In late 2025, physicists proposed a new and surprising candidate for dark matter: superheavy charged gravitinos. This new particle is radically different from the leading candidates that have been pursued for decades.  

Why Is This Candidate Surprising?

For years, the most popular dark matter candidates were electrically neutral particles like axions and WIMPs (Weakly Interacting Massive Particles). The name “dark matter” itself implies it doesn’t interact with light, which is carried by charged particles.  

However, a new theory unifying particle physics and gravity suggests the existence of superheavy gravitinos that have an electrical charge. These particles are not expected to be found on Earth, as they’re thought to be extremely rare. Despite their charge, they would remain “dark” because they are too massive and scarce to interact with ordinary matter in a detectable way.  

How Would This Explain Dark Matter?

• Non-interaction with Light: While charged, their extreme mass and limited abundance mean they wouldn’t interact with light as a normal charged particle would, thus making them undetectable through traditional means.

• Gravitational Effects: Their immense mass could account for the gravitational effects observed in galaxies and galaxy clusters that are attributed to dark matter.

The hunt for this new particle is now underway, with new detectors like the JUNO detector being specifically prepared to search for them. If discovered, this would be a monumental breakthrough, not only solving the dark matter mystery but also providing the first direct evidence of physics near the Planck scale, the theoretical frontier where gravity and quantum mechanics are unified.  

Dark matter

Dark Matter remains one of the biggest mysteries in fundamental physics. Many theoretical proposals (axions, WIMPs) and 40 years of extensive experimental search failed to provide any explanation of the nature of Dark Matter. Several years ago, in a theory unifying particle physics and gravity, new, radically different Dark Matter candidates were proposed, superheavy charged gravitinos. Very recent paper in Physical Review Research by scientists from the University of Warsaw and Max Planck Institute for Gravitational Physics, shows how new underground detectors, in particular JUNO detector starting soon to take data, even though designed for neutrino physics, are also extremely well suited to eventually detect charged Dark Matter gravitinos. The simulations combining two fields, elementary particle physics and very advanced quantum chemistry, show that the gravitino signal in the detector should be unique and unambiguous.

In 1981 Murray Gell-Mann, Nobel Prize laureate for the introduction of quarks as fundamental constituents of matter, noticed the intriguing fact that the particles of the Standard Model, quarks and leptons, are contained in a theory formulated purely mathematically 2 years earlier, N=8 supergravity, distinguished by its maximal symmetry. N=8 supergravity contains, besides Standard Model matter particles of spin 1/2, also gravitational part: graviton (of spin 2) and 8 gravitinos of spin 3/2. If the Standard Model is indeed related to N=8 supergravity, the relation may possibly point to a path to solve the most difficult problem of fundamental theoretical physics — unifying gravity with particle physics. N=8 supergravity in the spin ½ sector contains exactly 6 quarks (u,d,c,s,t,b) and 6 leptons (electron, muon, taon and neutrinos) and forbids the presence of any other matter particles. After 40 years of intensive accelerator research failing to discover any new matter particles the N=8 supergravity matter content is not only consistent with our knowledge but remains the only known theoretical explanation of the number of quarks and leptons in the Standard Model! However, direct connection of N=8 supergravity with the Standard Model had several drawbacks, the main one being that the electric charges of quarks and leptons were shifted by ±1/6 with respect to the known values, for example electron had charge -5/6 instead of -1. Several years ago Krzysztof Meissner from the Faculty of Physics at the University of Warsaw, Poland and Hermann Nicolai from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI), Potsdam, Germany returned to the Gell-Mann’s idea and were able to go beyond N=8 supergravity and modify the original proposal obtaining correct electric charges of the Standard Model matter particles. The modification is very far reaching pointing to an infinite symmetry K(E10), little known mathematically and replacing the usual symmetries of the Standard Model.

One of the surprising outcomes of the modification, described in papers in Physical Review Letters and Physical Review, is the fact that the gravitinos, presumably of the extremely large mass close to the Planck scale i.e. billion billion proton masses, are electrically charged: 6 of them have charge ±1/3 and 2 of them ±2/3. The gravitinos, even though they are extremally massive, cannot decay since there are no particles they could decay into. Meissner and Nicolai proposed therefore that 2 gravitinos of charge ±2/3 (the other 6 have much lower abundance) could be Dark Matter particles of very different kind than anything proposed so far. Namely, the widely advertized usual candidates, either extremely light like axions or intermediate (proton) mass like WIMPs (weakly interacting massive particles) were electrically neutral, in compatibility with the name ‘Dark Matter’. However, after more than 40 years of intensive search by many different methods and devices no new particles beyond the Standard Model were detected.

However, gravitinos present a new alternative. Even though they are electrically charged, they can be Dark Matter candidates because being so massive they are extremely rare and therefore observationally ‘do not shine on the sky’ and avoid the very tight constraints on the charge of Dark Matter constituents. Moreover, the electric charge of gravitinos suggested a completely different way of trying to prove their existence. The original paper in 2024 in Eur. Phys. J. by Meissner and Nicolai pointed out that neutrino detectors, based on scintillators different from water, could be suitable for the detection of Dark Matter gravitinos. However, the search is made enormously difficult by their extreme rarity (presumably only one gravitino per 10,000 km3 in the Solar System), which is why there is no prospect of detection with currently available detectors. However, new giant, oil or liquid argon underground detectors, are either constructed or planned and realistic possibilities for searching for these particles are now opening up.

Superheavy charged gravitons what can it change in study of dark matter

The proposed existence of superheavy charged gravitinos could fundamentally change the study of dark matter by challenging the long-held assumption that dark matter particles must be electrically neutral.  

Why the Shift is Significant

For decades, the search for dark matter has been dominated by theories involving neutral particles like WIMPs (Weakly Interacting Massive Particles) and axions. The name “dark matter” itself implies that it does not interact with light, which is an electromagnetic phenomenon. However, recent theories unifying gravity and particle physics have suggested a new candidate:  

• Radically Different Properties: These gravitinos are theorized to be extremely massive (on the order of the Planck mass, far heavier than a proton) and, surprisingly, carry a fractional electric charge (e.g., ±2/3).  

• “Dark” Despite Being Charged: They can still be considered a dark matter candidate because their extreme mass means they would be incredibly rare. This scarcity would prevent them from interacting frequently with ordinary matter and light, making them “dark” from an observational standpoint.  

• A New Search Paradigm: Instead of searching for non-interacting, neutral particles, physicists can now hunt for a unique signature: a faint, glowing trail of light created as a charged gravitino passes through a liquid scintillator detector. This distinct “glowing filament” signal would be unlike anything produced by known particles like neutrinos or cosmic rays, making it impossible to confuse.  

The potential discovery of this particle would not only solve the dark matter mystery but also provide the first experimental evidence of physics at the Planck scale, bringing us a step closer to a unified theory of all fundamental forces.

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