs sector

One of the most interesting yet-to-be answered questions in Particle Physics is the nature of the Higgs Yukawa couplings and their universality. Key information in our understanding of this question arises from studying the coupling of the Higgs boson to second generation quarks. Some puzzles in the flavor sector and potential additional sources of CP violation could also have their origins in an extended Higgs sector. Rare Higgs decay modes to charm or strange quarks are very challenging or nearly impossible to detect with the current experiments at the Large Hadron Collider, where the large multi-jet backgrounds makes it difficult to study light quark couplings with inclusive $h\rightarrow q\bar{q}$ decays. Future $e^{+}e^{-}$ machines are thus the perfect avenue to study such phenomena. This contribution presents the development of a novel algorithm for tagging jets originating from the hadronisation of strange quarks (strange-tagging) and the first application of such a strange-tagger to a direct Higgs to strange ($h\rightarrow s\bar{s}$) analysis. The work is performed with the International Large Detector (ILD) concept at the International Linear Collider (ILC), but it is easily applicable to other Higgs factories. The study includes as well a preliminary investigation of a Compact Ring Imaging Cerenkov system (RICH) capable of maximising strange-tagging performance in future Higgs factory detectors.