Curtis Meyer

MCS Associate Dean for Faculty and Graduate Affairs

Professor, Physics

Education

Ph.D., University of California, Berkeley

BS, Oregon State University, 1982

Research

Most of the visible mass of the universe is composed of protons and neutrons---particles which build up the cores of atoms. However, the protons and neutrons (nucleons) are themselves composed of more fundamental particles known as quarks and gluons and interestingly, these small constituents appear to be forever trapped inside their respective parent. An article in an August 2000 issue of the New York Times listed understanding confinement of quarks inside of protons and neutrons as one of the ten fundamental questions in physics to ponder for the 'next millennium or two'. While we believe that the theory of Quantum Chromodynamics, (QCD), can explain this confinement, an exact understanding of how QCD works has been extremely elusive.

We know that QCD works under the extreme conditions found in high energy particle collisions, but our knowledge of what it is doing under normal conditions found in the every day world is quite limited. Using advances in high speed computing and experimental facilities that could soon be available at laboratories in the United States, scientists hope to go a long way in answering this question within the next decade.  In addition to the question of confinement, there has been a long-standing question on how the nominal three quarks inside of a nucleon behave. Are they free to bounce around like marbles in a fishbowl or are they somehow constrained to move together---what are the degrees of freedom inside the nucleon? This latter question can be answered by looking at what happens when the quarks inside a nucleon are excited, and thereby creating new particles. The spectrum of these particles is connected to the degrees of freedom.

Surprising, the data seem to indicate that they are somehow constrained, but there are still crucial questions on our understanding of this spectrum. We are carrying out a large-scale effort to use new high-statistics data from Jefferson Lab to look in previously unexplored reactions to see if there are new particles to be found. The observation of even a small number of additional states could settle this question.

First results which just appeared late in 2007 hint at new states, and we hope for more definitive results over the next year or so.  While the theory of QCD has been known for quite some time, we have only recently reached a point where we can start to understand confinement. Advances in a technique called lattice gauge QCD and significant improvements in computation power have combined to make the solution to QCD within reach. Lattice QCD solves QCD exactly in a discretized space-time world, but to do so, it requires massive computational power. Multi-teraflop computers are needed to allow theorists to do these calculations and to make detailed predictions for the spectrum of exotic hybrid mesons. Such computers are just now being put together. However, the final arbiter in determining which model of confinement is correct is experiment. So in parallel, experimenters are using recent developments in technology to carry out experiments that will map out the spectrum of this new type of matter with a focus on those hybrids that are distinctly different from normal mesons.

They are the smoking gun unambiguous evidence of gluonic excitations. The GlueX experiment which is being built at Jefferson Lab is aimed at addressing these issues.  I am the spokesperson of the GlueX experiment and we are currently building a large tracking detector at Carnegie Mellon for use in the experiment. For more detailed information on the experiment, and our activities are Jefferson Lab, the following links may be useful:

• Curtis Meyer's Web Site site at CMU.

• The GlueX Wiki at Jefferson Lab.

• The GlueX Portal

• The Hall D  website at Jefferson Lab.

Selected Publications

• Jozef Dudek et al., Physics opportunities with the 12 GeV upgrade at Jefferson Lab, The European Physical Journal A 48, 187 (2012)
• K. Park et al., Measurement of the generalized form factors near threshold via γ*p→nπ⁺ at high Q², Physical Review C 85, 035208 (2012)
• D. Keller et al., Publisher’s Note: Branching ratio of the electromagnetic decay of the Σ⁺(1385) Phys. Rev. D 85, 052004 (2012), Physical Review D 85, 059903 (2012)
• D. Keller et al., Branching ratio of the electromagnetic decay of the Σ⁺(1385), Physical Review D 85, 052004 (2012)
• M. Aghasyan et al., Precise measurements of beam spin asymmetries in semi-inclusive production, Physics Letters B 704, 397 (2011)
• D. Keller et al., Electromagnetic decay of the Σ⁰(1385) to Λγ, Physical Review D 83, 072004 (2011)
• Biplab Dey, Michael E. McCracken, David G. Ireland, Curtis A. Meyer, Polarization observables in the longitudinal basis for pseudo-scalar meson photoproduction using a density matrix approach, Physical Review C 83, 055208 (2011)
• Biplab Dey, Michael E. McCracken, David G. Ireland, Curtis A. Meyer, Polarization observables in the longitudinal basis for pseudo-scalar meson photoproduction using a density matrix approach, Physical Review C 83, 055208 (2011)
• C. A. Meyer, Y. Van Haarlem, Status of exotic-quantum-number mesons, Physical Review C 82, 025208 (2010)
• B. Dey et al., Differential cross sections and recoil polarizations for the reaction γp→K⁺Σ⁰, Physical Review C 82, 025202 (2010)
• M. E. McCracken et al., Differential cross section and recoil polarization measurements for the γp→K⁺Λ reaction using CLAS at Jefferson Lab, Physical Review C 81, 025201 (2010)
• M. Williams et al., Differential cross sections and spin density matrix elements for the reaction γp→pω, Physical Review C 80, 065208 (2009)
• M. Williams et al., Partial wave analysis of the reaction γp→pω and the search for nucleon resonances, Physical Review C 80, 065209 (2009)
• M. Williams et al., Differential cross sections for the reactions γp→pη and γp→pη', Physical Review C 80, 045213 (2009)
• M Williams, M Bellis, C A Meyer, Multivariate side-band subtraction using probabilistic event weights, Journal of Instrumentation 4, P10003 (2009)
• V. Crede, C.A. Meyer, The experimental status of glueballs, Progress in Particle and Nuclear Physics 63, 74 (2009)
• Alex Dzierba, Eric Swanson, Curtis Meyer, The Search for QCD Exotics, American Scientist 88, 406 (2000)
• R. Tribble, Frontiers of Nuclear Science: A Long Range Plan, (2007).