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There is something mysterious rising from the frozen ground of Antarctica that could break the physics as we know it.
Physicists do not know exactly what it is. But they know it's a kind of cosmic ray – a high-energy particle that has traveled through space, headed for Earth, and gone. But the particles that physicists know – the collection of particles that is what scientists call the Standard Model (MS) of particle physics, should not be able to do that. Of course, there are low-energy neutrinos that can cross miles and miles of uninjured rocks. But high energy neutrinos, as well as other high energy particles, have "large cross sections". This means that they will almost always come up against something shortly after entering the Earth without ever reaching the outside.
And yet, since March 2016, researchers are puzzled over two events in Antarctica where cosmic rays have sprung from the Earth and have been detected by NASA's ANITA antenna (ANT), a balloon antenna drifting across the continent.
ANITA is designed to chase cosmic rays out of space. The high-energy neutrino community was buzzing with enthusiasm when the instrument detected particles appearing to be projected from Earth instead of away from space. Because cosmic rays should not do that, scientists began to wonder if these mysterious beams were made up of particles never seen before.
Since then, physicists have come up with all kinds of explanations for these "ascending" cosmic rays, from sterile neutrinos (neutrinos that never enter the matter) to "atypical dark matter distributions within the Earth ", referring to the mysterious form of the material does not interact with light [The 18 Biggest Unsolved Mysteries in Physics]
All the explanations intrigued and suggested that ANITA could have detected a particle not taken into account in the standard model. But none of the explanations conclusively proved that something more ordinary could not have caused the signal at ANITA.
A new paper uploaded today (September 26th) on the arXiv preprint server is changing this. In this paper, a team of astrophysicists from Penn State University showed that there had been more particles of high energy than those detected at both ANITA events. Three times, they write, IceCube (another larger neutrino observatory in Antarctica) has detected similar particles, although no one has yet linked these events to the mystery of ANITA. And, by combining the IceCube and ANITA data sets, Penn State researchers have calculated that no matter how much of the Earth's exploding particle, it is much less likely to be part of the Earth. standard model. (In technical and statistical terms, their results had confidences of 5.8 and 7.0 sigma, depending on the calculation you are considering.)
Break the physics
Derek Fox, the main author of the new article, said he first met with ANITA events in May 2018, in one of the first documents attempting to explain them.
"I thought," This model does not make much sense, "Fox told Live Science. [ANITA] The result is very intriguing, so I started checking. I started talking to my office neighbor Steinn Sigurdsson [the second author on the paper, who is also at Penn State] whether we could perhaps obtain more plausible explanations than the documents published to date. "
Fox, Sigurdsson and their colleagues started looking for similar events in the data collected by other detectors. When they came across possible events on the rise in the IceCube data, he realized that he might have found something really revolutionary for physics. [5 Mysterious Particles Lurking Underground]
"That's what really made me start looking at ANITA events with the utmost seriousness," he said, adding later: "That's what physicists live for . Break the patterns, establish new constraints [on reality], learn about the universe we did not know. "
As Live Science has already pointed out, experimental high-energy particle physics has been stalled for several years. When the $ 17 billion (27 km) Large Hadron Collider (LHC) was completed at the French-Swiss border in 2009, scientists thought it would solve the mysteries of supersymmetry, the mysterious theoretical class of particles that scientists suspect. could exist outside the current physics, but had never detected. According to supersymmetry, each particle existing in the standard model has a supersymmetric partner. The researchers suspect that these partners exist because the masses of known particles are out of wack, not symmetrical to each other.
"Although the SM is very good at explaining a plethora of phenomena, it still has many disabilities," said particle physicist Seyda Ipek at UC Irvine, who did not participate in ongoing research. "For example, he can not explain the existence of dark matter, [explain mathematical weirdness in] the neutrino masses, or the matter-antimatter asymmetry of the universe.
Instead, the LHC confirmed the Higgs boson, the last undetected part of the standard model, in 2012. And then, it stopped detecting anything that is important or interesting. The researchers began to wonder if existing physics experiments could ever detect a supersymmetric particle.
"We need new ideas," Jessie Shelton, a theoretical physicist at the University of Illinois at Urbana-Champaign, told Science Now in May, about the same time Fox was interested in ANITA data.
Now, several scientists not involved in Penn State's paper told Live Science that it offered solid evidence (if incomplete) that something new had actually happened.
"It was clear from the start that if ANITA's anomalous events were due to particles being spread over thousands of kilometers of Earth, these particles were probably not SM particles. "Said Mauricio Bustamante, astrophysicist at the Niels Bohr Institute of the University of Copenhagen, who was not an author on the new document.
"The document released today is the first systematic calculation of the probability that these events are due to SM neutrinos," he added. "Their result strongly disavows an explanation of SM."
"I think it's very convincing," said Bill Louis, a neutrino physicist at the Los Alamos National Laboratory, who did not participate in the document and who has been tracking research on ANITA events since then. several months.
If the particles of the standard model created these anomalies, they should have been neutrinos. The researchers know that because of the particles in which they have broken down, and because no other standard model particle would even have a fragment of chance to get through the Earth.
But the neutrinos of this energy, says Louis, should not cross the Earth often enough for ANITA or IceCube to detect it. It is not like that that they work. However, neutrino detectors such as ANITA and IceCube do not detect neutrinos directly. Instead, they detect particles in which neutrinos decompose after breaking in the Earth's atmosphere or the Antarctic ice. And there are other events that can generate these particles, triggering the detectors. This article strongly suggests that these events must have been supersymmetric, said Louis, although he added that more data was needed.
Fox and his colleagues went on to say that particles would most likely be a kind of theoretical supersymmetric particle called "stau dormptons". Stau dormers are supersymmetric versions of a standard model particle called tau lepton. The "S" is for "supersymmetric" (really). [Sparticles to Neutrinos: The Coolest Little Particles in the Universe]
Louis said that at this point, he thinks this level of specificity is "a little exaggerated".
The authors present a strong statistical case that no conventional particle would be likely to cross the Earth in this way, he said, but there is still not enough data to be certain. And there are certainly not enough resources for them to definitively determine which particle made the trip.
Fox did not dispute that.
"As an observer, I can not possibly know it's a stau," he said. "From my point of view, I try to discover new things about the universe, I come across a really weird phenomenon, and then with my colleagues, we do a little literature search to see if anyone. one has already thought that it could happen. And then, if we find articles in the literature, including an article from 14 years ago, that predict something like this phenomenon, then it takes all its weight. "
His colleagues and himself have found a long series of theorists' articles predicting that stau sleepers could end up in neutrino observatories. And because these articles were written before ANITA's anomaly, Fox said, this strongly suggests to him that these theorists were on something.
But there is still a lot of uncertainty on this front, he said. At present, researchers know that whatever particle it is, it interacts very weakly with other particles, otherwise it would never have survived the journey through the dense mass of the planet.
And after
All physicists who discussed with Live Science agreed that researchers needed to collect more data to verify that ANITA and IceCube had cracked supersymmetry. It's possible, Fox said, that when IceCube researchers dig into their data archives, they find other similar events that previously went unnoticed. Both Louis and Bustamante said that NASA should conduct more ANITA flights to see if similar, rising particles are present.
"For us to be certain that these events are not due to unknown unknowns – say, unmapped properties of the Antarctic ice – we would like other instruments to also detect this kind of. events, "said Bustamante.
In the long run, if these results are confirmed and the details of the particle causing them are grounded, several researchers have stated that ANITA's anomaly could open up even more physics at the LHC.
"Any observation of a non-SM particle would change the game because it would tell us which way to go after the SM," Ipek said. "The type of [supersymmetric] particle they claim to have produced, the sleep signals, are very difficult to produce and detect at the LHC. "
"So it's very interesting if they can be observed by other types of experiments. Of course, if this is true, we expect a scale of others [supersymmetric] particles to be observed at the LHC, which would be a complementary test of the claims. "
In other words, ANITA anomalies could provide scientists with the key information needed to properly adjust the LHC to unlock more supersymmetry. These experiences could even provide an explanation for dark matter.
Right now, Fox said, he just wants more data.
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