‘Tantalizing’ outcomes of two experiments defy physics rulebook


Results from two experiments within the United States and Europe are shaking the world of particle physics

April 7, 2021, 4: 31 PM

5 min learn

Preliminary outcomes from two experiments counsel one thing may very well be flawed with the essential method physicists assume the universe works, a prospect that has the sphere of particle physics each baffled and thrilled.

The tiniest particles aren’t fairly doing what is anticipated of them when spun round two totally different long-running experiments within the United States and Europe. The confounding outcomes — if confirmed proper — reveal main issues with the rulebook physicists use to explain and perceive how the universe works on the subatomic stage.

Theoretical physicist Matthew McCullough of CERN, the European Organization for Nuclear Research, mentioned untangling the mysteries may “take us beyond our current understanding of nature.”

The rulebook, called the Standard Model, was developed about 50 years ago. Experiments performed over decades affirmed over and again that its descriptions of the particles and the forces that make up and govern the universe were pretty much on the mark. Until now.

“New particles, new physics might be just beyond our research,” said Wayne State University particle physicist Alexey Petrov. “It’s tantalizing.”

The United States Energy Department’s Fermilab announced results Wednesday of 8.2 billion races along a track outside Chicago that while ho-hum to most people have physicists astir: The magnetic field around a fleeting subatomic particle is not what the Standard Model says it should be. This follows new results published last month from CERN’s Large Hadron Collider that found a surprising proportion of particles in the aftermath of high-speed collisions.

Petrov, who wasn’t involved in either experiment, was initially skeptical of the Large Hadron Collider results when hints first emerged in 2014. With the latest, more comprehensive results, he said he is now is “cautiously ecstatic.”

The point of the experiments, explains Johns Hopkins University theoretical physicist David Kaplan, is to pull apart particles and find out if there’s “something funny going on” with each the particles and the seemingly empty house between them.

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“The secrets and techniques don’t simply stay in matter. They stay in one thing that appears to fill in all of house and time. These are quantum fields,” Kaplan mentioned. “We’re putting energy into the vacuum and seeing what comes out.”

Both units of outcomes contain the unusual, fleeting particle known as the muon. The muon is the heavier cousin to the electron that orbits an atom’s middle. But the muon just isn’t a part of the atom, it’s unstable and usually exists for under two microseconds. After it was found in cosmic rays in 1936 it so confounded scientists {that a} well-known physicist requested “Who ordered that?”

“Since the very beginning it was making physicists scratch their heads,” mentioned Graziano Venanzoni, an experimental physicist at an Italian nationwide lab, who is among the prime scientists on the U.S. Fermilab experiment, known as Muon g-2.

The experiment sends muons round a magnetized observe that retains the particles in existence lengthy sufficient for researchers to get a more in-depth take a look at them. Preliminary outcomes counsel that the magnetic “spin” of the muons is 0.1% off what the Standard Model predicts. That might not sound like a lot, however to particle physicists it’s big — greater than sufficient to upend present understanding.

Researchers want one other yr or two to complete analyzing the outcomes of the entire laps across the 50-foot (14-meter) observe. If the outcomes do not change, it’s going to rely as a significant discovery, Venanzoni mentioned.

Separately, on the world’s largest atom smasher at CERN, physicists have been crashing protons in opposition to one another there to see what occurs after. One of the particle colliders’ a number of separate experiments measures what occurs when particles known as magnificence or backside quarks collide.

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The Standard Model predicts that these magnificence quark crashes ought to lead to equal numbers of electrons and muons. It’s form of like flipping a coin 1,000 instances and getting about equal numbers of heads and tails, mentioned Large Hadron Collider magnificence experiment chief Chris Parkes.

But that’s not what occurred.

Researchers pored over the info from a number of years and some thousand crashes and located a 15% distinction, with considerably extra electrons than muons, mentioned experiment researcher Sheldon Stone of Syracuse University.

Neither experiment is being known as an official discovery but as a result of there may be nonetheless a tiny likelihood that the outcomes are statistical quirks. Running the experiments extra instances — deliberate in each instances — may, in a yr or two, attain the extremely stringent statistical necessities for physics to hail it as a discovery, researchers mentioned.

If the outcomes do maintain, they’d upend “every other calculation made” on the earth of particle physics, Kaplan mentioned.

“This is not a fudge factor. This is something wrong,” Kaplan mentioned.

He defined that there could also be some sort of undiscovered particle — or drive — that would clarify each unusual outcomes.

Or these could also be errors. In 2011, an odd discovering {that a} particle known as a neutrino appeared to be touring sooner than gentle threatened the mannequin, nevertheless it turned out to be the results of a free electrical connection drawback within the experiment.

“We checked all our cable connections and we’ve done what we can to check our data,” Stone mentioned. “We’re kind of confident, but you never know.”


AP Writer Jamey Keaten in Geneva contributed to this report.


Follow Seth Borenstein on Twitter at @borenbears.


The Associated Press Health and Science Department receives assist from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely liable for all content material.

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