Physicists Cast Doubt on Neutrino Theory – Exotic Subatomic Particle May Not Exist at All

Neutrino Animation Concept

Exotic subatomic particles, sterile neutrinos, are no-shows in experiments, increasing doubts about their existence.

University of Cincinnati physicists, as part of an international research team, are raising doubts about the existence of an exotic subatomic particle that failed to show up in twin experiments.

UC College of Arts and Sciences associate professor Alexandre Sousa and assistant professor Adam Aurisano took part in an experiment at the Fermi National Accelerator Laboratory in search of sterile neutrinos, a suspected fourth “flavor” of neutrino that would join the ranks of muon, tau, and electron neutrinos as elementary particles that make up the known universe.

Finding a fourth type of neutrino would be huge, Sousa said. It would redefine our understanding of elementary particles and their interactions in what’s known as the Standard Model.

Alexandre Sousa Neutrino Model

UC associate professor Alexandre Sousa holds a neutrino model that changes color when tossed in the air to demonstrate how neutrinos change “flavor.” Credit: Joseph Fuqua II/UC Creative + Brand

Researchers in two experiments called Daya Bay and MINOS+ collaborated on complementary projects in an intense effort to find sterile neutrinos using some of the world’s most advanced and precise tools.

“We apparently don’t see any evidence for them,” Aurisano said.

“It’s an important result for particle physics. It provides an almost definitive answer to a question that has been lingering for over 20 years.” — Alexandre Sousa, UC associate professor of physics

The study was published in the journal Physical Review Letters and was featured in Physics Magazine, published by the American Physical Society.

“It’s an important result for particle physics,” Sousa said. “It provides an almost definitive answer to a question that has been lingering for over 20 years.”

The research builds on previous studies that offered tantalizing possibilities for finding sterile neutrinos. But the new results suggest sterile neutrinos might not have been responsible for the anomalies researchers previously observed, Aurisano said.

Fermilab Data

Experiments at Fermilab gather so much data that it takes supercomputers to analyze it. Credit: Photo/Reidar Hahn/Fermilab

“Our results are incompatible with the sterile neutrino interpretation of the anomalies,” he said. “So these experiments remove a possibility – the leading possibility – that oscillations into sterile neutrinos solely explain these anomalies.”

Adam Aurisano

UC assistant professor Adam Aurisano. Credit: University of Cincinnati

Exploring new physics

Neutrinos are tiny, so tiny they can’t be broken down into something smaller. They are so small that they pass through virtually everything — mountains, lead vaults, you — by the trillions every second at virtually the speed of light. They are generated by the nuclear fusion reactions powering the sun, radioactive decays in nuclear reactors or in the Earth’s crust, and in particle accelerator labs, among other sources.

And as they travel, they often transition from one type (tau, electron, muon) to another or back.

But theorists have suggested there might be a fourth neutrino that interacts only with gravity, making them far harder to detect than the other three that also interact with matter through the weak nuclear force.

The experiment Daya Bay is composed of eight detectors arrayed around six nuclear reactors outside Hong Kong. MINOS+ uses a particle accelerator in Illinois to shoot a beam of neutrinos 456 miles through the curvature of the Earth to detectors waiting in Minnesota.

“We would all have been absolutely thrilled to find evidence for sterile neutrinos, but the data we have collected so far do not support any kind of sterile neutrino oscillation,” said Pedro Ochoa-Ricoux, associate professor at the University of California, Irvine.

Fermilab MINOS Map

Fermilab’s MINOS+ experiment uses two neutrino detectors 450 miles apart in Illinois and Minnesota. Credit: Fermilab

Researchers expected to see muon neutrinos seemingly vanish into thin air when they transitioned into sterile neutrinos. But that’s not what happened.

“We expected to see muon neutrinos oscillating to sterile neutrinos and disappear,” Aurisano said.

Physics in a pandemic

Despite the findings, Aurisano said he thinks sterile neutrinos do exist, at least in some form.

“I think sterile neutrinos are more likely than not to exist at high energies. At the very beginning of the universe, you’d expect there would be sterile neutrinos,” he said. “Without them, it’s hard to explain aspects of neutrino mass.”

But Aurisano is skeptical about finding light sterile neutrinos that many theorists expected them to find in the experiments.

“Our experiment disfavors light or lower-mass sterile neutrinos,” he said.

Sousa said some of his research was truncated somewhat by the global COVID-19 pandemic when Fermilab shut down accelerator operations months earlier than expected. But researchers continued to use massive supercomputers to examine data from the experiments, even while working from home during the quarantine.

“It’s one of the blessings of high energy physics,” Aurisano said. “Fermilab has all the data online and the computing infrastructure is spread out around the world. So as long as you have the internet you can access all the data and all the computational facilities to do the analyses.”

Still, Aurisano said it takes some adjusting to work from home.

“It was easier when I had dedicated hours at the office. It’s a challenge sometimes to work from home,” he said.

Reference: “Improved Constraints on Sterile Neutrino Mixing from Disappearance Searches in the MINOS, MINOS+, Daya Bay, and Bugey-3 Experiments” by P. Adamson et al. (Daya Bay Collaboration, MINOS+ Collaboration), 10 August 2020, Physical Review Letters.
DOI: 10.1103/PhysRevLett.125.071801

6 Comments on "Physicists Cast Doubt on Neutrino Theory – Exotic Subatomic Particle May Not Exist at All"

  1. Gordan Krnjaic | August 13, 2020 at 5:01 pm | Reply

    This is a catastrophically misleading title. They did not find evidence to cast doubt on *neutrinos* whose existence has been known since the 1930 — rather the this evidence disfavors the existence *an additional 4th neutrino* beyond the 3 which are already known to exist. Shameful clickbait or ignorance, but not good journalism either way

  2. Gregory Phillip Dearth | August 13, 2020 at 8:41 pm | Reply

    Sensationalism will destroy scientific journalism. This title is simply not true. Finding out there are three neutrinos is actually pretty boring as it fits the standard model predictably. That fourth one was a long shot at best. Not finding what you don’t expect to find isn’t really a story.

  3. I would shut down this project and use the Fermilabs super computers full time in solving the Covid pandemic. Covid 19 won’t be the last virus to lay waste to humanity, why are we not focusing very single gram of human energy and ingenuity together to stay alive.

  4. ….
    ”Doubt on Neutrino Theory”, the doubts are sometimes good, one can reassure some basic things, and find many things along the way!
    However, now I have some questions…
    Like
    1. could Higgs be a base for our mass and then some entity of higher dimensions are wrapped around, and dark matter is also wrapped around but in other dimensions that are not like ours, and there are different types of dark matter.
    Since the Higgs are shared then can influence to each other with the mass, but not “see each other”….

    2. If there is a space-time entity, what would be its resonant frequency, and could this be a proof that space time exists…

    … so many things … and

  5. Agree that the title is misleading. The suggestion that ALL neutrinos do not exist is the only reason I read the article.

  6. Ronald Patrick Marriott | August 18, 2020 at 6:09 am | Reply

    Did you know that the aether field is made in three energy levels ? You can’t remove the aether field from your particle collider experiments at #CERN so you’re going to be getting different results in at least three different energy levels and that gives you different particles. Same particle three or more results depending upon time and position in the field.
    Super string Theory supports this!
    #energy #physics #plasma #science
    #mantledynamics

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