Particle physics experiments

‘Tending’ results of 2 experiments defy the rules of physics

Preliminary results from two experiments suggest that something is wrong with the way physicists think the universe works, a prospect that has baffled and delighted the field of particle physics.

Tiny particles called muons don’t quite do what they’re expected to do in two different long-running experiments in the US and Europe. The disconcerting results – if proven correct – reveal major problems with the rulebook used by physicists to describe and understand the workings of the universe at the subatomic level.

“We think we’re swimming in a sea of ​​background particles all the time that just haven’t been directly discovered,” Chris Polly, co-science director of the Fermilab experiment, told a news conference. . “There could be monsters that we haven’t yet imagined emerging from the void and interacting with our muons, giving us a window to see them.”

The rulebook, called the standard model, was developed about 50 years ago. Experiments conducted over decades have repeatedly asserted that his descriptions of the particles and forces that make up and govern the universe were nearly accurate. So far.

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

The U.S. Department of Energy’s Fermilab on Wednesday announced the results of 8.2 billion runs along a track outside Chicago that, although most people have restless physicists: The muon magnetic fields don’t seem to be what the Standard Model says they should be. This follows new results published last month by the European Center for Nuclear Research’s Large Hadron Collider which found a surprising proportion of particles from high-speed collisions.

If confirmed, the US findings would be the biggest discovery in the bizarre world of subatomic particles in nearly 10 years since the discovery of the Higgs boson, often called the ‘God particle’, Aida El-Khadra said. from the University of Illinois, who is working on theoretical physics for the Fermilab experiment.

The purpose of the experiments, says David Kaplan, a theoretical physicist at Johns Hopkins University, is to separate the particles and find out if “something funny” is going on with both the particles and the seemingly empty space between them. they.

“Secrets do not reside only in matter. They live in something that seems to fill all space and time. These are quantum fields,” Kaplan said. “We put energy into the void and see what comes out of it.”

Both sets of results involve the strange fleeting particle called the muon. The muon is the heavier cousin of the electron which orbits around the center of an atom. But the muon is not part of the atom, it is unstable and normally only exists for two microseconds. After its discovery in cosmic rays in 1936, it baffled scientists so much that a famous physicist asked “Who ordered this?”

“From the very beginning, physicists racked their brains,” said Graziano Venanzoni, an experimental physicist at an Italian national laboratory who is one of the top scientists in the US Fermilab experiment, called Muon g-2.

The experiment sends muons around a magnetized track that keeps the particles alive long enough for researchers to observe them up close. Preliminary results suggest that the magnetic “spin” of muons is 0.1% lower than predicted by the Standard Model. It may not seem like a lot, but for particle physicists it’s huge – more than enough to shake up current knowledge.

Researchers need a year or two to finish analyzing the results of all laps around the 50-foot (14-meter) track. If the results don’t change, it will count as a major discovery, Venanzoni said.

Separately, in the world’s largest atom breaker at CERN, physicists crashed protons into each other to see what would happen next. One of many separate experiments at particle colliders measures what happens when particles called beauty or bottom quarks collide.

The standard model predicts that these collisions of beauty quarks should produce an equal number of electrons and muons. It’s a bit like tossing a coin 1,000 times and getting roughly the same number of heads and tails, said the Large Hadron Collider beauty experiment. chef Chris Parkes.

But that’s not what happened.

Researchers looked at data from several years and a few thousand crashes and found a 15% difference, with many more electrons than muons, said experimental researcher Sheldon Stone of Syracuse University.

Neither experiment is yet qualified as an official discovery, as there is still a small chance that the results are statistical oddities. Running the experiments multiple times — both planned — could, within a year or two, hit the incredibly stringent statistical requirements for physics to hail it as a breakthrough, the researchers said.

If the results hold, they would upend “every other calculation done” in the world of particle physics, Kaplan said.

“It’s not a fudge factor. It’s something that’s wrong,” Kaplan said. This something could be explained by a new particle or force.

Or these results may be errors. In 2011, a bizarre discovery that a particle called a neutrino appeared to move faster than light threatened the model, but it turned out to be the result of a loose electrical connection problem in the experiment.

“We checked all of our wired connections and did what we could to verify our data,” Stone said. “We are a little 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 is supported by the Howard Hughes Medical Institute Department of Science Education. The AP is solely responsible for all content.