Dr. Matthias Burkardt, Distinguished Achievement Professor

Office: Gardiner Hall 258A

MSC 3D
New Mexico State University
PO Box 30001
Las Cruces, NM
88003-8001

Phone: 575-646-1928

FAX: 575-646-1934

Personal Web Page >>
E-mail: burkardt@nmsu.edu

About

Research Interests:

My primary research interest is in non-perturbative strong interaction physics and the quark/gluon (=parton) structure of hadrons and nuclei. I am particularly interested in understanding the role of non-perturbative Quantum Chromo Dynamics (QCD) from medium energy to high-energy scattering experiments.
Within this area, the main focus of my recent research has been to better understand what one can actually learn from these experiments and/or related calculations. More specifically, even though mathematical expressions in terms of matrix elements of complicated operators exist to describe the outcome of a certain experiment, the complicated nature of these matrix elements often obscures the intuitive physical interpretation of results from both experiments as well as numerical simulations.

• Generalized Parton Distributions (GPDs): These correlation functions were originally introduced to parameterize the quark/gluon aspects of nucleon structure in high-energy Compton scattering. It was also recognized that these very abstract GPDs play a role in other observables. What I was able to demonstrate is that GPDs themselves are interesting: By taking a suitable Fourier transform they provide a 3 dimensional image of the nucleon, where one axis corresponds to the quark or gluon momentum and the other two axes correspond to the location of the quark/gluon in the transverse plane.
• Single-Spin Asymmetries (SSAs): When a nucleon target is polarized transversly relative to an incoming electron beam, many hadrons produced in a collision tend to show a left-right asymmetry in their distribution relative to the nucleon spin direction. One of the aspects that is remarkable about such SSAs is that they persist at high energies and that they normally exhibit very stable patterns (e.g. as a function of the beam energy). Theoretical calculations of SSAs depend simultaneously on several aspects of hadron structure (interference between complex phases, orbital angular momentum, final state interactions) that makes the interpretation of the SSAs mysterious. What I found is that there is a simple semi-classical interpretation for the origin of these SSAs that has to do with the transverse deformation of the distribution of quarks and gluons in a transversely polarized target and that there is a qualitative connection between GPDs and SSAs. This observation now allows turning things around and takeing a measured SSA and deducing what the deformation in the target nucleon must have been.
• Transverse Force on Quarks: Certain observables in high-energy polarized electron-nucleon scattering (longitudinal-beam/ transverse-target double-spin asymmetries) are sensitive to correlations between quarks and gluons at the same position. Being a multi-parton correlation function, these matrix elements have eluded a simple physics interpretation for a long time. Recently, I realized that, in a semi-classical sense, these correlation functions can teach us something about the color Lorentz forces that act on a quark in a nucleon after it has been struck by a high-energy photon. This novel interpretation now provides fresh momentum for both measurements as well as numerical calculations for these observables.
• I continue to search for ’simple pictures’ and to indentify the physical interpretation for complicated observables.

Publications