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Neutron-Deuteron Scattering and Three-Body Interactions / Neutron-Deuteronspridning och TrekropparväxelverkanMermod, Philippe January 2006 (has links)
<p>High-precision differential cross section data of the neutron-deuteron elastic scattering reaction at 95 MeV are presented. The neutron-proton scattering differential cross section was also measured and used as a reference to allow an accurate absolute normalization of the neutron-deuteron data.</p><p>Two multi-detector arrays were used, MEDLEY and SCANDAL, at the neutron beam facility at The Svedberg Laboratory in Uppsala. Three different configurations of the detectors allowed to perform three independent measurements. The first experiment involved detecting recoil deuterons from thin deuterated polyethylene targets with the MEDLEY setup and allowed a large angular coverage. In the second experiment, high-precision data were obtained at neutron backward angles, using the SCANDAL setup with the same technique. For the third experiment, data were obtained in the forward angular range using the SCANDAL setup with a technique where neutrons scattered on heavy water were detected by neutron-proton conversion in plastic scintillators and tracking the protons through the detectors. Events from elastic neutron-deuteron scattering were identified in the data analysis, and differential cross sections were obtained after applying corrections and evaluating systematic uncertainties due to effects which could affect the shape or the absolute normalization of the data.</p><p>The results are compared with modern Faddeev calculations using realistic nucleon-nucleon potentials combined with three-nucleon interactions. The effects of three-nucleon forces are expected to increase the differential cross section by about 30% in the region of the minimum. The data agree with this prediction, thus providing evidence for three-nucleon force effects.</p>
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Neutron-Deuteron Scattering and Three-Body Interactions / Neutron-Deuteronspridning och TrekropparväxelverkanMermod, Philippe January 2006 (has links)
High-precision differential cross section data of the neutron-deuteron elastic scattering reaction at 95 MeV are presented. The neutron-proton scattering differential cross section was also measured and used as a reference to allow an accurate absolute normalization of the neutron-deuteron data. Two multi-detector arrays were used, MEDLEY and SCANDAL, at the neutron beam facility at The Svedberg Laboratory in Uppsala. Three different configurations of the detectors allowed to perform three independent measurements. The first experiment involved detecting recoil deuterons from thin deuterated polyethylene targets with the MEDLEY setup and allowed a large angular coverage. In the second experiment, high-precision data were obtained at neutron backward angles, using the SCANDAL setup with the same technique. For the third experiment, data were obtained in the forward angular range using the SCANDAL setup with a technique where neutrons scattered on heavy water were detected by neutron-proton conversion in plastic scintillators and tracking the protons through the detectors. Events from elastic neutron-deuteron scattering were identified in the data analysis, and differential cross sections were obtained after applying corrections and evaluating systematic uncertainties due to effects which could affect the shape or the absolute normalization of the data. The results are compared with modern Faddeev calculations using realistic nucleon-nucleon potentials combined with three-nucleon interactions. The effects of three-nucleon forces are expected to increase the differential cross section by about 30% in the region of the minimum. The data agree with this prediction, thus providing evidence for three-nucleon force effects.
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Meson production in pd collisionsSchönning, Karin January 2009 (has links)
Meson production in proton-deuteron collisions has been studied using the WASA detector facility at the CELSIUS storage ring in Uppsala. Data were obtained at two different beam energies, 1360 MeV and 1450 MeV, slightly above threshold for η and ω mesons. The differential cross sections of pd → 3He ω constitute the first measurements of this reaction covering the whole angular range. The ω angular distributions are isotropic at 1360 MeV but have strong forward and backward enhancements at 1450 MeV. Theoretical calculations using a two-step model fail to reproduce the shapes of the angular distributions and underestimate the total cross sections. The tensor polarisation of the ω meson has been derived from the measured angular distributions of the ω decay products. The π+ π- π0 and the π0 γ decay channels gave consistent results, showing that the ω meson is produced unpolarised at both energies. This is in contrast to a recent MOMO measurement which showed that the Φ meson is produced almost completely polarised in the pd → 3HeΦ reaction. Different production dynamics of ω and Φ mesons close to threshold raises the question whether the Okubo-Zweig-Iizuka (OZI) rule is applicable in low-energy nucleon-nucleon reactions. The angular distributions of the η meson produced in the pd → 3He η reaction are strongly enhanced for forward going η mesons at both energies. The σ(pd → 3He π+ π- π0 )/σ(pd → 3He π0 π0 π0 ) ratio has been measured and discussed in terms of isospin amplitudes. A rough estimate of the pd → 3He π0 π0 π0 π0 cross sections has also been obtained and the pd → 3He η π0 reaction has been studied for the first time near threshold.
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Effects of surface temperature in gas-surface interaction : quantum-state resolved studies of H₂ scattering from Si(100)Zhang, Shengyuan 09 February 2011 (has links)
The scattering of H2 from Si(100) has been studied using pulsed molecular beam techniques and quantum state-specific
detection methods. These studies can be used to test theoretical calculations and give insight into new theories of molecule-surface interactions, a fundamental study in a diverse field of science and technology.
In this work, time-of-flight (TOF) spectra of the elastic scattering of H2(v=1. J=1) and H2(v=0, J=1) from clean Si were recorded over a wide range of surface temperatures. Two data processing strategies were developed to extract rich kinematic information from the scattering experiments, e.g., mean translational energy exchange, absolutely survival probability, and angular and speed distribution of the scattered molecules. No such set of quantitative results has been reported before for this system. Compared with close packed metal surfaces, these scattering experiments from a covalently bonded semiconductor surface showed a completely distinct dynamics, e.g. the finding of energy gain instead of loss from the substrate, much broader angular distribution and some counterintuitive surface temperature effects. From the studies of molecules/surface scattering experiments, the thermal excitation on Si(100) surface which depends on surface temperature can substantially alter the adsorption barrier and its distribution, and therefore changes the kinematics of scattered molecules. As a result, even the most basic understanding of the dynamics has to include phonon excitation and deexcitation of the silicon substrate. / text
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A study of the (₉Be, ₁₀B) reactionWinfield, John Stuart January 1983 (has links)
Angular distributions have been measured for the (<sup>9</sup>Be, <sup>10</sup>B<sub>0</sub>, <sub>1</sub>) reactions on <sup>63</sup>Cu, <sup>54</sup>Fe, <sup>26,24</sup>Mg and <sup>16</sup>O at 43 MeV and on <sup>40</sup>Ca at 45 and 30 MeV. Several of these experiments were performed with the Oxford MDM-2 spectrometer and the design and testing of its 30 cm focal plane detector, which is of the "hybrid" type, is described. Despite the size of the counter, in particular the large cathode to Frisch-grid separation, the resolution of the ionization signals is comparable with that of smaller counters. The position resolution is < 0.6 mm. Optical potentials have been obtained from the measured elastic scattering of <sup>9</sup>Be from <sup>16</sup>O, <sup>26</sup>Mg and <sup>40</sup>Ca, and <sup>10</sup>B from <sup>25</sup>Mg and <sup>39</sup>K. The exact finite-range DWBA calculations have generally well reproduced the shape of the experimental reaction cross-sections. However, inconsistencies of up to 50% between the extracted spectroscopic factors for <sup>10</sup>B<sub>0</sub> and <sup>10</sup>B<sub>1</sub> have been found. This anomaly was found insensitive to changes in either optical potential or bound state parameters. A new method of form factor calculation is described that uses a shell model potential in conjunction with a surface-peaked potential, the depth of which is adjusted to give the correct asymptotic form to the wavef unctions. Whilst this form factor showed some success, it did not account for the <sup>10</sup>B<sub>0</sub>/<sup>10</sup>B<sub>1</sub> anomaly. Collective model DWBA analyses of the inelastic excitation of the first 2<sup>+</sup> state in <sup>26</sup>Mg and 3<sup>-</sup> state in <sup>40</sup>Ca have given values for deformation parameters in reasonable agreement with light-ion work. A CCBA analysis of the <sup>26</sup>Mg 2<sup>+</sup> state was carried out to estimate the effect of the coupling. Calculations performed for a two-step reaction process through inelastic excitation of a strongly coupled 5/2<sup>-</sup> state in the projectile showed that this indirect route is important, but it could not solve the <sup>10</sup>B<sub>0</sub>/<sup>10</sup>B<sub>1</sub> problem alone. The conclusion is that other routes (projectile or target excitation) must be included.
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Study of the N to Delta Transition via p({rvec e}, e{prime}{rvec p}){pi}{sup 0} reactionZhengwei Chai January 2003 (has links)
Thesis (Ph.D.); Submitted to Massachusetts Inst. of Tech., Cambridge, MA (US); 1 Aug 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "JLAB-PHY-03-174" "DOE/ER/40150-2747" Zhengwei Chai. 08/01/2003. Report is also available in paper and microfiche from NTIS.
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Antiproton-proton cross sections at 1.0, 1.25, and 2.0 BevCoombes, Charles A. January 1960 (has links)
Thesis--University of California, Berkeley, 1960. / "Physics and Mathematics" -t.p. "TID-4500 (15th Ed.)" -t.p. Includes bibliographical references (p. 50-51).
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The production of neutral hyperons by 5-Bev [pi]⁻ mesonsHotz, David Franklin. January 1959 (has links)
Thesis--University of California, Berkeley, 1959. / "Physics and Mathematics" -t.p. Includes bibliographical references (p. 50-51).
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Mechanisms of the ([alpha], pn) reactionSilva, Robert Joseph. January 1959 (has links)
Thesis--University of California, Berkeley, 1959. / "Chemistry-General" -t.p. Includes bibliographical references (p. 75-79).
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Positive-pion production by negative pionsPerkins, Walton A., January 1959 (has links)
Thesis (Ph.D.)--University of California, Berkeley, 1959. / "Physics and Mathematics"-t.p. Includes bibliographical references (p. 59-60).
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