Virtual Compton Scattering at Low Energy and the Generalized Polarizabilities of the Nucleon o

Virtual Compton Scattering on the nucleon: $\gamma^* N \to \gamma N$ is a new and rapidly developing field at low and high energies. This lecture is about the low energy part, i.e. for energies in the $(\gamma p)$ center-of-mass mainly up to the $\Delta(1232)$ resonance region. I review the concept of Generalized Polarizabilities of the Nucleon, and the experiments dedicated to their measurement.Comment: 16 pages, 8 figures. lecture given at the Erice School "Lepton Scattering and the Structure of Hadrons and Nuclei," Erice, 16 - 24 Sept. 2004; to appear in "Progress in Particle and Nuclear Physics

Vegetation and the importance of insecticide-treated target siting for control of Glossina fuscipes fuscipes

Control of tsetse flies using insecticide-treated targets is often hampered by vegetation re-growth and encroachment which obscures a target and renders it less effective. Potentially this is of particular concern for the newly developed small targets (0.25 high × 0.5 m wide) which show promise for cost-efficient control of Palpalis group tsetse flies. Consequently the performance of a small target was investigated for Glossina fuscipes fuscipes in Kenya, when the target was obscured following the placement of vegetation to simulate various degrees of natural bush encroachment. Catches decreased significantly only when the target was obscured by more than 80%. Even if a small target is underneath a very low overhanging bush (0.5 m above ground), the numbers of G. f. fuscipes decreased by only about 30% compared to a target in the open. We show that the efficiency of the small targets, even in small (1 m diameter) clearings, is largely uncompromised by vegetation re-growth because G. f. fuscipes readily enter between and under vegetation. The essential characteristic is that there should be some openings between vegetation. This implies that for this important vector of HAT, and possibly other Palpalis group flies, a smaller initial clearance zone around targets can be made and longer interval between site maintenance visits is possible both of which will result in cost savings for large scale operations. We also investigated and discuss other site features e.g. large solid objects and position in relation to the water's edge in terms of the efficacy of the small targets

Virtual Compton scattering and the generalized polarizabilities of the proton at Q(2)=0.92 and 1.76 GeV2

Virtual Compton scattering (VCS) on the proton has been studied at the Jefferson Laboratory using the exclusive photon electroproduction reaction ep -\u3e ep gamma. This paper gives a detailed account of the analysis which has led to the determination of the structure functions P-LL - P-TT/epsilon and P-LT and the electric and magnetic generalized polarizabilities (GPs) alpha(E) (Q(2)) and beta(M) (Q(2)) at values of the four-momentum transfer squared Q(2) = 0.92 and 1.76 GeV2. These data, together with the results of VCS experiments at lower momenta, help building a coherent picture of the electric and magnetic GPs of the proton over the full measured Q(2) range and point to their nontrivial behavior

Real and Virtual Compton Scattering: the nucleon polarisabilities

We give an overview of low-energy Compton scattering (gamma^(*) p --> gamma p) with a real or virtual incoming photon. These processes allow the investigation of one of the fundamental properties of the nucleon, i.e. how its internal structure deforms under an applied static electromagnetic field. Our knowledge of nucleon polarisabilities and their generalization to non-zero four-momentum transfer will be reviewed, including the presently ongoing experiments and future perspectives.Comment: 20 pages, 12 figures. Minireview/Proceedings of "Many-Body Structure of Strongly Interacting Systems", Mainz, Germany, Feb. 23-25 2011 . V2: typos corrected. version to appear in EPJ Special Topic

Unitary Isobar Model - MAID2007

The unitary isobar model MAID2007 has been developed to analyze the world data of pion photo- and electroproduction. The model contains both a common background and several resonance terms. The background is unitarized according to the K-matrix prescription, and the 13 four-star resonances with masses below 2 GeV are described by appropriately unitarized Breit-Wigner forms. The data have been analyzed by both single-energy and global fits, and the transverse and longitudinal helicity amplitudes have been extracted for the four-star resonances below 2 GeV. Because of its inherent simplicity, MAID2007 is well adopted for predictions and analysis of the observables in pion photo- and electroproduction.Comment: 32 pages including 13 tables and 24 figure

Virtual Compton Scattering and the Generalized Polarizabilities of the Proton at Q\u3csup\u3e2\u3c/sup\u3e = 0.92 and 1.76 GeV\u3csup\u3e2\u3c/sup\u3e

Virtual Compton scattering (VCS) on the proton has been studied at the Jefferson Laboratory using the exclusive photon electroproduction reaction ep → epγ. This paper gives a detailed account of the analysis which has led to the determination of the structure functions PLL − PTT/ε and PLT and the electric and magnetic generalized polarizabilities (GPs) αE(Q2)and βM(Q2) at values of the four-momentum transfer squared Q2 = 0.92 and 1.76 GeV2. These data, together with the results of VCS experiments at lower momenta, help building a coherent picture of the electric and magnetic GPs of the proton over the full measured Q2 range and point to their nontrivial behavior

Virtual Compton scattering and neutral pion electroproduction in the resonance region up to the deep inelastic region at backward angles

We have made the first measurements of the virtual Compton scattering (VCS) process via the H(e, e\u27p). exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the W-dependence at fixed Q(2) = 1 GeV(2) and for the Q(2) dependence at fixed W near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed Q(2) dependence is smooth. The measured ratio of H(e, e\u27p). to H(e, e\u27p) pi(0) cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to real Compton scattering (RCS) at high energy and large angles, our VCS data at the highest W (1.8-1.9 GeV) show a striking Q(2) independence, which may suggest a transition to a perturbative scattering mechanism at the quark level