A long life of Heavy Neutral Leptons: from the LHC to the FCC
Project title: A long life of Heavy Neutral Leptons: from the LHC to the FCC
Main applicant: Rebeca Gonzalez-Suarez, Division of High Energy Physics
Almost 10 years after the Higgs boson discovery, the Standard Model of particle physics is still unable to answer key questions posed by experimental data, like the nature of dark matter or why there is so little antimatter in the Universe. One of these questions relates to how neutrinos acquire mass, and finding the answer would be a milestone of at least the same magnitude as the Higgs boson observation.
The Standard Model predicts neutrinos to be massless, but experimentally we know that they do have mass. Additional neutrinos, generally called Heavy Neutral Leptons, could solve this contradiction, explain the Baryon asymmetry of the Universe, and even provide a dark matter candidate.
Searches for Heavy Neutral Leptons are ongoing, but a very large search area is still out of reach: Heavy Neutral Leptons with masses similar to the W mass, and small couplings to the regular neutrinos. This region is characterized by displaced signatures, as Heavy Neutral Leptons with small couplings are long-lived; making it experimentally challenging.