Curtis A. Meyer

The world around us is made up of atoms, which, in turn, are composed of electrons mov- ing around an atomic nucleus of protons and neutrons. In probing this microscopic matter, we have learned that the protons and neutrons are themselves composed of even smaller par- ticles, quarks and gluons. The interaction bewteen these quarks and gluons is described by Quantum Chromo Dynamics (QCD), part of the Standard Model of particle physics. These gluons interact with the quarks through the three different charges of QCD, named: “red”, “blue” and “green”, and hence the “chromo” in the name. Because of the nature of QCD, quarks and gluons are confined inside the particles they form—it is not possible to study the quarks and gluons in isolation, they are always in bound together. It is also not possible to directly observe the three color charges of QCD, as not only are the quarks and gluons confined, but they are confined in such a way that they have no net color charge—they are said to be white or colorless. Either one of each of the three color charges, or a colr charge and its anti-color charge.

While many of the properties of the proton can be described by considering it to be a relatively simple system containing three bound “valence quarks”, such a picture is unable to predict some of the proton’s most basic properties. Most notably is the mass of the proton which we understand as being generated by an intense field of gluons that interact amongst themselves and with the quarks, generating the phenomenon of QCD known as confinement. In fact, this confining gluonic field of QCD is responsible for generating most of the mass of the protons, and hence the visible universe.

My research aims to study QCD in its confined regime with the goal of understanding the nature of the visible matter of which we are made. We do this with a large particle physics experiment, GlueX, which is just now running at Jefferson Lab in Newport News Virginia. The experiment uses intense beams of very high energy polarized photons to create a form of matter in which the gluonic field has been excited. This new form of matter is expected to have properties that can uniquely separate it form the normal particles, and learning the mass, patterns and properties of these “exotic hybrids” will let us see effects of the strong gluonic field. For more information, see my YouTube video: Quarks and Gluons at https://www.youtube.com/watch?v=F1Vyk9N0U04.