Experimental Elementary Particle Physics
David G. Cassel
Professor of Physics
B.S., 1960, Physics, California Institute of Technology. M.S., 1962, Physics, Princeton University. Ph.D., 1965, Princeton University. Postdoctoral Fellow, CERN, Geneva, Switzerland, 1965. Assistant Professor, Physics, Cornell University, 1966-71. Associate Professor, Physics, Cornell University, 1971-79. Professor, Physics, Cornell University, 1979-present. Associate Director, Laboratory for Elementary-Particle Studies (LEPP), Cornell University, 1984-present. Acting Director, LEPP, Cornell University, 1991-92. Visiting appointments at: University of Bonn, Germany; DESY, Hamburg, Germany; and CERN, Geneva, Switzerland. Alexander von Humboldt Foundation Senior Scientist Award, 1972-73. Member, American Association of University Professors. Fellow, American Physics Society.
Research Areas
Experimental elementary particles: charged pion form factor, CP violation in neutral K meson decay, photoproduction and electroproduction of scalar and vector mesons, weak decays of B and D mesons, construction of charged particle detectors, development of software for processing elementary particle physics data, magnetic confinement of neutrons
Current Research
In collaboration with other members of the LEPP experimental faculty, my research interests are focused on the CLEO-c experimental program.
In the CLEO-c program, we study electron-positron annihilation, at center of mass energies in the neighborhood of 3 and 4 GeV, the threshold region for production of charm quarks. This program is closely related to our principal previous research interest, studying weak decays of B mesons. Drawing crisp conclusions from many of the measurements in B meson physics (including measurements of CP violation) has been hampered by uncertainties in theoretical parameters that are required to extract significant physical constants from experimental results. In principal, Lattice QCD (LQCD) theorists can calculate these parameters in the charm quark sector where they can be measured precisely and in the beauty quark sector where they are needed. A principal goal of the CLEO-c program is measurement of these parameters in charm quark decay to provide experimental verification of the LQCD calculations. We reconstruct enormous numbers of D mesons and their antiparticles decaying to strongly interacting particles called hadrons. These decays identify events with D mesons (containing c quarks) and we examine the rest of the decay products to measure hadronic, semileptonic, and leptonic D meson decays. From earlier data of the CLEO-c experiment, we already have many important new published results on these key decays of D+ and D0 mesons. Now we are in the midst of studying our final data sample that is about a factor of two larger.
We also acquired a substantial data sample at an energy where Ds mesons are produced with relatively modest backgrounds. We have already published results from about half of our total sample of these particles. Studying Ds mesons has always been more difficult than studying the more ordinary D+ and D0 mesons, so the results already published have an enormous impact on our understanding of Ds meson decays.
The CLEO-c experiment is currently the best arena in which to study most D meson decay phenomena and to provide the experimental challenges that LQCD theorists and other theorists require. At this time, my principal research effort in CLEO is as the collaboration’s Analysis Coordinator, which means that I coordinate the analysis and publication of CLEO results produced by all members of the collaboration.
Professors Jim Alexander, Anders Ryd, and I are working with graduate students Xin Shi (studying hadronic decays of D+ and D0 mesons) and Souvik Das (studying Dalitz decays of Ds* mesons).