title: Searching for the rules that govern hadron construction.
abstract: Just as quantum electrodynamics describes how electrons are bound in atoms by the electromagnetic force, mediated by the exchange of photons, quantum chromodynamics (QCD) describes how quarks are bound inside hadrons by the strong force, mediated by the exchange of gluons. QCD seems to allow hadrons constructed from increasingly many quarks to exist, just as atoms with increasing numbers of electrons exist, yet such complex constructions seemed, until recently, not to be present in nature. Here we describe advances in the spectroscopy of mesons that are refining our understanding of the rules for predicting hadron structure from QCD.
authors.affiliation: Department of Physics, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Shepherd
authors.affiliation: Department of Physics, Old Dominion University, Norfolk, Virginia 23529, USA.|Jefferson Lab, Newport News, Virginia 23606, USA.
authors.forename: Jozef J
authors.initials: JJ
authors.lastname: Dudek
authors.affiliation: Department of Physics, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Ryan E
authors.initials: RE
authors.lastname: Mitchell