A Window onto New Invisible Particles via Semi-Visible Higgs Decays

Searches for new physics continue at the LHC in several forms, including new-particle searches, precision measurements of SM couplings, and searches for signals of new invisible particles. In this talk, we discuss the reach in parameter space of new invisible particles with the semi-visible Higgs decay modes $H\to \ell^+\ell^- + ~\rm E{\!\!\!/}_T$ and $H\to jj + ~\rm E{\!\!\!/}_T$. We first parametrise the new invisible particles and their interactions with the SM through an effective field theory at dimension six. We then study the respective signals and the corresponding background, finding small signals with large backgrounds. We find, however, that the kinematics of these processes are sufficiently rich to allow a signal extraction that we first quantify with a cut-based analysis and later with a multivariate BDT.