Besides the visible matter that surrounds us and that we are made of, astrophysics observations point to another form of matter we call dark matter. If dark matter is made of new particles, it can be produced under laboratory conditions at particle colliders. Due to their weak interactions with visible matter, however, dark matter particles escape the detectors. Yet they can be observed indirectly as missing energy through the momentum imbalance of visible particles from the same process.
In this project, we explore the production of two Higgs bosons and missing energy as a novel signature at the Large Hadron Collider (LHC). Such a signal is expected in models where dark matter interacts with visible matter mainly through the Higgs boson. We have identified two classes of models that predict a di-Higgs dark matter signature, while being in agreement with previous searches and astrophysical observations.
The detection of two Higgs bosons and missing energy at the LHC is complicated by other processes that fake our signal. For instance, the production of two top-quarks decaying into invisible neutrinos and visible particles can look very similar to dark matter production. Using modern analysis tools for collider observables, we have investigated how to best distinguish our signal from such background processes. Kinematic features, such as the amount of missing energy or the distributions of the Higgs boson decay products, allow us to interpret the observed collision patterns in terms of our dark matter models.
We find that di-Higgs production plus missing energy is indeed a promising new signature at the LHC. Since the signal process is rare, the experimental prospects to observe dark matter will improve significantly with the large amount of data collected during the coming years.