Speaker
Description
In this talk, I will discuss the prospects of probing a light scalar state in the Type-I Two-Higgs Doublet Model (2HDM) at the LHC. In this framework, one of the additional scalar states can be as light as $\lesssim 100$ GeV while remaining consistent with current collider and flavour constraints, yet it can evade conventional search strategies due to its suppressed couplings to the SM Higgs and fermions. I will focus on electroweak production channels where the light scalar $h$ is produced in association with heavier states such as a pseudoscalar $A$ or a charged scalar $H^\pm$, followed by cascade decays yielding multiple $h$ in the final state. Owing to the mass hierarchy, the light scalar is typically boosted, allowing its decay $h \to b\bar{b}$ to be reconstructed as a fat-jet with two $b$-subjets. I will show that such ``multi double-$b$'' fat-jet signatures provide a promising probe of this scenario, particularly in regions with large mass splittings, and can extend the LHC sensitivity beyond the reach of conventional resolved analyses.