Traditionally, dark matter candidates have been neutral, such as axions or weakly interacting massive particles (WIMPs). Yet none have been found. In contrast, gravitinos are predicted to be extraordinarily heavy, close to the Planck mass-around a billion billion times heavier than a proton-and, unusually, electrically charged. Although extremely rare, their sheer mass and stability make them viable dark matter candidates.
The concept stems from work originally inspired by Nobel laureate Murray Gell-Mann's insights on N=8 supergravity in the 1980s. Building on this, Krzysztof Meissner of the University of Warsaw and Hermann Nicolai of the Max Planck Institute refined the theory to align correctly with the Standard Model's known electric charges. Their modification pointed toward an infinite symmetry called K(E10), a framework that unexpectedly allowed for charged, long-lived gravitinos.
Six of the gravitinos would carry charges of +/-1/3, while two others would carry +/-2/3. The researchers argue that the latter pair, despite their immense mass, could constitute dark matter. Unlike conventional candidates, they might leave visible traces in large-scale neutrino detectors.
One such facility, the Jiangmen Underground Neutrino Observatory (JUNO) in China, is nearly ready to begin operations. Containing 20,000 tons of specialized liquid scintillator in a 40-meter sphere surrounded by more than 17,000 photomultipliers, JUNO was designed to study antineutrinos. However, its size and sensitivity also make it an excellent laboratory for detecting hypothetical gravitinos.
In their recent study, Meissner, Nicolai, Adrianna Kruk, and Michal Lesiuk combined theoretical particle physics with advanced quantum chemistry simulations to predict how gravitinos would interact inside JUNO's detector medium. The simulations accounted for numerous backgrounds-such as radioactive decay, photon absorption, and sensor noise-and found that a passing gravitino would leave a unique and unmistakable signature.
The team also emphasized the relevance for future detectors, including the Deep Underground Neutrino Experiment (DUNE) in the United States. If confirmed, the detection of gravitinos would mark the first experimental evidence of physics at the Planck scale, offering a potential pathway to unifying gravity with the Standard Model of particle physics.
Research Report:Signatures of supermassive charged gravitinos in liquid scintillator detectors
Related Links
University of Warsaw, Faculty of Physics
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