Research and Education with GlueX

One goal of the experimental program in nuclear physics at Jefferson Lab in Newport News, Virginia is to look for new resonances, or states reinforced at certain energies, that may exist at the deepest level of the nucleus within the web-like fields known as gluons, which are the primary energy stores in the nucleus. At present, the best evidence for the existence of gluonic resonances is theoretical, but the PI and his students at the University of Connecticut are seeking experimental proof of their existence, working together with a team of 150 physicists on the GlueX experiment in Hall D at Jefferson Lab.

The UConn group is responsible for the source of polarized gamma rays, which are produced by passing the 12 GeV electron beam from the Jefferson Lab accelerator through a carefully crafted and oriented diamond crystal. Polarized gamma rays from the source are directed onto a liquid hydrogen target where resonances are produced, whose subsequent decays are picked up and identified in the GlueX Spectrometer, an apparatus surrounding the target, to uncover new information about the organization of quarks inside the proton and other nuclei.

The GlueX experiment aims at clarifying the role played by gluonic degrees of freedom in the excitation spectrum of light-quark hadrons. Data collected in pursuit of this goal also shed light on a number of additional topics in nuclear physics, including near-threshold J/psi photoproduction, rare decays of the eta(550) meson, the 2gamma decay width of the eta and eta prime mesons, and the polarizability of the charged and neutral pions (CPP, NPP).

GlueX has now completed 30% of its approved data collection for GlueX Phase 2, and is quickly reaching the point where systematic effects take over from statistics as the primary source of experimental uncertainty for many studies. The UConn group is playing a critical role in quantifying and reducing systematics related to the properties of the photon beam, in addition to supporting the ongoing operation of the photon beamline and tagger.

Support under this grant enables the PI and two PhD students to provide and enhance the quality of diamond radiators for Hall D experiments, maintain and operate the tagger microscope, and lead the ongoing development of the physics simulation for the GlueX experiment. In parallel with these efforts, UConn students will also carry out physics analysis in line with the primary GlueX physics program in hybrid spectroscopy and related topics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.