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PreprintarXiv licencearXiv

A Warped Extra Dimensional Candidate for the LZ 248 keV Event

  • Vincent S. H. Lee1,2
  • Lisa Randall3
  1. 1Department of Physics , University of California , Berkeley , Berkeley , CA 94720 , USA and
  2. 2Department of Physics , University of California , San Diego , La Jolla , CA 92093-0319 , USA
  3. 3Gravity, Spacetime, and Particle Physics (GRASP) Initiative , Harvard University , 17 Oxford Street , Cambridge , MA 02138 , USA
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Abstract

The recent result by the LUX-ZEPLIN (LZ) experiment of a single nuclear-recoil event at 248 keV suggests an interpretation in terms of inelastic scattering between dark matter (DM) and the xenon target. The widely considered thermal Higgsino DM with mχ∼~TeV and mass splitting δ∼ 350~keV is essentially excluded as it would be captured efficiently by the Sun, with a resulting neutrino flux from its annihilation in excess of the IceCube limit, and expected recoils above the LZ nominal search window, where none were seen. However we argue that although these tensions apply to a Higgsino with constrained cross section, they need not apply to the broader set of inelastic candidates that alternative solutions to the hierarchy problem might suggest. We show that a new massive gauge boson, Z' with a candidate DM sector and Majorana mass splitting of order ∼ 10−7 of the Dirac mass, evades current constraints. We propose an inelastic dark matter (iDM) candidate that can arise naturally in a Randall-Sundrum warped extra-dimensional model. The DM candidate involves a vector-like fermion confined to the TeV brane and a bulk field. The brane Lagrangian contains Dirac mass terms that are also naturally exponentially suppressed. The left-handed component of the bulk field has a Majorana mass with origin on the UV brane, while the interaction with Standard Model nucleons is mediated by a massive dark Kaluza-Klein (KK) gauge boson whose mass is also automatically in the right range. We propose a concrete model of thermal DM with mχ∼~TeV in an RS geometry with warp factor πkR≃ 31.7 and the Z' a KK mode with natural TeV-ish scale mass in which the ratio of neutrino to quark coupling is also natural, giving a mass splitting of δ∼ 300~keV, and show how it could explain the LZ signal while being consistent with existing constraints.

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Cite

BibTeXRIS
BibTeX
@misc{lee2026warped,
  title = {{A Warped Extra Dimensional Candidate for the LZ 248 keV Event}},
  author = {Vincent S. H. Lee and Lisa Randall},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.09136},
  eprint = {2609.09136},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.09136},
}
RIS
TY  - UNPB
TI  - A Warped Extra Dimensional Candidate for the LZ 248 keV Event
AU  - Vincent S. H. Lee
AU  - Lisa Randall
PY  - 2026
DA  - 2026/09/08
PB  - arXiv
DO  - 10.48550/arxiv.2609.09136
UR  - https://arxiv.org/abs/2609.09136
AB  - The recent result by the LUX-ZEPLIN (LZ) experiment of a single nuclear-recoil event at 248 keV suggests an interpretation in terms of inelastic scattering between dark matter (DM) and the xenon target. The widely considered thermal Higgsino DM with m_χ∼~TeV and mass splitting δ∼ 350~keV is essentially excluded as it would be captured efficiently by the Sun, with a resulting neutrino flux from its annihilation in excess of the IceCube limit, and expected recoils above the LZ nominal search window, where none were seen. However we argue that although these tensions apply to a Higgsino with constrained cross section, they need not apply to the broader set of inelastic candidates that alternative solutions to the hierarchy problem might suggest. We show that a new massive gauge boson, Z' with a candidate DM sector and Majorana mass splitting of order ∼ 10^−7 of the Dirac mass, evades current constraints. We propose an inelastic dark matter (iDM) candidate that can arise naturally in a Randall-Sundrum warped extra-dimensional model. The DM candidate involves a vector-like fermion confined to the TeV brane and a bulk field. The brane Lagrangian contains Dirac mass terms that are also naturally exponentially suppressed. The left-handed component of the bulk field has a Majorana mass with origin on the UV brane, while the interaction with Standard Model nucleons is mediated by a massive dark Kaluza-Klein (KK) gauge boson whose mass is also automatically in the right range. We propose a concrete model of thermal DM with m_χ∼~TeV in an RS geometry with warp factor πkR≃ 31.7 and the Z' a KK mode with natural TeV-ish scale mass in which the ratio of neutrino to quark coupling is also natural, giving a mass splitting of δ∼ 300~keV, and show how it could explain the LZ signal while being consistent with existing constraints.
SN  - 2331-8422
ER  -