On the migdal-watson approach to FSI effects in meson production in NN collisions
The influence of the nucleon-nucleon final-state interaction (FSI) on properties of the meson-production amplitude near threshold is discussed. For nucleon-nucleon interaction, a simple Yamaguchi potential and realistic potential models are considered. It is shown that FSI effects cannot be factorized from the production amplitude. The absolute magnitude of FSI effects depends on the momentum transfer (or on the mass of the produced meson) and hence is not universal. Only in the case of the production of rather heavy mesons like η′ or φ FSI do effects become universal. The Jost function approach to FSI effects is critically examined.
Coupled-channel potential for nucleons and deltas.
We propose a nucleon-nucleon potential for which the [ital NN], [ital N][Delta], and [Delta][Delta] channels are coupled by energy-independent, nonlocal interactions constructed from meson-exchange interactions. The same vertex couplings that were utilized in earlier studies based on the Bonn single-channel [ital NN] potential are adopted. We arrive at our interaction by applying an extension of the folded diagram expansion to coupled channels. The coupled-channel formalism facilitates studies of the interplay between nucleon and delta degrees of freedom and bound-state properties of nuclear matter and finite nuclei. It also establishes a framework that might simplify the treatment of nucleon-nucleon scattering to energies above pion-production threshold.
UV-B radiometry and dosimetry for solar measurements.
Biologically effective irradiance or dose of solar UV radiation was determined using a spectroradiometer, two broadband radiometers and two types of passive UV-dosimeters. The absolute erythema irradiance and the actinic irradiance were calculated from the solar spectrum measured with the spectroradiometer. It was demonstrated that the erythema irradiance is proportional to the actinic irradiance of solar radiation. The erythema irradiance was also determined using the two broadband radiometers which utilize a filter transmitting erythema spectra. Personal UV-dosimeters such as polysulphone and CR-39 were used to determine the erythema dose for a selected period of time. These results were used to estimate the accuracy of the broadband radiometers and UV-dosimeters. It was found that the results obtained from the broadband radiometers deviate from the absolute erythema irradiance by less than 20% during clear days between the hours of 11:00 and 13:00 Eastern Standard Time (EST) in Australia. The assessment of the erythema dose using passive dosimeters such as polysulphone and CR-39 could introduce an error as high as 40% if the calibration was not performed before undertaking experimental measurements.