28730 2506.21659 10.1007/JHEP04(2026)158 158 158 Ultralight Dilatonic Dark Matter Regular Article - Theoretical Physics 1 36 2026 4 20 2025 12 7 2026 2 25 2026 4 20 2026 4 20 National Science Foundation PHY2210361 National Science Foundation PHY-2309456 United States-Israel Binational Science Foundation 2016153 Israel Science Foundation 1302/19 Israel Science Foundation 1424/23 United States-Israel Binational Science Foundation 2018236 National Science Foundation - United States-Israel Binational Science Foundation 2021779 Deutsche Forschungsgemeinschaft EXC-2094-390783311 The Author(s) 2026 Open Access. This article is distributed under the terms of the Creative Commons Attribution License ( CC-BY 4.0 ), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. 13130 2026 2026 4 4 Abhishek Banerjee abanerj4@umd.edu Csaba Csáki csaki@cornell.edu Michael Geller mic.geller@gmail.com Zamir Heller-Algazi zamir.heller@gmail.com Ameen Ismail ameenismail@uchicago.edu https://ror.org/047s2c258 grid.164295.d 0000 0001 0941 7177 Maryland Center for Fundamental Physics University of Maryland College Park MD 20742 USA https://ror.org/05bnh6r87 grid.5386.8 0000 0004 1936 877X Department of Physics, LEPP Cornell University Ithaca NY 14853 USA https://ror.org/04mhzgx49 grid.12136.37 0000 0004 1937 0546 School of Physics and Astronomy Tel-Aviv University 69978 Tel-Aviv Israel https://ror.org/024mw5h28 grid.170205.1 0000 0004 1936 7822 Enrico Fermi Institute University of Chicago Chicago IL 60637 USA Abstract The dilaton, a pseudo-Nambu-Goldstone boson (pNGB) of broken scale invariance, is an appealing ultralight dark matter (DM) candidate. Its mass is protected by conformal invariance and it can be searched for in tabletop experiments. However, contrary to standard pNGBs of internal symmetries, the dilaton generically has a large non-derivative self-coupling, leading to radiative contributions to its mass of the order of its decay constant. Hence typical ultralight dilatons should also have sub-eV decay constants, which would incur significant deviations from standard DM behavior at structure formation times, in severe tension with observations. Therefore, a fine-tuning is required to generate a hierarchy between the mass and the decay constant. In this work, we consider whether supersymmetry (SUSY) can be used to protect this hierarchy from quantum corrections. To ensure an ultralight dilaton mass robust against realistic SUSY-breaking contributions, we must consider a novel dilaton stabilization mechanism. The observed DM abundance can be produced by the misalignment mechanism for dilaton masses ranging from 10−11 to 1 eV. Unfortunately, irreducible SUSY-breaking corrections due to gravity restrict the couplings between the dilaton and the Standard Model to be extremely small, beyond the reach of any current or proposed experiments. Our work demonstrates that constructing a consistent model of ultralight dilaton DM is quite involved. Keywords Compositeness Extra Dimensions Models for Dark Matter Supersymmetry ArXiv ePrint: 2506.21659