The proton and neutron are the fundamental building blocks of the cores of atoms. However, they themselves are composed of more fundamental constituents, quarks and gluons. These interact via quantum chromodynamics (QCD) and are confined inside their parent proton or neutron. Mesons are bound states of quarks and antiquarks, and in many ways can be though of like a hydrogen atom, where the excited states are themselves new particles.

However, unlike hydrogen, where the levels are pure exictations of the elctron, in mesons it is possible to also excite the gluonic field that binds the quark and the antiquark together. Such an excitation is known as a gluonic excitation, or a hybrid. Interestingly, many of these expected excitations have so-called exotic quantum numbers-a signature that makes them experimentally very interesting.

I am currently the spokeperson of the GlueX experiment at Jefferson Lab in Newport News, Virginia. The experiment will be built in a new expereimental hall as part of a 310 million dollar upgrade to the laboratory which will start construction in 2009. The project went through its last major review in July of 2008.