Speaker
Description
The Light Dark Matter eXperiment (LDMX) is a fixed-target experiment that will be placed at the LCLS-II electron beamline at SLAC, sensitive to production of sub-GeV dark matter with missing momentum and missing energy signatures. This precision search for rare dark matter production requires strong veto capabilities to separate those events from standard model background processes. After initially running at a 4 GeV beam energy, the LCLS-II beamline will be upgraded to 8 GeV, where LDMX will take the bulk of its data. The energy increase is expected to improve both the dark matter production cross sections, as well as the background rejection capabilities.
The most challenging backgrounds for LDMX are muon conversions and photo-nuclear reactions, into complex and possibly neutral final-states, induced by an energetic bremsstrahlung photon, that can mimic the missing momentum and missing energy signature of dark matter. This simulation study shows that LDMX, with the combined veto performance of all its subsystems, can reject every standard model background event for each of $2\times10^{14}$ electrons scattering in the target, at 8 GeV beam energy. Furthermore, the veto capabilities are shown to improve at 8 GeV beam energy compared to 4 GeV.
