With the discovery of a charmed pentaquark, the LHCb Collaboration has shown that a new configuration of 4 quarks plus one antiquark can exist as a short-lived particle. But not any combination of quarks will do this, as this case containing both a charm and an anticharm quark is the only pentaquark yet known. Searches for other types of pentaquarks have come up empty. Why should this particular combination exist? What makes it so special? These and similar questions will be discussed in this seminar, along with a brief look at other exotic particles such as tetraquarks and hybrids. What new kind of particle might be the next one to be discovered?

Argonne Physics Division Seminar Schedule