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The (p, pα) reaction on 12 C was investigated experimentally using polarized incident protons of 100 MeV. Coincident data, which were obtained at ten quasifree angle pairs for proton angles ranging from 25 • to 110 • , were analyzed in terms of the distorted-wave impulse approximation (DWIA). Calculated energy-sharing cross section and analyzing power distributions reproduce the data reasonably well. The observed agreement allows the extraction of distorted momentum distributions from experimental data. These distributions are very consistent over a wide range of angle pairs at which cross section energy-sharing distributions vary considerably. Since measurements of analyzing powers were made, spin-orbit distortions were included in the DWIA calculations. The effects of spin-orbit distortions were found to be very small near zero recoil momentum and did not destroy the validity of the factorization approximation where the two-body p-α cross section enters as a multiplicative factor in the three-body (p, pα) cross section expression. Spectroscopic factors derived from the data are fairly consistent with the trend of the theoretical predictions. Analyzing power data also follow the trend of free p-4 He scattering data, and comparisons with DWIA predictions are in reasonable agreement. The theory reproduces also very well analyzing power angular distributions of the projectile-cluster two-body scattering at large angular momentum of the residual nucleus. This indicates that a quasifree knockout mechanism dominates the reaction. The two-body interaction response between the projectile and the α cluster was found to resemble the scattering of protons from a free α particle to a remarkable degree, the present results strongly imply the existence of preformed α clusters in 12 C. I wish to express my sincere gratitude to my Promoter Prof. A.A. Cowley for suggesting this exciting project and for providing patient guidance throughout the period of my research work. I consider it an honour to have had the privilege of working with him. I am grateful to my Co-promoter Dr. S.V. Förtsch for his constant encouragement, guidance and friendship. I wish to acknowledge the help of Dr. R. Neveling for his invaluable help during the data analysis and for many fruitful discussions I had with him.
The thermodynamics of excited nuclear systems allows one to explore the second-order phase transition in a two-component quantum mixture. Temperatures and densities are derived from quantum fluctuations of fermions. The pressures are determined from the grand partition function of Fisher's model. Critical scaling of observables is found for systems which differ in neutron to proton concentrations thus constraining the equation of state of asymmetric nuclear matter. The derived critical exponent β = 0.35 ± 0.01, belongs to the liquid-gas universality class. The critical compressibility factor P c /ρ c T c increases with increasing neutron number.
The experimental determination of freeze-out temperatures and densities from the yields of light elements emitted in heavy ion collisions is discussed. Results from different experimental approaches are compared with those of model calculations carried out with and without the inclusion of medium effects. Medium effects become of relevance for baryon densities above $\approx 5 \times 10^{-4}$ fm$^{-3}$. A quantum statistical (QS) model incorporating medium effects is in good agreement with the experimentally derived results at higher densities. A densitometer based on calculated chemical equilibrium constants is proposed.Comment: 5 pages, 3 figure
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