VOA慢速英语--科学家们对潜在新的自然力量感到激动（在线收听）

Have you ever heard of a muon?

A muon is a very small particle similar to an electron. Electrons and protons are parts of the atoms that make up all matter.

Muons were discovered during an experiment in 1936. Until now, most physicists have only been able to study muons for an extremely short period of time: two microseconds. There are one million microseconds in one second.

But scientists are using new technology to study these particles for a longer period of time than in the past. And with that extra time, they think they have made an exciting discovery. By watching the muons, they found that these particles do not behave as predicted.

Scientists have developed a group of expectations, or rules, in the years that they have studied particles that are smaller than an atom. That group of rules is called the Standard Model.

Scientists agreed on the Standard Model about 50 years ago. The Standard Model lets physicists make assumptions about the way extremely small particles move. Over time, experiments have proved that the assumptions of the Standard Model are correct.

However, results of two different recent tests in Europe and America have scientists thinking again about their ideas.

The scientists who work at the research center called Fermilab, near Chicago, Illinois have done 8.2 billion tests with muons. They send them around a 14-meter magnetic track. The special track keeps the muons from disappearing for longer than usual, so they can be studied. The tests showed scientists that the muons were behaving differently than the Standard Model predicted.

In tests going on at a research center near Geneva, Switzerland, scientists crash particles known as "beauty quarks" into each other. The Standard Model says these crashes should produce an equal number of electrons and muons each time. However, researchers looked at data over several years and found 15 percent more electrons than muons resulted from the collisions. They had expected nearly an equal number of both particles.

The physicists are excited to be able to question the Standard Model. They think it means an important discovery might be coming in the near future.

However, they say the information from the experiments still requires a lot of study. It will take another one or two years before they can make a firm statement.

David Kaplan is a physicist at Johns Hopkins University. He said if the experiments turn out to be correct, they could upset the world of particle physics.

What the early data show is that there is an unknown particle or force acting on the muons. Aida El-Khadra who works at Fermilab said it would be the first big discovery in this part of physics in about 10 years.

Chris Polly is one of the leaders of the project at Fermilab. He said there could be a "sea of background particles" that have not yet been discovered. He called them: "monsters we haven't yet imagined."

Alexey Petrov is a particle physicist at Wayne State University in Michigan. He said the news of the discovery is "tantalizing."

Both groups doing the experiments want people to understand that their findings need to be confirmed with more tests. In 2011, physicists thought they found something that made them question the Standard Model. They said another particle, known as a neutrino, was traveling faster than the speed of light. But after careful reexamination, they found the result came from loose electrical wiring in the experiment.

Sheldon Stone of Syracuse University is working on the project in Switzerland. Because of the problem in 2011, he said the scientists are being extra careful.

"We're kind of confident," about the results, he said. "But you never know."

Words in This Story

exciting –adj. causing feelings of interest and enthusiasm : causing excite

assume –v. to think that something is true or probably true without knowing that it is true

spin –v. to think that something is true or probably true without knowing that it is true

track –n. a structure that is often circular that lets something go around it in a set path

monster –n. a strange or horrible imaginary creature

tantalize –v. to cause (someone) to feel interest or excitement about something that is very attractive, appealing, etc.

confident –adj. having a feeling or belief that you can do something well or succeed at something : having confidence