Humanity has labored itself right into a place the place we will detect a single high-energy particle from house and surprise the place in Nature it got here from. Billions of individuals possible do not care in any respect about such issues, however for these which can be naturally curious and are lucky sufficient to have the time to indulge their curiosity, a particularly energetic neutrino detected in 2023 was a exceptional occasion, and will even transform an historic one.
The Cubic Kilometre Neutrino Telescope, or KM3NeT, detected the extraordinarily energetic neutrino from its location on the underside of the Mediterranean Sea. AT 220 PeV, the particle was extra energetic than something produced in our strongest particle accelerator, the Giant Hadron Collider.
The Solar emits an unceasing stream of neutrinos referred to as photo voltaic neutrinos, however they are not very energetic. KM3-230213A, the title given to the 100 PeV neutrino, dwarfs the Solar’s neutrino output. That occasion was one billion instances extra energetic than your common photo voltaic neutrino.
There’s not an extended listing of astrophysical phenomena that would probably juice a neutrino like this. In reality, no presently well-understood object or course of can account for it.
When Nature sends us a message like this, one thing essential is encoded in it. It is as much as physicists to find out what it means. And within the intervening couple of years since its detection, totally different physicists have generated totally different explanations for it.
Explanations embody pulsar-powered optical transients, gamma-ray bursts, dark matter decay, lively galactic nuclei, black hole mergers, and a number of other explanations primarily based on various kinds of primordial black holes.
New analysis in Bodily Overview Letters has one other rationalization, and this one is predicated on primordial black holes, too. The analysis is titled “Explaining the PeV neutrino fluxes at KM3NeT and IceCube with quasiextremal primordial black holes,” and the lead creator is Michael Baker. Baker is an assistant professor of physics on the College of Massachusetts, Amherst.
“The KM3NeT experiment has lately noticed a neutrino with an vitality round 100 PeV, and IceCube has detected 5 neutrinos with energies above 1 PeV,” the authors write. “Whereas there are not any identified astrophysical sources, exploding primordial black holes may have produced these high-energy neutrinos.”
Primordial black holes are completely hypothetical. Principle says that in contrast to stellar-mass black holes, PBH did not want a large star to blow up and collapse with a view to kind. As a substitute, they shaped instantly after the Large Bang from dense clumps of sub-atomic matter, when the physics underlying the Universe had been a lot totally different.
*There’s plenty of questions on primordial black holes. It is potential that they might’ve helped the very first stars kind, in the event that they exist. Picture Credit score: NASA and G. Bacon/STSCI*
PBH are a lot smaller than stellar mass black holes, however they’re nonetheless incrediby dense and the previous adage that “nothing, not even mild, can escape a black gap” nonetheless applies to them. However PBH share one thing else with their cousins: Hawking Radiation.
Stephen Hawking developed the concept for Hawking Radiation (HR). Mainly, it says that over time HR reduces a black gap’s mass, and that ultimately a black gap will evaporate, until it accretes extra matter. Sadly, HR is often so weak that it is properly beneath the detection threshold of even our most succesful telescopes.
This HR-inspired evaporation might be behind KM3-230213A. Whereas it is undetectable round stellar mass black holes, the state of affairs could also be totally different in relation to a lot lighter PBH.
“The lighter a black gap is, the warmer it ought to be and the extra particles it is going to emit,” stated co-author Andrea Thamm, an assistant professor of physics at UMass Amherst, in a press release. “As PBHs evaporate, they turn out to be ever lighter, and so hotter, emitting much more radiation in a runaway course of till explosion. It’s that Hawking radiation that our telescopes can detect.”
As a PBH evaporates through runaway HR, they ultimately expertise a closing burst. Of their closing second, they turn out to be extraordinarily scorching and endure an explosive evaporation. This closing act can produce high-energy neutrinos like KM3-230213A.
The researchers suppose that this might occur each decade, roughly, and that the explosions can produce a cornucopia of sub-atomic particles. They suppose that these PBH evaporative explosions may produce a list of all the sub-atomic particles that exist. Not simply those we learn about, like electrons and quarks, but additionally ones which can be solely hypothesized at the moment, and others that which may be fully unknown.
The analysis group thinks that KM3-230213A might be the proof for PBH evaporation. However there’s one drawback.
The IceCube Neutrino Observatory did not detect the occasion, and in reality has by no means detected any neutrino near being as energetic as KM3-230213A. If a PBH evaporation explosion occurs each decade, should not IceCube have detected at the least one? IceCube has been observing for 20 years.
*That is the IceCube Neutrino Observatory in Antarctica. The neutrino detectors are connected to an array of strings which can be sunk into the ice. Picture Credit score: By Christopher Michel – Personal work, CC BY-SA 4.0,
The researchers say that there is an uncommon kind of PBH concerned.
“We predict that PBHs with a ‘darkish cost’—what we name quasi-extremal PBHs—are the lacking hyperlink,” says Joaquim Iguaz Juan, a postdoctoral researcher in physics at UMass Amherst and one of many paper’s co-authors. The researchers say that PBHs with a darkish cost, which is principally a really heavy, hypothesized model of the electron, a “darkish electron,” spend most of their time in a quasi-extremal state. On this state, the PBH is nearly at its most potential charge-to-mass ratio.
IceCube and KM3NeT are tuned to totally different energies. IceCube is proscribed to 10 PeV, and that may clarify why it by no means detected KM3-230213A.
For PBH within the quasi-extremal state, “the neutrino emission at 1 PeV could also be extra suppressed than at 100 PeV,” the authors clarify. “The burst charges implied
by the KM3NeT and IceCube observations and the oblique constraints can then all be constant at 1σ.”
For examine co-author Baker, the added complexity of darkish cost PBH provides extra veracity to their rationalization.
“There are different, less complicated fashions of PBHs on the market,” says Michael Baker, co-author and an assistant professor of physics at UMass Amherst. “Our dark-charge mannequin is extra advanced, which implies it might present a extra correct mannequin of actuality. What’s so cool is to see that our mannequin can clarify this in any other case unexplainable phenomenon.”
“A PBH with a darkish cost,” provides Thamm, “has distinctive properties and behaves in methods which can be totally different from different, less complicated PBH fashions. We have now proven that this will present a proof of all the seemingly inconsistent experimental information.”
To non-physicists, physics can appear to be a puzzling, cryptozoological world filled with unusual particles on unusual journeys from unusual sources. However these particles all add as much as the cosmos we see round us. And solutions to a few of our greatest questions reside on this unusual world.
We all know darkish matter exists, or we expect we all know, as a result of there’s a lot proof of lacking mass. However we merely do not know what it’s. There’s rising confidence in PBH as a candidate for darkish matter, and this analysis provides to that.
“If our hypothesized darkish cost is true,” stated Iguaz Juan, “then we imagine there might be a big inhabitants of PBHs, which might be according to different astrophysical observations, and account for all of the lacking darkish matter within the universe.”
Will this neutrino be part of our reply to the darkish matter query? Will it assist physicists fill within the blanks in relation to our patchy understanding of the cosmos?
“Observing the high-energy neutrino was an unbelievable occasion,” Baker stated. “It gave us a brand new window on the universe. However we may now be on the cusp of experimentally verifying Hawking radiation, acquiring proof for each primordial black holes and new particles past the Commonplace Mannequin, and explaining the thriller of darkish matter.”
