Preliminary results from two experiments suggest that something could be wrong with the basic way physicists believe the universe works, a view that has both the field of particle physics both amazed and excited.
Small particles called muons do not quite do what is expected of them in two different long-term experiments in the United States and Europe. The confusing results – if they turn out to be true – reveal major problems with the rulebook that physicists use to describe and understand how the universe functions at the subatomic level.
“We think we might be swimming in a sea of background particles all the time that just hasn̵
The rulebook, called the standard model, was developed about 50 years ago. Experiments conducted over decades repeatedly confirmed that its descriptions of the particles and the forces that make up and control the universe were largely on the mark. Until now.
“New particles, new physics may be just outside our research,” said Wayne State University particle physicist Alexey Petrov. “It’s tempting.”
US Department of Energy Fermilab announced results on Wednesday of 8.2 billion runs along a track outside Chicago that while humming for most people have physicists excited: The muons’ magnetic fields do not appear 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 in the wake of high-speed collisions.
If confirmed, the U.S. results would be the largest find in the bizarre world of subatomic particles in nearly 10 years since the discovery of the Higgs boson, often called the “God particle,” said Aida El-Khadra of the University of Illinois, working on theoretical physics for the Fermilab experiment.
The point of the experiments, explains Johns Hopkins University theoretical physicist David Kaplan, is to pull particles apart and find out if there is “something fun going on” with both the particles and the seemingly empty space between them.
“Secrets do not only live in matter. They live in something that seems to fill all the time and time. These are quantum fields, ”said Kaplan. “We put energy into the vacuum and see what comes out.”
Both sets of results involve the strange, volatile particle called muon. Muon is the heavier cousin of the electron orbiting the center of an atom. But the muon is not part of the atom, it is unstable and usually exists for only two microseconds. After it was discovered in cosmic rays in 1936, it confused scientists that a famous physicist asked “Who ordered it?”
“Right from the start, it made physicists scratch their heads,” said Graziano Venanzoni, an experimental physicist at an Italian national laboratory that is one of the largest researchers in the American Fermilab experiment, called Muon g-2.
The experiment sends muons around on a magnetized track that keeps the particles present long enough for scientists to take a closer look at them. Preliminary results suggest that the magnetic “spin” of muons is 0.1% relative to what the standard model predicts. It may not sound like much, but for particle physicists it’s huge – more than enough to maintain current understanding.
Researchers need another year or two to complete the analysis of the results of all laps around 50-foot (14-meter) tracks. If the results do not change, it counts as a big discovery, Venanzoni said.
Separately, world physicists at the world’s largest nuclear sprayers at CERN have crashed protons against each other there to see what happens next. One of the particle collider’s several separate experiments measures what happens when particles called beauty or bottom quark collide.
The standard model predicts that these beauty quark crashes will result in equal numbers of electrons and muons. It’s like flipping a coin 1,000 times and getting about as many heads and tails, said the Large Hadron Collider beauty experiment chef Chris Parkes.
But that’s not what happened.
Researchers pored over data from several years and a few thousand crashes and found a 15% difference with significantly more electrons than muons, says experimental researcher Sheldon Stone of Syracuse University.
None of the experiments is called yet another official discovery because there is still a small chance that the results are statistical properties. Running the experiments several times – planned in both cases – could in a year or two reach the incredibly strict statistical requirements of physics to hail it as a discovery, researchers said.
If the results hold, they would raise “any other calculation made” in the world of particle physics, Kaplan said.
“This is not a fudge factor. This is something wrong, ”said Kaplan. That something could be explained with a new particle or force.
Or these results may be incorrect. In 2011, the model threatened with a strange discovery that a particle called neutrino was running faster than light, but it turned out to be the result of a solved electrical connection problem in the experiment.
“We checked all our cable connections and we’ve done what we can to check our data,” Stone said. “We’re a little sure, but you never know.”
AP author Jamey Keaten in Geneva contributed to this report.
Follow Seth Borenstein on Twitter at @borenbears.
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