Physicists Link High-Energy Neutrino to Exploding Primordial Black Hole, Hinting at New Physics
A recently detected ultra-high-energy neutrino, captured by the KM3NeT experiment, may be the first observational evidence of an exploding primordial black hole, according to physicists at the University of Massachusetts Amherst. The findings, published in in Physical Review Letters, suggest the existence of these theorized objects and potentially unlock new understanding of dark matter and particles beyond the Standard Model.
Black holes, formed from the collapse of massive stars, are well-established phenomena. However, primordial black holes are a different concept, proposed by Stephen Hawking in 1970. These hypothetical black holes wouldn’t originate from stellar collapse but from density fluctuations in the very early universe, shortly after the Big Bang. Unlike their stellar counterparts, primordial black holes could be significantly smaller.
Hawking also theorized that black holes aren’t entirely “black,” but emit particles through a process now known as Hawking radiation. The rate of this emission, and therefore the temperature of the black hole, is inversely proportional to its mass. “The lighter a black hole is, the hotter it should be and the more particles it will emit,” explains Dr. Andrea Thamm, a physicist at the University of Massachusetts Amherst. As a primordial black hole evaporates, it becomes lighter and hotter, accelerating the emission of radiation until a final, explosive burst.
Detecting this Hawking radiation is a major goal for physicists. The KM3NeT experiment’s detection of a neutrino with an energy around 220 PeV (Peta electronvolts) in presented a tantalizing possibility. “If such an explosion were to be observed, it would give us a definitive catalog of all the subatomic particles in existence, including the ones we have observed, such as electrons, quarks and Higgs bosons, the ones that we have only hypothesized, like dark matter particles, as well as everything else that is, so far, entirely unknown to science,” says Dr. Thamm.
However, the detection presented a puzzle. The IceCube Neutrino Observatory, another major neutrino detector, failed to register the event, and has never detected a neutrino with even one-hundredth of the energy observed by KM3NeT. If primordial black holes were common and frequently exploding, a more widespread detection of high-energy neutrinos would be expected.
To address this discrepancy, the UMass Amherst team proposed a model involving a “dark charge” – or quasi-extremal primordial black holes. “The dark charge is essentially a copy of the usual electric force as we know it, but which includes a very heavy, hypothesized version of the electron — a dark electron,” explains Dr. Joaquim Iguaz Juan, a physicist at the University of Massachusetts Amherst. This dark charge alters the behavior of the black hole, potentially explaining the rarity of the observed event.
Dr. Michael Baker, also from UMass Amherst, notes that while simpler models of primordial black holes exist, their “dark-charge model is more complex, which means it may provide a more accurate model of reality.” He adds, “What’s so cool is to see that our model can explain this otherwise unexplainable phenomenon.”
The implications extend beyond confirming the existence of primordial black holes. The team believes their model could also provide a solution to the mystery of dark matter. Observations of galaxies and the Cosmic Microwave Background indicate the presence of dark matter, a substance that doesn’t interact with light. “If our hypothesized dark charge is true, then we believe there could be a significant population of primordial black holes, which would be consistent with other astrophysical observations, and account for all the missing dark matter in the Universe,” says Dr. Iguaz Juan.
The detection of the high-energy neutrino, according to Dr. Baker, “gave us a new window on the Universe.” He suggests that the research is now poised to potentially “experimentally verify Hawking radiation, obtaining evidence for both primordial black holes and new particles beyond the Standard Model, and explaining the mystery of dark matter.”
Further research and observations will be crucial to validate the dark-charge model and confirm the existence of primordial black holes. The team’s work represents a significant step towards understanding these elusive objects and the fundamental nature of the universe.
