Speaker
Description
Beam-dump experiments provide powerful probes of light and feebly interacting particles, but their sensitivity to visibly decaying mediators is ultimately limited by the requirement that the new particle survive the shielding or baseline before reaching the detector. This geometric requirement produces a characteristic “beam-dump ceiling” in the coupling–mass parameter space, beyond which the mediator decays too promptly to be observed. In this talk, we discuss how the LHC can access part of the parameter space above this ceiling by exploiting its high collision energy, broad detector coverage, and short source-to-detector distances. Focusing on visibly decaying dark photons, we will present ongoing work on two complementary production mechanisms: dark-photon bremsstrahlung from energetic hadrons interacting in the calorimeters, and direct production in association with a hard jet. These channels lead respectively to displaced dimuon and dielectron signatures, allowing the LHC detector to operate, in different ways, as both the source and detector of light dark-sector states. We will discuss realistic trigger and reconstruction requirements, the use of displaced-lepton and parking data sets, preliminary background estimates, and the resulting sensitivity to previously unexplored regions of dark-photon parameter space.