- Physical Review Journals
All JournalsPhysics Magazine

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
  • Open Access

X-rays from inelastic dark matter freeze-in

Gordan Krnjaic1,2,*, David McKeen3,†, Riku Mizuta3,4,‡, Gopolang Mohlabeng5,3,§, David E. Morrissey3,∥, and Douglas Tuckler3,5,¶

  • 1Theory Division, Fermilab, Batavia, Illinois, USA
  • 2Department of Astronomy and Astrophysics, Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois, USA
  • 3TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
  • 4Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada
  • 5Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada

  • *Contact author: krnjaicg@fnal.gov
  • †Contact author: mckeen@triumf.ca
  • ‡Contact author: rmizuta@triumf.ca
  • §Contact author: gmohlabe@sfu.ca
  • ∥Contact author: dmorri@triumf.ca
  • Contact author: dtuckler@triumf.ca
PDF

Phys. Rev. D 112, 115039 – Published 24 December, 2025

DOI: https://doi.org/10.1103/99z7-kz4s

Abstract

We study inelastic dark matter produced via freeze-in through a light mediator with a mass splitting below the electron-positron threshold. In this regime, the heavier dark matter state is naturally long-lived compared to the age of the Universe and decays to the lighter state in association with photons. Given a light mediator, the dark matter abundance is directly related to the decay rate of the heavier dark matter. We show that observations of photons from the Galactic Center can effectively probe inelastic dark matter freeze-in with mediators at the 100 MeV scale and dark matter at the GeV scale.

View figure in article

Physics Subject Headings (PhySH)

Article Text

References (97)

  1. G. Jungman, M. Kamionkowski, and K. Griest, Phys. Rep. 267, 195 (1996).
  2. G. Bertone, D. Hooper, and J. Silk, Phys. Rep. 405, 279 (2005).
  3. T. Lin, Proc. Sci. 333 (2019) 009 [arXiv:1904.07915].
  4. N. Bozorgnia, J. Bramante, J. M. Cline, D. Curtin, D. McKeen, D. E. Morrissey, A. Ritz, S. Viel, A. C. Vincent, and Y. Zhang, Can. J. Phys. 103, 671 (2025).
  5. J. D. Bjorken, R. Essig, P. Schuster, and N. Toro, Phys. Rev. D 80, 075018 (2009).
  6. R. Essig et al., in Proceedings of the 2013 Community Summer Study on the Future of U.S. Particle Physics: Snowmass on the Mississippi, Minneapolis, MN, USA (2013).
  7. J. Alexander et al., arXiv:1608.08632.
  8. D. Tucker-Smith and N. Weiner, Phys. Rev. D 64, 043502 (2001).
  9. D. Tucker-Smith and N. Weiner, Phys. Rev. D 72, 063509 (2005).
  10. N. Arkani-Hamed, D. P. Finkbeiner, T. R. Slatyer, and N. Weiner, Phys. Rev. D 79, 015014 (2009).
  11. M. Pospelov and A. Ritz, Phys. Lett. B 671, 391 (2009).
  12. D. P. Finkbeiner, T. R. Slatyer, N. Weiner, and I. Yavin, J. Cosmol. Astropart. Phys. 09 (2009) 037.
  13. B. Batell, M. Pospelov, and A. Ritz, Phys. Rev. D 79, 115019 (2009).
  14. J. Kopp, T. Schwetz, and J. Zupan, J. Cosmol. Astropart. Phys. 02 (2010) 014.
  15. S. Chang, N. Weiner, and I. Yavin, Phys. Rev. D 82, 125011 (2010).
  16. D. E. Morrissey and A. P. Spray, J. High Energy Phys. 06 (2014) 083.
  17. E. Izaguirre, G. Krnjaic, and B. Shuve, Phys. Rev. D 93, 063523 (2016).
  18. E. Izaguirre, Y. Kahn, G. Krnjaic, and M. Moschella, Phys. Rev. D 96, 055007 (2017).
  19. A. Berlin, N. Blinov, G. Krnjaic, P. Schuster, and N. Toro, Phys. Rev. D 99, 075001 (2019).
  20. A. Berlin and F. Kling, Phys. Rev. D 99, 015021 (2019).
  21. M. Baryakhtar, A. Berlin, H. Liu, and N. Weiner, J. High Energy Phys. 06 (2022) 047.
  22. I. M. Bloch, A. Caputo, R. Essig, D. Redigolo, M. Sholapurkar, and T. Volansky, J. High Energy Phys. 01 (2021) 178.
  23. H. An and D. Yang, Phys. Lett. B 818, 136408 (2021).
  24. H.-J. He, Y.-C. Wang, and J. Zheng, Phys. Rev. D 104, 115033 (2021).
  25. M. Carrillo González and N. Toro, J. High Energy Phys. 04 (2022) 060.
  26. S. Heeba, T. Lin, and K. Schutz, Phys. Rev. D 108, 095016 (2023).
  27. N. Brahma, S. Heeba, and K. Schutz, Phys. Rev. D 109, 035006 (2024).
  28. R. A. Gustafson, G. Herrera, M. Mukhopadhyay, K. Murase, and I. M. Shoemaker, Phys. Rev. D 111, L121303 (2025).
  29. G. Mohlabeng, A. Mondol, and T. M. P. Tait, Phys. Rev. D 111, 056003 (2025).
  30. G. Krnjaic, D. Rocha, and I. R. Wang, Phys. Rev. Lett. 134, 161801 (2025).
  31. A. Berlin, J. W. Foster, D. Hooper, and G. Krnjaic, arXiv:2504.12372.
  32. I. V. Voronchikhin and D. V. Kirpichnikov, arXiv:2505.04290.
  33. D. Hooper, G. Krnjaic, D. Rocha, and S. Roy, arXiv:2507.22975.
  34. A. Berlin, G. Krnjaic, and E. Pinetti, Phys. Rev. D 110, 035015 (2024).
  35. G. Mohlabeng, Phys. Rev. D 99, 115001 (2019).
  36. A. M. Abdullahi, M. Hostert, D. Massaro, and S. Pascoli, Phys. Rev. D 108, 015032 (2023).
  37. J. McDonald, Phys. Rev. Lett. 88, 091304 (2002).
  38. L. J. Hall, K. Jedamzik, J. March-Russell, and S. M. West, J. High Energy Phys. 03 (2010) 080.
  39. L. B. Okun, Sov. Phys. JETP 56, 502 (1982).
  40. P. Galison and A. Manohar, Phys. Lett. 136B, 279 (1984).
  41. B. Holdom, Phys. Lett. 166B, 196 (1986).
  42. H. Ruegg and M. Ruiz-Altaba, Int. J. Mod. Phys. A 19, 3265 (2004).
  43. B. Batell, N. Lange, D. McKeen, M. Pospelov, and A. Ritz, Phys. Rev. D 95, 075003 (2017).
  44. X. Chu, T. Hambye, and M. H. G. Tytgat, J. Cosmol. Astropart. Phys. 05 (2012) 034.
  45. P. Gondolo and G. Gelmini, Nucl. Phys. B360, 145 (1991).
  46. N. Aghanim et al. (Planck Collaboration), Astron. Astrophys. 641, A6 (2020); 652, C4(E) (2021).
  47. P. Ilten, Y. Soreq, M. Williams, and W. Xue, J. High Energy Phys. 06 (2018) 004.
  48. A. Fradette, M. Pospelov, J. Pradler, and A. Ritz, Phys. Rev. D 90, 035022 (2014).
  49. A. Belyaev, N. D. Christensen, and A. Pukhov, Comput. Phys. Commun. 184, 1729 (2013).
  50. G. Bélanger, F. Boudjema, A. Goudelis, A. Pukhov, and B. Zaldivar, Comput. Phys. Commun. 231, 173 (2018).
  51. G. Krnjaic, J. High Energy Phys. 10 (2018) 136.
  52. M. Pospelov, A. Ritz, and M. B. Voloshin, Phys. Rev. D 78, 115012 (2008).
  53. S. D. McDermott, H. H. Patel, and H. Ramani, Phys. Rev. D 97, 073005 (2018).
  54. T. Linden, T. T. Q. Nguyen, and T. M. P. Tait, Phys. Rev. D 112, 023026 (2025).
  55. J. Berteaud, F. Calore, J. Iguaz, P. D. Serpico, and T. Siegert, Phys. Rev. D 106, 023030 (2022).
  56. F. Calore, A. Dekker, P. D. Serpico, and T. Siegert, Mon. Not. R. Astron. Soc. 520, 4167 (2023); 538, 132(E) (2025).
  57. T. Siegert, J. Berteaud, F. Calore, P. D. Serpico, and C. Weinberger, Astron. Astrophys. 660, A130 (2022).
  58. J. F. Navarro, C. S. Frenk, and S. D. M. White, Astrophys. J. 462, 563 (1996).
  59. J. F. Navarro, C. S. Frenk, and S. D. M. White, Astrophys. J. 490, 493 (1997).
  60. M. Cautun, A. Benitez-Llambay, A. J. Deason, C. S. Frenk, A. Fattahi, F. A. Gómez, R. J. J. Grand, K. A. Oman, J. F. Navarro, and C. M. Simpson, Mon. Not. R. Astron. Soc. 494, 4291 (2020).
  61. C. Winkler et al., Astron. Astrophys. 411, L1 (2003).
  62. G. Vedrenne et al., Astron. Astrophys. 411, L63 (2003).
  63. G. Vianello, R. J. Lauer, P. Younk, L. Tibaldo, J. M. Burgess, H. Ayala, P. Harding, M. Hui, N. Omodei, and H. Zhou, arXiv:1507.08343.
  64. D. Foreman-Mackey, D. W. Hogg, D. Lang, and J. Goodman, Publ. Astron. Soc. Pac. 125, 306 (2013).
  65. G. Bernardi et al., Phys. Lett. 166B, 479 (1986).
  66. A. Konaka et al., Phys. Rev. Lett. 57, 659 (1986).
  67. E. M. Riordan et al., Phys. Rev. Lett. 59, 755 (1987).
  68. J. D. Bjorken, S. Ecklund, W. R. Nelson, A. Abashian, C. Church, B. Lu, L. W. Mo, T. A. Nunamaker, and P. Rassmann, Phys. Rev. D 38, 3375 (1988).
  69. A. Bross, M. Crisler, S. H. Pordes, J. Volk, S. Errede, and J. Wrbanek, Phys. Rev. Lett. 67, 2942 (1991).
  70. M. Davier and H. Nguyen Ngoc, Phys. Lett. B 229, 150 (1989).
  71. J. Blumlein et al., Z. Phys. C 51, 341 (1991).
  72. J. Blumlein et al., Int. J. Mod. Phys. A 07, 3835 (1992).
  73. F. Bergsma et al. (CHARM Collaboration), Phys. Lett. 157B, 458 (1985).
  74. P. Astier et al. (NOMAD Collaboration), Phys. Lett. B 506, 27 (2001).
  75. J. R. Batley et al. (NA48/2 Collaboration), Phys. Lett. B 746, 178 (2015).
  76. J. P. Lees et al. (BABAR Collaboration), Phys. Rev. Lett. 113, 201801 (2014).
  77. F. Archilli et al. (KLOE-2 Collaboration), Phys. Lett. B 706, 251 (2012).
  78. A. Anastasi et al. (KLOE-2 Collaboration), Phys. Lett. B 757, 356 (2016).
  79. R. Aaij et al. (LHCb Collaboration), Phys. Rev. Lett. 120, 061801 (2018).
  80. J. P. Lees et al. (BABAR Collaboration), Phys. Rev. Lett. 125, 181801 (2020).
  81. D. Biswas et al. (Belle Collaboration), Phys. Rev. D 109, 032002 (2024).
  82. H. Liu and T. R. Slatyer, Phys. Rev. D 98, 023501 (2018).
  83. A. Mitridate and A. Podo, J. Cosmol. Astropart. Phys. 05 (2018) 069.
  84. S. Clark, B. Dutta, Y. Gao, Y.-Z. Ma, and L. E. Strigari, Phys. Rev. D 98, 043006 (2018).
  85. Y. Bai and R. J. Hill, Phys. Rev. D 82, 111701 (2010).
  86. D. McKeen, R. Mizuta, D. E. Morrissey, and M. Shamma, Phys. Rev. D 111, 015044 (2025).
  87. J. Bagnasco, M. Dine, and S. D. Thomas, Phys. Lett. B 320, 99 (1994).
  88. M. Pospelov and T. ter Veldhuis, Phys. Lett. B 480, 181 (2000).
  89. K. Sigurdson, M. Doran, A. Kurylov, R. R. Caldwell, and M. Kamionkowski, Phys. Rev. D 70, 083501 (2004); 73, 089903(E) (2006).
  90. T. Banks, J.-F. Fortin, and S. Thomas, arXiv:1007.5515.
  91. P. W. Graham, D. E. Kaplan, S. Rajendran, and M. T. Walters, Phys. Dark Universe 1, 32 (2012).
  92. X. Chu, J. Pradler, and L. Semmelrock, Phys. Rev. D 99, 015040 (2019).
  93. R. Caputo et al. (AMEGO Collaboration), arXiv:1907.07558.
  94. T. Aramaki et al., arXiv:2203.06894.
  95. Y. Watanabe, S. Matsumoto, C. M. Karwin, T. Melia, M. Negro, T. Siegert, Y. Watanabe, H. Yoneda, and T. Takahashi, J. High Energy Phys. 09 (2025) 078.
  96. J. Cooley et al., arXiv:2209.07426.
  97. T. Siegert, Galactic diffuse emission spectrum between 0.5 and 8.0 MeV and between 30 keV and 8 MeV for the search of PBH and light dark matter [Data set], Zenodo (2021), 10.5281/zenodo.5618447.

Outline

Information

Phys. Rev. D 112, 115039– Published 24 December, 2025
  • Received 10 October 2025
  • Accepted 26 November 2025
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