Speaker
Volker Credé
(Florida State University)
Description
Nucleons are complex systems of confined quarks and exhibit characteristic spectra of excited states. Highly-excited nucleon states are sensitive to details of quark confinement which is poorly understood within Quantum Chromodynamics (QCD), the fundamental theory of strong interactions. Observing and understanding these higher-mass resonances is crucial, but they are difficult to observe since they are broad and overlapping. Very often, these higher-lying states reveal themselves more clearly through interference with dominant amplitudes. These interference terms can be isolated via polarization observables.
At Jefferson Lab, extensive data sets on photo- as well as electro-production of pseudo-scalar mesons ($\pi$, 2$\pi$, $\eta$, K) and vector mesons ($\rho$, $\omega$, $\phi$) have been accumulated over the last few years using the CEBAF Large Acceptance Spectrometer (CLAS). The current efforts with CLAS focus on utilizing highly-polarized hydrogen and deuterium targets in combination with polarized photon beams toward a complete measurement of a large number of reaction channels. In particular, the CLAS g9a (FroST) experiment, as part of the $N^\ast$ program at Jefferson Laboratory, has accumulated photoproduction data using linearly- and circularly-polarized photons incident on a longitudinally-polarized butanol target in the energy range 0.3 to 2.4 GeV. This contribution discusses recent results on (mostly) single- and double-pion photoproduction.
Primary author
Volker Credé
(Florida State University)