Long-sought "glueball" particles may be found.

Physicists have been on a three decades' long search for a strange type of subatomic particle called a glueball.

But the hunt may be almost, or already, over, a researcher claims. And if that's true, it could clarify what nature's most fundamental particles are.

The glueball quest is connected with a popular theory called quantum chromodynamics, which claims matter's most basic components are tiny entities called quarks. Other particles, called "gluons," act as a "glue" that binds quarks together to form the protons and neutrons of the atomic nucleus.

Most particle physicists consider the theory definitive; atom-smashing experiments have confirmed it, says Michael Chanowitz, a theoretical physicist at Lawrence Berkeley National Laboratory in Berkeley, Calif.

Yet one of its most dramatic predictions, he added, has yet to be verified. That is the existence of glueballs, particles made only of gluons.

Glueballs would be "an intriguing new form of matter," he said. Little is known about what they're like, and what they might be useful for—probably nothing, he added. But their discovery could raise new questions that lead to further progress in physics, and as for their practical applications, "you never know."

Either way, he said, glueballs would certainly be unique, because they would be the only force-carrying particles known to stick together.

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