Scientists Detect Evidence of a Rare, Elusive New Subatomic Particle

Physicists have found evidence of an unusual new kind of subatomic particle that may help them explain how the universe is stuck together.

After a three-decade search, the world’s first “exotic meson” has been detected in a particle accelerator at the Brookhaven National Laboratory in Upton, N.Y. Physicists announced the detection in today’s issue of Physics Review Letters.

“This is a very satisfying confirmation for us,” said Brookhaven physicist Suh-Urk Chung.

In the standard model of physics, a theoretical body of knowledge that has accumulated over 30 years, three quarks make a proton or neutron, and two can combine to make another subatomic particle known as a meson. Quarks are the most basic type of subatomic particle known.

That standard model also predicted that quarks could combine in unusual ways to form what are known as exotic mesons.

“If somebody eventually didn’t find this, it would be quite a problem,” said Neil Cason, one of 51 physicists who collaborated on the exotic meson research.

If the observation is confirmed, physicists said, the study of exotic mesons could reveal details of how quarks--and thus everything in the universe--are stuck together.

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These subatomic particles were difficult to observe, however, because of their rarity and the fact that they can only exist for about a trillionth of a trillionth of a second.

The Brookhaven experiments didn’t actually see an exotic meson but found evidence for them in the debris created by a high-energy collision between particles. The experiment, known as E852, involved hitting liquid hydrogen with an 18-billion-electron-volt particle beam in a multi-particle spectrometer.

After about five years of slamming atoms together in this particle accelerator, about 500 out of 40,000 collisions produced a pattern inconsistent with a regular meson, Chung said. The debris came from the decay of an exotic meson composed of four quarks, or possibly a particle made of two quarks and another type of subatomic beast known as a gluon.

“It’s certainly a very important result,” said Ted Barnes, a physicist at the Oak Ridge National Laboratory and the University of Tennessee. “If it’s confirmed, it really would be the first.

“Theorists have predicted the existence of exotic hybrid mesons, which contain both quarks and gluons, since the late 1970s, but E852 may have found the smoking gun for their existence. It’s a benchmark that will set the mathematical scales for future experimentation and study.”

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“To find evidence of a particle that has never been detected before, and one that’s so important to our understanding of elementary physics, is hugely satisfying,” said Chung.