The Search for QCD Exotics

For the past quarter-century, physicists have suspected that a subatomic particle unlike any other must exist?one made of the very glue that holds matter together at the most fundamental level. This glue acts within the nucleus of every atom, binding together charged particles that would otherwise repel one another. But might this force itself exist as a form of matter? Recently, the search for this elusive particle, nicknamed the "glueball," has intensified as tantalizing hints of its presence have appeared. And investigators have found evidence of related particles that are just as exotic. Now, more than a century after the first subatomic building block, the electron, was discovered, physicists may be on the verge of uncovering a whole new class of matter.