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My primary research interests are in the closely related fields of experimental particle physics and computational physics. My current research focuses on testing Quantum Chromodynamics (QCD) in the non-perturbative regime by studying hadronic spectroscopy using partial wave analysis. The data I use for my analysis was obtained at the Thomas Jefferson National Accelerator Facility (Jefferson Lab).

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The CLAS detector is located in Hall-B at Jefferson Lab. The large acceptance of the CLAS detector, along with the continuous nature of JLab's CEBAF electron beam results in production of the world's largest multi-particle datasets for beam energies below 6 GeV. The CLAS collaboration, of which I've been a member since 2004, has member instiutions in 11 countries (click here to see a map).

The Missing Baryons Problem

Constituent quark models predict the existance of many more excited nucleon resonance states than have been observed experimentally. This dilema is known as the Missing Baryons Problem and is the prime motivation for the research discussed below. Studying the spectrum of excited nucleon states provides us with a window into the inner workings of the nucleon, allowing us to study QCD in the non-perturbative regime.

My Ph.D. Thesis

My thesis research involved the reaction γp→pω using data from the CLAS dataset labeled g11a. The energy range of the photons was from threshold up to 4 GeV. In this energy regime, I made differential cross section and spin density matrix element measurements at about 2000 points (greatly increasing the precision of the world's data and, in a number of kinematic regions, producing the world's first results). I also performed a mass-independent partial wave analysis on the data and found strong evidence for contributions from several nucleon resonance states. I am currently working on publishing these results (should be 3 papers). To see a copy of my thesis, click here.

Current Projects

I am currently working on producing final differential cross section results from the same CLAS dataset for the reactions γp→pη and γp→pη'. These should be done soon (at which point I'll publish them). I'd then like to finish a PWA on these datasets incorporating beam asymmetry measurements.

I've also been working closely for the last couple of years at CMU with Matt Bellis on the reactions γp→pπ⁺π^-, γp→pπ^- and γp→nπ⁺, with Mike McCracken on γp→ΛK⁺ and Biplab Dey on γp→Σ⁰K⁺. We will hopefully have final differential cross section results for the double charged pion channel soon. Matt has also been working on finishing differential cross section measurements on both single pion channels. Once these are done, we would like to perform a coupled PWA on these reactions (also including beam asymmetry results). A lot of progress has been made on completing differential cross section measurements in both kaon channels, along with recoil polarization measurements for the Λ. We are just now beggining to perform PWA's on both of these channels (also including previous double polarization measurements).

As if this (and my work on GlueX, discussed below) wasn't enough, I've also been working with South Carolina professor Dave Tedeschi on setting up a PWA for the channel γp→pφ.

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The GlueX detector (currently in the R&D stage) will be built at Jefferson Lab to look for exotic hybrid meson states (states where the gluonic degrees of freedom have been excited). Experimental verification of the existence of these states is crucial to understanding confinement of quarks and gluons in Quantum Chromodynamics.

The New York Times listed as one of its 10 Physics Questions to Ponder for a Millennium or Two (selected by physicists, including David Gross, at a conference at the University of Michigan in 2000): "Can we quantitatively understand quark and gluon confinement in Quantum Chromodynamics?" This is one of the most important unanswered questions in all of physics. Studying hybrid states should provide insight into this problem.

The GlueX detector will be uniquely poised to:

• Discover these exotic hybrid states
• Map out their spectrum
• Measure their properties

My previous PWA code development was meant to serve as a prototype for GlueX's software. I am also currently working on developing grid-computing tools for this collaboration (which I will most likely join at some point).