LDMX -- The Light Dark Matter eXperiment

TL;DR

LDMX is a proposed experiment at SLAC designed to detect sub-GeV dark matter via missing momentum, promising significant sensitivity improvements and broad physics reach including dark sectors and neutrino interactions.

Contribution

This paper introduces the technical design, simulated performance, and physics potential of the LDMX detector for dark matter searches at SLAC.

Findings

LDMX can improve dark matter detection sensitivity by up to three orders of magnitude.

The experiment provides broad sensitivity to dark sector scenarios and visible signatures.

LDMX offers unique insights into electron-nuclear interactions relevant for neutrino experiments.

Abstract

The Light Dark Matter eXperiment (LDMX) is an electron fixed-target experiment optimized to search for sub-GeV dark matter production through the missing momentum signature. LDMX is designed to operate in End Station A at SLAC, using an 8 GeV electron beam accelerated alongside the LCLS-II drive beam. The design of the apparatus is strongly motivated by the performance requirements of a high-rate missing momentum search and leverages detector technologies and designs from other experiments along with existing facilities at SLAC. LDMX will improve on previous results by up to three orders of magnitude, enabling broad sensitivity to dark sector scenarios including the dark matter interaction strengths motivated by freeze-out of MeV-GeV mass dark matter to the observed relic abundance. With hermetic forward coverage, LDMX also has sensitivity to visible signatures of dark sectors and provides a unique probe of electron-nuclear interactions important to interpreting data from accelerator-based neutrino experiments. This report encompasses the technical design of the LDMX Detector, its simulated performance, and the physics capabilities of the experiment.