Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV

The three-body photodisintegration of 3He has been measured with the CLAS detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first time to cover a wide momentum and angular range for the two outgoing protons. Three kinematic regions dominated by either two- or three-body contributions have been distinguished and analyzed. The measured cross sections have been compared with results of a theoretical model, which, in certain kinematic ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications: removed 2 figures, improvements on others, a few minor modifications to the tex

A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments

We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.Comment: revtex4 18 pp., 12 figure

Linking behaviour and climate change in intertidal ectotherms: insights from littorinid snails

A key element missing from many predictive models of the impacts of climate change on intertidal ectotherms is the role of individual behaviour. In this synthesis, using littorinid snails as a case study, we show how thermoregulatory behaviours may buffer changes in environmental temperatures. These behaviours include either a flight response, to escape the most extreme conditions and utilize warmer or cooler environments; or a fight response, where individuals modify their own environments to minimize thermal extremes. A conceptual model, generated from studies of littorinid snails, shows that various flight and fight thermoregulatory behaviours may allow an individual to widen its thermal safety margin (TSM) under warming or cooling environmental conditions and hence increase species’ resilience to climate change. Thermoregulatory behaviours may also buffer sublethal fitness impacts associated with thermal stresses. Through this synthesis, we emphasise that future studies need to consider not only animals' physiological limits but also their capacities to buffer the impact of climate change through behavioural responses. Current generalizations, made largely on physiological limits of species, often neglect the buffering effects of behaviour and may, therefore, provide an over-estimation of vulnerability, and consequently poor prediction of the potential impacts of climate change on intertidal ectotherms

Basic Formal Education Quality, Information Technology and Inclusive Human Development in Sub-Saharan Africa

This study assesses the relevance of basic formal education in information technology for inclusive human development in 49 countries in sub-Saharan Africa for the period 2000-2012. The question it aims to answer is the following: what is the relevance of basic formal education in the effect of mobile phone penetration on inclusive human development in sub-Saharan Africa when initial levels of inclusive human development are taken into account? The empirical evidence is based on instrumental quantile regressions. Poor primary education dampens the positive effect of mobile phone penetration on inclusive human development. This main finding should be understood in the perspective that, the education quality indicator represents a policy syndrome because of the way it is computed, notably: the ratio of pupils to teachers. Hence, an increasing ratio indicates decreasing quality of education. It follows that decreasing quality of education dampens the positive effect of mobile phone on inclusive development. This tendency is consistent throughout the conditional distribution of inclusive human development. Policy implications for sustainable development are discussed

Spin-isospin excitation in 12C(γ, π+)12B∗ using tagged photons

The energy spectra of positive pions from the reaction 12C(γ, π+)12B∗ were measured at five angles, using quasi-monochromatic, tagged photons in the energy range from 176 to 182 MeV. Strong transitions to the isovector nuclear states in 12B at 0–1, 4.5, and 7.5 MeV were observed. The differential cross sections to these states have been obtained for the momentum transfers 0.5 &#60; q &#60; 1.2 fm−1. DWIA calculations have been carried out in momentum space for each observed state or group of states. Comparisons are made between the present data, previous data from bremsstrahlung experiments, and various DWIA calculations

Spin-isospin excitation in 12C(γ, π+)12B∗ using tagged photons

The energy spectra of positive pions from the reaction 12C(γ, π+)12B∗ were measured at five angles, using quasi-monochromatic, tagged photons in the energy range from 176 to 182 MeV. Strong transitions to the isovector nuclear states in 12B at 0–1, 4.5, and 7.5 MeV were observed. The differential cross sections to these states have been obtained for the momentum transfers 0.5 &#60; q &#60; 1.2 fm−1. DWIA calculations have been carried out in momentum space for each observed state or group of states. Comparisons are made between the present data, previous data from bremsstrahlung experiments, and various DWIA calculations

Detection of low energy pions at a tagged photon beam

In order to measure pions in the range 10–30 MeV from the reaction 12C(γ, π+)12B∗ using monochromatic photons, for a study of excited collective spin-isospin analog states [1], a detection system for positive pions, which reduces the backgrounds from electrons and protons by very large factors, was developed. The techniques and detectors used, namely a ΔE - E plastic scintillation telescope with separate photomultipliers and a glued triple sandwich of CaF2-plastic-CaF2 scintillators, are described here

Total photoabsorption cross sections for H-1, H-2, and He-3 from 200 to 800 MeV

The total photoabsorption cross sections for 1H, 2H, and 3He have been measured for incident photon energies ranging from 200 to 800 MeV. The 3He data are the first for this nucleus. By using the large acceptance detector DAPHNE in conjunction with the tagged photon beam facility of the MAMI accelerator in Mainz, cross sections of high precision have been obtained. The results show clearly the changes in the nucleon resonances in going from 1H to 3He. In particular, for the D13 region the behavior for 3He is intermediate between that for 1H, 2H, and heavier nuclei. This will provide a strong constraint to the theories that are presently being developed with a view to explaining the apparent ‘‘damping’’ of higher resonances in heavy nuclei