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Dark Matter Boosted by Terrestrial Collisions

Zamiul Alam, Christopher V. Cappiello, Francesc Ferrer

TL;DR

This paper addresses inelastic dark matter models with a mass splitting $\delta$ that suppresses standard elastic scattering in direct detection. It introduces a terrestrial mechanism where DM upscatters in the Earth to a heavier state $\chi_2$ and then downscatters in a Xenon detector, exploiting high-velocity DM and heavy target nuclei to access larger $\delta$. By computing Earth-based upscattering on Pb, incorporating a velocity distribution with LMC-tail enhancement, and evaluating the Xe downscattering signal, the authors derive new limits from XENON1T and XENON100 data, extending the reachable $\delta$ up to roughly $350$ keV for $m_{\chi}=1$ TeV and surpassing previous bounds in the high-$\delta$ regime. The approach broadens IDM search strategies and can be adapted to other detectors and target materials, boosting the practical impact of direct-detection campaigns for inelastic DM.

Abstract

Inelastic dark matter (IDM) models feature an energy threshold for scattering with Standard Model particles, which enables their consistency with the increasingly stringent limits placed by direct detection experiments. In a typical construction, elastic scattering is absent at tree level, and a lighter dark matter state must first upscatter into a heavier state in order to interact with the nuclei in the detector. We model the excitation of IDM in the Earth followed by its downscattering inside a detector, and we show that considering this process markedly enhances the sensitivity of existing detectors. In particular, current limits based on XENON100 and XENON1T data can be extended to significantly larger mass splittings.

Dark Matter Boosted by Terrestrial Collisions

TL;DR

This paper addresses inelastic dark matter models with a mass splitting that suppresses standard elastic scattering in direct detection. It introduces a terrestrial mechanism where DM upscatters in the Earth to a heavier state and then downscatters in a Xenon detector, exploiting high-velocity DM and heavy target nuclei to access larger . By computing Earth-based upscattering on Pb, incorporating a velocity distribution with LMC-tail enhancement, and evaluating the Xe downscattering signal, the authors derive new limits from XENON1T and XENON100 data, extending the reachable up to roughly keV for TeV and surpassing previous bounds in the high- regime. The approach broadens IDM search strategies and can be adapted to other detectors and target materials, boosting the practical impact of direct-detection campaigns for inelastic DM.

Abstract

Inelastic dark matter (IDM) models feature an energy threshold for scattering with Standard Model particles, which enables their consistency with the increasingly stringent limits placed by direct detection experiments. In a typical construction, elastic scattering is absent at tree level, and a lighter dark matter state must first upscatter into a heavier state in order to interact with the nuclei in the detector. We model the excitation of IDM in the Earth followed by its downscattering inside a detector, and we show that considering this process markedly enhances the sensitivity of existing detectors. In particular, current limits based on XENON100 and XENON1T data can be extended to significantly larger mass splittings.
Paper Structure (9 sections, 6 equations, 3 figures)

This paper contains 9 sections, 6 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Kinematics of inelastic dark matter collisions
  3. Inelastic dark matter upscattering in the Earth
  4. Target Nuclei
  5. Dark matter velocity
  6. Event Rate
  7. Shielding by Earth
  8. Results
  9. Conclusions

Figures (3)

  • Figure 1: Fraction of DM particles capable of producing a xenon recoil between 4.9 and 40.9 keV. The red curves are for upscattering, while the blue curves are for downscattering. The dashed curves are including only the Standard Halo Model (SHM), while the solid curves include the contribution from the Large Magellanic Cloud (LMC) Smith-Orlik:2023kyl.
  • Figure 2: Present limit from XENON1T (shaded gray), taken from Ref. Song:2021yar, and a search using metastable tantalum Lehnert:2019tuw, compared to our results (red). Dotted black is a projection of what a xenon-based detector could probe by searching for nuclear recoils up to 500 keV Bramante:2016rdh. Dashed red is the maximum cross section that can be excluded by considering only DM that does not downscatter and re-upscatter on its way to the detector (see text for an explanation of the shape).
  • Figure 3: Our limit from XENON100 (solid red), compared to a compilation of direct detection limits assuming the Standard Halo Model (dashed black, from Ref. Song:2021yar), a limit from PICO-60 PICO:2023uff assuming a contribution from the LMC (solid black, taken from Ref. Graham:2024syw), limits from Ref. Song:2021yar (gray), and a limit based on metastable tantalum Lehnert:2019tuw. Dashed red is as above. For reference, we also show our limit from XENON1T in dotted red.