Sensitivity of an Early Dark Matter Search using the Electromagnetic Calorimeter as a Target for the Light Dark Matter eXperiment

TL;DR

This paper explores the potential of the LDMX electromagnetic calorimeter as an active target in early dark matter searches, achieving sensitivity to very weak interactions in previously unexplored light dark matter parameter space.

Contribution

It introduces a novel missing-energy-based search method using the calorimeter as an active target, extending sensitivity to lower interaction strengths for light dark matter.

Findings

Sensitivity down to interaction strength y of ~2×10⁻¹³ for 1MeV dark matter.

Projections into new regions of light dark matter phase space.

Feasibility of early running detection with calorimeter-based approach.

Abstract

The Light Dark Matter eXperiment (LDMX) is proposed to employ a thin tungsten target and a multi-GeV electron beam to carry out a missing momentum search for the production of dark matter candidate particles. We study the sensitivity for a complementary missing-energy-based search using the LDMX Electromagnetic Calorimeter as an active target with a focus on early running. In this context, we construct an event selection from a limited set of variables that projects sensitivity into previously-unexplored regions of light dark matter phase space -- down to an effective dark photon interaction strength $y$ of approximately $2\times10^{-13}$ ($5\times10^{-12}$) for a 1MeV (10MeV) dark matter candidate mass.