- Physical Review Journals
All JournalsPhysics Magazine
Access Provided by Xinjiang University

Physical Review D

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Featured in Physics
  • Editors' Suggestion
  • Open Access
  • Access by Xinjiang University

Electric accumulation of millicharged particles

Asher Berlin1,2,*, Zachary Bogorad1,2,†, Peter W. Graham3,4,‡, and Harikrishnan Ramani5,§

  • *Contact author: aberlin@fnal.gov
  • †Contact author: zbogorad@fnal.gov
  • ‡Contact author: pwgraham@stanford.edu
  • §Contact author: hramani@udel.edu
PDF

Phys. Rev. D 114, 015016 – Published 10 July, 2026

DOI: https://doi.org/10.1103/gj7k-9wkr

Abstract

A terrestrial population of millicharged particles that interact significantly with normal matter can arise if they make up a dark matter subcomponent or if they are light enough to be produced in cosmic-ray air showers. Such particles thermalize to terrestrial temperatures through repeated scatters with normal matter in Earth’s environment. We show that a simple electrified shell (for example, a Van de Graaff generator) functions as an efficient accumulator of such room-temperature millicharged particles, parametrically enhancing their local density by as much as 12 orders of magnitude. This can be used to boost the sensitivity of any detector housed in the shell’s interior, such as ion traps and tests of Coulomb’s law. In a companion paper, we apply this specifically to Cavendish tests of Coulomb’s law, and we show that a well-established setup can probe a large region of unexplored parameter space, with sensitivity to the irreducible density of millicharged particles generated from cosmic rays that outperforms future accelerator searches for sub-GeV masses.

View figure in article

Physics Subject Headings (PhySH)

Focus

A Simple Search for Tiny Charges

Published 10 July, 2026

Decades-old experiments have now been enlisted to set new bounds on the properties of a hypothetical particle that bears a tiny fraction of the electron’s charge.

See more in Physics

See Also

Cavendish Tests of Millicharged Particles

Asher Berlin, Zachary Bogorad, Peter W. Graham, and Harikrishnan Ramani
Phys. Rev. Lett. 137, 021804 (2026)

Article Text

References (64)

  1. G. Aad et al. (ATLAS Collaboration), The quest to discover supersymmetry at the ATLAS experiment, Phys. Rep. 1116, 261 (2025).
  2. R. Essig et al., Working group report: New light weakly coupled particles, in Snowmass 2013: Snowmass on the Mississippi (2013), arXiv:1311.0029.
  3. M. Battaglieri et al., US Cosmic Visions: New ideas in dark matter 2017: Community report, in U.S. Cosmic Visions: New Ideas in Dark Matter (2017), arXiv:1707.04591.
  4. P. Agrawal et al., Feebly-interacting particles: FIPs 2020 workshop report, Eur. Phys. J. C 81, 1015 (2021).
  5. B. Holdom, Two U(1)’s and Epsilon charge shifts, Phys. Lett. 166B, 196 (1986).
  6. E. Zavattini et al. (PVLAS Collaboration), Experimental observation of optical rotation generated in vacuum by a magnetic field, Phys. Rev. Lett. 96, 110406 (2006); 99, 129901(E) (2007).
  7. J. Chang et al., An excess of cosmic ray electrons at energies of 300–800 GeV, Nature (London) 456, 362 (2008).
  8. O. Adriani et al. (PAMELA Collaboration), An anomalous positron abundance in cosmic rays with energies 1.5–100 GeV, Nature (London) 458, 607 (2009).
  9. R. Barkana, Possible interaction between baryons and dark-matter particles revealed by the first stars, Nature (London) 555, 71 (2018).
  10. A. Berlin, D. Hooper, G. Krnjaic, and S. D. McDermott, Severely constraining dark matter interpretations of the 21-cm anomaly, Phys. Rev. Lett. 121, 011102 (2018).
  11. R. Barkana, N. J. Outmezguine, D. Redigolo, and T. Volansky, Strong constraints on light dark matter interpretation of the EDGES signal, Phys. Rev. D 98, 103005 (2018).
  12. H. Liu, N. J. Outmezguine, D. Redigolo, and T. Volansky, Reviving millicharged dark matter for 21-cm cosmology, Phys. Rev. D 100, 123011 (2019).
  13. M. Pospelov and H. Ramani, Earth-bound millicharge relics, Phys. Rev. D 103, 115031 (2021).
  14. A. Berlin, H. Liu, M. Pospelov, and H. Ramani, Terrestrial density of strongly-coupled relics, Phys. Rev. D 109, 075027 (2024).
  15. T. Gao and M. Pospelov, Constraints on millicharged particles from nuclear gamma-decays, arXiv:2507.17955.
  16. R. Plestid, V. Takhistov, Y.-D. Tsai, T. Bringmann, A. Kusenko, and M. Pospelov, New constraints on millicharged particles from cosmic-ray production, Phys. Rev. D 102, 115032 (2020).
  17. D. Carney, H. Häffner, D. C. Moore, and J. M. Taylor, Trapped electrons and ions as particle detectors, Phys. Rev. Lett. 127, 061804 (2021).
  18. D. Budker, P. W. Graham, H. Ramani, F. Schmidt-Kaler, C. Smorra, and S. Ulmer, Millicharged dark matter detection with ion traps, PRX Quantum 3, 010330 (2022).
  19. G. Afek, F. Monteiro, J. Wang, B. Siegel, S. Ghosh, and D. C. Moore, Limits on the abundance of millicharged particles bound to matter, Phys. Rev. D 104, 012004 (2021).
  20. A. Berlin, R. Tito D’Agnolo, S. A. R. Ellis, and J. I. Radkovski, Signals of millicharged dark matter in light-shining-through-wall experiments, J. High Energy Phys. 08 (2023) 017.
  21. A. Berlin, Z. Bogorad, P. W. Graham, and H. Ramani, companion paper, Cavendish tests of millicharged particles, Phys. Rev. Lett. 137, 021804 (2026).
  22. A. Berlin, R. T. D’Agnolo, S. A. R. Ellis, P. Schuster, and N. Toro, Directly deflecting particle dark matter, Phys. Rev. Lett. 124, 011801 (2020).
  23. N. Arkani-Hamed and N. Weiner, LHC signals for a SuperUnified theory of dark matter, J. High Energy Phys. 12 (2008) 104.
  24. T. Gherghetta, J. Kersten, K. Olive, and M. Pospelov, Evaluating the price of tiny kinetic mixing, Phys. Rev. D 100, 095001 (2019).
  25. X.-G. Wen and E. Witten, Electric and magnetic charges in superstring models, Nucl. Phys. B261, 651 (1985).
  26. M. Gell-Mann, P. Ramond, and R. Slansky, Color embeddings, charge assignments, and proton stability in unified gauge theories, Rev. Mod. Phys. 50, 721 (1978).
  27. G. G. Athanasiu, J. J. Atick, M. Dine, and W. Fischler, Remarks on Wilson lines, modular invariance and possible string relics in Calabi-Yau compactifications, Phys. Lett. B 214, 55 (1988).
  28. P. Langacker and G. Steigman, Requiem for an FCHAMP? fractionally charged, massive particle, Phys. Rev. D 84, 065040 (2011).
  29. C. A. Argüelles Delgado, K. J. Kelly, and V. Muñoz Albornoz, Millicharged particles from the heavens: Single- and multiple-scattering signatures, J. High Energy Phys. 11 (2021) 099.
  30. R. Harnik, R. Plestid, M. Pospelov, and H. Ramani, Millicharged cosmic rays and low recoil detectors, Phys. Rev. D 103, 075029 (2021).
  31. S. Davidson, S. Hannestad, and G. Raffelt, Updated bounds on millicharged particles, J. High Energy Phys. 05 (2000) 003.
  32. A. Haas, C. S. Hill, E. Izaguirre, and I. Yavin, Looking for milli-charged particles with a new experiment at the LHC, Phys. Lett. B 746, 117 (2015).
  33. A. A. Prinz et al., Search for millicharged particles at SLAC, Phys. Rev. Lett. 81, 1175 (1998).
  34. R. Acciarri et al. (ArgoNeuT Collaboration), Improved limits on millicharged particles using the ArgoNeuT experiment at Fermilab, Phys. Rev. Lett. 124, 131801 (2020).
  35. A. Ball et al. (milliQan Collaboration), Sensitivity to millicharged particles in future proton-proton collisions at the LHC with the milliQan detector, Phys. Rev. D 104, 032002 (2021).
  36. R. Alemany Fernández et al. (PBC Collaboration), Summary report of the physics beyond colliders study at CERN, arXiv:2505.00947.
  37. A. Hayrapetyan et al. (CMS Collaboration), Search for fractionally charged particles in proton-proton collisions at s=13  TeV, Phys. Rev. Lett. 134, 131802 (2025).
  38. S. Alcott et al., Search for millicharged particles in proton-proton collisions at s=13.6  TeV, Phys. Rev. Lett. 135, 121802 (2025).
  39. J. H. Chang, R. Essig, and S. D. McDermott, Supernova 1987A constraints on sub-GeV dark sectors, millicharged particles, the QCD axion, and an axion-like particle, J. High Energy Phys. 09 (2018) 051.
  40. M. Marinelli and G. Morpurgo, Searches of fractionally charged particles in matter with the magnetic levitation technique, Phys. Rep. 85, 161 (1982).
  41. P. C. Kim, E. R. Lee, I. T. Lee, M. L. Perl, V. Halyo, and D. Loomba, Search for fractional-charge particles in meteoritic material, Phys. Rev. Lett. 99, 161804 (2007).
  42. D. C. Moore, A. D. Rider, and G. Gratta, Search for millicharged particles using optically levitated microspheres, Phys. Rev. Lett. 113, 251801 (2014).
  43. S. L. Dubovsky, D. S. Gorbunov, and G. I. Rubtsov, Narrowing the window for millicharged particles by CMB anisotropy, JETP Lett. 79, 1 (2004).
  44. R. de Putter, O. Doré, J. Gleyzes, D. Green, and J. Meyers, Dark matter interactions, helium, and the cosmic microwave background, Phys. Rev. Lett. 122, 041301 (2019).
  45. E. D. Kovetz, V. Poulin, V. Gluscevic, K. K. Boddy, R. Barkana, and M. Kamionkowski, Tighter limits on dark matter explanations of the anomalous EDGES 21 cm signal, Phys. Rev. D 98, 103529 (2018).
  46. M. A. Buen-Abad, R. Essig, D. McKeen, and Y.-M. Zhong, Cosmological constraints on dark matter interactions with ordinary matter, Phys. Rep. 961, 1 (2022).
  47. K. Griest and M. Kamionkowski, Unitarity limits on the mass and radius of dark matter particles, Phys. Rev. Lett. 64, 615 (1990).
  48. A. Berlin, H. Liu, M. Pospelov, and H. Ramani, Low-energy signals from the formation of dark-matter–nucleus bound states, Phys. Rev. D 105, 095028 (2022).
  49. X. Gan and Y.-D. Tsai, Cosmic millicharge background and reheating probes, J. High Energy Phys. 07 (2023) 094.
  50. K. K. Boddy, K. Freese, G. Montefalcone, and B. Shams Es Haghi, Minimal dark matter freeze-in with low reheating temperatures and implications for direct detection, Phys. Rev. D 111, 063537 (2025).
  51. N. Bernal, C. S. Fong, and O. Zapata, Probing low-reheating scenarios with minimal freeze-in dark matter, J. High Energy Phys. 02 (2024) 161.
  52. T. Emken, R. Essig, C. Kouvaris, and M. Sholapurkar, Direct detection of strongly interacting sub-GeV dark matter via electron recoils, J. Cosmol. Astropart. Phys. 09 (2019) 070.
  53. D. Dunsky, L. J. Hall, and K. Harigaya, CHAMP cosmic rays, J. Cosmol. Astropart. Phys. 07 (2018) 015.
  54. M. Du, R. Fang, and Z. Liu, Millicharged particles from proton bremsstrahlung in the atmosphere, J. High Energy Phys. 08 (2022) 174.
  55. H. Wu, E. Hardy, and N. Song, Searching for heavy millicharged particles from the atmosphere, Phys. Rev. D 110, 115037 (2024).
  56. R. G. Harrison, The global atmospheric electrical circuit and climate, Surv. Geophys. 25, 441 (2004).
  57. S. Tulin, H.-B. Yu, and K. M. Zurek, Beyond collisionless dark matter: Particle physics dynamics for dark matter halo structure, Phys. Rev. D 87, 115007 (2013).
  58. B. Colquhoun, S. Heeba, F. Kahlhoefer, L. Sagunski, and S. Tulin, Semiclassical regime for dark matter self-interactions, Phys. Rev. D 103, 035006 (2021).
  59. B. M. of Science, Giant Van de Graaff, https://spark.iop.org/giant-van-de-graaff.
  60. R. Lasenby, Long range dark matter self-interactions and plasma instabilities, J. Cosmol. Astropart. Phys. 11 (2020) 034.
  61. W. DeRocco and P. Giffin, Dark plasmas in the nonlinear regime: Constraints from particle-in-cell simulations, Phys. Rev. D 111, 095031 (2025).
  62. A. Berlin and K. Schutz, Helioscope for gravitationally bound millicharged particles, Phys. Rev. D 105, 095012 (2022).
  63. A. Berlin, S. Rajendran, H. Ramani, and E. H. Tanin, Direct deflection of millicharged radiation, J. High Energy Phys. 04 (2024) 198.
  64. S. J. Plimpton and W. E. Lawton, A very accurate test of Coulomb’s law of force between charges, Phys. Rev. 50, 1066 (1936).

Outline

Information

Phys. Rev. D 114, 015016– Published 10 July, 2026
  • Received 17 November 2025
  • Accepted 19 February 2026
Crossmark - Check for updates button
Creative Commons Logo

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation