Illuminating Light Dark Matter with Fixed-Target Experiments
Abstract
Astronomical and cosmological observations provide overwhelming evidence for a non-luminous matter component, dark matter (DM), whose particle nature remains unknown. Experimental searches for non-gravitational DM interactions have largely targeted DM with GeV-TeV masses via nuclear recoils, yielding no discovery thus far. DM in the MeV-GeV mass range, however, is theoretically motivated, reproducing the observed relic abundance while remaining invisible to nuclear recoil searches. Such light DM is better probed via electron recoils or at fixed-target experiments. This thesis advances the theoretical and statistical toolkit for light DM searches at fixed-target experiments, spanning model building, statistical inference, global fits, and signal simulation. We survey the landscape of fixed-target searches for light DM, focusing on the Light Dark Matter eXperiment (LDMX). We also simulate DM signatures at the next-generation experiment SHiP to assess its sensitivity. Within minimal DM models, we present a likelihood-based statistical framework for LDMX using the full two-dimensional recoil electron distribution, spanning exclusion, discovery, parameter estimation, and model comparison in frequentist and Bayesian formulations. This establishes the discovery potential of LDMX, and we quantify the direct detection exposure needed to independently confirm a potential signal. Beyond this paradigm, we perform global fits of scalar and fermionic light DM, combining cosmological, astrophysical, and laboratory constraints. We then extend fixed-target searches to spin-1 DM and higher electromagnetic moment dark photons, yielding rich signatures with strong complementarity to other probes. Finally, we go beyond standard nuclear modelling of dark photon production, incorporating elastic nuclear form factors and spectral functions from many-body ab initio methods in place of analytic treatments.
Related
- Probing Lorentz-violating scalar forces and dark matter with precision matter and antimatter experiments
- Are neutrinos Majorana? Fixed-target and high-energy astrophysical searches decide
- Proposal for the resolution of the disagreement between DAMA and other Underground Dark Matter Experiments
- Indirect Dark Matter Detection in the Multi-Messenger Era: Experiments, Systematics, Anomalies, and Prospects for Discovery
- Testing the inelastic dark matter interpretation of the LZ event with heavy-element experiments
BibTeX
@misc{gray2026illuminating,
title = {{Illuminating Light Dark Matter with Fixed-Target Experiments}},
author = {Taylor R. Gray},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.27131},
eprint = {2610.27131},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.27131},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Illuminating Light Dark Matter with Fixed-Target Experiments
AU - Taylor R. Gray
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.27131
UR - https://arxiv.org/abs/2610.27131
AB - Astronomical and cosmological observations provide overwhelming evidence for a non-luminous matter component, dark matter (DM), whose particle nature remains unknown. Experimental searches for non-gravitational DM interactions have largely targeted DM with GeV-TeV masses via nuclear recoils, yielding no discovery thus far. DM in the MeV-GeV mass range, however, is theoretically motivated, reproducing the observed relic abundance while remaining invisible to nuclear recoil searches. Such light DM is better probed via electron recoils or at fixed-target experiments. This thesis advances the theoretical and statistical toolkit for light DM searches at fixed-target experiments, spanning model building, statistical inference, global fits, and signal simulation. We survey the landscape of fixed-target searches for light DM, focusing on the Light Dark Matter eXperiment (LDMX). We also simulate DM signatures at the next-generation experiment SHiP to assess its sensitivity. Within minimal DM models, we present a likelihood-based statistical framework for LDMX using the full two-dimensional recoil electron distribution, spanning exclusion, discovery, parameter estimation, and model comparison in frequentist and Bayesian formulations. This establishes the discovery potential of LDMX, and we quantify the direct detection exposure needed to independently confirm a potential signal. Beyond this paradigm, we perform global fits of scalar and fermionic light DM, combining cosmological, astrophysical, and laboratory constraints. We then extend fixed-target searches to spin-1 DM and higher electromagnetic moment dark photons, yielding rich signatures with strong complementarity to other probes. Finally, we go beyond standard nuclear modelling of dark photon production, incorporating elastic nuclear form factors and spectral functions from many-body ab initio methods in place of analytic treatments.
ER -