Exothermic nuclear recoils from thermal quasi-pNGB dark matter
Abstract
We study a two-component dark matter scenario comprising a stable pseudo-Nambu-Goldstone boson (pNGB) and its nearly degenerate long-lived quasi-pNGB partner. An approximate scalar symmetry relates their masses and suppresses the tree-level Higgs-mediated elastic scattering of the excited state through the small mass splitting. Their coupled thermal evolution yields comparable relic populations, while requiring the observed total abundance fixes the dark scalar symmetry-breaking scale and hence the dark gauge coupling. At the studied benchmark, an excited fraction of approximately one half survives under the adopted evolution assumptions. The quasi-pNGB excited state can therefore produce exothermic nuclear recoils despite a suppressed tree-level elastic signal. As an application, we examine the high-energy LUX-ZEPLIN event. For relic compatible parameters, the recoil normalization fixes the kinetic mixing, allowing this interpretation to be tested by independent mediator searches.
Related
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BibTeX
@misc{sheikh2026exothermic,
title = {{Exothermic nuclear recoils from thermal quasi-pNGB dark matter}},
author = {Riasat Sheikh and Takashi Toma and Koji Tsumura},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.09516},
eprint = {2610.09516},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.09516},
}
RIS
TY - UNPB
TI - Exothermic nuclear recoils from thermal quasi-pNGB dark matter
AU - Riasat Sheikh
AU - Takashi Toma
AU - Koji Tsumura
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.09516
UR - https://arxiv.org/abs/2610.09516
AB - We study a two-component dark matter scenario comprising a stable pseudo-Nambu-Goldstone boson (pNGB) and its nearly degenerate long-lived quasi-pNGB partner. An approximate scalar symmetry relates their masses and suppresses the tree-level Higgs-mediated elastic scattering of the excited state through the small mass splitting. Their coupled thermal evolution yields comparable relic populations, while requiring the observed total abundance fixes the dark scalar symmetry-breaking scale and hence the dark gauge coupling. At the studied benchmark, an excited fraction of approximately one half survives under the adopted evolution assumptions. The quasi-pNGB excited state can therefore produce exothermic nuclear recoils despite a suppressed tree-level elastic signal. As an application, we examine the high-energy LUX-ZEPLIN event. For relic compatible parameters, the recoil normalization fixes the kinetic mixing, allowing this interpretation to be tested by independent mediator searches.
ER -