Thesis (PhD (Physics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The (p, pα) reaction on 12C 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-4He 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 12C. / AFRIKAANSE OPSOMMING: Die (p, pα) reaksie op 12C is eksperimenteel ondersoek deur middel van gepolariseerde
protone met n invalsenergie van 100 MeV. Ko¨ınsidensie data, wat verkry is by tien kwasievrye
hoekpare, met proton hoeke tussen 25◦ en 110◦, is geanaliseer in terme van die
vervormde-golf-impuls-benadering (DWIA). Die berekende energie-verdeelde kansvlak en
analiseervermo¨e verspreidings reproduseer die data redelik goed. Die waargenome ooreenstemming
maak dit moontlik om vervormde momentumverdelings uit die eksperimentele
data te verkry.
Aangesien analiseervermo¨e metings gedoen is, is spin-baan wisselwerking by die DWIA
berekenige ingesluit. Die bydra as gevolg van spin-baan wisselwerking blyk baie klein te
wees naby nul terugslag momentum en het nie die geldigheid van die faktoriseringsbenadering,
waartydens die twee-deeltjie, p-α kansvlak as ’n vermenigvuldigingsfaktor in die
uitdrukking vir die drie-deeltjie (p, pα) kansvlak verskyn, vernietig nie. Spektroskopiese
faktore wat uit die data herlei is, is redelik konsistent met die verloop van die teoretiese
voorspellings.
Analiseervermo¨e data volg ook die verloop van die vrye p-4He verstrooiings-data en vergelyk
redelik goed met DWIA voorspellings. Die teorie reproduseer ook die hoekverdelings
in die analiseervermo¨e van die twee-deeltjie projektiel-bondel verstrooiing by groot hoekmomentum
waardes vir die oorblywende kern baie goed. Dit dui daarop dat ’n kwasie-vrye
uitslaanmeganisme die reaksie domineer.
Die twee-deeltjie wisselwerkingsgedrag tussen die projektiel en die α-bondel toon sterk
ooreenkomste met die verstrooiing van protone vanaf ’n vrye α-deeltjie. Die huidige resultate
lewer sterk bewyse vir die bestaan van voorafgevormde α-bondels in 12C.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4012 |
| Date | 03 1900 |
| Creators | Mabiala, Justin |
| Contributors | Cowley, A. A., Fortsch, S. V., University of Stellenbosch. Faculty of Science. Dept. of Physics. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 131 p. : ill. |
| Rights | University of Stellenbosch |
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