CTP Seminar
Future lepton colliders offer a powerful tool for advancing our understanding of fundamental physics through both high-precision measurements and searches for new physics beyond the standard model. In the first part of the talk, I will present a study of the production of dark matter from decay of new extra vector-like leptons in the context of Lepton portal dark matter (LPDM) from electron-positron collisions at the International Linear Collider (ILC) at a centre of mass energy of 500 GeV. The study revealed the possibility of studying different scenarios of the mass splitting between the dark matter and the vector-like leptons, where we showed that it is possible to study the case of narrow mass splitting, not accessible by the LHC. In the second part, I will discuss a precision measurement of the Higgs boson production cross section at the Future Circular Collider (FCC-ee) operating at a centre-of-mass energy of 240 GeV. The analysis considers the Higgsstrahlung process (e⁺e⁻ → ZH), where the Z boson decays either hadronically or into invisible states, and the Higgs boson decays into four charged leptons. While the Higgs boson was discovered in 2012 at the LHC, future lepton colliders will significantly improve our ability to measure its properties. Precise determination of Higgs couplings and the total width is essential to constrain possible contributions from beyond the Standard Model or anomalous interactions. This study demonstrates that a 10% precision on the cross section can be achieved in this decay channel alone, at 68% confidence level.