Deuteron Photodisintegration at Intermediate Energies

High energy physics, Nuclear physics and radiation

Wallace, Peter Anthony

University:University of Glasgow

关键词: High energy physics, Nuclear physics and radiation;   

Others  :  http://theses.gla.ac.uk/77940/1/10999258.pdf

来源: University of Glasgow

【 摘 要 】

This thesis describes an experiment whose aim was to measure the angular differential cross-section d2s/dpdEt for the two-body photodisintegration of the deuteron D(t,p)n at photon energies in the region of 140 MeV. The experiment was performed using the Glasgow tagged photon spectrometer which was installed at the Mainz Institut fur Kernphysik to take advantage of the high quality d. c. electron beam provided by the racetrack microtron MAMI-A. The experimental work and subsequent data analysis took place in the period from March 1986 to December 1988. The motivation for the project was provided by the recent renewal of theoretical interest in the deuteron photodisintegration reaction which has lead to a call for new and more reliable data on the process. The significance of the reaction lies in its use as a test case for the application of modern models of the N --- N interaction. Such models seek to describe the nuclear force in terms of the underlying hadronic dynamics of the nucleon-meson system as opposed to the essentially phenomenological parameterisations which have been used previously. Photons, both real and virtual, provide the ideal tool for such studies since the electromagnetic interaction is the best understood of all the elementary processes. The experiment was performed with a 0.45 g cm-2 liquid deuterium target cell placed in a tagged photon beam with a total intensity of 10e7 s-1 in the range Et=133 --- 158MeV. Protons were detected in a large solid angle (0. 9 steradian) position sensitive plastic scintillator telescope which had an energy resolution of 5% and an angular resolution of 3. Measurement of the proton energy and angle together with knowledge of photon energy overdefined the reaction kinematics thus facilitating a very clean rejection of background events. Reliable normalisation was assisted by the tagging technique which determined the photon flux to +/-1%. A complete Monte Carlo simulation of the experiment was developed in order to evaluate the systematic corrections to the data. Included in the simulation are effects due to the beam-target geometry, energy losses of the protons in the target, energy deposition in the detector, light production non-linearities and nuclear interactions of the protons in the CH scintillator medium, and also variations in the light collection efficiency throughout the scintillator blocks. The monte carlo simulation produces an efficiency correction factor specific to each data point, as well as providing global normalisation factors to account for the tagging efficiency and the combination of beam and target geometries. The data is presented in the form of two angular distributions corresponding to mean photon energies of 140 and 150 MeV. The total systematic error is estimated to be not greater than 6 %. The results are found to be in good general agreement with other recent experiments but it is observed that none of the available theoretical calculations can give a fully satisfactory account of the data.