Dark Matter, Millicharges, Axion and Scalar Particles, Gauge Bosons, and Other New Physics with LDMX

TL;DR

The LDMX experiment aims to explore new physics such as dark matter, millicharged particles, and axions by using a novel fixed-target setup with high sensitivity to various rare particle decays and interactions.

Contribution

This paper demonstrates the potential of LDMX to achieve world-leading sensitivity to a broad range of sub-GeV new physics particles through missing momentum and displaced decay signals.

Findings

LDMX can probe sub-GeV dark matter with unprecedented sensitivity.

The experiment is capable of detecting millicharged particles and axions.

It offers new discovery opportunities for invisible and short-lived particle decays.

Abstract

The proposed LDMX experiment would provide roughly a meter-long region of instrumented tracking and calorimetry that acts as a beam stop for multi-GeV electrons in which each electron is tagged and its evolution measured. This would offer an unprecedented opportunity to access both collider-invisible and ultra-short lifetime decays of new particles produced in electron (or muon)-nuclear fixed-target collisions. In this paper, we show that the missing momentum channel and displaced decay signals in such an experiment could provide world-leading sensitivity to sub-GeV dark matter, millicharged particles, and visibly or invisibly decaying axions, scalars, dark photons, and a range of other new physics scenarios.