Speaker
Description
The Light Dark Matter eXperiment (LDMX) is a fixed-target search for thermal relic light dark matter. The LDMX hadronic calorimeter (HCal) is primarily designed to act as a highly efficient veto detector for few-GeV neutral hadrons produced in photo-nuclear background reactions, which is necessary for sensitivity to models with invisible missing momentum and missing energy signatures. For models with visible decays within the detector, such as long-lived dark photon or ALP decays, the HCal must also reconstruct shower energies and efficiently discriminate between electromagnetically and hadronically induced showers using shower shape information. A prototype HCal was tested in 2022 at CERN's East Area T9 beamline in a mixed muon, electron, and pion beam between 0.3 - 4 GeV, giving a first estimate of the HCal's energy resolution and neutral hadron veto power. In 2025, a slice of each LDMX sub-detector was installed in SLAC's End-station A and tested with a 4 GeV electron beam from the newly commissioned Linac to End Station A (LESA) beamline. Prototypes of the HCal, ECal, silicon tracker, trigger scintillator arrays, and a proposed active target, were simultaneously tested, and is our first activity in the beam hall where LDMX will be constructed.