Physicists at the University of Massachusetts Amherst propose that a record-breaking neutrino detected in 2023 originated from the explosion of a primordial black hole carrying a 'dark charge.' The particle's energy, 100,000 times greater than that produced by the Large Hadron Collider, puzzled scientists since only the KM3NeT experiment recorded it. Their model, published in Physical Review Letters, could also hint at the nature of dark matter.
In 2023, the KM3NeT Collaboration detected a neutrino striking Earth with unprecedented energy, far exceeding any known cosmic acceleration process. The IceCube experiment, another major neutrino detector, recorded no similar event, raising questions about the phenomenon's rarity. Now, researchers including Andrea Thamm, Joaquim Iguaz Juan, and Michael Baker from UMass Amherst suggest the neutrino came from a quasi-extremal primordial black hole—a relic from the early universe—undergoing explosive evaporation via Hawking radiation. These black holes, proposed by Stephen Hawking in the 1970s, shrink and heat up as they emit particles, culminating in a burst detectable by current instruments, potentially once per decade, the team estimates. The researchers introduce a 'dark charge' in these black holes, akin to an electric force but involving a heavier 'dark electron.' 'We think that PBHs with a dark charge—what we call quasi-extremal PBHs—are the missing link,' said Iguaz Juan, a postdoctoral researcher at UMass Amherst. This model reconciles the KM3NeT observation with IceCube's silence and matches the predicted signal. Baker noted the theory's complexity makes it more realistic than simpler alternatives. 'What's so cool is to see that our model can explain this otherwise unexplainable phenomenon,' he said. Thamm added that such explosions could reveal new particles beyond the Standard Model, including dark matter candidates. The study suggests a population of these black holes could account for all missing dark matter, aligning with galaxy and cosmic microwave background observations. Baker described the neutrino as 'a new window on the universe,' potentially verifying Hawking radiation and primordial black holes.