GlueX at Jefferson Lab: a search for exotic states of matter in photon-proton collisions

Abstract

The GlueX Experiment, which is currently under construction as a component of the 12 GeV up- grade to Jefferson Lab, will utilize photoproduction on a proton target to search for hybrid mesons in the light quark sector. Recent first-principles calculations of the hadron spectrum in Quantum Chromodynamics suggest the presence of bound states in the meson spectrum that cannot arise from a quark and an anti-quark. Such states appear to have valance gluonic content or gluonic degrees of freedom and are called hybrid mesons. An interesting subset of these, the “exotic hybrid mesons, have total angular momentum, parity, and charge conjugation quantum numbers that cannot be formed with a pair of spin-1/2 fermions. By performing an amplitude analysis of photon-proton reactions, the GlueX experiment will attempt to experimentally establish the spectrum of hybrid mesons. In this article, the present theoretical and experimental landscape is reviewed, the design of the GlueX detector presented, and the GlueX startup plans are briefly discussed.