Exotic Higgs decays into displaced jets at the LHeC

Profiling the Higgs boson requires the study of its non-standard decay modes. In this work we discuss the prospects of the Large Hadron electron Collider (LHeC) to detect scalar particles with masses $\gtrsim$ 10 GeV produced from decays of the Standard Model (SM) Higgs boson. These scalar particles decay mainly to bottom pairs, and in a vast portion of the allowed parameter space they acquire a macroscopic lifetime, hence giving rise to displaced hadronic vertices. The LHeC provides a very clean environment that allows for easy identification of these final states, in contrast to hadronic colliders where the overwhelming backgrounds and high pile-up render such searches incredibly challenging. We find that the LHeC provides a unique window of opportunity to detect scalar particles with masses between 10 GeV and half the SM Higgs mass. In the Higgs Portal scenarios we can test the mixing angle squared, $\sin^2 \alpha$, as low as $10^{-5} - 10^{-7}$, with the exact value depending on the vacuum expectation value of the new scalar. Our results are also presented in a model-independent fashion in the lifetime-branching ratio and mass-branching ratio planes. We have found that exotic branching ratios of the Higgs boson at the sub-percent level can be probed, for the scalar decay length in the range $10^{-4}$ m $\lesssim c \tau \lesssim 10^{-1}$ m. The expected coverage of the parameter space largely exceeds the published sensitivity of the indirect reach at the high-luminosity Large Hadron Collider via the invisible Higgs branching ratio.