0000000000139028
AUTHOR
W. Konen
Threshold pion photoproduction in a light-cone quark model
Abstract The instantaneous and seagull graphs are calculated for pion photoproduction in a relativistic light-cone model of the nucleon. In both pseudoscalar and pseudovector coupling we find the ratios A (−) : A (0) : A (+) = 1: ( −1 2 μ):( −9 5 μ) in the nonrelativistic limit. These results correspond to the sum of seagull and Z -graph in the nonrelativistic quark model. In pseudovector coupling also the numerical results for realistic-model parameters are close to those values.
Nuclear Contact Times in Dissipative Heavy Ion Collsions Measured Via γ-Ray Spectroscopy
Electron spectra have been measured for elastic and dissipative U + Au collisions at 8.6 MeV/u and analysed within a simple schematic model which describes γ-ray emission in the presence of a nuclear contact time and a total kinetic energy loss (TKEL). A nearly linear dependence of the mean nuclear contact time τ and TKEL was found, reaching τ = 1.1 * 10-21 s with a variance σ = ±0.4 * 10-21 s for a TKEL of (400 ± 50) MeV.